CA2825234A1

CA2825234A1 - Accessible cooling system, especially for cryopreserving biological samples, and method for the operation thereof

Info

Publication number: CA2825234A1
Application number: CA2825234A
Authority: CA
Inventors: Guenter R. Fuhr; Heiko Zimmermann; Bernd KRANZ; Tomm Schmidt
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV; Helmholtz Zentrum Muenchen Deutsches Forschungszentrum fuer Gesundheit und Umwelt GmbH
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV; Helmholtz Zentrum Muenchen Deutsches Forschungszentrum fuer Gesundheit und Umwelt GmbH
Priority date: 2011-02-02
Filing date: 2012-02-01
Publication date: 2012-08-09
Anticipated expiration: 2032-02-01
Also published as: DE102011010121B4; CA2825234C; WO2012104080A8; CN103459949A; JP2014504716A; US20140000307A1; EP2671034A2; WO2012104080A2; WO2012104080A3; CN103459949B; DE102011010121A1

Abstract

A cooling system (1), especially for cryopreserving biological samples (2), comprises a cooling chamber (100) delimited by a bottom area (110), side walls (120), and a top area (130), and a cooling device (200) for cooling the cooling chamber (100) using liquid nitrogen (220). The bottom area (110) is designed for direct cooling using the liquid nitrogen, and the cooling chamber (100) is dimensioned such that an operator (3) can access and move around in the cooling chamber (100). The bottom area (110) has a platform (111) which is permeable to vapor of the liquid nitrogen (220) and forms a support zone for the operator (3). Methods for operating the cooling system are also described.

Description

ACCESSIBLE COOLING SYSTEM, ESPECIALLY FOR CRYOPRESERVING
BIOLOGICAL SAMPLES, AND METHOD FOR THE OPERATION THEREOF
The invention concerns a cooling system, in particular for cryopreservation of biological samples, which has a cooling chamber (cold room) cooled with liquid nitrogen (LN2). The invention furthermore concerns methods for operating the cooling system. Applications of the invention are given in long-term storage of samples in the cooled state, in particular for cryopreservation of biological samples.
It is known to store biological samples for the purpose of preservation in the frozen state in a cooling system, e.g. in a cryobank (cryopreservation). Cryobanks are typically operated at temperatures below -80 C, in particular at a temperature below the recrystallization temperature of water ice (-138 C). They contain a cooling agent reservoir with liquid nitrogen (temperature: about -195 C) and a plurality of individual tanks (so-called cryotanks, mostly Dewar flasks made of double-walled steel, see e.g. EP 1 223 393 A2, WO
2008/009840 Al, GB 812 210) with the size ranging from a few liters up to about 2 or 3 cubic meters. The cryotanks stand in rooms at normal temperature (room temperature) and are supplied with the liquid nitrogen from the cooling agent reservoir. In the cryotanks, boxes in which tubes, bags or other closed receptacles with the samples (e.g. liquids, cells, cell constituents, serums, blood, cell suspensions, pieces of tissue or the like) are stored are arranged in shelves. The samples can be fully arranged in the liquid nitrogen. To prevent contamination of samples by the liquid nitrogen, the samples are, however, mostly stored in a cool gaseous phase in the vapor of the liquid nitrogen at less than about -145 C. This gaseous phase is formed above a nitrogen lake at the bottom of the cryotank.

- 2 -For cooling in the cryotanks, it would be advantageous if they would be maintained permanently closed. In practice, they must, however, be opened repeatedly, e.g. when accessing the samples. In practice, sample storing or taking or inventories are required, which, for cryobanks with e.g.
10,000 up to 1 million or more samples, leads to a critical limitation for the effectiveness of the cryotank operation and for the provision of constant cooling conditions.
In addition, automation of all operations, in particular of the sample handling, is required for such a large number of samples. Previous automation approaches (see e.g. DE 10 2005 031 648 Al, US 2006/0156753 Al, US 2006/0283197 Al, US
2007/0267419 Al) are restricted to the individual cryotanks and entail considerable costs. For cryobanks with more than twenty cryotanks, automation between the cryotanks is extremely complicated, because it would require overlaying automatic machines, which, however, are currently not available.
It is further known to store food in cooling chambers.
Effective storage and automation are achieved when the cooling chambers form a walkable large-capacity warehouse.
This technique is, however, not applicable to cooling systems for the cryopreservation of biological samples. Even the lowest temperatures provided for cooling of food are too high for the long-term cryopreservation of biological samples.
Operation of conventional cooling chambers at lower temperatures is, however, not readily possible. Below -30 C, the conventional automation techniques fail due to functional and material limitations, mainly of motors, bearings, lubricants and the fits of moving parts. In the case of an incident or failure of a component in the cooling chamber, the latter would have to be heated completely, because operators can not safely enter rooms with a temperature below

- 3 --80 C wearing conventional protectional clothing. A deep breath would cause damage to pulmonary alveoli through freezing and then lead to life-threatening conditions. The quick frosting-up and freezing when opening and entering the rooms is also to be taken into account. Furthermore, there are problems with the thermal insulation of conventional deep-cooled cooling chambers and their safeguarding in case of an accident. Since cryobanks must be kept uninterruptedly cold for decades, probably in future for centuries, the accident problem is particularly critical. So far, there is a lack of techniques to keep large halls at temperatures of at least -80 C in case of total failure of the cooling system until appropriate repair has been effected.
The objective of the invention is to provide an improved cooling system, in particular for cryopreservation of biological samples, which allows to overcome disadvantages and limitations of conventional cooling systems. The cooling system should in particular provide effective cooling operation even with a high number of samples and/or improve automation of access to samples. The objective of the invention is also to provide an improved method for operation of a cooling system, in particular for cryopreservation of biological samples, with which disadvantages and limitations of conventional methods are overcome.
These objectives are solved by cooling systems and methods for operating the same having the features of the independent claims. Advantageous embodiments and applications result from the dependent claims.
According to a first aspect of the invention, a cooling system, in particular for cryopreservation of biological samples, is provided, which has a cooling chamber and a first cooling device, which are adapted for cooling of the cooling

- 4 -chamber using liquid nitrogen. The cooling chamber is generally a room delimited by a floor area, side walls and a ceiling area, which is cooled in its entirety with the first cooling device and is adapted for accommodating the samples to be preserved. Cooling of the entire cooling chamber is provided in a targeted way at least from its floor. To this effect, the floor area of the cooling chamber is adapted for direct cooling with the liquid nitrogen. This advantageously supports uniform cooling of the cooling chamber. Due to the cooling of the cooling chamber from the bottom up through the vapor of the liquid nitrogen, a gas layering with a temperature gradient can be formed in the cooling chamber.
The temperature may rise in a stable and reproducible way from the bottom upward. This advantageously supports the provision of reproducible storage conditions, in particular of a reproducible storage temperature at the location of the sample deposition.
According to the invention, the cooling chamber is dimensioned such that at least one operator can stay and move in the cooling chamber. The internal volume of the cooling chamber is selected such that the at least one operator completely fits in the cooling chamber and can stand and/or walk therein. Preferably, the internal volume is equal to at least 10 m3, in particular at least 100 m3, such as at least 500 m3, or even 1000 m3 or more. For an internal volume of e.g. 10 m3, the cooling chamber forms a small cryo chamber, while with e.g. 100 m3 a cryo room, with e.g. 500 m3 a cryo room array, and with more than 1000 m3 a cryo hall, possibly with several rooms, is given.
The cooling chamber of the cooling system according to the invention is adapted for accommodating a sample receiving device. Any holding structure, which is suitable for accommodating samples, in particular of sample containers

- 5 -with biological samples, can be used as the sample receiving device. Sample containers comprise e.g. test tubes, tubelets, capillaries, so-called "straws", bags or other closed receptacles. The sample receiving device may be arranged permanently in the cooling chamber (in particular fixed) or is at least in parts releasable. According to the invention, the cooling chamber is preferably dimensioned such that the operator can stay and move in the cooling chamber equipped with the sample receiving device.
In accordance with the invention, the floor area of the cooling chamber has a platform that comprises, for instance, at least a perforated plate, rust, and/or grating. The platform has a multiple function. First, the platform is formed in such a way that vapor of the liquid nitrogen can ascend through the platform into the cooling chamber. The platform is permeable to vapor. Thus, a cooling surface is created on the floor of the cooling chamber, which enables immediate, direct cooling of the interior of the cooling chamber through outflowing vapor, which has an advantageous effect on the effective and uniform cooling of the cooling chamber. Secondly, the platform forms a support area for the operator and typically also for a sample receiving device in the cooling chamber. The platform is configured as a stand area and/or walking surface for the operator. For this purpose, the platform is formed with such mechanical load-carrying capacity that it remains stable and in particular undeformed under load with the operator. Preferably, the mechanical load-carrying capacity of the platform is at least 100 kg/m2 (particularly suitable for light shelves and an operator), in particular at least 500 kg/m2 (particularly suitable for multiple shelves and operators), such as at least 1000 kg/m2 (particularly suitable for multiple shelves, machines and operators), or even 5000 kg/m2 (especially suitable for security shelves, machines and operators), or

- 6 -more. Furthermore, the platform is preferably formed in such a way that it extends at least over half of the surface of the floor of the cooling chamber. Particularly preferably, the platform extends over the entire surface of the floor of the cooling chamber.
According to a second aspect of the invention, a method for operating the cooling system according to the preceding first aspect of the invention is provided, for which cooling of the cooling chamber with the first cooling device and positioning of samples, in particular biological samples, in the cooling chamber is provided for.
Advantageously, the first cooling device can be adapted for filling with liquid nitrogen in such a way that a free surface of the liquid nitrogen is formed below the floor area. The first cooling device has, for example, a vessel, which is open upwards to the floor area and to the cooling chamber, such as a trough (floor trough) for receiving liquid nitrogen. The platform of the floor area may include for example a grating, which extends over the vessel. Further advantageous is that a trough with a flat bowl shape can be used since no demands are made on the volume of the liquid nitrogen arranged in the first cooling device. Thus, it is in particular provided for that the volume of the liquid nitrogen arranged in the first cooling device is less than the volume of the vaporous nitrogen existing inside the cooling chamber. Preferably, the floor area and the first cooling device are equipped laterally and downwardly with thermal insulation.
Advantageously, with the inventive combination of nitrogen cooling, cooling chamber sizing and provision of the platform, a new cooling system is created which overcomes the disadvantages and limitations of conventional techniques. The

- 7 -conventional individual tank principle for cryobanks is overcome with the invention. The cooling system represents a freely scalable cryobank architecture. Compared to the conventional cryotanks, the advantage results that permanently constant storage conditions are provided for a larger number of samples. The samples can be stored in sample containers in the cooling chamber without requiring tanks, thermal insulation or the like within the cooling chamber.
Access to individual samples is possible without compromising the cooling of the remaining samples.
With the sizing of the cooling chamber, the internal volume of conventional cryotanks is far exceeded. The sizing provides not only sufficient space for automation and/or one or also more operators, but also high heat capacity of the cooled system. Thus, the supply of a sample or the insertion of a tool represents only a negligibly low heat input, so that the whole of the samples is hardly disturbed.
Compared with the cooling of food in large stores, there is the advantage that the cooling chamber is cooled with the liquid nitrogen to a temperature that is sufficiently low for cryopreservation of biological samples. Liquid nitrogen as a coolant is advantageous, for it is cheap, easy to handle and complies in its liquid form with a boiling temperature at atmospheric pressure of about -195.8 C with all requirements for cryopreservation of biological samples. At the same time, providing the platform allows that the cooling chamber can be accessed independently of its size by the operator in order to resolve eventual failures or errors.
In addition, the cooling system according to the invention is characterized by the following advantages. The cryobank architecture can be formed with large, automatable rooms with sample receiving devices. The cooling system is scalable from

- 8 -small banks (a few hundred samples) up to industrial hall systems (millions of samples). A temperature below -130 C can be targetedly adjusted in the cooling chamber. The cooling system allows a semi- or fully-automated storing and taking of samples. Another advantage consists is in the long-term operation capacity and maintenance without any change in temperature in the cooling chamber.
Further advantages of the invention consist in the complete freedom from moisture and icing-of the cooling chamber, the rapid cooling ability of the cooling system without frost formation, high access speed to all samples in the cooling chamber, the same access ability for all stocks in the cooling chamber, the optionally provided electronic responsiveness of the samples and storage systems, the controllability of the temperature in predeterminable areas of the cooling chamber, and the rapid storing and destocking of samples at a documented sample temperature. In particular, the freedom from moisture and icing (freedom from water, storage in dry gas) of the cooling chamber is supported by the production according to the invention of cooling nitrogen vapor from the floor area of the cooling chamber. The invention can be used to implement alternative energy concepts (use of hydrogen for cooling and power generation).
Furthermore, a strongly redundant design of the safety-relevant systems and keeping constant the temperature through controlled cooling in the cooling chamber or its parts is possible.
According to a preferred embodiment of the invention, the cooling system is equipped with at least one further cooling device (hereinafter: second cooling device), which is operational independently of the first cooling device. The second cooling device is also provided for cooling of the cooling chamber. According to a first variant, the second

- 9 -cooling device is arranged for cooling of at least one of the side walls of the cooling chamber. Cooling elements of the second cooling device are embedded, for example, as a hollow wall structure in at least one of the side walls, or positioned on the side pointing towards the interior of the cooling chamber. According to another variant, the second cooling device is alternatively or additionally configured for electric cooling and/or cooling using liquid helium (LHe).
The second cooling device advantageously allows a hybrid operation of the cooling system. For example, at least two different cooling principles can be switched temporally in series (e.g., 8 h of electrical cooling, 10 h of cooling with LN2) or in parallel and/or with different cooling capacities.
According to another example, electrical cooling to -150 C
and in addition cooling with LN2, or LN2 cooling and operator-selectable cooling with LH, or electric cooling to -80 C of an anteroom, then electrical cooling to -150 C and cooling with LN2 can be provided for. A full hybrid system or a semi-hybrid system can be realized with the hybrid operation. In the full hybrid system, both cooling devices are each alone fully efficient, i.e. each of the cooling devices allows permanent cooling of the cooling chamber down to temperatures < -130 C. In the semi-hybrid system, one of the cooling devices (main cooling system, e.g. LN2) is permanently in operation, while the other one of the cooling devices (auxiliary system) is switched on only if required.
The second cooling device can in particular form an emergency cooling system, which ensures, in case of failure of all other cooling devices, in particular of the first cooling device, that the temperature does not rise above -138 C in the entire cooling chamber where the samples are located.

- 10 -According to a preferred embodiment of the invention, the ceiling area of the cooling chamber has at least one ceiling opening. The ceiling opening is particularly preferably a permanently free through-hole through which cool gas flows out of the cooling chamber, always upwards, through the ceiling. Furthermore, the ceiling opening represents an access opening for samples and/or an entry and exit opening for the operator. It can advantageously be provided for that the cooling chamber has no further openings, e. g. on the side walls or in the floor area, so that the at least one ceiling opening represents the single connection of the interior of the cooling chamber with an environment, which is suitable for the passage of the samples, the operator or further mechanical components. Thus, it is particularly preferably provided for that the entry and exit of the operator take place exclusively above the cooling chamber through the ceiling area. However, the entry and exit the operator through a side wall can be provided alternatively or additionally.
The at least one ceiling opening advantageously offers the option to place a hood chamber onto the cooling chamber, in which the sample receiving device or at least the cryopreservation samples can be accommodated e. g. in the case of an accident.
In addition, according to a further variant of the invention, it has proved advantageous if at least one operation room is provided for above the ceiling opening. The temperature of the operation room can be increased compared with the temperature of the cooling chamber. To minimize thermal losses, the operation room is, however, preferably thermally insulated from the external environment of the cooling system. The operation room contains technical systems, which

- 11 -have an effect on the cooling chamber. Preferably, a drive device with mechanical control elements, such as robot arms for access to samples, and/or a conveying device for driving the operator into or out of the cooling chamber are provided for in the operation room. Alternatively or additionally, the operation room can be connected with at least one lock device (person lock device and/or sample lock device).
According to a preferred variant of the invention, the mechanical control elements, such as gripping arms, levers or actuation elements, can be introduced into the cooling chamber. If at least parts of the control elements, in particular connection areas between parts of the control element, which are movable relative to one another, are heatable, the operability of the drive device in the cooling chamber is improved. The connection areas can be equipped with locally acting heaters.
According to further preferred variants of the invention, the conveying device comprises in the operation room a rope hoist and/or a step device. The rope hoist is adapted for transporting the operator into and/or out of the cooling chamber. For this variant, the operator is transported suspended on a rope or a chain. This advantageously increases in particular the safety during evacuation of the operator out of the cooling chamber. The step device comprises, for example, a step ladder or stairs, which extends between the interior of the cooling chamber, in particular its floor area, and the operation room above the ceiling area.
Further advantages can result for reducing thermal losses if supply connections run between the cooling chamber and its environment through the ceiling area. Supply connections comprise medium lines, in particular coolant or breathing air lines, electric cables, in particular for power supply or for

- 12 -signal transmission, and/or optical cables, in particular for signal transmission.
According to a further preferred embodiment of the invention, at least one of the side walls can have a multi-layer structure with at least two wall layers. The inventors have found that the structure with the at least two thermally insulated wall layers allow effective insulation of the cooling chamber with respect to an environment at room temperature and with a moderate coolant consumption.
Furthermore, the operability of the cooling system can be achieved, in particular in case of failure of the cooling, at least over a plurality of days. The use of multiple wall layers has the particular advantage that they can be optimally designed with respect to the use of space and the dense filling of the side wall. Each wall layer is a wall layer, which extends along the extension of the side wall.
Each of the wall layers has thermally insulating effect, i.e.
a thermal conductivity, which is lower than 0.05 W/m2 (simple insulating foam materials), in particular lower than 0.004 W/m2 (vacuum pads), in particular lower than 0.001 W/m2 (vacuum insulation), and/or a moisture-repellent effect. A
plurality of wall layers are stacked vertical to the extension of the side wall. A wall layer comprises at least one plastic layer, at least one vacuum component layer and/or at least one vapor-blocking layer. The plastic layer comprises e.g. a board made of foamed plastics, in particular a rigid foam board. With the plastic layer, the cubature can be advantageously optimized with respect to a further wall layer. The vacuum component layer comprises e.g. vacuum insulation panels, which are advantageous due to their low thermal conductivity. The vapor-blocking layer comprises, for example, a foil, which is impermeable for water vapor. In particular, a plurality of vapor locks can be available within the side wall to prevent failure due to moisture.

- 13 -At least one of the wall layers can be formed in particular from a material (composite material, e.g. foam, liquid;
inflatable body, e.g. with suitable sealing material), which is suitable to close autonomously any interruption, such as cracks or holes. At least one of the side walls can thus be a self-healing wall.
At least one of the wall layers can furthermore have a switchable thermal conductivity. The thermal conductivity can be switched e.g. by means of evacuation from a vacuum component layer or supply of a gas or a liquid into a vacuum component layer.
At least one of the side walls can be covered according to the invention on the inner side facing toward the cooling chamber with a metallic material in order to, for example, form a cooling layer and/or in order to accommodate cooling elements of the second (electric) cooling device.
Furthermore, according to the invention, at least one of the side walls can be constructed in a modular manner with at least one wall element, which, with a vertical movement with respect to the respective side wall, can be released from its compound. The at least one wall element is shiftable and can be separated from the side wall. The at least one wall element advantageously allows a structure of the side wall with individually interchangeable insulation media without risks for the samples. Alternatively or additionally, the at least one wall element allows an emergency opening of the cooling chamber for rapid removal of samples from the cooling chamber in case of an accident (evacuation). The wall element can be instantaneously shiftable off the side wall, for example by means of blowing-up. Advantageously, for the case of accident, a docking device for a mobile evacuation container can be provided for on an external side of the side

- 14 -wall, corresponding to the position of the at least one shiftable wall element.
According to a further preferred embodiment of the invention, at least one of the side walls can have a door opening, which is closed by a movable door leaf. The door leaf is, such as the surrounding side wall, designed in a thermally insulating manner. The lateral door opening can be advantageous for sidewards access by the operator to the cooling chamber.
Preferably, the door opening is arranged with a predetermined distance above the floor area. The distance is preferably equal to at least 10 cm, in particular at least 50 cm, up to several meters. The door opening is connected via stairs with the floor area. In this case, a downwardly closed space is formed up to a level below the door opening and above the floor area to receive the vaporous nitrogen. At least part of the vaporous nitrogen cannot escape from the cooling chamber even if the door opening is open. Alternatively or additionally, it can be provided for that the door leaf is arranged shiftable parallel to the respective side wall. In this case, a wall surface (bulkhead), which can be drawn e.g.
in the height or to the side, is created. A docking device for an evacuation container or a lock device can be provided for on an external side of the side wall, corresponding to the position of the door opening.
Advantageously, a sample receiving device in the cooling chamber can comprise shelves (so-called "racks"), which form the support structure for the biological samples. In this case, advantages result for automated access to samples, e.g.
with the mechanical control elements. Shelves comprise carrier plates (racks) on which the containers with the biological samples are freely located. Particularly preferably, the shelves are formed from a material with increased thermal conductivity, e. g. metal. This

- 15 -advantageously allows a homogeneous temperature distribution in the sample receiving device.
The sample receiving device can be designed for an electric and/or optical connection with a control device (operational control). This advantageously allows an electronic responsiveness of the shelves and, if necessary, of the samples on the shelves.
According to a variant of the invention, the sample receiving device can be equipped with thermal bridges, which protrude into the floor area. The thermal bridges consist of materials with an increased thermal conductivity, e.g. of metal. This advantageously creates a thermally well conductive connection to the LN2-lake of the first cooling device. According to a further variant the invention, the sample receiving device can alternatively or additionally form a rigid component. For example, the shelves are connected to a rigid structure. In this case, advantages result for the position accuracy and the reproducibility of the weight load of the platform.
According to a further variant of the invention, the cooling chamber can be subdivided by partition walls into subrooms.
The partition walls can extend in the vertical and/or horizontal direction in the cooling chamber. This advantageously achieves a segmentation into pre- and main cooling chambers and, if necessary, into secondary cooling chambers. For example, samples can be cooled targetedly according to the storage capacity used and the access frequency and/or storage temperature demand. For example, the temperature can be targetedly decreased or increased in certain parts of the cooling chamber, such as in a front, central, upper, rear and/or below part. Furthermore, heat corridors can be formed, through which an increased temperature is provided in the case of an accident for rapid

- 16 -evacuation of the samples.
With the partition walls, a structure can be created, which is characterized by mutually surrounding subrooms with different temperatures. For example, a subroom can have the lowest temperature in the middle of the cooling chamber and offer the highest safety for maintaining the cryopreservation temperature. This allows a storage strategy for which the most valuable frozen live samples are stored in the subroom in the middle of the cooling chamber, frozen dead material in the surrounding subrooms, and liquid, genetic material, serines etc. in an external subroom.
According to general features of the invention, the cooling system can be equipped with at least one of the following components:
- ventilators for thorough mixing of the cool gaseous phase in the interior of particular rooms, - gas sensors, e.g. oxygen sensors, - temperature sensors, in particular for a spatially distributed temperature measurement in the cooling chamber, - alarm devices, e. g. alarm lamps, - lighting equipment with minimized entry of infrared or thermal radiation, e.g. using light-emitting diodes (LED) or other cold light sources, glass fibers for light coupling in the ceiling area, in the floor area or in at least one of the side walls (glass fibers can be supplied into the cooling chamber in particular via thermal insulation, e.g. via coupling-in via an evacuated vacuum component), - contactless energy and signal entry (inductive or optical coupling), - monitoring devices, e.g. a camera monitoring system, a movement detector and/or a heat detector, - emergency power supply with self-connection, bridging-free voltage supply,

- 17 -- coolant sprinkler system in the upper area of the cooling chamber, e.g. for supply of liquid nitrogen or helium for rapid cooling of the cooling chamber, and - connecting device for external liquid gas supply, e.g.
from a tanker, in the case of an accident, - a nitrogen liquefaction system, - a coolant container, which is provided for receiving a reserve volume of liquid nitrogen, and/or - condensate collection elements, which protrude from the floor area into the cooling chamber.
Further advantages and details of the invention are described below with reference to the attached drawings. The figures show as follows:
Figures 1 and 2: schematic cross-sectional views of preferred embodiments of the cooling system according to the invention;
Figures 3 and 4: schematic perspective views of further embodiments of the cooling system according to the invention;
Figure 5: schematic cross-sectional views of a side wall of the cooling system according to the invention;
Figure 6: a schematic overview representation of the cooling system with additional drive devices according to the invention;
Figure 7: schematic top and cross sectional views of a further embodiment of the cooling system according to the invention having a segmented cooling chamber and an illustration of taking a sample off a shelf;

- 18 -Figure 8: a schematic cross-sectional view of a further embodiment of the cooling system according to the invention;
Figure 9: a schematic illustration of the adaptation of a cooling chamber of the cooling system according to the invention depending on the conditions of application; and Figure 10: a schematic illustration of a further operating mode of the cooling system according to the invention.
Preferred embodiments of the cooling system according to the invention and of the methods for operating the same are described in the following with exemplary reference to a cooling system with a cooling chamber, which is dimensioned such that an operator can perform several walking steps in the cooling chamber. The realization of the invention is not restricted to the cooling chamber size exemplary shown, but is rather accordingly possible even with considerably larger cooling chambers (halls) or also with smaller cooling chambers. Embodiments are described in the following in particular with reference to the structure of the cooling system and the novel operating modes, which are allowed by the cooling system according to the invention. Details of the cryopreservation of biological samples, such as the sample preparation or the realization of certain cooling procedures or the deposition of the samples together with stored sample data can be realized with the cooling system according to the invention as is known per se from the prior art.
Figure 1 shows a first embodiment of the cooling system according to the invention 1 in a schematic cross-sectional view with a cooling chamber 100, a first cooling device 200, a second cooling device 300, an operation room 400 and a

- 19 -coolant supply 500.
The cooling chamber 100 is delimited downwards by a floor area 110, sidewards by side walls 120 and upwards by a ceiling area 130. The internal volume of the cooling chamber 100 is equal to e.g. 10 m * 5 m * 3 m. A sample receiving device 140 is arranged in the cooling chamber 100, standing on the floor area 110 and adjacent to the side walls 120. The inner surface of the cooling chamber 100 is provided with a cooling layer 101, which is formed from a material having high thermal conductivity, e.g. metal. The cooling layer 101 has the advantageous effect that a temperature compensation in the cooling chamber 100 takes place in the vertical direction. In particular, the temperature can be adjusted below -130 C also in the upper area of the cooling chamber 100, which is important for the long-term storage of living biological samples.
Temperature sensors 103 are arranged in the cooling chamber 100 and in the operation room 400. Several temperature sensors 103 are provided at different distances from the floor area 110. This allow the detection of a temperature distribution in the cooling chamber 100. If required, additional cooling with the second cooling device 300 and/or a ventilation device (not shown) in the cooling chamber 100 can take place to achieve compensation of the temperature, in particular sinking of the temperature in the upper regions of the cooling chamber 100.
The floor area 110 comprises a platform 111, which extends over the first cooling device 200 with a trough 210. The trough 210 has a double-walled trough body with an evacuated interior and is provided on its outer side with thermal insulation. The thermal insulation has the same structure as the side walls 120. Alternatively or additionally, the trough

- 20 -is insulated with an infrared mirrored vacuum region. During operation of the cooling system 1, liquid nitrogen 220 is contained in the trough 210. The liquid nitrogen 220 preferably has a free surface towards the floor area 110. A
nitrogen lake is formed. Filling of the trough 210 and maintaining the reservoir of liquid nitrogen 220 during operation of the cooling system 1 takes place by means of the coolant supply 500.
The platform 111 comprises a grating, e.g. made of steel, which extends over the trough 210 and is equipped with step platforms 112. The step platforms 112 reduce any possible mechanical contact between an operator 3 and the platform 111, so that any heat flow from the operator 3 to the platform 111 is minimized. Since the platform 111 forms a support area for the operator 3 and also the sample receiving device 140, the platform 111 can be mechanically supported in the trough 210 by additional components (not represented).
The side walls 120 comprise several stratiform wall layers with an inner plastic layer 121 and two outer vacuum component layers 122.1, 122.2. The plastic layer 121 comprises a layer made of a polymer foam, e.g. a polyurethane foam. The thickness of the plastic layer 121 can e.g. be selected in the range of 10 cm to 1 m or also above 1 m. The vacuum component layers comprise an internal layer 122.1 of evacuated components (so-called "vacuum components") and an external evacuated hollow wall 122.2. The evacuated components of the internal vacuum component layer 122.1 are formed parallelepipedic, in particular like conventional building stones or bricks for building purposes, and are made out of plastic with an evacuated or evacuatable interior. The hollow wall of the external vacuum component layer 122.2 is evacuated in a normal operation mode or optionally filled with a cooling liquid. The hollow wall has in particular an

- 21 -advantageous function for the case that one of the cooling devices fails. If one of the cooling devices fails, the hollow wall of the external vacuum component layer 122.2 can be filled from a swichtable external auxiliary container 540 (see Figure 6) with a coolant such as liquid nitrogen in order to prevent undesirable heating of the cooling chamber 100, since heat penetration from the outside is prevented, even though it occurs with high coolant expenditure. In this case, this hollow wall should not form the outermost layer.
Deviating from the illustration in Figure 1, the order of the plastic layer and the vacuum component layer can be reversed.
Furthermore, further plastic and/or vacuum component layers can be provided for. Further details of the side walls 120 are described below with reference to Figure 5.
The ceiling area 130 comprises a plastic layer 132, formed e.g. out of polymer foam, in which a ceiling opening 131 is formed. Above the ceiling opening 131 is provided the operation room 400 with a drive device 410 and mechanical control elements 411, which project into the interior of the cooling chamber 100. Figure 1 shows by way of example a rod assembly with a vertical (412) and a horizontal (413) shifting units, which can be actuated with the drive device 410. With the mechanical control elements 411, samples 2 can be introduced into the sample receiving device 140 or removed therefrom. The mechanical control elements 411 are driven from above, i.e. from the operation room 400, e.g. using rope hoists, chains, toothed belts and the like, whose drive device 410 is arranged in the operation room 400. If required, motors, deflection rollers or other mechanical connection areas can be encapsulated in a thermally insulating manner or locally heated. To prevent thermal bridges, thermally insulating elements (not shown) are contained in the mechanical control elements 411.

- 22 -The sample receiving device 140 comprises shelves 141 (so-called "cryo racks") in which biological samples 2 are stored in sample containers. The shelves 141 have frames made of thermally well conductive material, e.g. made of metal, which have thermal contact to the platform 111 and via thermal bridges 142 directly to the liquid nitrogen 220 in the first cooling device 200. This advantageously ensures effective cooling up to the upper compartments of the shelves 141.
The second cooling device 300 is provided for on the side walls 120, in particular arranged on its surface facing inwardly or embedded therein. The second cooling device 300 is configured for electric cooling. It comprises cooling elements 310, which are connected with cooling aggregates 320. The cooling aggregates 320 are located outside the cooling chamber 100, preferably above it. With the second cooling device 300, it is e.g. possible to provide electric cooling down to a temperature of -150 C. According to alternative variants of the invention, the second cooling device 300 can be formed as a substitute by nitrogen cooling or cooling with liquid helium.
The operation room 400 contains the drive device 410 for the mechanical control elements 411. In addition, the operations room 400 can further contain drive devices (see e.g. Figure 2) and/or be connected with a person and/or sample lock device 450, 460 (see e.g. Figures 3, 6).
The coolant supply 500 comprises a coolant-storage container 510 and a coolant line 520. The coolant line 520 leads from the coolant storage container 510 through the ceiling area 130 and through the cooling chamber 100 into the first cooling device 200. The coolant line 520 is thermally insulated outside the cooling chamber 100, e.g. formed by a vacuum line. In contrast, inside the cooling chamber 100 (at

- 23 -521), a thermal insulation of the coolant line 520 is not provided for. This improves cooling of the interior of the cooling chamber 100. In addition, the coolant line 520 represents in the cooling chamber 100 a condensate collection element (moisture trap). Any residual moisture in the cooling chamber 100 settles on the coldest place, i.e. on the surface of the coolant line 520, until a dry and cold nitrogen atmosphere is formed in the whole cooling chamber 100 and there are no further ice deposits.
The function of the coolant line 520 as condensate collection element is advantageous in particular during the initial cooling of the cooling chamber. Moisture is bound by means of the condensate collection element, so that a dry storage is guaranteed during operation the cooling system 1. The dry storage (storage preventing ice deposition) is not advantageous only for the shelf-life of the samples, but also for the automation of the sample handling. In this way, movable parts of the mechanical control elements 411 can be moved easier.
Figure 1 illustrates an important design principle of the cooling system according to the invention. All supply connections, in particular supply lines and openings, into the interior of the cooling chamber 100 exclusively occur through the ceiling area 130, i.e. from above. This leads to minimization of the heat supply. Furthermore, warmer top attachments can be arranged in the operations room 400 or above it (see Figure 2) for devices, which cannot operate at low temperatures. In particular, chambers with higher temperature or even with an internal heater for operation of movable parts, such as motors, can be put on top. A plurality of chambers of this type can be constructed tower-like one above the other (see Figure 2). Since gas is formed continuously from the first cooling device 200 with clear

- 24 -increase of volume and the cooling system 1 is designed pressure-free, i.e. not gas-tight, nitrogen continuously flows through the cooling chamber 100 from below. For discharge of the nitrogen, an outlet 102, e.g. in the form of a siphon, is arranged in the uppermost part of the cooling system. Also significant for the reliable operation of the cooling system 1 is heating in the case of an incident, which is as delayed as possible, in particular in case of failure of cooling devices. This is in particular achieved with the thermally insulating structure of the side walls 120.
For operation of the cooling system 1, the cooling chamber 100 with the first cooling device 200, eventually supported by the second cooling device 300, is cooled down to the desired cryopreservation temperature. Subsequently, using the mechanical control elements 411, the biological samples 2 are arranged in the sample receiving device 140 in the cooling chamber 100. In the case of an incident or for the purpose of maintenance, control or operating work, the operator 3 can step into the cooling chamber 100 through the ceiling opening 131 or through a lateral door (see Figure 4). The operator 3 wears a protective suit with thermal insulation and a head protection, which guarantees protection of the operator against thermal loss.
Figure 2 illustrates in a schematic cross-sectional view of a modified embodiment of the cooling system 1 according to the invention, which is constructed with respect to the cooling chamber 100, the first cooling device 200, the second cooling device 300 and the coolant supply 500, as was described above with reference to Figure 1. With respect to the operation room 400, following differences arise. According to Figure 2, the operation room 400 comprises a first chamber 420, which is essentially constructed like the operation room 400 according to Figure 1, a second chamber 430 and a third

- 25 -chamber 440. In the second and third chambers 430, 440, further operating equipment 431, 441, such as measurement and/or control devices or further drives, are arranged. The chambers of the operation room 400 are each arranged thermally insulated. A specific temperature can be adjusted in each of the chambers. Typically, the temperature rises from the first (420) up to third (440) chamber. For conveying the gas atmosphere formed in the cooling chamber 100, the chambers of the operations room 400 are connected via tube connections 401 (or other through-holes). On the upper side of the third chamber 440, an outlet 102 with a siphon is provided for.
Between the chambers 420, 430 and 440, partition walls with each at least one chamber door 402 are provided for. This facilitates the setting of different temperatures in the chambers 420, 430 and 440. If, for example, a temperature in the range of -196 C to -140 C is adjusted in the cooling chamber 100, a temperature of round -80 C could be adjusted in the second chamber 430 and a temperature in the range of -40 C to -20 C adjusted in the third chamber 440.
Accordingly, different operating devices, which have different operating temperatures, can be accommodated in the chambers 420, 430 and 440. For monitoring of the temperatures, a temperature sensor 403 is arranged in each one of the chambers 420, 430 and 440.
Deviating from Figure 2, the chambers 420, 430 and 440 could be open relative to one another. In this case, too, in case of undisturbed cooling, a sequence of horizontally arranged gas layers with upwardly increasing temperatures can be formed. Furthermore, a local heater, in particular with a resistance heating or an infrared lamp, can be arranged in at least one of the chambers 420, 430 and 440 in order to heat temperature sensitive components for the operation at least

- 26 -in certain operation phases. This is advantageously possible without having to accept influencing the temperature in the cooling chamber 100.
Figure 3 illustrates features of the walk-in access by the operator 3 to the cooling chamber 100 by means of a further embodiment of the cooling system 1 according to the invention. The illustration of the cooling chamber 100 with the floor area 110, the side walls 120 and the ceiling area 130 is represented in a simplified manner in a schematic perspective view. In a practical implementation, the cooling system 1 can be constructed with respect to these components, as is described above with reference to Figures 1 and 2.
In the ceiling area 130 is a ceiling opening 131 provided for, which can be closed with a cover 132. The temperature stratification in the cooling chamber 100 is advantageously hardly affected due to providing the opening for the access by the operator 3 on the top side of the cooling chamber 100 when the operator 3 accesses it. Alternatively, the opening can be provided for the access by the operator 3 in one of the side walls (see Figure 4).
The operation room 400 is arranged above the ceiling opening 131. There is a conveying device 150 arranged in the operation room 400, which is configured for introducing the operator 3 into the cooling chamber 100 and/or for removing the operator 3 from the cooling chamber 100. The conveying device is exemplarily illustrated with a rope hoist 151 having a hoist and a step device 152 (ladder). The components 151, 152 can be provided for individually. For safety reasons, it is, however, preferred to provide both components in order to be able to remove the operator 3 rapidly and securely from the cooling chamber 100 if this is required.
The rope hoist 151 can also be used for the transport of

- 27 -samples 2 and/or shelves 141.
The operation room 400 is connected with a person lock device 450, which can be accessed to from the outside via a thermally insulated external lock door 451. The person lock device 450 is separated from the operation room 400 by a thermally insulating, internal lock door 453. Between the operation room 400 and the person lock device 450, a tube connection 452 is provided for pressure equalization, so that no pressure difference can arise between both rooms and nitrogen gas can escape from the cooling chamber 100 via the operation room 400 into the person lock device 450 and from the latter outwardly via an outlet 102.
The walk-in access to the cooling chamber 100 via the person lock device 450 is done such that the operator 3 first wears a protective suit 4 with a breathing air supply 5 outside the person lock device 450. In the person lock device 450, a preliminary cooling to a medium temperature range, e.g. -80 C, then takes place. For this purpose, the person lock device 450 is equipped with a cooling device (not shown).
Alternatively, the person lock device 450 can be cooled with a part of the vapor flowing out of the cooling chamber 100.
If the operator 3 is sufficiently cooled down, he is transferred into the operation room 400 and from there, using the rope hoist 151 and/or by means of the step device 152, transferred into the cooling chamber 100. In the cooling chamber 100, the operator 3 can move, for example in order to carry out maintenance work on the sample receiving device 140.
The lock door 451 of the person lock device 450, the internal lock door 453 and the cover 132 are provided with electric contacts and a closing control system, which is adapted for at least one of the following procedures.

- 28 -Firstly, an inspection of the cooling chamber 100 can be provided during normal operation of the cooling system 1. The operator puts on the protective suit 4 with the breathing air supply 5 outside. In this case, the outer lock door 451 of the person lock device 450 can only be opened if the inner lock door 453 and the cover 132 are closed. If the operator 3 is in the lock device 450, the outer lock door 451 is closed, and the inner lock door 453 can only be opened if a dry nitrogen atmosphere with a predetermined temperature has been formed in the person lock device 450. For this purpose, gaseous or liquid nitrogen can be blown in from the outside.
As soon as the predetermined temperature and the dryness of the atmosphere are reached in the person lock device 450, the inner lock door 453 is opened and the operator 3 can walk into the operation room 400. Here, there is a further cooling of the operator 3 to a predetermined temperature. As soon as the operator 3 is sufficiently cooled down and the atmosphere in the operations room 400 has reached predetermined standard values, the cover 132 is opened so that the operator 3 can enter in the cooling chamber 100. In the cooling chamber 100, the operator 3 is video-monitored and stays in contact via wireless audio connection with helpers outside the cooling system 1. Leaving the cooling system 1 is done during normal operation in reverse order.
Secondly, it is provided for in an emergency situation that the cover 132 and the inner and outer lock door 451, 453 can be opened simultaneously by means of emergency switches (not shown). In this situation, rapid access to the interior of the cooling chamber 100, in particular for rescue of the operator 3 and/or for safeguarding stored samples, is allowed. In the emergency situation, the operator 3 can leave the cooling chamber 100 by himself through the ceiling opening 131 and the person lock device 450 or be drawn out from there. Simultaneously, it can be provided for that

- 29 -heated dry air is blown in from the outside by means of a blower 460 into the cooling chamber 100 and from there into the operation room 400 and the person lock device 450. The temperature can thereby be increased to a value above -5000 and oxygen can be supplied. This operation can be monitored by means of oxygen sensors (not shown). As a result, further helpers can act in the cooling chamber 100, if necessary without a protective suit and without their own oxygen supply.
Figure 4 schematically illustrates features of the inspection of the cooling chamber 100 and the supply or withdrawal of the sample receiving device 140 into or out of the cooling chamber 100 by means of a further embodiment of the cooling system 1 according to the invention. As shown in Figure 3, the cooling system 1 is illustrated in a simplified schematic perspective view with the floor area 110, the side walls 120 and the ceiling area 130.
For the supply or withdrawal of the sample receiving device 140, the ceiling opening 131 is provided in the ceiling area 130 with an operation room 400 located above it. The operation room 400 has a tower-shaped hood chamber 400.1 with a height, which is such that a shelf 141 of the sample receiving device 140 can be accommodated completely in the operation room 400. A drive device 410 with a rope hoist 414, with which the shelves 141 can be drawn into the operation room 400 in particular in the case of an accident, is located in the operation room 400.
Deviating from Figure 3, a door opening 125 having a shiftable door leaf 126 is arranged in one of the side walls 120 to allow walk-in access by the operator 3. The door opening 125 is at a predetermined height above the floor area 110. The elevated entrance is preferred so that the cold gas

- 30 -filling in the cooling chamber 100 does not flow away to the outside when the door opening 125 is opened. Between the door opening 125 and the floor area 110, there are stairs 127 via which the operator 3 can get into the cooling chamber 100.
The door leaf 126 is configured for shifting parallel to the even extension of the side wall 120. A vertical or horizontal movement parallel to the side wall is preferred, since the horizontal stratification of the cold gas filling would otherwise be impaired in the cooling chamber 100 in case of pivoting off the side wall.
Outside the cooling chamber 100, a person lock device 450 with at least two chambers 455, 456 and an outer (451), a central (454) and an inner (126, 457) lock door is arranged on the side wall 120. The inner lock door 457 is formed by the door leaf 126. Tube connections 452 through which cold gas can flow out from the cooling chamber 100 to the outside are provided for between the cooling chamber 100 and the cooling chambers 455, 456. From the outer chamber 455, the gas flows through the outlet 102 to the environment. In the outer chamber 455, a temperature of e.g. -20 C is provided for, whereas a temperature of -80 C is provided for in the inner chamber 456.
For inspection of the cooling chamber 100, the operator 3 puts on the protective suit 4 with the breathing air supply 5 outside the person lock device 450. The operator 3 is cooled down step by step in the person lock device 450 until he can walk through the door opening 125 into the cooling chamber 100. The doors 451, 454, 457 of the person lock device 450 can be controlled for the normal operation or the emergency situation, as was described above with reference to Figure 3.

- 31 -Since it may be required to stay for a longer period of time (> 15 minutes) in the cooling chamber 100, schematically shown supply connections 104 are arranged in the cooling chamber 100. The protective suit 4 and/or the breathing air supply 5 can temporarily or permanently be connected to the supply connections 104, e.g. in order to save an energy source in the protective suit 4 or in order to supply oxygen.
Figures 5A to 50 show further details of a side wall 120 of the cooling chamber 100 of the cooling system according to the invention. The features of the side wall 120 can also be provided accordingly for thermal insulation of the first cooling device 200 (see Figure 1) below the floor area of the cooling chamber. In the schematic cross-sectional view of Figures 5A to 5C, the cooling chamber 100 is arranged respectively to the right of the side wall 120, i.e. the external side of the side wall 120 is, in Figures 5A to 5C, respectively to the left of the side wall 120.
According to Figure 5A, there is first on the inner side of the side wall 120 a cooling layer 101, which consists of metal, e.g. aluminium or steel, with a thickness in the range of a few mm up to 1 cm. The cooling layer 101 is in direct thermal contact with the first cooling device 200 (see Figure 1), in particular with the liquid nitrogen 220 of the first cooling device 200, so that cooling of the interior of the cooling chamber 100 is supported with the cooling layer 101.
Then, there is a first vacuum component layer 122.1, which comprises an evacuated hollow wall, which extends along the side wall 120. The outer surface of the evacuated hollow wall is designed for reflection of infrared radiation (thermal radiation) and is provided for this purpose with a reflective surface finish or a reflecting foil 120.1. Thereby, thermal radiation coming from the outside is advantageously

- 32 -reflected.
Then, there is a further vacuum component layer 122.2, which comprises a brickwork made of brick-shaped insulating components. The insulating components are hollow plastic bodies with an evacuated, closed interior. Each insulating component is a self-contained system. Within the vacuum component layer 122.2, the insulating components are arranged in a multi-layered offset manner as in a brickwork, so that this is advantageous for the suppression of the heat transport through the side wall 120.
Outwardly, there is then a plastic layer 121 made of a foamed plastics, e.g. of polyurethane. The thickness of the plastic layer 121 is equal to e.g. 10 cm up to 1 m (for insulation and stability purposes). On the external side of the plastic layer 121, a protective layer 121.1 for mechanical protection of the side wall 120, a further wall expansion and/or a further vacuum component layer (see Figure 1) are arranged.
An advantage of the invention consists in particular in that the thickness of the side wall 120 can be increased as needed without any essential practical limitations. An overall thickness in the range of 1 m to 6 m or 10 m or above is possible and recommended depending on the dimension of the cooling system. For conventional cryotanks, tank walls as thin as possible are required in order to save store room. In contrast thereto, the thickness of the side wall 120 of the cooling system according to the invention plays no critical role.
The embodiment of Figure 5A can be modified in such a way that a further hollow wall is inserted, which is part of a further, in particular electric, cooling device. In the case of an incident (e.g. in case of failure of the first cooling device below the floor area of the cooling chamber), cooling

- 33 -of the cooling chamber can be carried out completely by the side wall 120, while the first cooling device is simultaneously serviced and repaired. Cooling from the side wall 120 can be provided e.g. when the stock of liquid nitrogen 220 of the first cooling device 200 is running short and cannot be filled up rapidly enough. This modification is shown with further details in Figure 53.
Figure 5B shows the side wall 120, for which the vacuum component layer 122.1 is arranged with an increased thickness and, additionally, a cooling element 310 of the second cooling device 300 (see Figure 1) is arranged on the inner side of the side wall 120. The cooling element 310 comprises a further stratiform, hollow-walled component, such as a plurality of hollow lines made of metal. The hollow lines can be arranged on the whole surface or with mutual distances on the inner side of the side wall 120. The cooling element 310 is connected with a cooling aggregate 320 (see Figure 1). In addition, the cooling element 310 can be in communication with the liquid nitrogen 220 of the first cooling device 200 (see Figure 1).
During normal operation, cooling of the interior of the cooling chamber 100 is supported by the cooling element 310.
In the case of an incident, the cooling element 310 can be flown through from the outside by an additional coolant. The additional coolant can be provided by an electric cooling system or from a coolant tank or a connected tanker, e.g.
with liquid nitrogen.
Figure 5C shows a further modified variant of the side wall 120, for which the order of the vacuum component layer 122.3 and the plastic layer 121 is inverted. In detail is, at first, the metallic cooling layer 101 is provided for on the inner side of the side wall 120, the first vacuum component

- 34 -layer 122.1 being arranged under the metallic cooling layer.
The latter can be equipped with a reflecting element 120.1 as can be seen in Figure 5A. Then come the plastic layer 121 and the brickwork made of insulating components of the vacuum component layer 122.2. Outwardly, there is then a further protective layer 122.3 with which the vacuum component layer 122.2 is stabilized. Furthermore, conventional wall structures can follow outwardly for protection Or stabilization purposes.
The schematic representation in Figure 6 illustrates the connection of the cooling system 1 according to the invention with the coolant supply 500 and an operational control system 600. The cooling system 1 is equipped with a cooling chamber 100, which is configured for long-term storage of biological samples at temperatures below -80 C, in particular below -130 C. Typically, the temperature in the cooling chamber 100 is less than -140 C. For this purpose the first cooling device 200 (see Figure 1) is supplied with liquid nitrogen as follows.
The coolant supply 500 comprises a first (510) and a second (511) coolant storage container (tank). The coolant storage containers 510, 511 can, if required, be filled up by means of external mobile reservoirs (tankers). Preferred is, however, a variant of the invention for which the coolant supply 500 is equipped with its own liquefaction system 530.
The liquefaction system 530 continuously delivers liquid nitrogen into the coolant storage container 510, 511. The liquefaction system 530 has the advantage that uninterrupted long-term cooling can be ensured over long time periods, months, years or decades. For electric supply of the liquefaction system, a current generator 531 is provided for, which can also serve, in the case of an incident, to supply the second cooling device.

- 35 -The first coolant storage container 510 is connected via the coolant line 520 with the first cooling device 200 (see Figure 1). Furthermore, the first coolant storage container is connected with a coolable hood chamber 400.1 (see Figure 4) of the operation room 400 in order to set therein a temperature of e.g. -80 C in the case of an incident.
The second coolant storage container 511 is connected via an evaporation system and a second coolant line 521 and a temperature control device 522 with the person lock device 450 for the operator(s). The temperature control device 522 is actuated in such a way that a temperature of -40 C is set in a first chamber and a temperature of -80 C is set in a second chamber in the person lock device 450. The temperature control device 522 is furthermore used for additionally tempering a sample lock device 460 for samples.
The subsequent supply of liquid nitrogen into the first cooling device 200 is performed using a control loop. The level of the liquid nitrogen of the first cooling device 200 is recorded with a fill level sensor. In the event of it falling below a critical level, liquid nitrogen is additionally supplied to the first cooling device 200 via the coolant line 520.
The coolant supply 500 is, in addition, provided with an external auxiliary container 540 for supply of the cooling system 1 with liquid nitrogen in the case of an incident. The auxiliary container 540 is preferably connected via a blocking element, such as a valve, with the hollow wall 122.2 in the side wall 120 (see Figure 1).
In addition, the second cooling device, which comprises an electric cooling aggregate 320 that is configured for setting a temperature of -80 C, preferably of -150 C, in the cooling chamber 100, is connected to the cooling system 1. The

- 36 -coolant of the second cooling device 300 is delivered to the cooling element 310 in the side wall of the cooling chamber 100 (see e.g. Figures 1, 5B).
Figure 6 also illustrates the components of the operational control device 600 of the cooling system 1 according to the invention. In particular, the operational control device 600 comprises a first control device 601 for the sample storing and withdrawal automatic machine and a second control device 602 for system control. The second control device 602 comprises in particular a temperature-setting device and/or control of the sensors, of the light and the monitoring system, such as of video cameras. Furthermore, the operational control device 600 comprises a first database 603, which is coupled with data storage devices of the samples deposited in the cooling system 1. Electronic components of the sample containers and/or alarm systems are controlled with data from the first database 603 for detecting critical sample states. The second database 604 is adapted for coupling to the electronic components of the samples. The data connection between the operational control system 600 and the cooling system 1 can be wired or wireless.
Finally, the operational control device 600 comprises a vacuum system 605, which is arranged for evacuation of components of the side walls 120 of the cooling chamber 100 and, if required, can be supplied with the generator 531.
Figure 7 shows a further embodiment of the cooling system 1 according to the invention in a schematic cross-sectional view from above (Figure 7A) and in a schematic cross-sectional view from the side (Figure 7B). Furthermore, Figure 7 shows a variant of the removal of samples from a shelf provided for in the cooling system 1 according to the invention (Figure 7C). For the cooling system 1 according to Figure 7, the cooling chamber 100 is segmented by means of

- 37 -partition walls 160 into a plurality of cooling chambers 105, 106, 107. The arrangement of the cooling chambers 105, 106 and 107 is bounded outwardly by a floor area 110, side walls 120 and a ceiling area 130, as is described above with reference to the exemplary embodiment e.g. according to Figure 1. The cooling chamber 100 can exclusively be accessed from above through the ceiling area 130. The cooling chamber 100 is free of openings, which lead in the horizontal direction through one of the side walls 120. Thus, any disturbances of a horizontal stratification of the gases in the cooling chamber 100 are avoided.
Furthermore, the cooling system 1 is completely adapted for automated operation. During normal operation, there is no inspection of the cooling chamber 100. Instead, the supply or removal of samples is performed via automated systems exclusively through the ceiling area 130 (see e.g. Figure 7C).
The partition walls 160 contain door openings 161, which are arranged with a distance above the floor area 110 (see also Figure 4). An operator 3 can access, via stairs 162, each of the cooling chambers 105, 106 and 107 through the door openings 161. The door leaves of the door openings 161 can be drawn through chutes 415 into the operation room 400 via the ceiling area 130. The door openings 161 are arranged in such a way that they have a greatest possible mutual distance. As can be seen in Figure 7A, the door opening 161 is arranged on a side of the inner cooling chamber 105, which is positioned opposite the side of the central cooling chamber 106 in which the second door opening 161 is arranged. The arrangement of the door openings 161 advantageously allows that there is no direct gas flow from the outermost cooling chamber to the innermost cooling chamber when both door openings are simultaneously opened.

- 38 -Alternatively, it can be provided for that all cooling chambers 105, 106 and 107 are accessed to exclusively from above and the door openings 161 are kept merely for access in the case of an incident. In this case, the door openings 161 can be arranged in height of the floor area, wherein the stairs 162 are then not necessary.
Windows (not represented) can be provided in the partition walls 160. They advantageously facilitate the observation and lighting of the interior of the cooling chambers. The windows preferably have a reduced thermal conductivity, and vacuum composite windows are preferably used.
Figure 7B illustrates how the cooling chamber 100 can be accessed to via a person lock device 450. An operator 3 accesses the person lock device 450 via stairs. The operator 3 wearing the protective suit can climb from the person lock device 450 via the ceiling opening 131 into the outermost cooling chamber 107. From there, the operator 3 can walk through the door openings 161 into the inner cooling chambers 106, 105.
The cooling system 1 according to Figure 7 has the advantage that different temperatures can be adjusted in the cooling chambers 105, 106 and 107. Due to its included position, the innermost cooling chamber 105 is the safest room of the cooling system 1. The cooling chamber 105 will warm up the slowest in the case of an accident on the, since it is protected against heat penetration by the outer cooling chambers 106, 107. Accordingly, the cooling system 1 according to Figure 7 is preferably used as follows.
The most valuable samples, such as living material, e.g.
individual cells, cell suspensions, blood or tissue parts are deposited in the innermost cooling chamber 105. Typically, these comprise rarely moving stocks that require only a few

- 39 -sample accesses. In particular reserve or backup stocks are accommodated in the innermost cooling chamber 105. The middle cooling chamber 106 contains samples, which require frequent access. This area can be used as a workspace of the cryobank.
Finally, samples, which tolerate an increased storage temperature of up to -50 C, if required even up to -20 C, are stored in the outermost cooling chamber 107. The samples comprise dead material, serines, plasma, genetic material or the like.
Figure 70 illustrates how shelves 141 of the sample receiving device can be drawn from the cooling chamber 100 through an opening in the ceiling area 130 into the upper operations room 400 in order to take individual samples from the shelves 141. In the operation room 400 is arranged a movable isolation tower 480, which consists at least on its inner side of a porous material 481, e.g. silicate-based aerogel.
The shelves 141 are drawn up along vertical rails 143 out of the low temperature area into the isolation tower 480. The lifting is performed up to a height, which allows removal of the desired sample from the shelf 141 through a slit 482 in the isolation tower 480. The isolation tower 480 is connected with a reservoir of liquid nitrogen (not shown). The porous material is loaded with liquid nitrogen, so that a temperature of e.g. -160 C is given within isolation tower 480 and only the removed sample is exposed for a short time to an ambient temperature of e.g. -20 C, while all other samples of the shelf 141 remain in a mobile extension of the low temperature range formed by the isolation tower 480 in the cooling chamber 100.
The use of porous material, e.g. silicate-based aerogel, for storage of coolant, in particular liquid nitrogen, is not mandatory for active cooling of the isolation tower 480. The isolation tower 480 can also be formed from a thermally

- 40 -insulating material. Furthermore, according to the invention, the use of porous material, e.g. silicate-based aerogel, can in general be provided for also on other parts of the cooling chamber 100, in particular of the floor area 110, the side walls 120 or of the ceiling area 130.
Figure 8 illustrates a further embodiment of the cooling system 1 according to the invention with additional details.
During normal operation, this cooling system 1 also works automatically, so that operators do not enter the cooling chamber. An inspection of the cooling chamber 100 is done only in special situations, such as in the case of an accident, for maintenance work, installation works or checks.
Although the normal operation is intended without any inspection of the cooling chamber 100, the special case of inspection of the cooling chamber 100 is represented here.
The cooling system 1 is, as described above, constructed with a cooling chamber 100 and an operation room 400 located above it. The cooling chamber 100 is delimited by the floor area 110, side walls 120 and the ceiling area 130. The first cooling device 200 is located under the floor area 110. The second cooling device 300 is connected with the side wall 120. In the ceiling area 130, there is at least one ceiling opening 131 through which the conveying device 150 with a rope hoist 151 and a ladder 152 protrudes from the operation room 400 into the cooling chamber 100.
For inspection of the cooling chamber 100, an operator 3 steps through the person lock device 450 into the operation room 400. Between the person lock device 450 and the operation room 400, there is a lock door through which the operator 3 can access the operation room 400 via stairs 457.
From the operation room 400, the inspection of the cooling chamber 100 is done through the ceiling opening 131. Above

- 41 -the operation room 400, there is the hood chamber 400.1 (accident tower) into which sample receiving devices 140, in particular the tower-like shelves 141, can be transferred in the case of an accident.
Figure 8 shows as a further advantageous feature of the cooling system 1 according to the invention a nitrogen sprinkler system 108, which is arranged in the cooling chamber 100. The nitrogen sprinkler system 108 is preferably located on the underside of the ceiling area 130.
Advantageously, rapid cooling can be achieved with the nitrogen sprinkler system 108 at first use of the cooling chamber or in case of an accident. The nitrogen sprinkler system 108 is supplied out of the coolant supply apparatus 500 (see Figures 1, 6) via coolant lines.
Furthermore, condensate collection elements 109 are illustrated in the cooling chamber 100. The condensate collection elements 109 comprise e.g. sheet metals, which are in communication with the first cooling device 200, in particular the liquid nitrogen 220. The condensate collection elements 109 form an ice trap. Any ice coating can be removed by replacing the condensate collection elements 109 by means of mechanical scraping, sucking or by means of sublimation using locally inflated dry warm gas. Thus, in contrast to conventional cryopreservation techniques, ice formation can be suppressed in the remaining cooling chamber.
Ventilation of the cooling chamber 100 and of the operation room 400 is performed via a tube connection with a siphon. In the case of an accident, an external ventilation equipment can supply dry, tempered air to the operation room 400. A
flexible tubular element 128 is provided for this purpose.
Advantageously, a breathable atmosphere with a temperature in the range of -5 C to -50 C can be supplied so quickly in the

- 42 -operating state of the cooling system 1 that the operation room 400 can be accessed to within less than one minute, in particular within 20 s. If this is also required for the cooling chamber 100, a rolled-up pipe can be led through the ceiling opening 131 along the ladder 152 into the cooling chamber 100. In the case of active ventilation of the cooling chamber 100, the latter can likewise be accessed to within 10 to 20 s without a breathing apparatus and a protective suit.
For the case that immediate removal of the samples is required (evacuation), a wall element 123 is arranged in a lateral wall region. The wall element 123 is connected via an opening joint 124 with the side wall 120 and can be removed from it or knocked out of it. On the external side of the side wall 120 can be arranged a schematically illustrated docking device 700 for a mobile evacuation container.
The automatic sample deposition or sample removal is performed with a sample access automatic machine 470, which is located in the operation room 400 and contains a drive device 410 for the mechanical control elements 411. An horizontal movement of the control elements 411 is performed in the operations room 400 above a temperature of -80 C. A
vertical arm 416 of the control elements 411 engages through a slit that opens in the ceiling opening 131 during the movement into the cooling chamber 100, so that all trays of the shelves 141 are accessible. A sample is taken out, transported upwards, arrives in the sample access automatic machine 470 and is transferred to a tempered lock (-60 to -80 C) where the sample is conveyed to a place of removal 458, which can be accessed to without any thermal protective clothing.

- 43 -Figure 9 illustrates that, in case the cooling system 1 is designed with the size of an industrial hall, using variable partition walls 160 is advantageous. Partition walls 160 can be inserted in the cooling chamber 100 or removed therefrom as required. The partition walls 160 run in a transverse and/or longitudinal direction relative to a longitudinal extension of the cooling chamber 100. Preferably, the partition walls 160 can be moved in the vertical direction, i.e. upwards, so that it is advantageously prevented that undesirable gas flows or uncontrolled thermal gradients arise in the cooling chamber 100. Furthermore, the partition walls 160 allow separate cooling in individual chambers of the cooling chamber 100 wit variable temperatures. In this way, cryobanks can be realized with a storage capacity of millions of samples.
Alternative to the representation in Figure 9, according to Figure 10, a modular structure of the cooling system 1 can be provided for, wherein all chambers or sample receiving devices form separate elements in the cooling chamber 100, which, if necessary, can be supplied in a fully autarkic manner. Such an approach has the advantage of free extensibility.
The features of the invention which are disclosed in the above description, the claims and the drawings may be important both individually and in any combination for implementing the invention in its various designs.

Claims

1. A cooling system (1), in particular for cryopreservation of biological samples (2), comprising:
- a cooling chamber (100), which is delimited by a floor area (110), side walls (120) and a ceiling area (130), and - a first cooling device (200), which is provided for cooling of the cooling chamber (100) with liquid nitrogen (220), wherein - the floor area (110) is configured for direct cooling with the liquid nitrogen, characterized in that - the cooling chamber (100) is dimensioned such that an operator (3) can stay and move in the cooling chamber (100), and - the floor area (110) has a platform (111), which is permeable to the vapor of the liquid nitrogen (220) and forms a support area for the operator (3).

2. The cooling system according to claim 1, which comprises:
- a second cooling device (300), which can be actuated independently of the first cooling device (200) for cooling of the cooling chamber (100).

3. The cooling system according to claim 2, in which - the second cooling device (300) is provided for cooling of at least one of the side walls (120) of the cooling chamber (100) and/or configured for electrical cooling operation.

4. The cooling system according to any one of the preceding claims, in which - the ceiling area (130) has a ceiling opening (131), wherein at least one operation room (400), which contains a drive device (410) with mechanical control elements (411), contains a conveying device (150) for the insertion of the operator (3) into the cooling chamber (100) and/or is connected with a lock device (450), is provided above the ceiling opening (131).

5. The cooling system according to claim 4, in which - the mechanical control elements (411) can be inserted into the cooling chamber (100), wherein at least parts of the control elements (411) can be heated, and/or - the conveying device (150) comprises a rope hoist (151) or a step device (152).

6. The cooling system according to any one of the preceding claims, in which - the side walls (120) have a multi-layer structure with several wall layers, which comprise at least one plastic layer (121), at least one vacuum component layer (122.1, 122.2) and/or at least one vapor locking layer.

7. The cooling system according to any one of the preceding claims, in which - at least one of the side walls (120) is constructed in a modular manner with at least one wall element (123), which is shiftable vertically with regard to the respective side wall (120) and can be separated from the side wall (120).

8. The cooling system according to claim 7, in which - a docking device (700) for an evacuation container is provided on an external side of the side wall (120) with the at least one wall element (123).

9. The cooling system according to any one of the preceding claims, in which - at least one of the side walls (120) has a door opening (125) with a door leaf (126).

10. The cooling system according to claim 9, in which - the door opening (125) is arranged with a predefined distance above the floor area and/or the door leaf (126) is arranged movably parallel to the respective side wall (120).

11. The cooling system according to any one of the preceding claims, in which - a sample receiving device (140) with shelves (141) is provided in the cooling chamber (100), which is adapted for receiving the samples.

12. The cooling system according to claim 11, in which - the sample receiving device (140) is equipped with thermal bridges (142), which protrude into the floor area (110).

13. The cooling system according to any one of the preceding claims, which comprises - partition walls (160), which extend in the vertical and/or horizontal direction in the cooling chamber, - a coolant auxiliary container (540), which is provided for receiving a reserve volume of liquid nitrogen, - a nitrogen liquefaction system (530), - condensate collection elements (109, 521), which are arranged in the cooling chamber (100), - a nitrogen sprinkler system (108), which is arranged in an upper area of the cooling chamber (100), and/or - a helium supply system, which is configured for cooling of the cooling chamber (100).

14. A method for operating a cooling system according to any one of the preceding claims, with the steps of:
- cooling of the cooling chamber (100) with the first cooling device (200), and - positioning of biological samples in the cooling chamber (100).

15. The method according to claim 14, in which - an operator (3) executes control, maintenance and/or operating steps in the cooling chamber (100).