JP4621581B2 - Cask resin and filling method thereof - Google Patents

Description

  The present invention relates to a resin for cask related to the composition of a resin used for a cask for transporting or storing spent nuclear fuel and a filling method thereof.

  Generally, in order to transport or store a spent nuclear fuel body from a nuclear power plant to a reprocessing plant, a transport container (hereinafter referred to as a cask) for transportation, storage, or transportation / storage is used.

  This cask is comprised from the cask main body which accommodates a spent nuclear fuel body. An outer cylinder is provided outside the cask body.

  The space surrounded by the cask main body and the outer cylinder, the inside of the secondary lid on the upper part of the cask main body, the inside of the bottom plate of the cask main body, the inside of the trunnion as a suspension, etc. are each filled with resin. . This resin functions as a neutron shielding body that shields neutron beams from the spent nuclear fuel body housed in the cask body.

  When filling this resin in each part of the cask, conventionally, a batch type mixer that stirs a resin with a filler such as the resin main agent, curing agent, neutron absorber and flame retardant, and stirs with a stir bar. Was used. The mixed liquid stirred by the batch mixer was immediately filled in the cask.

However, in this resin filling method, the filling amount to be mixed at one time is limited to an amount that can be injected in a limited time until the viscosity of the mixed solution is maintained. In order to inject a predetermined amount of resin into the above cask, it was necessary to repeat the work of preparing a mixed solution and then immediately filling it. In order to improve the above-described resin filling operation, a technical example is known in which the resin mixture is cooled to reduce the reaction rate, and the curing time is delayed to fill the resin as long as possible at once ( For example, see Patent Document 1).
JP 2001-116885 A

  In the above-described conventional cask, a resin or the like is filled in a space surrounded by the cask main body and the outer cylinder in order to shield neutron beams from the spent nuclear fuel body accommodated in the cask main body.

  However, since the amount of the liquid mixture to be produced at a time is limited by the curing time of the resin, the number of times of producing the liquid mixture increases and the filling operation is delayed each time. Therefore, it is necessary to fill all the resins. There was a problem that the time was long.

  In addition, when measures are taken to delay the resin curing time by cooling, the resin curing time after resin injection becomes longer and the production efficiency decreases, the viscosity of the resin increases by cooling, making it difficult to inject, Furthermore, there was a problem that an auxiliary device such as a cooling device was required.

  Also, as a cask resin, the viscosity after mixing is low and easy to inject, and it takes a long time to reach a viscosity at which injection is impossible. Is desired to be cured. In addition, since energy is absorbed and the speed is reduced by collision with a hydrogen element having almost the same mass as a neutron beam, there is a problem that increasing the hydrogen density of the resin is more useful as a cask resin. .

  Furthermore, regarding the injection method, there is a problem that the injection time can be further shortened by continuously mixing and injecting instead of the batch method.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a cask resin capable of continuously filling the resin into the cask and greatly reducing the work time of the resin filling, and a filling method thereof. .

In order to achieve the above object, in the resin for cask of the present invention, a main agent composed of an epoxy resin, a curing agent composed of polyoxypropylenediamine and curing the main agent, and mixed in the main agent absorb neutrons. a neutron absorber, have a, a flame retardant which flame retardant is mixed into the base resin, the base resin, first liquid produced by mixing the neutron absorber and a flame retardant, wherein the curing agent, the neutron absorption And a second liquid produced by mixing the agent and the flame retardant .

  In order to achieve the above object, in the cask resin filling method of the present invention, the first liquid is prepared by mixing the main component composed of epoxy resin, the neutron absorber that absorbs neutrons, and the flame retardant that makes flame retardant. And a second liquid generating step of mixing the curing agent composed of polyoxypropylenediamine and curing the main agent, the neutron absorber and the flame retardant to generate a second liquid. And a filling step of continuously filling the cask while mixing the first liquid and the second liquid.

  According to the cask resin and the filling method of the present invention, by using a curing agent composed of polyoxypropylene diamine, the cask resin is continuously filled in the cask and the working time for resin filling is greatly increased. It can be shortened.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a cask resin and a filling method thereof according to the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

  FIG. 1 is a longitudinal sectional view showing a configuration of a transportation / storage cask according to an embodiment of the present invention, and FIG. 2 is a transverse sectional view of the transportation / storage cask of FIG. It is. As an example of a cask filled with a resin for cask, a transport container also serving as a transport storage will be described.

  As shown in the figure, the cask is composed of a vertical cylindrical cask body 1 that houses a spent nuclear fuel body 6. A bottom plate 14 is provided at the bottom of the cask body 1 and integrated. A primary lid 2 for sealing the upper opening end of the cask main body 1 and a secondary lid 3 are detachably attached to the upper portion of the primary lid 2. A lid metal seal 4 is detachably attached to the lower surfaces of the primary lid 2 and the secondary lid 3 in order to ensure sealing performance with the cask main body 1.

  A lattice-like basket 7 is inserted into the cask main body 1. The spent nuclear fuel body 6 is accommodated in the lattice-like space of the basket 7. A plurality of heat transfer fins 13 for removing the decay heat of the spent nuclear fuel body 6 to the outside are provided on the outer peripheral portion of the cask body 1. Further, an outer cylinder 8 is provided so as to cover the outer periphery of the heat transfer fin 13. A plurality of trunnions 5 for handling the cask are attached to the outer periphery of the cask body 1.

  A space surrounded by the cask main body 1 and the outer cylinder 8 is filled with a resin 9. Similarly, the resin 10 is filled in the secondary lid 3 at the top of the cask body, and the resin 11 is filled in the bottom plate 14 of the cask body. Further, the resin 12 is also filled in the trunnion 5 which is a hanging tool. The resins 9 to 12 function as neutron shields that shield neutron beams from the spent nuclear fuel body 6 housed in the cask main body 1.

  As described above, the resins 9 to 12 used for the purpose of shielding the neutron beam radiated from the spent nuclear fuel body 6 to the outside of the cask below the allowable limit are the spaces between the cask main body 1 and the outer cylinder 8. The inside of the bottom plate 14 of the cask main body 1, the inside of the secondary lid 3, and the inside of the trunnion 5 are filled.

  Here, the characteristics of the above-mentioned resin for cask will be described. The above cask resin has a low viscosity after mixing, is easy to inject, has a long time until it becomes impossible to inject, and has a characteristic that it cures in dozens of hours (for example, day and night) after injection. If desired, a higher hydrogen density is more effective. As a result of intensive studies on a cask resin having this characteristic, it has been found that when a polyoxypropylene diamine is used as a curing agent, a cask resin satisfying the above requirements can be obtained.

The above-mentioned polyoxypropylenediamine is liquid at room temperature, has a viscosity as low as 10 to 20 mPa · s, and has a larger amount of addition to the epoxy resin than other amines, so that the viscosity of the mixture can be lowered. Moreover, the mixture of an epoxy resin and polyoxypropylene diamine can obtain the time which can be inject | poured for several hours at room temperature, and can harden | cure in ten and several hours. In addition, since polyoxypropylene diamine contains a large number of hydrogens in the main chain composed of carbon atoms, a cured product of the epoxy resin and this curing agent can obtain a high hydrogen density.
For example, when about 30-50 g of the above polyoxypropylenediamine is added to 100 g of bisphenol A type epoxy resin (viscosity 12500 mPa · s at room temperature, epoxy equivalent 188), the viscosity of the mixture at room temperature is 600 mPa · s. Can be about.

  According to this embodiment, this mixture has a flowability that can be poured for 3 to 4 hours at room temperature, but can be cured to a degree of sufficient hardness in about one day.

  In addition, the cask resin according to another embodiment of the present invention includes two types of liquids: a liquid in which a main agent, a neutron absorber and a flame retardant are mixed, and a liquid in which a curing agent, a neutron absorber and a flame retardant are mixed. It is characterized by preparing in advance.

  According to the present embodiment, a neutron absorber and a flame retardant are mixed in advance with each of the main agent and the curing agent, and these two liquids are mixed when used, so that it is conventionally performed. It becomes possible to obtain a resin that can be injected in a shorter time than a method in which all materials are mixed at once from the beginning.

  In addition, the resin for cask of still another embodiment of the present invention has a molecular main chain length of polyoxypropylenediamine having a molecular structure represented by the following structural formula (1) as a curing agent. A polyoxypropylene diamine having x value of 2 to 7 is used.

NH ₂ —CH (CH ₃ ) —CH ₂ — [— 0CH ₂ —CH (CH ₃ ) —] x—NH ₂
(1)
This polyoxypropylenediamine has different reactivity depending on the length of the main chain. When this main chain is shortened (x in the above structural formula is small), the reactivity is large, and the time for maintaining the castable viscosity and the curing time are shortened. On the other hand, when this main chain becomes long (x in the above structural formula becomes large), the reactivity becomes small, and the time for maintaining the castable viscosity and the curing time become long. As described above, it is necessary to optimize the reactivity of the cask resin as described above so that it takes a long time to reach a viscosity at which injection is impossible, and cures after dozens of hours (for example, all day and night). There is.

  According to the embodiment, as a result of various studies, when a polyoxypropylene diamine having a value of x in the above structural formula of 2 to 7 is used, the time until the viscosity becomes impossible to be injected is long. After the injection, a cask resin that can be cured in several tens of hours (for example, one day and night) can be obtained.

  A cask resin according to still another embodiment of the present invention uses at least one selected from boron carbide and boron nitride to absorb neutrons decelerated by hydrogen atoms. .

  According to this embodiment, boron carbide has a structure in which 4 atoms of boron are bonded to 1 atom of carbon, so that a large number of boron atoms can be introduced into the resin in a small amount. Thus, a resin having a high neutron absorption capability can be obtained. Boron nitride has a thermal conductivity of 25 to 34 W / (m · K), which is as high as that of alumina, so filling it increases the thermal conductivity of the cask resin, and the heat generated in the resin by neutron shielding. Can be efficiently diffused. Further, by using boron carbide and boron nitride in combination, a cask resin having high neutron absorption capability and high thermal conductivity can be obtained.

  Further, the resin for cask according to still another embodiment of the present invention is characterized in that two kinds of inorganic substances having different average particle diameters are filled as a flame retardant. When an inorganic substance is filled as a flame retardant, a resin having a good flowability can be obtained even if the amount of the filler is increased by filling a large particle size. However, since the inorganic substance with a large particle size becomes heavy for each particle, it tends to settle in the resin. On the other hand, when an inorganic substance having a small particle size is filled, it becomes difficult to settle, but the viscosity of the resin becomes high, and it becomes difficult to fill an amount necessary for obtaining sufficient flame retardancy.

  According to the present embodiment, in consideration of both characteristics of the above-mentioned particles, by using particles having different average particle sizes in combination, the flowability is improved and the cask resin in which the inorganic substance is difficult to settle is obtained. Obtainable.

  Further, a resin for cask according to still another embodiment of the present invention is characterized by using aluminum hydroxide as the flame retardant. Hydroxide minerals are suitable as the flame retardant used in the cask resin. It is preferable to fill aluminum hydroxide that contains three OH groups composed of oxygen and hydrogen per atom of aluminum and decomposes at 200 to 250 ° C. to generate moisture. Magnesium hydroxide has similar characteristics, but magnesium hydroxide contains only two OH groups per one atom of magnesium, and the decomposition temperature for generating moisture is close to 350 ° C.

  According to the present embodiment, it is desirable to use aluminum hydroxide in order to obtain sufficient flame retardancy. In the case of magnesium hydroxide, it is necessary to add a large amount in order to obtain sufficient flame retardancy, because the viscosity of the resin when casting is increased and the cured product becomes heavy.

  Further, the resin for cask according to still another embodiment of the present invention is characterized in that two types of aluminum hydroxide having an average particle diameter of 1 to 5 μm and 10 to 40 μm are used as a flame retardant. . As a result of evaluating the sedimentation and viscosity by changing the average particle size and amount of the hydroxide hydroxide which is a flame retardant and filling the resin, the average particle size is 1 to 5 μm and 10 to 40 μm combined. The present inventors have found that the filled aluminum hydroxide does not settle while having a castable viscosity.

  FIG. 3 shows a table in which sedimentation properties and viscosities when polyoxypropylene diamine according to an embodiment of the present invention is filled with aluminum hydroxide are evaluated.

  As shown in this figure, for example, polyoxypropylene diamine having a low viscosity and in which inorganic substances are likely to settle was filled with aluminum hydroxide by changing the average particle size and amount, and the sedimentation property and viscosity were evaluated. As a result, as shown in Formulation Example 3, when the average particle size of 85 μm was filled, the viscosity was sufficiently low, but the filler settled within a few minutes. In addition, as shown in Formulation Example 2, when a material having an average particle diameter of 30 μm was filled, the filler settled. On the other hand, as shown in Formulation Example 1, when the average particle diameter is 1 μm, the viscosity increases with a small amount, and it is difficult to add a sufficient amount to the curing agent. However, as shown in Formulation Example 4, by using a combination of an average particle size of 1 μm and 30 μm, a sufficient amount of curing agent could be added and a filler that did not settle could be obtained. .

  In practice, aluminum hydroxide having an average particle diameter of 1 μm is desirably practically having an average particle diameter of 1 to 5 μm. Further, practically, aluminum hydroxide having an average particle diameter of 30 μm is desirably one having an average particle diameter of 10 to 40 μm.

  According to the present embodiment, when a composite of alumina hydroxide having an average particle diameter of 1 to 5 μm and 10 to 40 μm is used as a flame retardant, the filled aluminum hydroxide has a viscosity capable of being cast. A cask resin that does not settle can be obtained.

  The cask resin filling method of the present embodiment is a first method in which a main liquid composed of an epoxy resin, a neutron absorber that absorbs neutrons, and a flame retardant that flame retardants are mixed to generate a first liquid. The liquid production step consists of: Moreover, it is comprised from the 2nd liquid production | generation step which mixes the hardening | curing agent comprised from polyoxypropylene diamine and hardens the said main ingredient, the said neutron absorber, and a flame retardant, and produces | generates a 2nd liquid. Furthermore, it comprises a filling step of continuously filling the cask while mixing the first liquid and the second liquid.

  According to the present embodiment, the cask resin has a viscosity that can be transferred, but the filler does not settle, so that the prepared resin can be stored for a long period of time. A filling method can be obtained.

  Next, this embodiment will be specifically described. In this example, a liquid in which epoxy resin was previously filled with boron carbide or boron nitride and aluminum hydroxide was prepared as a stock solution used for filling the cask resin. In addition, a liquid in which polyoxypropylenediamine was filled with boron carbide or boron nitride and aluminum hydroxide was prepared. At this time, among the polyoxypropylene diamine having the molecular structure represented by the above structural formula (1), a curing agent having a value x of 2 to 7 indicating the length of the main chain of the molecule is used. To do.

  Aluminum hydroxide having an average particle size of 1 μm and 30 μm was used in combination. The filling amount and the blending ratio of the aluminum hydroxide on the epoxy resin side and the polyoxypropylene diamine side are set to such an amount that the filled aluminum hydroxide does not settle while having a castable viscosity.

  The amount of total aluminum hydroxide in the cask resin is such that the cured resin has sufficient flame retardancy. For mixing these materials, an apparatus capable of stirring under vacuum was used, and stirring and mixing were performed so as to be homogeneous while performing vacuum defoaming so that air was not mixed in the liquid.

  The epoxy resin-side liquid and the curing agent-side liquid thus produced are placed in separate tanks, and each resin is transferred to a static mixer capable of continuous mixing while maintaining a predetermined mixing ratio. The resin continuously mixed through this static mixer is filled in the cask as it is. As used herein, the static mixer means that the mixer itself has no moving parts, and the fluid is mixed only by passing through an element fixed inside the pipe. As this element, for example, a rectangular plate twisted 180 degrees in the left-right reverse direction is used.

  In the present embodiment, a cured product having sufficient hardness can be obtained by pouring the cask resin mixed in this way into the cask and leaving it at room temperature for a whole day and night.

  According to the present embodiment, the cask resin can be cured by allowing it to stand for a whole day and night while securing the time required for the filling operation by using polyoxypropylenediamine as a curing agent. . In addition, by using two types of aluminum hydroxides with different particle sizes, the filler does not settle while having a castable viscosity, so that the epoxy resin and polyoxypropylene diamine are filled with aluminum hydroxide in advance. It can be stored for a long time, and the mixing work time can be shortened.

  Further, by continuously mixing and injecting the two-liquefied cask resin into the cask, the mixing / injecting time can be further shortened, and stable workability and quality can be obtained.

  Further, the present invention is not limited to the above-described embodiments, and two-liquefied cask resin may be injected after being mixed into one liquor, and departs from the gist of the present invention. Various modifications can be made without departing from the scope.

The longitudinal cross-sectional view which shows the structure of the cask for transportation storage of embodiment of this invention. The cross-sectional view which cuts and shows the AA arrow direction of the cask for transportation storage of FIG. The table | surface which evaluated the sedimentation property and viscosity when filling the polyoxypropylene diamine of embodiment of this invention with aluminum hydroxide.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cask main body, 2 ... Primary lid, 3 ... Secondary lid, 4 ... Metal seal for lids, 5 ... Trunnion, 6 ... Used nuclear fuel body, 7 ... Basket, 8 ... Outer cylinder, 9 ... Resin, 10 ... Resin 11 ... Resin, 12 ... Resin, 13 ... Heat transfer fin, 14 ... Bottom plate.

Claims (7)

A main agent composed of an epoxy resin;
A curing agent composed of polyoxypropylenediamine and curing the main agent;
A neutron absorber mixed in the main agent and absorbing neutrons,
A flame retardant mixed in the main agent to make it flame retardant;
I have a,
A first liquid produced by mixing the main agent, neutron absorber and flame retardant;
A second liquid produced by mixing the curing agent, neutron absorber and flame retardant;
A cask resin characterized by comprising: The polyoxypropylene diamine used as the curing agent is
NH2-CH (CH3) -CH2-[-0CH2-CH (CH3)-] x-NH2
2. The cask resin according to claim 1, wherein the value x of the molecular chain satisfying the structural formula is from 2 to 7 . 3. The cask resin according to claim 1, wherein the neutron absorber is at least one selected from boron carbide and boron nitride . The resin for cask according to any one of claims 1 to 3 , wherein the flame retardant is composed of two kinds of inorganic substances having different average particle diameters . The resin for cask according to any one of claims 1 to 4 , wherein the flame retardant is composed of aluminum hydroxide . The resin for cask according to any one of claims 1 to 5 , wherein the flame retardant is composed of aluminum hydroxide having an average particle diameter of 1 to 5 µm and 10 to 40 µm . A first liquid generation step of mixing a main agent composed of an epoxy resin, a neutron absorber that absorbs neutrons, and a flame retardant that flame retardants to generate a first liquid;
  A second liquid producing step of producing a second liquid by mixing a curing agent composed of polyoxypropylenediamine and curing the main agent, the neutron absorber and the flame retardant;
  A filling step of continuously filling the cask while mixing the first liquid and the second liquid;
  A method for filling a resin for cask, characterized by comprising:

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