WO1991004559A1 - Centrale a reacteur nucleaire - Google Patents

Centrale a reacteur nucleaire Download PDF

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Publication number
WO1991004559A1
WO1991004559A1 PCT/CA1990/000175 CA9000175W WO9104559A1 WO 1991004559 A1 WO1991004559 A1 WO 1991004559A1 CA 9000175 W CA9000175 W CA 9000175W WO 9104559 A1 WO9104559 A1 WO 9104559A1
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WO
WIPO (PCT)
Prior art keywords
coolant
tank
core
nuclear reactor
inlet
Prior art date
Application number
PCT/CA1990/000175
Other languages
English (en)
Inventor
John S. Hewitt
Hani C. Ajus
Terrance J. Jamieson
Antonino F. Oliva
Bruce M. Pearson
William P. Wong
Original Assignee
Ecs-Power Systems Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ecs-Power Systems Inc. filed Critical Ecs-Power Systems Inc.
Publication of WO1991004559A1 publication Critical patent/WO1991004559A1/fr

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Classifications

    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C11/00—Shielding structurally associated with the reactor
    • G21C11/02—Biological shielding ; Neutron or gamma shielding
    • G21C11/04—Biological shielding ; Neutron or gamma shielding on waterborne craft
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C15/00—Cooling arrangements within the pressure vessel containing the core; Selection of specific coolants
    • G21C15/18—Emergency cooling arrangements; Removing shut-down heat
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21D—NUCLEAR POWER PLANT
    • G21D9/00—Arrangements to provide heat for purposes other than conversion into power, e.g. for heating buildings
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

Definitions

  • This invention relates to a nuclear reactor plant to serve as the heat source component of a power plant for the production of heat or electricity.
  • the reactor plant includes means for cooling the reactor core in the event of impairment of the primary heat transport circuit of the power plant.
  • the reactor plant serves as a major component in a heat transport circuit which also contains a pump and one or more heat exchangers as other major components of the circuit.
  • Such a circuit is referred to as the primary heat transport circuit of the power plant.
  • the said reactor draws on a supply of reserve coolant contained in a tank which is an integral part of the reactor plant.
  • the consequent exchange of coolant between the reactor core and the reserve coolant tank provides, in the interests of reactor safety, auxiliary cooling to the core of the reactor under conditions of zero or reduced primary flow, loss of heat sink, or other form of impairment of the primary heat transport circuit.
  • the reserve coolant tank together with the other plant associated with this action is referred to as the passive cooling system.
  • the reactor core, the coolant-carrying components of the primary heat transport circuit, and the said passive cooling system, together with the coolant itself, are identified as the primary heat transport system of the said nuclear power plant.
  • a nuclear reactor plant comprising a core, means for controlling the reactivity of said core, radiological shielding around said core, inlet means to conduct coolant into said core, outlet means to conduct coolant out of said core, a reserve coolant tank; and port means in said inlet means and in said outlet means for conducting coolant between said reserve coolant tank and said inlet means and outlet means by convection during impairment of normal flow of coolant through said inlet and outlet means, and for permitting a through-flow of coolant through said inlet means and outlet means during normal operating conditions.
  • the reactor plant comprises a light-water-cooled reactor core, bracketed by inlet and outlet coolant plena, each coupled to one or more ducts leading away from the core at various orientations. At any given time each duct carries some fraction of the coolant flow through the core.
  • each duct terminates in a special branching device, herein referred to as a port, designed in any one of a number of ways, such that:
  • branch flow in the ports can develop such that the combination of such flows in all of the ports produces rates of net coolant exchange between the core and the reserve coolant tank that are adequate for assuring the safety of the reactor plant.
  • the specific type, or principle of operation, of the said ports applied within the reactor primary heat transport system is not critical to the nominal functioning of the said nuclear plant.
  • such ports, any associated auxiliary equipment, and the primary heat transport system that accommodates their effective operation may be specified as necessary to meet the particular reactor application requirements.
  • Such specification would accommodate a prescribed level of safety and include the design approach to safety, as may be required or deemed appropriate in a particular reactor application.
  • auxiliary cooling system operation not only is sustained by passive means but also is initiated by purely passive means.
  • the said reactor plant further comprises a reactor vessel, gamma and neutron shields, a primary circuit delay tank and reactivity control mechanisms, all located together with such previously mentioned components as the reactor core, the plena, the ducts, the ports, and the headers within the boundary of the reserve tank and submerged in the bulk of the reserve coolant, which is itself thermally coupled to an ultimate heat sink. All such components are arranged in a highly integrated manner, relative to each other and in accordance with measures taken to restrict (i) space requirements, (ii) total mass of reactor plant, and (iii) radiological dose as determined both at the reactor boundary and in the vicinity of coolant inventory found circulating through the various primary heat transport components external to the reactor plant.
  • An objective of certain embodiments of the present invention is to achieve a nuclear reactor plant which (i) in the case of marine applications, is sufficiently compact in design to permit its installation as a component of a nuclear plant within small quarters such as are found on board a submarine of significantly smaller dimensions and displacement than are generally characteristic of nuclear powered submarines; (ii) which presents manageable operational radiological fields at its boundaries and in its circulating coolant; and (iii) which accommodates a simplicity of design and operation appropriate to peculiar characteristics required of the plant and its application.
  • Such characteristics include: (a) a modest plant output,
  • a further objective of the invention is that the reactor plant, when installed on an unsteady platform, such as on board a submarine, be capable of sustaining normal operation over a sufficiently wide range of motion.
  • a still further objective is that the passive cooling system remain functional when plant motion and orientation both extend outside the normal operating range, even when operator intervention and internal and external power sources become unavailable.
  • the reactor plant is also of a physical make-up that can be embodied in a form and structure which exhibits strength and resilience appropriate to the accelerating motion and displacement that can be anticipated for a submarine platform.
  • the flow pattern in the delay tank is arranged, by the positioning of internal baffles and the inlet and outlet locations, so that the segments of the tank which contain coolant of the highest specific radioactivity during reactor operation are at the side of the reactor core where they least expose operating personnel and sensitive equipment to radiation, (iii) Employing commonly accepted methods for safely managing the excess reactivity required for long fuel burnup life and acceptable demand load- following capability. These may include the use of fuel which contains burnable absorber and, as well, provides a large, prompt negative temperature coefficient of reactivity.
  • the present invention accommodates such avoidance by the addition of dissolved neutron absorber in low concentrations to the coolant of the primary heat transport circuit and in high concentrations to that of the reserve coolant tank, and providing outside the said reactor plant the chemical plant necessary to maintain the concentration difference as necessary.
  • the dominance of the large mass of the reserve coolant at the higher absorber concentration and the incorporation of suitable ports, will result in reactor shutdown immediately following the development of coolant exchange flow
  • Some embodiments of the invention provide a self- shielding/self-contained reactor plant for power production that is accommodated in a small space, i.e., characteristically 3.7 m in diameter, 30 m 3 in volume and 70 tonnes in weight. It is anticipated that such reactors may be successfully scaled-up by as much as 10 to 30 times in power, accompanied by an approximate doubling in linear dimensions, while still retaining most of the design and operating features of the basic invention.
  • Some embodiments also provide a power reactor, sized to operate at the low end of power level range normally associated with nuclear reactors dedicated to power production, and which, on the one hand, delivers its heat energy at a temperature as high as within a few degrees of the saturation temperature of its coolant at normal operating conditions, and, on the other hand, retains the safety of the passive (convective) cooling of a swimming- pool type of research reactor, which is characterized by a large thermal ballast maintained as the massive highly sub- cooled pool water.
  • a massive body of highly sub-cooled reserve coolant is likewise freely available at all times as auxiliary cooling, and particularly during those times when operating conditions depart from normal.
  • Some embodiments also provide a reactor with a passive cooling system designed to function at orientations departing from normal and under accelerating motion (as when a ship in which such a reactor is installed is subjected to currents and surface waves) , and in which the said cooling system is such that it does not detract from the ability of the reactor to operate efficiently under normal conditions.
  • the drawing is a vertical cross-section of an embodiment of the reactor plant made according to the invention and shown in normal operation, and at a normal orientation with regard to the direction of gravitational forces.
  • the drawing shows, by means of arrows, a finite amount of exchange flow of coolant between the reactor core 1 and the reserve coolant tank 30, superimposed on the dominant flows for normal operation.
  • the reactor plant configuration has substantially radial symmetry about the vertical centre line indicated.
  • reactor core 1 is built up of a plurality of fuel elements 2 arranged so that water circulating among the elements serves as both moderator and coolant.
  • fuel type depends on the particular reactor embodiment, but the choice of uranium-zirconium-hydride fuel, or similar fuel consisting of a fissile-fertile nuclide mixture alloyed with metal hydride to yield significant hydrogen moderation within the fuel matrix, provides the advantages of (i) a strongly enhanced prompt negative temperature coefficient of reactivity, (ii) a favourable through-core coolant velocity profile and magnitude for a given mass flow, and (iii) a reduced in-core water volume and, hence, a reduced production rate of radioactive isotopes which are subject to transport throughout the primary heat transport circuit.
  • the fuel elements, or assemblies of such elements as the case may be, are suspended between the upper and lower grid plates 3 and 4 which, in addition to supporting the fuel, provide openings to facilitate the passage of coolant traversing the core component of the primary heat transport circuit.
  • the grid plates are designed also in such a way that they hold the fuel elements or assemblies firmly in place in the face of acceleration imposed externally on the reactor plant, while providing for their insertion, securing, release and removal by remote manipulation during refuelling operations.
  • the core-adjacent components of the primary heat transport circuit consist of the inlet and outlet plena 12 and 13, and the inlet and outlet ducts 14 and 15. Only four of the ducts are shown in the sectional drawing although, in general, a plurality of at least eight of such ducts arranged with radial symmetry about the axis shown may be preferred for installations on mobile platforms such as those arising in marine applications.
  • Each of the inlet and outlet ducts leads outward from the reactor core and connects with an inlet port 21 or an outlet port 22, respectively.
  • the ports and their means of control are designed in such a way that, during normal reactor operation, they accommodate predominantly through-flow in which essentially all of the coolant circulating through the core is matched, by means of the said ports, to the flow circulating in the remaining components of the primary heat transport circuit.
  • Such components include the inlet and outlet header networks 23 and 24, the delay tank 26, the main inlet and outlet conduits 28 and 29, as well as the other major components of the primary heat transport circuit located externally to the reactor plant as currently defined.
  • These latter components include the primary coolant circulation pump and the primary heat exchangers, which are parts of the primary heat transport circuit but not parts of the subject reactor plant. It is noted, however, that in some embodiments of the reactor plant such components might be located within the reserve coolant tank.
  • the ports and their means of control are designed so that for a range of off-normal operating conditions, such as those arising during an accidental impairment of operation of the circulation pump or the heat exchangers of the primary heat transport circuit, the ports accommodate lateral flow.
  • Such flow provides for a naturally convected exchange of coolant to be established and maintained between the reactor core 1 and the reserve coolant tank 30, in response to one or more of a wide range of accident scenarios.
  • the reserve tank 30 is normally maintained full of coolant water maintained at a temperature considerably lower than that of the primary heat transport circuit, by virtue of (i) layers of insulation 25 applied to all of the outer boundaries of those components of the primary heat transport circuit enclosed by the reserve tank, and (ii) provision of facilities, not shown in the drawing, for the removal of heat from the reserve coolant to external heat sinks.
  • Such facilities may be designed by those skilled in the art of thermal hydraulics so that, under normal operating conditions, the heat removal rate is sufficient to maintain the reserve coolant temperature at a stand-by level low enough to provide the necessary thermal ballast to meet anticipated accident scenarios, and, under reactor shutdown conditions, to accomplish the passive removal of decay heat in a manner which avoids possibility of overheating the fuel elements in the absence of further operator intervention.
  • the equipment used to maintain the stand-by temperature may be in common with that for passive decay heat removal, although this would not be a necessity from an operational or safety point of view.
  • the natural convection circuit consists of (i) the core 1 in combination with the several outlet ducts 15 acting in parallel with each other to serve as the hot leg of the circuit, (ii) the reserve coolant tank 30 in combination with the several inlet ducts 14 acting in parallel with each other to serve as the cold leg of the circuit, and (iii) the ports themselves, 21 and 22, operating in lateral-flow to complete the various branches of the circuit, thus creating a thermosyphon. All of the said components are designed to assure that, once the convective coolinq paths are established following a safety-related initiating event, adequate cooling may be maintained for an indefinite period without the requirement of further action on the part of human operators, automatic safety systems, or external energy sources.
  • the circuit, so described, constitutes the passive cooling system of the subject reactor operating in its most likely mode, namely, the one in which the reactor remains in its upright orientation.
  • a novel aspect of the present invention is that it provides for passive cooling to be sustained even if the reactor departs radically from its normal orientation with respect to the direction of gravitation, as in the case of postulated accident conditions on board a ship powered by the reactor.
  • Inlet ports 21 and outlet ports 22 are designed to perform a switching operation from through-flow to lateral- flow mode, and vice-versa, in response to changing operating circumstances.
  • the ports are designed to allow in some circumstances the superposition of through-flow and lateral-flow, for the further enhancement of operational and safety performance.
  • the choice of a port design fulfilling prevailing safety and reliability requirements may be undertaken by those skilled in the art of thermal hydraulic design.
  • a passive cooling system which has already the property of being able to continue indefinitely to cool the reactor without need of external action or energy supply, once passive cooling is established, now has, in addition, the quality of being able to initiate such passive cooling without external action or energy.
  • Such a system may be described as possessing passive cooling initiated by passive means.
  • a cooling system matching such a description, including specific aspects of the port design is the subject of the copending patent application referred to above.
  • the inlet header network, 23, consists of a manifold or other piping arrangement which distributes, via the inlet ports 21 operating in the through-flow mode, the pumped flow from the main inlet conduit 28 in equal measure to the several inlet ducts 14.
  • the outlet header network, 24, consists of a manifold or other piping arrangement which collects, via the outlet ports 22 operating in the through- flow mode, pumped flow in equal measure from the several outlet ducts 15 and directs it to the delay tank 26.
  • the primary purpose of the delay tank 26 is to provide a dwelling place for the short-lived neutron activation products, created in the primary coolant as it flows through the core, to decay to acceptable levels before they are carried in the coolant to primary heat transfer components located outside the reactor plant.
  • Such components include heat exchangers which may have secondary media that are particularly vulnerable to radiation damage or which may be approached occasionally by operators.
  • the delay tank is annular in shape, co-axial with the reactor itself, and located at the periphery of the shielding tank 19 with which it shares a common boundary. In this configuration the delay tank is shielded from significant secondary neutron activation, but is itself relatively shielded as viewed from locations outside the reactor plant.
  • the primary heat transport system of the subject reactor operates as follows. Under normal operating conditions the cooling water is circulated through the primary heat transport circuit by means of the pump located externally the reactor plant.
  • the ports, 21 and 22 remain closed to lateral flow due either to physical boundaries or hydrodynamic effects, depending on the type of port specifically incorporated in the design.
  • the reactor power is regulated to achieve the desired conditions in the circuit, taking into account the usual plant operation considerations such as the thermal load demanded by the external equipment.
  • the ports switch from the through-flow mode to lateral-flow mode and the reactor core is subsequently cooled by natural convection exchange flow between the core and the reserve coolant tank.
  • This passive mode of cooling which delivers no power to the normal load, can be allowed to continue until the reserve coolant, which was originally maintained at a temperature considerably lower than that of the primary circuit, approaches the boiling temperature of water at the maintained pressure.
  • the total time required for this condition to be reached is considerably lengthened if, in the meantime, the reactor core is placed in the shutdown state. Following reactor shutdown it is possible, by virtue of the reserve tank cooling system, to assume that the reactor will be adequately cooled from a safety point of view for an indefinitely long period. For these reasons and because at long times after shutdown, only the decay heat is produced in the reactor core, such a reactor is said to possess a passive decay heat removal system. It is seen that, so long as the ports remain open to lateral flow, the passive decay heat removal process continues to operate regardless of the orientation of the reactor with respect to gravity.
  • the passive cooling system can be said to have been initiated by passive means.
  • the reactor may be said to have a passive reactor shutdown system.
  • the preferred embodiment is capable of such a feature through the addition of absorber to the reserve coolant, as well as the necessary plant to manage the absorber content in the primary circuit of the system as the reactor becomes critical and assumes normal operation. This system variant would be seen to be particularly meritorious from a safety point of view if deployed in conjunction with the passively initiated passive cooling system.
  • the reactor relies for its safety on either neutronic feedback, as provided by the prompt negative fuel temperature coefficient, or on secondary effects caused by changes in the coolant condition.
  • changes include phase change, or the induction of absorber dissolved in the reserve coolant as mentioned above.
  • the penetrations of the reserve tank boundary to admit the main inlet and outlet conduits are located high up on the walls of the reserve tank. This location is chosen to minimize the effect of a postulated breakage, in either the conduits or the connected components occurring outside the reserve tank, on the inventory of water in the reserve tank.
  • the appropriate placing of syphon breaks within the system may be of assistance in this regard.
  • the beryllium reflector 10 plays an important role keeping the basic radial power peaking factor close to unity. To this end, such a reflector is both necessary and particularly effective when used in conjunction with a small hydrogen moderated core. Also in this regard, the preferred use of "burnable" neutron absorber interspersed in the fuel matrix, in order to provide uniform reactivity compensation throughout the core over the fuel burnup lifetime, avoids the severe flux perturbations which would otherwise be caused by necessary movable mechanical absorbers.
  • the presence of both the reflector and the burnable absorber support radial uniformity of the neutron flux, and hence uniformity of power density and coolant conditions throughout the core.
  • This uniformity is a vital requirement in a low-pressure power reactor in which acceptable efficiency of the energy conversion process requires the average core temperature to be close to the maximum core temperature, which, in turn, will have the saturation temperature corresponding to the operating pressure as its extreme upper limit.
  • burnable or controllable absorber added to the coolant is disregarded in the compact reactor embodiment depicted in the drawing, because of the need to avoid the added plant and operational complications.
  • the regulating absorber rods 5, which are of sufficient number and unit reactivity worth to cover with some redundancy the reactor's operating reactivity margin, are made to travel by rod drive mechanisms 9 within associated guide tubes 5 located in a distributed manner throughout the core.
  • Interspersed among the regulating rods and fuel rods of the core are shutoff rods 7, which are of sufficient number and reactivity worth to cancel under all conceivable operating circumstances the reactor's operating reactivity margin, are made to travel by separate rod drive mechanisms 9 within associated guide tubes 8.
  • Each shutoff rod has an attached fuel rod which, under normal operating conditions with the shutoff rods fully withdrawn, occupies the core lattice site reserved for the receiving of the shutoff rod on shutdown.
  • shutoff rods and their associated mechanisms it is possible to eliminate the need for the shutoff rods and their associated mechanisms, if, for example, the shutoff function is made to follow the onset of passive cooling by means of neutron absorber previously dissolved in the reserve coolant being drawn into the core. Also, the required total reactivity worth of the regulating rods may be reduced by adding and subtracting chemical shim in controlled amounts with respect to the circulating primary coolant, or by reliance on the built-in tendency of the reactor for self regulation to a constant core temperature by virtue of the negative temperature coefficient of reactivity.
  • the reactor vessel 11 serves as a principal support structure for many components of the reactor plant. Its layout also accommodates the remote disassembly of certain components, including the rod drive mechanisms and the fuel elements or assemblies, for the purpose of servicing and refuelling the reactor.
  • the vessel supports the reflector 10, the lower and upper gamma shield inserts 17 and 18, and the control rod mechanism deck 31. It also provides for the coupling of the inlet and outlet ducts 14 and 15 to the inlet and outlet plena 12 and 13, respectively, and for the locating of the radial component of the gamma shield 16.
  • the space enclosed by the shielding tank 19, and not occupied by other reactor components, is filled by reactor shielding material possessing the ideal reactor shielding properties of (i) hydrogen moderation, (ii) relatively radiation-free thermal neutron capture, and (iii) gamma radiation absorption.
  • this space is filled with a composite made up of thermal neutron and gamma ray absorbing plates interlaminated with water.
  • the plates are composed of a readily available stainless steel alloy, containing boron as a major constituent.
  • the water of the shielding tank 19 communicates with the water of the primary heat transport circuit through relatively small openings not shown in the drawing. Under normal operating conditions, a small fraction of the coolant flow returning through the main inlet conduit is diverted into the shielding tank while an equal amount is entrained with the flow emerging from the reactor core and eventually leaving the reactor plant through the main outlet conduit.
  • the magnitude of such flow through the shielding tank is such that the merging core and shielding flows combine at more or less the same temperature.
  • the shield tank water will share not only operating pressures and temperatures similar to those of the reactor core, but will undergo continual chemical upgrading by virtue of the main water chemistry plant normally connected to the primary heat transport circuit.
  • the advantages of this arrangement with regard to the elimination of the added weight, volume and complexity of a water management plant explicitly for the maintenance of shielding solution, will be particularly apparent in applications where compactness of plant is essential.
  • Provisions similar to those described above for coupling the shielding water system to the primary cooling system under normal operating conditions should, in principle, also be present when the reactor is being cooled by the passive cooling system. Under these latter conditions, however, the reactor will have been placed in the shutdown state, during which transition the radiation heating is reduced disproportionately faster than the core power, and it is unlikely that any special cooling provisions will be required. In any case, small passages to facilitate adequate natural convection between the shielding water and the main passive cooling circuit under shutdown conditions, without compromising either of the primary cooling functions, may be readily devised if necessary.
  • the principle of sharing a single water chemistry plant may be extended, depending primarily on the particular port design adopted, to include the reserve coolant which resides in the reserve coolant tank 30.
  • Such inclusion is particularly appropriate in reactor plants using the hydrodynamic ports referred to above, or other port designs which can allow a small constant exchange of coolant between the circulating coolant and that of the reserve tank. In such cases, the normal residual rate of coolant exchange between the reserve coolant tank and the circulating primary coolant may suffice.
  • both the shielding tank 19 and the delay tank 26, which share a common hydraulic boundary may be considered for present purposes as components of the primary circuit, as all components located within them are allowed to rise to general level of the normal operating temperature of the primary circuit and need not be insulated individually.
  • the insulation used may be of the wettable type, but it must be capable of physically withstanding the effects of hot water suddenly depressurizing within the matrix of the insulation and flashing to steam, if the insulation system is to remain intact following a loss of coolant event involving coolant phase change.
  • gamma shielding components 16, 17 and 18 are of a high-Z variety, typically, lead, or tungsten. If necessary to prevent distortion due to overheating, cooling passages may be arranged in these components to permit the circulation of the water from the nearby shielding tank 19.
  • the surfaces of the gamma shielding components, including the cooling passages, are clad with material which is chemically compatible with the shielding tank water.
  • the actual dimensions of the gamma shielding components, including the laminate structures of the shielding tank 19, may be optimised for a particular application by those skilled in the art of radiation shielding design.
  • auxiliary shielding components may be added in and around the reactor plant, and in the vicinity of adjacent equipment.
  • Such localized shielding may be necessary to counteract the possible streaming of radiation from the core through the inlet or outlet ducts and ports.
  • Such shielding may be arranged as an integral part of the ducts or ports themselves.
  • the head space above the control rod mechanism deck 31, is likewise filled with water communicating marginally with the main body of reactor coolant. This water, as well as contributing to the general shielding, also may provide cooling and lubrication to the rod drive mechanisms, depending on their particular design. For a reactor designed to operate at temperatures elevated above the operating temperature for the rod drive mechanisms, the thermal insulation must be applied to the control rod mechanism deck, rather than over the upper part of the reactor vessel and its cover 32, as shown.
  • the reserve coolant tank 30, and the reactor assembly it contains have low elevation profiles to facilitate installation in a low-profile environment such as on board a small or medium-sized submarine vehicle.
  • the reserve coolant tank may stand alone within the vehicle structure or it may be an integral part of the submarine structure, namely, the main pressure hull or a secondary inner hull.
  • the reserve tank could be in the form of an in- ground pool, or could serve as a liner for an in-ground tank structure which serves as a backup container for the reserve tank, offering, at the same time, an opportunity for monitoring for leaks in the reserve tank using methods which are commonly applied in the industry.
  • the arrangement of the reactor plant while determined largely by thermal hydraulic and compactness considerations, also facilitates refuelling and other aspects of reactor servicing.
  • the reactor core region is accessed by first erecting auxiliary shielding, if necessitated by a small shielding space allowance in the particular installation.
  • the tank is in the form of vertical extension sealed temporarily to the reserve tank 30 and enclosing a large area around the reserve tank access hatch 34. After filling the extension with water of reactor purity, the hatch cover 34 is removed, followed by the reactor vessel cover 32. At this point, the water of the auxiliary shielding tank will have become united with the water of the reactor systems, thus forming a single body of liquid.
  • shutoff rods, 5 and 7 are decoupled from their control mechanisms 9. The latter are then removed, leaving the shutoff rods in the core.
  • the control rod mechanisms deck 31, some boron absorbing laminates, and the upper axial gamma shield 18, which also serves as the upper boundary of the outlet plenum 13, are removed in that order from within the reactor vessel 11.
  • defuelling operations may begin, followed, at the last, by the removal of the control and shutoff absorbers, including the follower fuel rods. Fuelling operations involve the same procedural steps, but in reverse order and with an approach-to-critical procedure before reassembly of the shielding components and reconnection of the reactivity mechanisms.
  • Embodiments which do not require that the passive cooling circuit be available at all physical orientations of the plant may have a configuration with as few as one inlet duct and one outlet duct, connecting with the reactor core. These can be offset relative to the core axis in order that ready access to the core for servicing and refuelling is available. In the case of a research reactor, such ready access may facilitate the design and operation of experimental facilities installed in or near the reactor core.

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Abstract

Une centrale à réacteur nucléaire comporte un noyau (1), un moyen de commande de la réactivité du noyau (5, 6, 7, 8, 9), un bouclier radiologique (16, 17, 18, 19), ainsi que des conduits d'admission (14) et des conduits de sortie (15) destinés à conduire du liquide de refroidissement dans le noyau et hors de celui-ci. La centrale se caractérise en ce que les orifices (20, 21) sont aménagés dans les conduits d'admission et de sortie afin de conduire du liquide de refroidissement entre un réservoir (30) de liquide de refroidissement de réserve et les conduits d'admission et de sortie par convection naturelle lors d'une défaillance du circuit de refroidissement du réacteur. Un réservoir de désactivation (26) reçoit du liquide de refroidissement provenant des conduits de sortie; il entoure le noyau et constitue un bouclier radiologique supplémentaire. Un réservoir faisant écran (19), contenant des stratifiés (20) absorbant le rayonnement, et du liquide de refroidissement entourent le noyau.
PCT/CA1990/000175 1989-09-15 1990-05-30 Centrale a reacteur nucleaire WO1991004559A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA000611549A CA1333941C (fr) 1989-09-15 1989-09-15 Reacteur nucleaire
CA611,549 1989-09-15

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WO1991004559A1 true WO1991004559A1 (fr) 1991-04-04

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EP (1) EP0491700A1 (fr)
CA (1) CA1333941C (fr)
WO (1) WO1991004559A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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CN112397208A (zh) * 2020-11-13 2021-02-23 中广核研究院有限公司 一种用于紧凑布置反应堆的屏蔽罩布置结构
CN113963817A (zh) * 2021-10-14 2022-01-21 中国舰船研究设计中心 一种核动力船舶穿堆舱管道的核辐射局部屏蔽结构

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US6594333B2 (en) * 2001-11-16 2003-07-15 Japan Nuclear Cycle Development Institute Thermal load reducing system for nuclear reactor vessel
CN112397208A (zh) * 2020-11-13 2021-02-23 中广核研究院有限公司 一种用于紧凑布置反应堆的屏蔽罩布置结构
CN113963817A (zh) * 2021-10-14 2022-01-21 中国舰船研究设计中心 一种核动力船舶穿堆舱管道的核辐射局部屏蔽结构

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