WO2002035552A1

WO2002035552A1 - Method for handling nuclear waste from a nuclear facility and transport and/or storage container for waste of this type

Info

Publication number: WO2002035552A1
Application number: PCT/EP2001/012115
Authority: WO
Inventors: Klaus Knecht; Wolfgang Hummel; Alfons LÜHRMANN
Original assignee: Framatome Anp Gmbh
Priority date: 2000-10-25
Filing date: 2001-10-19
Publication date: 2002-05-02
Also published as: AU2002226311A1; DE10052735A1

Abstract

A method for handling nuclear waste from a nuclear facility should permit, with a comparably low level of complexity and a high degree of versatility, a reliable and secure disposal of waste elements also those of a comparatively high level of radioactivity. To this end, a number of fuel elements (20), especially burned down fuel elements (20), of a nuclear reactor are transferred together with a number of built-in parts of the nuclear facility that need to be disposed of into a common transport and/or storage container (1). A transport and/or storage container (1) particularly suited for use in this method comprises an interior space (4). A number of first compartments (12) for accommodating fuel elements (20) of a nuclear reactor and a number of second compartments (14) for accommodating built-in parts of the nuclear facility that need to be disposed of are provided inside this interior space.

Description

2 description

3 Processes for the treatment of nuclear waste from a nuclear facility and transport and / or storage containers for such waste

5

6 The invention relates to a method for treating nuclear waste from a

7 a nuclear plant. It also relates to a transport and / or β storage container for nuclear waste from a nuclear facility. G

10 When operating a nuclear facility, there are usually

11 types of nuclear waste that can be disposed of safely and reliably.

12 supply. For example, the operation of a nuclear reactor

13 fissile fraction of a fuel in a number of fuel assemblies for the production of heat and thus indirectly for the production of electricity.

15 gen. If in one or more of these fuel elements the fissile fraction

16 of the fuel is below a minimum threshold, the

17 chain or nuclear reaction no longer required due to electricity

18 can be obtained. Therefore, at this point in time, the fuel assembly is usually

19 replaced by a new one, the spent fuel element being to be disposed of as a comparatively highly radioactive waste for disposal or reprocessing 1. 2 3 In addition, when operating a nuclear facility, in particular ₄ a nuclear reactor, there are also a large number of other 5 passive components that are exposed to a radiation load when they are used and 6 themselves become radioactive as a result. These components or parts 7 are thus also to be disposed of after their operating time has expired. 8, depending on the activity of the respective component or the respective component 9, a distinction can be made between low, medium or high level radioactive waste products. 1 2 When disposing of nuclear waste, the goal is usually 3 to deposit the respective waste products in final deposits. The request

BESTATIGUNGSKOPIE- 1 to the final deposit, depending on the type of nuclear waste,

2 different from its radiation intensity. In any case

3 When selecting the final deposit, ensure that the post-decay heat of the nuclear waste is safely dissipated, that the radiation exposure to the environment is harmless, and that no highly toxic substances can escape. e Especially when disposing of fuel elements as nuclear waste, the

7 a decay phase should be provided in a water basin of the reactor prior to the transfer to an intermediate or final deposit in order to

9 Dioactivity and heat development of the fuel elements initially for one

10 transport to bring acceptable level.

11

12 In the treatment of nuclear waste, particularly related to

13 of its disposal, it is often intended to be placed in a container. It can be a transport container or a storage container. For example, is used to treat spent fuel

16 of the decay phase is usually provided in the water basin of the nuclear reactor,

17 to pack the spent fuel in special containers, in particular transport containers. B. are known under the name "Castor".

19 containers are used to transport the fuel elements to an interim storage facility in the

20 the containers filled with the fuel assemblies are stored until the fuel

21 reached the final storage conditions.

22 3 Such a container has a thick radiation protection cover, for example made of ₄ cast iron, also called spheroidal cast iron, with embedded spherical graphite particles, in order to withstand all mechanical stresses even in the event of accidents through the combination of mechanical strength and ductility. 7 To ensure reliable radiation protection, usually 8 moderator rods, for example made of polyethylene, are embedded under the outer surface, ie in the outer edge region of the radiation protection sleeve. The fast neutrons emitted during radioactive decay are largely moderated and reflected 1 and then absorbed in the iron of the radiation protection cover. Inside the radiation protection cover, inserts form compartments in which the 3 individual fuel elements are held with practically no play. 1

2 In addition, other containers are usually provided for other types of waste.

3 see that in particular the expected radioactive pollution from the

₄ are adapted to each type of waste. Concrete or cast containers are used in particular for low and medium-level waste. When loading β or loading these containers, however, the integral or overall specified radiation limit values must be observed. Containers of this type thus have a disposal, particularly when it comes to the disposal of comparatively highly radioactive components

9 only a very limited absorption capacity, so that such disposal

10 is comparatively complex and costly.

11

12 The invention is therefore based on the object of a method for treatment

13 of nuclear waste from a nuclear facility, with the u comparatively little effort reliable and safe disposal

15 comparatively highly radioactive waste elements with high flexibility

16 is possible. In addition, a particularly suitable for use in this method

1 suitable transport and / or storage container for nuclear waste from a core technical system can be specified.

19

20 As regards the method this object is achieved according to the invention, by 1, a number of fuel assemblies, instruments, in particular of spent fuel 2, a nuclear reactor together with a number of entsorgungsbedürfti- 3 gen built-in parts of a nuclear installation in a common transport _4, and / or storage container is spent. The invention is based on the consideration that reliable disposal of even highly radioactive built-in parts can be ensured with comparatively little effort, by combining the built-in parts in a suitable manner with 9 also highly radioactive further waste products. This is possible in a particularly favorable manner by providing a combination with the fuel elements to be disposed of. In particular, the already existing, comparatively high safety standards for the disposal 3 of the fuel elements can be used, so that the disposal of the input 1 components can be done particularly reliably. In addition, in particular

2 the allocation of the containers with fuel elements with regard to the total

3 taking into account radiation limit values available capacity reserves on

4 are used particularly cheap and flexible way, so that such

5 combination of particular economy.

6

7 The storage of the built-in parts requiring disposal in the common transport and / or storage container can be provided in specially designed for the built-in parts.

9 separate built-in compartments or in suitably chosen

10 gaps between the fuel elements, which are arranged at a higher level, take place.

11

12 The method is particularly suitable for the treatment of comparative

13 wise highly active or highly activated components. Advantageously, such highly activated components with an activity of, for example, more than 10 ¹² Bq / m ³ are therefore provided as built-in parts requiring disposal. It can be

16 special components that are located in the immediate core area of the core

17 tors and / or in the neutron flux have been used without

18 was originally radioactive. Here, for example, tax

19 be, measuring lances, throttle bodies, sample holders and / or poisoning plates in loading

20 costume. Alternatively or additionally, neutron sources can also be provided

Be 21. 2 3 In order to safely fall below the radiation limit values for the loading 5 of the transport and / or storage container, which are mandatory with regard to safe disposal with negligible pollution _4, the combination of those for transport in the common transport 7 is advantageously made The fuel elements and components required to be disposed of in the port and / or storage container are made on the basis of a cumulative analysis of the characteristic values characterizing the fuel elements and the components requiring disposal. In other words: to compile the entire load of the transport and / or storage container, for example in 2 of the type of a computer simulation, it is expedient to first of all form the intended total package 3 of the individual waste products and then to dispose of them as a whole 1 Radiation and / or heat output determined. Instead of the singular evaluation

2 individual components, the overall intended

3 NEN loading volume as a whole, so that a particularly reliable comparison with A the limit values to be observed is made possible.

5 e With regard to the transport and / or storage container, the stated task

7 solved by in the interior of a number of first compartments for receiving fuel elements of a nuclear reactor and a number of second compartments

9 Inclusion of built-in parts of the nuclear facility 0 that require disposal are provided. 1 2 The dimensions of the second compartments can be adapted approximately to the 3 built-in parts to be disposed of. Alternatively, however, disposal of the built-in parts in a reduced state, for example dismantled 5 or dismantled, is also possible. This applies in particular to comparatively long built-in parts, such as measuring lances or control rods, which are comparatively bulky due to their shape. 8 9 For a reliable transport of the fuel elements, in which the risk of slipping and subsequent destabilization is kept particularly low, the dimensions of the first compartments are advantageously adapted to the cross-sectional dimensions of a fuel element.

In a further advantageous embodiment, the interior of the transport and / or storage container is surrounded by a radiation protection cover. In a further advantageous embodiment, the first and the second compartments are each formed by internals.

To ensure particularly high safety standards, the internals and / or the radiation protection cover are provided with an absorber material in a particularly advantageous embodiment. The nature and quantity of the absorber material can in particular be such that the absorption of thermal neutrons is so high that even a transport container that only contains fuel elements with fresh contains fuel and has run full of water due to special circumstances, has a reactivity that is well below the criticality limit. A suitable absorber material is, for example, hafnium, which can be used as an alloy component of a metallic material or directly as a metallic material. Likewise, boron, for example as an alloy component of boron steel, or a compound of boron, for example boron carbide, can be provided.

In order to avoid undesired heating of the container interior, for example due to the post-decay heat of the fuel elements carried there, the transport and / or storage container is advantageously designed for the reliable removal of a comparatively large heat flow from its interior into the radiation protection cover. For this purpose, the internals expediently have an enveloping wall which is in flat contact with the radiation protection envelope.

The advantages achieved by the invention are, in particular, that the combined and combined movement of preferably spent fuel elements and comparatively highly active built-in components of the nuclear plant into a common transport and / or storage container specially designed for this purpose provides reliable and flexible treatment the built-in parts is made possible with comparatively little effort. The combination of fuel assemblies and built-in components when disposing of them means that existing capacity can be used in a particularly favorable way while strictly observing safety-related limit values.

An embodiment is explained in more detail with reference to a drawing. It shows:

1 schematically shows a transport and / or storage container,

2 schematically shows an end region of a fuel assembly in side views, and Fig. 3 shows schematically a fuel assembly in supervision.

Identical parts are provided with the same reference symbols in all figures.

The transport and / or storage container 1 according to FIG. 1 is provided for receiving nuclear waste from a nuclear facility. The transport and / or storage container 1 loaded with nuclear waste can be used for transporting the waste, for example for moving the waste from its place of origin into an intermediate storage or final storage location or for moving the waste from the intermediate storage location to the final storage location Come into play. Alternatively or additionally, the transport and / or storage container 1 can also be used for the storage of the waste contained in it, for example as a container formed in this way.

The transport and / or storage container 1 has an inner space 4 surrounded by a radiation protection sheath 2. The radiation protection cover 2 is the usual radiation protection cover of a Castor container or a similar transport container, as is already provided for the transport and intermediate storage of spent fuel elements. The radiation protection cover 2 has bores in a manner not shown in its outer edge region, into which an effective moderator for fast neutrons is inserted. In the exemplary embodiment, polyethylene is provided as a moderator; however, another suitable moderator can also be used. The moderator-filled cavities provided in the radiation protection cover 2 convert a large part of the neutrons emitted by the waste located in the transport and / or storage container 1 into thermal neutrons, which are subsequently absorbed in the material of the radiation protection cover 2. To further improve radiation protection, an absorber for fast neutrons can also be used in the radiation protection sheath 2.

A number of structurally interconnected inner walls 6 are arranged in the interior 4 of the transport and / or storage container 1, which together form internals 8 of the transport and / or storage container 1. The internals 8 i are with regard to the

2 and / or storage container 1 to the expected mechanical loads

3 sioned. Furthermore, the internals 8 are special to ensure

4 high safety standards also provided with an absorber material. In the exemplary embodiment, drilling steel is provided, but it can also be different

6 suitable absorber material such as hafnium or boron carbide for

7 sets come.

8th

9 The internals 8 have an envelope wall 10 which is common to them and which directly surrounds the interior 4 and which is in direct, surface contact with the radiation protection cover 2 on its outside. This arrangement ensures that a comparatively large heat flow can be maintained in the 3 radiation protection cover 2 via the cover wall 10; This ensures reliable dissipation of heat generated in the interior 4, for example in the manner of post-decay heat, into the radiation protection cover 2 and from there into the environment. An undesirable and relatively high heating of the interior 4 is thus avoided.

The internals 8 form in the interior 4 of the transport and / or storage container 1 a type of scaffold for receiving the nuclear waste to be treated or disposed of. The transport and / or storage container 1 is designed for a common or combined treatment of, preferably burned, fuel elements from a nuclear reactor and from built-in components of a nuclear plant, in particular a nuclear reactor, which require disposal. According to this design, the internals 8 form a number of first compartments 12 and a number of second compartments 14 shown hatched in the exemplary embodiment. Each first compartment 12 is in each case provided for receiving a fuel element from a nuclear reactor and accordingly with regard to - Dimensioned to match the cross-sectional dimensions of a fuel assembly. The dimensions of the first compartments 12 are matched as precisely as possible to the external dimensions of the fuel assemblies, so that to a certain extent spatial fixation within the interior 4 is ensured for the fuel assemblies installed in the first compartments 12. 1

2 The second compartments 14 are for holding built-in components

3 len of the nuclear facility. In terms of their dimensions

4 dimension the second subjects 14 such that taking into account a

5 necessary or deemed favorable wall thickness for the inner walls 6, e as far as possible or complete utilization of the interior 4 is made possible. Accordingly, the second compartments 14 can have comparatively irregular cross sections.

9

10 The transport and / or storage container 1 is for use in treatment

11 provided by nuclear waste from a nuclear facility. At this

Treatment can be, for example, in advance or when initiating a

13 Disposal, transport or also storage of the waste. It is provided that the transport and / or storage container 1 in the manner

15 a combined or joint loading both with fuel elements from a nuclear reactor in the first compartments 12 and with disposal requirements

17 parts from the nuclear plant in the second compartments 14

18 loaded. The built-in parts requiring disposal are

19 special around so-called highly activated components with an activity of about

20 more than 10 ¹² Bq / m ³ . In the exemplary embodiment, the treatment of control rods, measuring lances, throttle bodies, sample holders, poisoning plates 2 and / or primary or secondary neutron sources is provided as built-in components which require disposal. These can be brought into the transport and / or storage container 1 in their form after their decommissioning, that is to say unchanged, or also in a disassembled or comminuted state. 6 7 When loading the transport and / or storage container 1, the β intended loading, i.e. the intended combination of fuel elements 9 and built-in components requiring disposal, is first specified, with corresponding characteristic values characterizing the 0 respective radiation intensities and any heat output that may be emitted be determined. These characteristic values 2 are then used in the manner of a simulation calculation for the proposed overall arrangement of fuel elements and built-in parts requiring disposal, ie taking into account the intended spatial arrangement in the transport and / or storage container 1, the total radiation and / or heat exposure emitted is determined integrally. On the basis of the knowledge gained in the process, it is determined whether the threshold values identified as safety-relevant will surely remain below. If it is recognized, the loading of the transport and / or storage container 1 is released in the intended manner. If, however, it is not certain that the specified limit values are not undershot, the intended loading of the transport and / or storage container 1 is modified accordingly.

After the approved loading has been released, the transport and / or storage container 1 is loaded with the correspondingly provided waste products. The fuel elements provided are placed in the first compartments 12 selected for this purpose, and due to the correspondingly adapted dimensions of the first compartments 12 they are also at least approximately spatially fixed. Furthermore, the built-in parts requiring disposal are placed in the transport and / or storage container 1. Basically and primarily, loading of the second compartments 14 provided for receiving the built-in parts requiring disposal is provided. As an alternative or in addition, however, it is also possible to provide installation parts which are to be disposed of in a position in the immediate vicinity of one of the fuel elements, as is shown schematically in FIGS.

FIG. 2 shows the top end piece of a fuel assembly 20 in a side view. The fuel assembly 20 has a so-called fuel assembly head 22, in which, for example, manipulator connections and also mechanical reinforcement elements and handling elements are arranged. Accordingly, the fuel assembly head 22 has a number of cavities 24. Depending on the type of built-in parts requiring disposal, these cavities 24 can also be loaded or filled with appropriate waste, with the analysis of the resulting radiation properties naturally taking place beforehand. 1 Likewise, 20 cavities present in the actual fuel assembly can

2 Inclusion of built-in parts requiring disposal. Beispiels-

3, the fuel element 20, as can be seen in the top view in FIG.

4 number of control rod guide tubes 26. Especially in the case of possibly necessary disposal of control rods or measuring lances, which by their nature have an elongated shape, the movement into a control rod guide tube 26 of the fuel element 20 is provided. In this case, a control rod to be disposed of is first introduced,

9, for example, into a control rod guide tube 26 of the fuel assembly 20. Then the fuel assembly 20 with the control rod that needs to be disposed of therein is moved into the associated first compartment 12 of the transport 2 and / or storage container 1.

LIST OF REFERENCE NUMBERS

1 transport and / or storage container

2 radiation protection cover

4 interior

6 inner wall

8 internals

10 envelope wall

12, 14 compartments 0 fuel assembly 2 fuel assembly head 4 cavity 6 control rod guide tube

Claims

e claims

7 β 1. Process for the treatment of nuclear waste from a nuclear

9 plant in which a number of fuel elements (20) of a nuclear reactor

10 together with a number of installation parts of the

11 nuclear plant in a common transport and / or storage

12 containers (1) is spent.

13

14 2. The method according to claim 1, in which as built-in parts requiring disposal

15 highly activated components, in particular neutron sources, control rods,

16 measuring lances, throttle bodies, sample holders and / or poisoning plates, pre-

17 are seen.

18

19 3. The method of claim 1 or 2, wherein the compilation of the

20 movement into the common transport and / or storage container (1)

21 provided fuel elements (29) and components requiring disposal in

22 With regard to a number of specifiable limit values based on a cumulative

23 Analysis of the fuel assemblies (20) and the construction

24 parts characterizing characteristic values is made.

25

26 4. Transport and / or storage container (1) for nuclear waste from a nuclear

27 technical system, in the interior (4) of which a number of first

Eβ ehern (12) for receiving fuel elements (20) of a nuclear reactor and

29 a number of second compartments (14) for receiving waste disposal

30 poor installation parts of the nuclear facility are provided.

1 5. Transport and / or storage container (1) according to claim 4, wherein the first

2 compartments (12) each dimensioned to the cross-sectional dimensions

3 solutions of a fuel assembly (20) are adapted.

4

6. Transport and / or storage container (1) according to claim 4 or 5, the in-

7 interior (4) is surrounded by a radiation protection cover (2).

8th

9 7. Transport and / or storage container (1) according to one of claims 4 to 6, o in which the first and the second compartments (12, 14) are each formed by internals 1 (8).

8. Transport and / or storage container (1) according to claim 7, the internals (8) of which comprise an absorber material.

9. Transport and / or storage container (1) according to claim 6 and according to claim 7 7 or 8, the internals (8) of which have an envelope wall (10) which is in contact with the radiation protective cover (2). 9