JPH05113489A - Installation method of neutron source and neutron source holder rack used in this method - Google Patents

Abstract

PURPOSE:To suppress exposure amount down to enough safe level and to intend cutting down of work schedule and cost down of an in-core installation of a neutron source. CONSTITUTION:Installation of a neutron source is carried out by inserting and fixing a neutron source holder rack 31 in which a neutron source holder 37 is housed freely attachably and detachably, into and in a mast adjusting pit 28 for a refueling machine. On the other hand, water is poured into the mast adjusting pit 28 in order to guide a housing block 33 which contains a neutron source 30 in the mast adjusting pit thereof, and, by under water works in the mast adjusting pit 28 for a refueling machine, the neutron source 30 is brought out of the housing block 33 to be housed into the neutron source holder 37. Subsequently, the neutron source holder 37 housing the neutron source 30 in it, is connected to a neutron source holder transfering jig 40, and the neutron source holder 37 is taken out of the neutron source holder 31 from the neutron source holder rack 31 by the neutron source holder tranfering jig 40, in order to transfer the holder 37 in the air, and thereafter the neutron source holder 37 is loaded to an initially loaded reactor core 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for loading a neutron source on a core of a nuclear reactor, and more particularly to a method for installing a neutron source for loading a neutron source on an initial mounting core of a light water reactor such as a boiling water nuclear reactor. The present invention relates to a neutron source holder rack used in this method.

[0002]

2. Description of the Related Art In a boiling water reactor as a light water reactor, a core is housed in a reactor pressure vessel, and a large number of four fuel assemblies are loaded in the core. A control rod having a cross-shaped cross section is inserted between the fuel assemblies of each set, and the start / stop of the nuclear reactor and the reactor output are controlled by moving the control rod into and out of the core.

FIG. 7 is a plan view showing the core structure of a 1100 MWe class boiling water reactor before initial mounting of fuel assemblies. Reference numeral 1 in the figure indicates a nuclear reactor core, and the square quadrangle displayed on the reactor core 1 is a control rod cell 2.
A set of four fuel assemblies (not shown) are loaded in the control rod cells 2.

The reactor core 1 is provided with a monitor (marked with X) 3 for detecting low-level neutron rays. The monitor 3 measures the neutron dose even when all the control rods are inserted, and the subcritical state is detected. You can check it.

In the case of the initially mounted core 1, neutrons are not automatically emitted from the fuel itself of the fuel assembly, so that the neutron source (neutron source) 4 must be loaded in the core 1 in advance. In the case of a 1100 MWe class nuclear reactor, there are, for example, seven neutron sources 4, and the seven neutron sources 4 are loaded into the core 1 from above the core before loading the fuel assemblies into the core 1. Since the neutron source 4 gives a certain amount of neutron dose to the fuel of the whole core 1, the neutron radiation intensity is very strong.

Considering this neutron radiation intensity, the installation work of the neutron source 4 on the initial mounting core 1 of the nuclear reactor was all performed underwater. In order to carry out this installation work completely in water, as shown in FIG. 8, a fuel pool (spent fuel pool) 5, a reactor well 6, a dryer / separator pool (steam dryer / water / water separator pit: , Called DS pool.) 7 must be filled with water, about 3500 m
³ and a large amount of pure water are required. In order to fill, purify, and drain pure water of about 3,500 m ³ , it took about 5 working days just to treat the water.

On the other hand, since the total number of working days for installing the neutron source for loading the neutron source 4 into the initial mounting core 1 is about 8 days, more than half of the work steps for installing the neutron source are flooded, purified and drained. Preparatory work will be occupied.

In recent nuclear power plants, shortening the construction period of the nuclear reactor is one of the important issues, but regarding the installation work of the neutron source, water treatment is one of the whole work processes. Most of the preparation work for water filling, purification, and drainage, unless the preparation period is shortened,
It was impossible to shorten the construction period.

In the conventional installation work of the neutron source, from the viewpoint of exposure, the moving work of the neutron source is all performed in water. However, the moving distance of the neutron source in water is, for example, several tens of meters for each neutron source storage block, and 5 to 10 meters for each neutron source pin (NS pin).
Underwater travel distance is long. Considering the risk of accidentally dropping the neutron source in the middle of the underwater movement, as shown in FIG. 9, the tum source 10 and the like are installed below the neutron source holding tool 8 to move the neutron source 4 underwater. I'm doing it. In this case, while grabbing the neutron source 4 with the neutron source gripping tool 8 and moving it underwater, another worker had to cooperate with the tampo 10 and the like to perform follow-up operations, and the workability was extremely poor. ..

As a method for solving the problem of workability, it is considered to move the neutron source 4 in the air without water filling the fuel pool 5, the reactor well 6 and the DS pool 7 during the installation work of the neutron source in the core. Be done.

However, when the neutron source is moved in the air, the exposure of workers becomes a new problem. When performing neutron source installation work in the air, instead of being uniformly exposed throughout the work of handling the neutron source, for example, air-moving work using a crane is a remote operation work, and the work time is also short. Because of the problem, radiation exposure does not pose a problem even in air transfer work. On the other hand, careful work such as positioning of the neutron source requires a long working time, and if it is left as it is, a high radiation dose may be received.

In the case of the work for installing the neutron source 4 in the core, there are three works that require time to handle the neutron source 4, and one is from the storage block 11 that stores a plurality of neutron sources 4 as shown in FIG. Work to take out the neutron source 4 and load it into the neutron source holder 12, second work is to join the neutron source holder 12 housing the neutron source 4 to a neutron source holder moving jig for moving it into the core 1, and three The eye is the work of installing the neutron source holder 12 in the core 1.

The third in-core installation work is an underwater work if the reactor pressure vessel is normally filled with water up to the water level, and it can be considered that there is no exposure dose, which is not a problem. The problem is the operation of loading the first neutron source 4 into the neutron source holder 12 and the operation of connecting the second neutron source holder 12 to the neutron source holder moving jig.

Of these, the neutron source 4 is replaced by the neutron source holder 1
The operation of loading the load 2 is performed as shown in FIG.

A plurality of neutron sources 4 are stored in the storage block 11, and the storage block 11 is moved to the temporary stand 14 on the work table 13 in advance by a crane or the like (not shown).

The worker 15 is a long operation pole 1
A grasping jig having a neutron source grasping tool 8 at the tip of 6 is used, and the neutron source 4 is grasped and attached to the grasping tool 8 by manually operating from the operation floor surface 17.

After confirming that the neutron source 4 has been attached to the grasping tool 8, the neutron source 4 is pulled up and moved to a position above the neutron source holder 12.

At this time, the neutron source gripping tool 8 equipped with the neutron source 4 moves in the fuel pool 5, but even if the neutron source 4 falls, it will not fail to see the bottom of the fuel pool 5. As described above, the neutron source 4 is moved underwater while being provided in the mesh container such as the taro 10 below.

On the other hand, a neutron source source guide 20 is placed above the neutron source holder 12 and guides the transported neutron source 4 into the neutron source holder 12 so that it can be easily loaded.

The neutron source grasping tool 8 is designed to release the neutron source 4 from the holding state by pulling the release wire (see reference numeral 38 in FIG. 2). Neutron source 4 released
Is guided by the source guide 20 and dropped into the neutron source holder 12 by its own weight to be loaded.

[0021]

A series of operations for loading the neutron source 4 on the neutron source holder 12 is repeated by the number of the neutron sources 4, and the loading operation on the neutron source holder 12 is performed. Requires a great deal of caution and takes a lot of time for this loading work.

Further, the above-mentioned second neutron source holder 1
Also in the case of the work of coupling 2 to the neutron source holder moving jig, the neutron source holder is repeatedly performed for each neutron source holder, which requires careful attention and takes a long working time.

Therefore, it is necessary to consider the problem of radiation exposure when performing the loading work to the neutron source holder 12 and the connecting work to the neutron source holder moving jig in the air.

For example, when loading the neutron instrumentation tube 4 into the neutron source holder 12 in the loading operation to the neutron source holder 12, the conventional neutron source 4 and one dose rate are 1 at a distance of 4 m.
Since the order is mSv (milli-sievert) / hr, the loading work on all (7) neutron source holders 12 is 10 m even if the total loading work time is 1 hour.
Since the exposure dose is close to Sv and cannot be tolerated, it is necessary to devise to reduce the exposure dose.

The method of reducing the exposure dose is roughly classified into a method using a shielding material and a method using remote control.

In the method using the shielding material, since the neutron source 4 uses a radiation source such as californium 252 (Cf-252) and the emitted radiation contains a large amount of γ rays, a complete dose level is obtained. In order to lower it to 10 tons, a shielding material of several tens of tons is required, which is a large amount.

Further, in the remote control method, since it is necessary to insert the neutron source 4 into the neutron source holder 12 so that the neutron source 4 can be loaded in the core, it is necessary to develop an accurate and precise remote control robot such as a small manipulator. There is.

On the other hand, the neutron source 4 is loaded into the core 1 only at the time of the initial mounting core, and it is very troublesome to develop a manipulator device which can be remotely controlled only for the installation work of the neutron source 4. In addition, it is expensive and causes a cost increase, which is not desirable.

For this reason, in the installation work of the neutron source in the core, in order to shorten the work period and reduce the cost without developing the manipulator device and the like, without fear of radiation exposure, It was a problem for me.

The present invention has been made in consideration of the above-mentioned circumstances, and does not require a new development of a manipulator device, and suppresses the radiation dose to a sufficiently safe level by only a minor change in the neutron source installation equipment. An object of the present invention is to provide a neutron source installation method and a neutron source holder rack used for this method, which can shorten the construction period and cost of the neutron source core installation work.

[0031]

In order to solve the above-mentioned problems, the present invention provides a mast adjustment for a refueling machine for a neutron source holder rack in which a neutron source holder is detachably accommodated as described in claim 1. While inserting and fixing in the pit, water is introduced into the mast adjusting pit to guide the storage block containing the neutron source in the mast adjusting pit, and the neutron source is supplied from the storage block to the mast for the refueling machine. By working underwater in the adjustment pit, it is taken out and stored in the neutron source holder, then the neutron source holder containing the neutron source is coupled to the neutron source holder moving jig, and the neutron source holder moving jig Remove the neutron source holder from the rack, move it into the reactor pressure vessel in air, and then install the neutron source to load the neutron source holder into the initial core. Lies in the way.

Further, in the neutron source holder rack according to the present invention, in order to solve the above-mentioned problems, as described in claim 2, a flange which can be seated is formed at the upper edge of the mast adjusting pit for the fuel exchanger. An upper fixing plate, an intermediate temporary stand supporting plate provided with a temporary stand capable of supporting the storage block, and a lower holder supporting plate supporting the neutron source holder are connected to each other by a plurality of columns. A holder rack is formed in a cage structure, and the neutron source holder is detachably mounted in the holder rack, and the holder rack is inserted and fixed in the mast adjusting pit for the refueling machine.

[0033]

According to the present invention, by positively utilizing the mast adjusting pit for the refueling machine, it is not necessary to fill the reactor well or the DS pool with water to form a temporary pool. Even if you do not use a temporary pool, you can support the temporary stand and neutron source holder on the neutron source holder rack and install it in water as before, and work of loading the neutron source into the neutron source holder and entering the neutron source The work of connecting the neutron source holder to the neutron source holder moving jig can be performed in the water in the mast adjusting pit for the refueling machine, and the exposure dose becomes almost the same as before.

Further, since the mast adjusting pit for a refueling machine is a vertical hole space having a limited diameter, for example, if a fall prevention plate is previously installed at an appropriate depth, loading work of a neutron source and neutrons as in the conventional case will be performed. It is not necessary to use a tack or the like for the connection work to the source holder moving jig, and the workability is improved.

Furthermore, by using the mast adjusting pit for the refueling machine, it is possible to perform underwater work without using a special temporary structure, and it is possible to reduce the exposure dose in the work of moving the neutron source in the air. It is possible to maximize the advantages of neutron source air transfer work.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic cross-sectional view showing the upper part of the reactor building of a boiling water nuclear reactor, in which reference numeral 20 is a reactor building 2.
1 is a reactor pressure vessel housed in 1. A reactor core 22 is housed in the reactor pressure vessel 20.

The core 22 is surrounded by the core shroud 23, while the core lower support plate 2 is provided below the core shroud 23.
4, upper core lattice plates 25 are provided on the upper portions thereof. 4 between the lower core support plate 24 and the upper lattice plate 25
A large number of fuel assemblies (not shown) of one body are loaded.

On the other hand, a reactor well 26 is formed above the reactor pressure vessel 20, and a dryer separator pool (DS pool) 27 is formed on one side of the reactor well 26. On the other side of the reactor well 26, a spent fuel pool (not shown) is provided.

A mast adjusting pit 28 for a refueling machine is generally provided in a part of the DS pool 27. The mast adjusting pit 28 is, for example, a cylindrical vertical hole having a diameter of about 1 m and a depth of about 10 m, and the peripheral wall surface of the mast adjusting pit 28 is lined with a stainless steel plate like the inner wall surface of the DS pool 27 to be formed smoothly. ..

The fuel exchange mast adjusting pit 28 formed in the DS pool 27 of the existing nuclear reactor plant is positively utilized for the installation work of the neutron source 30. Therefore, the neutron source holder rack 31 is detachably accommodated in the fuel exchange mast adjustment pit 28.

The neutron source holder rack 31 is provided with a temporary placement stand 32 at substantially the center thereof.
A storage block 33 accommodating the neutron source 30 is installed and temporarily placed. The storage block 33 is taken out of the transport container 34 by a hoist (not shown) of an overhead crane, moved by air movement, and carried to the temporary stand 32.

A neutron source (NS pin) 30, such as eight californium 252, is housed in the housing block 33 so that it can be taken in and out. As shown in FIG. 2, the neutron source 30 is gripped by a neutron source holding tool 36 attached to the tip of the operation pole 35, taken out from the storage block 33, and carried to above the neutron source holder 37.

The neutron source (NS pin) 30 carried to the upper side of the neutron source holder 37 is released by operating the release wire 38 at this upper position, and falls by its own weight. At this time, the fall of the neutron source (NS pin) 30 is guided by the source guide 39 having a tapered guide surface and guided into the neutron source holder 37.
Housed inside. The source guide 39 is attached to the tip of the operation pole 35.

Further, a plurality of neutron source holders 37 are stored in advance in a cylindrical neutron source holder rack 31 in an upright state, and can be detached from the neutron source holder rack 31.

Thus, the neutron source holder 37 accommodating the neutron source 30 is coupled to the neutron source holder moving jig 40 and taken out from the neutron source holder 31. This neutron source holder moving jig 40 is hung up and down on an auxiliary hoist 42 of a fuel exchanger 41 so that it can move between a fuel exchange mast adjusting pit 28 and a reactor core 22 of a reactor pressure vessel 20. There is. The refueling machine 41 is provided so that it can travel freely on the operation floor surface 43.

On the other hand, the mast adjusting pit 28 for the refueling machine
Source holder rack 31 that is detachably installed on the
3 has a basket-shaped structure as shown in FIG. 3, so that, for example, up to eight neutron source holders 37 can be detachably loaded in an upright state.

The neutron source holder rack 31 has a ring-shaped upper fixing plate 44 that also serves as a seating outer peripheral flange, an intermediate temporary stand supporting plate 45, and a lower holder supporting plate 46, for example, eight pillars. An intermediate fixing ring 48 for fixing each column 47 is provided between the upper fixing plate 44 and each of the supporting plates 45, 46 while being connected by 47. The intermediate fixing ring 48 enhances the rigidity of the neutron source holder rack 31. There is.

The total length of the neutron source holder rack 31 is about 7 m.
The temporary stand 32 of the storage block 33 is installed about 2 m from the upper end of the rack.

Therefore, as shown in FIG. 5, the neutron source holder rack 31 is inserted into the mast adjusting pit 28 for the refueling machine and fixed by seating the upper fixing plate 44 on the upper edge of the mast adjusting pit 28. , Suspended in the mast adjusting pit 28. When the water in the mast adjustment pit 28 for the refueling machine is full, the upper ends of the temporary stand 32 and the neutron source holder 37 are at sufficiently deep positions where they are not affected by radiation exposure, for example, 1.5 m or more from the free liquid surface. It is in the position.

Further, a fixing frame 50 having a seating flange on an intermediate fixing ring 48 located between the upper fixing plate 44 of the neutron source holder rack 31 and the temporary stand supporting plate 45.
By fitting as shown in FIG. 6, the neutron source holder rack 31 can be fixed at the position of the fixing frame 50.

A frame-shaped neutron source holder 37 is detachably loaded in advance on the neutron source holder rack 31, and the neutron source holder rack 31 is loaded in the mast adjustment pit 28 for the refueling machine with the neutron source holder 37 preloaded. Is installed in. On the other hand, a neutron source holder 37 accommodating the neutron source 30
Is loaded between the core lower support plate 24 and the reactor upper lattice plate 25 of the initially mounted core 22.

Next, the work of installing the neutron source in the core will be described.

In this embodiment, the reactor DS pool 27
By actively using the mast adjustment pit 28 for the fuel exchange machine, which is provided in advance, the neutron source 30 can be installed in the reactor in a safe manner almost similar to the installation work in the core of the conventional neutron source (NS pin) 30. It is possible to load the initially mounted core 22 in a short time.

Before the work of installing the neutron source 30 in the core, the following preparations and inspection items are checked.

(1) The refueling machine 41 and the overhead crane (not shown) can be used.

(2) Auxiliary hoist 42 of refueling machine 41
The neutron source holder moving jig 40 is attached to the.

(3) Mast adjustment pit 28 for refueling machine
Is full of water.

(4) The neutron source holder rack 31 in which the neutron source holder 37 and the temporary stand 32 of the storage block 33 are installed in advance is inserted into the mast adjusting pit 28 for the refueling machine and fixed.

When the preparation for the in-core installation work of the neutron source 30 is completed, the in-core installation work is advanced according to the following work procedure.

(1) The hoist 51 of the overhead crane is connected to the storage block 33 contained in the shipping container 34.

(2) The crane guide is left at a position far away from the storage block 33 to evacuate the worker.

(3) At the instruction of the crane guide, the storage block 33 is taken out of the transport container 34, moved in the air, and moved to the water in the fuel exchange mast adjusting pit 28.

(4) Release the evacuation of workers.

(5) The hoist 51 of the overhead crane is operated to slowly lower the storage block 33, seat it on the temporary stand 32, and disconnect it from the overhead crane.

(6) The neutron source (NS pin) 30 housed in the housing block 33 is held by the neutron source holding tool 36, and is loaded in the neutron source holder 37 by the operation shown in FIG.

(7) The remaining neutron sources (NS pins) 30 are sequentially loaded in the neutron source holder 37 by the same procedure.

(8) Using the overhead crane, the neutron source holder rack 31 is slightly lifted and fixed at the position of the intermediate fixing ring 48 shown in FIG.

(9) Auxiliary hoist 42 of refueling machine 41
Then, the neutron source holder moving jig 40 is coupled to the neutron source holder 37 in water, and it is confirmed whether or not they are securely coupled.

(10) The worker is evacuated.

(11) The neutron source holder 37 is pulled up and moved to above the core 22 in the air, and is lowered into the water in the reactor pressure vessel 20.

(12) Release the evacuation of the worker.

(13) The neutron source holder 37 is loaded on the initial mounting core 22.

(14) With respect to the other neutron source holders 37, the steps (9) to (13) are repeated to load the reactor core 22.

As described above, by positively utilizing the mast adjusting pit 28 for the refueling machine, all the work requiring a long time to handle the neutron source 30 can be performed in water. Further, in the work of installing the neutron source 30 in the core, the steps (5) to (9) are works in the mast adjustment pit 28 for the refueling machine, and in the work of installing the neutron source, the reactor well 26 and the DS pool are included. There is no need to fill 27 with water.

In the work of installing the neutron source 30 in the core,
The entire work receives an exposure of about 0.7 mSv / person, which is less than the allowable value, but the work in the fuel exchange mast adjusting pit 28 is underwater work, and the exposure dose is almost zero.

Further, there is no special preparation item for the installation work in the core, the preparation work is completed in a short time, and even if the preparation days are combined, the number of work days can be two days, and eight days are required. The number of working days can be significantly shortened compared to the conventional method.

Furthermore, the reactor well 26 and the DS pool 2
Since it is not necessary to fill 7 with water, the amount of water required for the installation work inside the core is about 10 m ³ which is the internal volume of the mast adjusting pit 28 for the fuel exchanger, and the amount of water used can be greatly reduced compared to the conventional case where 3500 m ^{3 is} required.

Therefore, the installation work of the neutron source 30 in the core does not require a new special device, has a merit that the exposure dose can be kept low, the number of working days can be greatly shortened, and the amount of water used can be reduced. ..

[0080]

Since the present invention is constructed as described above,
By filling water in the limited vertical hole space of the mast adjustment pit for the refueling machine, loading work of the neutron source that requires underwater work into the neutron source holder and joining work of the neutron source holder to the moving jig are performed underwater. It can be done and does not require the development of special tanks or neutron source loading machines. Also, without developing a new machine, careful and time-consuming work can be performed in the water in the mast adjustment pit for the refueling machine or the reactor pressure vessel during the installation work of the neutron source. Since the moving work can be performed in the air and the neutron source installation work can be carried out while maximizing the merit of moving the neutron source in the air, it is possible to reduce the exposure dose, shorten the installation work process days, and use. A reduction in water volume can be achieved at the same time.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a work procedure used in a method for installing a neutron source according to the present invention.

FIG. 2 is an explanatory view showing a work of taking out a neutron source from a storage block and loading it into a neutron source holder in a mast adjustment pit for a fuel exchange machine.

FIG. 3 is a side view schematically showing a neutron source holder rack according to the present invention.

4A is a plan view taken along the line AA of FIG. 3, FIG.
Is a plan sectional view taken along the line BB of FIG. 3, and (C) is a cross-sectional view of FIG.
The plane sectional view which follows the C line.

FIG. 5 is a view showing a state in which the neutron source holder rack according to the present invention is inserted into a mast adjustment pit for a refueling machine and seated.

FIG. 6 is a view showing a state in which a neutron source holder rack is slightly pulled out from a mast adjustment pit for a refueling machine and fixed.

FIG. 7 is a view showing an initial mounting core of a boiling water reactor.

FIG. 8 is a plan view showing the relationship between a reactor well, a dryer separator pool, and a spent fuel pool provided in the upper part of the reactor building.

FIG. 9 is an explanatory view showing a work of taking out a neutron source from a storage block and loading it into a neutron source holder among the work performed in the fuel pool.

[Explanation of symbols]

 20 Reactor Pressure Vessel 21 Reactor Building 22 Core (Initially Mounted Core) 23 Core Shroud 24 Lower Core Support Plate 25 Core Upper Lattice Plate 26 Reactor Well 27 Dryer Separator Well 28 Fuel Exchange Mast Adjustment Pit 30 Neutron Source (NS) Pin) 31 Neutron source holder rack 32 Temporary stand 33 Storage block 34 Transport container 35 Operation pole 36 Neutron source gripping tool 37 Neutron source holder 40 Neutron source holder moving jig 41 Fuel exchanger 42 Auxiliary hoist 43 Operation floor 44 Upper fixing plate 45 Temporary stand support plate 46 Holder support plate 47 Strut 48 Intermediate fixing ring 50 Fixed frame

Claims (2)

[Claims] 1. A neutron source holder rack in which a neutron source holder is detachably housed is inserted and fixed in a mast adjusting pit for a refueling machine, while water is put in the mast adjusting pit to put it in the mast adjusting pit. Guide the storage block containing the neutron source, the neutron source from this storage block, by underwater work in the mast adjustment pit for the refueling machine, taken out and stored in the neutron source holder, followed by neutrons containing the neutron source The source holder is coupled to the neutron source holder moving jig, and the neutron source holder is taken out from the neutron source holder rack by this neutron source holder moving jig,
A method for installing a neutron source, which comprises moving the neutron source holder into the reactor pressure vessel in the air, and then loading the neutron source holder on the initially loaded core. 2. An upper fixing plate having a flange that can be seated at the upper edge of the mast adjustment pit for a fuel exchange machine, an intermediate temporary stand supporting plate provided with a temporary stand capable of supporting a storage block, and a neutron source. The lower holder support plate supporting the holder is connected to each other by a plurality of columns to form a holder rack in a cage structure, and the neutron source holder is detachably mounted in the holder rack, while the holder is A neutron source holder rack, characterized in that the rack is inserted and fixed in the mast adjusting pit for the refueling machine so that it can be taken in and out.