JP2013007697A - Uranium refining equipment and method for refining uranium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for refining uranium for reducing an amount of adsorbent to be radioactive waste to reduce facility capacity.SOLUTION: Uranium refining equipment 22 has: adsorption towers 1, 3, 5 with which adsorbent is filled; and detection parts 2, 4, 6. Length of the respective adsorption layers of the respective adsorption towers in the flow direction of UFgas become shorter than length of an adsorption zone, and the sum of length of the respective adsorption layers becomes longer than the length of the adsorption zone even if any two adsorption towers of the adsorption towers 1, 3, 5 are taken. When saturation rate of the adsorbent in the adsorption layer of the adsorption tower located in the uppermost stream reaches the set saturation rate, supply of UFgas to the adsorption tower is stopped to replace the adsorbent in the adsorption tower. Then, other adsorption tower located just downstream of the adsorbent whose saturation rate of the adsorbent reaches the set saturation rate becomes the adsorption tower in the uppermost stream, and UFgas is supplied to the adsorption tower.

Description

  The present invention relates to a uranium refining apparatus and a uranium refining method, and more particularly to a uranium refining apparatus and a uranium suitable for application to facilities that handle uranium hexafluoride such as spent nuclear fuel reprocessing equipment and uranium conversion equipment. The present invention relates to a purification method.

There is a technology for converting uranium, which is a nuclear fuel material, into gaseous uranium hexafluoride (UF ₆ ) by reacting it with fluorine gas or fluoride gas. By converting uranium to UF _6, there is an advantage that uranium purification that removes impurities coexisting with UF ₆ and uranium enrichment that increases the specific isotope ratio of uranium can be performed.

A technique using uranium fluoride for reprocessing spent nuclear fuel has been developed (for example, JP 2002-257980 A). In the spent nuclear fuel generated from the nuclear power plant, much uranium and plutonium that can be reused as nuclear fuel remain. The technology described in Japanese Patent Laid-Open No. 2002-257980 is based on the fact that most of uranium contained in spent nuclear fuel is obtained by reacting spent nuclear fuel with fluorine gas in order to recover reusable uranium and plutonium from spent nuclear fuel. Is recovered as gaseous UF ₆ and the recovered uranium is concentrated again to form nuclear fuel.

On the other hand, spent nuclear fuel includes minor actinides (MA) such as plutonium and fission products (FP) produced by the nuclear reaction of uranium. When spent nuclear fuel is reacted with fluorine gas, uranium is fluorinated to produce gaseous UF ₆ and at the same time MA and FP are also fluorinated to produce their fluorine compounds. Some FP fluorine compounds become gas because of their high vapor pressure, and coexist as impurities in the UF ₆ gas.

In order to reuse the recovered UF ₆ in a nuclear reactor, it is necessary to reduce the concentration of impurities coexisting with the UF _6, and in the reprocessing of spent nuclear fuel described in JP-A No. 2002-257980, uranium refining is performed. Is done.

As a uranium purification method, there is a purification method using an adsorbent (see, for example, JP-A-2006-46967). JP 2006-46967 discloses the paragraphs 0021-0023 and FIG. 2, MgF ₂ filled _LiF-UO 2 _{F 2} trap filled with LiF and _UO 2 _{F 2} is adsorbent, the MgF ₂ is adsorbent It describes a uranium purification system in which a trap and a NaF trap filled with NaF as an adsorbent are connected in series. The UF ₆ gas generated by the fluorination treatment of the spent nuclear fuel is sequentially supplied to the LiF-UO ₂ F ₂ trap, the MgF ₂ trap and the NaF trap, and impurities contained in the UF ₆ gas are adsorbed in each trap. To be removed by adsorption. In the LiF-UO ₂ F ₂ trap, LiF adsorbs PuF ₆ and CsF, and UO ₂ F ₂ adsorbs PuF ₆ . In the MgF ₂ trap, MgF ₂ adsorbs NbF ₆ , MoF ₆ , TcF ₆ , RuF ₅ , SbF ₅ , and NpF ₆ . In the NaF trap, NaF removes RuF ₅ and NbF ₆ .

  In an adsorption tower that forms an adsorption layer filled with an adsorbent and removes impurities contained in the gas to be treated, the adsorption equilibrium is reached when the gas to be treated is supplied to the adsorption layer from the upstream end of the adsorption layer. Thus, a saturated region where no further impurities can be adsorbed is formed at the upstream end of the adsorption layer. When the gas to be treated is continuously supplied to the adsorption layer, the saturated region moves from the upstream end of the adsorption layer toward the downstream end of the adsorption layer. Eventually, the gas to be treated containing impurities that have not been adsorbed by the adsorption layer is discharged from the downstream end of the adsorption layer. When the gas to be treated containing impurities is exhausted from the adsorption layer, the adsorption layer reaches its end of life, and the adsorbent in the adsorption layer is replaced with a new adsorbent. As for the adsorbent present in the adsorption layer in the adsorption tower, it is desirable to use up 100% of the adsorbent in the adsorption layer, and it is desirable to reduce the amount of adsorbent to be discarded. Actually, when the gas to be treated containing impurities is exhausted from the adsorption layer, the adsorbent capable of adsorbing impurities still remains at the downstream end of the adsorption layer, and the adsorbent in the adsorption layer is replaced. Sometimes, the adsorbent that can adsorb the impurities along with the adsorbent that has reached the end of its life becomes waste and is replaced with a new adsorbent.

  Japanese Patent Application Laid-Open No. 2010-214285 discloses a gas treatment method that can reduce the amount of adsorbent that becomes waste and reduce the frequency of replacement of the adsorbent. In this gas treatment method, an adsorption device in which a plurality of adsorption layers filled with an adsorbent are arranged in series in the flow direction of the gas to be treated is used. Then, an adsorption band length that can reduce the impurity concentration contained in the gas to be treated to a predetermined value based on the gas properties and the adsorption operation conditions is obtained, and the thickness of the adsorption layer in the flow direction of the gas to be treated is determined by The adsorption band length is set. When the gas to be treated containing impurities to be removed is supplied to such an adsorption device, and the impurity concentration of the gas discharged from the adsorption layer at the most downstream stage exceeds a predetermined value, the adsorption at the most downstream stage is performed. The layer is transferred to the most upstream stage, and the adsorbent of the adsorption layer other than the adsorption layer of the most upstream stage after the transfer is replaced with a new adsorbent.

JP 2002-257980 A JP 2006-46967 A JP 2010-214285 A

For uranium purification, which selectively removes impurities (for example, FP fluoride gas) contained in UF ₆ generated by the fluorination treatment of spent nuclear fuel by selectively adsorbing them with an adsorbent packed in the adsorption layer, there are two main types. There are challenges.

The first problem is to reduce the amount of adsorbent that becomes radioactive waste. When the UF ₆ containing impurities is exhausted from the adsorption layer, all adsorbents filled in the adsorption layer are replaced with new adsorbents and then treated as radioactive waste. In the adsorption layer from which the UF ₆ containing impurities is exhausted, there is also an adsorbent that can adsorb impurities at the downstream end of the adsorption layer, together with the adsorbent that has adsorbed most of the impurities. When replacing the adsorbent in the adsorption layer with a new adsorbent, it is impossible to separate the adsorbent that has adsorbed impurities and the adsorbent that has not adsorbed impurities in the adsorption layer. The material is treated as radioactive waste. For this reason, in the adsorption layer from which the UF ₆ containing impurities is exhausted, it is desired to increase the number of adsorbents that have adsorbed impurities and reduce the amount of adsorbents that have not adsorbed impurities. Thereby, the quantity of the adsorbent used as radioactive waste can be reduced.

A second problem is to reduce the capacity of the uranium purification facility including the adsorption tower, that is, to reduce the size of the uranium purification facility. In uranium purification, uranium purification needs to be performed in a hot cell because of handling UF ₆ which is a radioactive substance. For this reason, it is required to reduce the capacity of the uranium refining equipment.

In the gas processing method described in Japanese Patent Application Laid-Open No. 2010-214285, the thickness of the adsorption layer in the flow direction of the gas to be treated is set to the length of the adsorption band, and the gas is discharged from the adsorption layer at the most downstream stage. When the gas impurity concentration exceeds a predetermined value, the adsorption layer in the most downstream stage is moved to the most upstream stage, and the adsorbent of the adsorption layer other than the adsorption layer in the most upstream stage after the transfer is replaced with a new adsorption material. We are exchanging. For this reason, the adsorbent discarded from the adsorbent layer in which the adsorbent is replaced other than the adsorbed layer at the uppermost stream after the transfer does not include an adsorbent that can adsorb impurities. With the gas treatment method described in JP 2010-214285 A, it is possible to reduce the amount of adsorbent that is generated as a radioactive waste when UF ₆ is purified.

However, the inventors have found a new finding that the adsorption band length of the adsorption layer needs to be increased in the purification of uranium by the investigation of the inventors. For this reason, when the gas treatment method described in JP 2010-214285 A is applied to the purification of uranium, the adsorption zone length in the flow direction of UF ₆ of the adsorption layer in the adsorption tower becomes long, Uranium refining facilities will be larger. That is, the capacity of the uranium purification facility cannot be reduced.

  An object of the present invention is to provide a uranium refining apparatus and a uranium refining method that can reduce the amount of adsorbent that becomes radioactive waste and can reduce the equipment capacity.

  A feature of the present invention that achieves the above-described object is that it has an adsorption layer filled with the same kind of adsorbent, and includes a plurality of adsorption towers connected in series, and the adsorption layers of each adsorption tower are supplied. The length in the flow direction of the uranium gas is shorter than the length of the adsorption zone, and the sum of the lengths of the respective adsorption layers of the two adsorption towers in any two adsorption towers of the plurality of adsorption towers. However, the length is longer than the length of the adsorption band.

  The length of each adsorption layer of the plurality of adsorption towers connected in series in the flow direction of the supplied uranium gas is shorter than the length of the adsorption zone, and any two adsorption towers among the plurality of adsorption towers In this case, the sum of the lengths of the adsorption layers of the two adsorption towers is longer than the length of the adsorption zone, so that the impurities contained in the supplied uranium gas are in the most upstream of the adsorption tower. Because the adsorption layer can adsorb to the adsorbent, and the length of the adsorption layer is shorter than the length of the adsorption band, and the adsorption layer of another adsorption tower exists downstream of this adsorption layer, this Impurities can be adsorbed by the adsorbent in the adsorption tower located in the uppermost stream until most of the adsorbent in the adsorption layer of the adsorption tower located upstream is saturated with the adsorbed impurities. For this reason, the adsorbent in an adsorption tower can be used effectively, and the quantity of the adsorbent used as a radioactive waste can be reduced.

  Further, the above object is that the length of the adsorption layer of each adsorption tower in the flow direction of the supplied uranium gas is shorter than the length of the adsorption zone, so that the equipment capacity of the uranium refining device can be reduced. it can.

The above-mentioned purpose has an adsorption layer filled with the same kind of adsorbent, and includes a plurality of adsorption towers connected in series, and the adsorption layer of each adsorption tower is long in the flow direction of the supplied uranium gas. Is shorter than the length of the adsorption zone, and in any two of these adsorption towers, the sum of the lengths of the respective adsorption layers of the two adsorption towers is the length of the adsorption zone. A uranium purification method for purifying uranium gas using a uranium purification apparatus that is longer than the above,
Sequentially supply uranium gas from the adsorption tower located at the uppermost stream, detect the saturation rate of the adsorbent in the adsorption layer of the adsorption tower located at the uppermost stream, and when the detected saturation ratio exceeds the set saturation ratio, This can also be achieved by stopping the supply of uranium gas to the adsorption tower located upstream and supplying the uranium gas to another adsorption tower located downstream of the adsorption tower where the supply of uranium gas is stopped.

Further, the above object is to provide an adsorption layer filled with the same kind of adsorbent material, comprising a plurality of adsorption towers connected in series, and the flow direction of the supplied uranium gas in each adsorption tower The length in the adsorption zone is shorter than the length of the adsorption zone, and in any two adsorption towers of these adsorption towers, the sum of the lengths of the respective adsorption layers of the two adsorption towers is the adsorption zone. A uranium purification method that purifies uranium gas using a uranium purification device that is longer than the length of
The uranium gas was sequentially supplied from the adsorption tower located in the uppermost stream, and the saturation rate of the adsorbent in the adsorption layer of the adsorption tower located in the uppermost stream was detected, and the detected saturation ratio became more than the first set saturation ratio. Sometimes, it can also be achieved by purifying uranium gas by flowing uranium gas in the reverse direction in the adsorption layer of the adsorption tower located at the uppermost stream.

  ADVANTAGE OF THE INVENTION According to this invention, in the refinement | purification of uranium, the generation amount of the adsorbent used as a radioactive waste can be reduced and an installation capacity can be made small.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the uranium refinement | purification apparatus applied to the uranium purification method of Example 1 which is one preferable Example of this invention. Is an explanatory view showing an adsorption isotherm in the adsorption of MoF ₆ to MgF _2. It is a characteristic view which shows the position dependency of the saturation rate of the adsorbent in an adsorption tower. It is a block diagram of the uranium refinement | purification apparatus applied to the uranium purification method of Example 2 which is another Example of this invention. It is a block diagram of the uranium refinement | purification apparatus applied to the uranium purification method of Example 3 which is another Example of this invention.

  The inventors conducted various studies on the purification of uranium using an adsorbent. The examination results are described below.

By circulating UF ₆ gas through an adsorption layer provided in the adsorption tower and filled with adsorbents (for example, sodium fluoride (NaF), magnesium fluoride (MgF ₂ ), barium fluoride (BaF ₂ )) FP fluoride gas (for example, ruthenium fluoride (RuF ₅ ), niobium fluoride (NbF ₅ ), and molybdenum fluoride (MoF ₆ )), which is an impurity contained in the UF ₆ gas, is selectively applied to the adsorption layer. It can be adsorbed and high purity UF ₆ can be recovered. In one adsorption tower, an adsorption layer filled with only one kind of adsorbent is provided. The respective adsorption towers provided with the respective adsorption layers filled with different adsorbents are connected in series, and UF ₆ gas is circulated through the adsorption towers sequentially.

For example, MoF ₆ which is an impurity contained in UF ₆ gas has an initial partial pressure in the uranium refining of the order of about 10 ⁻¹ KPa, and is about 3 digits to the order of about 10 ⁻⁴ KPa which is the uranium refining specification. It is thought that there is a need to reduce it.

An adsorption isotherm in the adsorption of MoF ₆ onto MgF ₂ is shown in FIG. When the MoF ₆ partial pressure is between 10 ⁻⁴ kPa and 1 kPa, the saturated adsorption amount of MoF _{6 on} MgF ₂ is a substantially constant value. It can be seen that MoF ₆ is adsorbed on MgF ₂ as an adsorbent with an MoF ₆ partial pressure of the order of 10 ⁻⁴ kPa, so that the uranium purification specifications can be satisfied by the adsorption of MoF ₆ by MgF ₂ .

Further, the adsorption mechanism is considered to be monomolecular layer adsorption on the MgF ₂ surface from the value of the saturated adsorption amount. When the adsorption mechanism is monolayer adsorption, there is Langmuir's theory as an equation for explaining the adsorption isotherm, and the adsorption amount to the adsorbent is expressed by the equation (1).

Here, p is the partial pressure of adsorbed gas, the adsorption amount when the q partial pressure p, q ₀ is the saturation adsorption amount, k _a is the adsorption rate constant, k _d is elimination rate constant, K is the adsorption equilibrium constant is there. If the adsorption equilibrium constant K becomes a very large value as compared to 1, that is, when the adsorption rate constant k _a becomes a very large value as compared with the desorption rate constant k _d, the adsorption amount q from equation (1) Regardless of the partial pressure, the saturated adsorption amount q ₀ is constant. This agrees with the result that the saturated adsorption amount becomes constant in the range of the MoF ₆ partial pressure from 10 ⁻⁴ kPa to 1 kPa in the adsorption isotherm shown in FIG. Therefore, it is considered that the adsorption rate of MoF ₆ adsorption to MgF ₂ is very high, but the desorption rate is very low, or the adsorbed MoF ₆ hardly desorbs.

On the other hand, RuF ₅ and NbF ₅ which are impurities contained in the UF ₆ gas form RuNaF ₆ and NbNaF ₆ by NaF which is an adsorbent and the reactions shown in the formulas (2) and (3).

RuF ₅ + NaF → RuNaF ₆ (2)
NbF ₅ + NaF → NbNaF ₆ (3)
Since UF ₆ does not adsorb to NaF at an adsorption temperature of 673 K, RuF ₅ and NbF ₅ can be separated from UF ₆ by selectively adsorbing NaF.

  However, as will be described below, the amount of radioactive waste generated in the purification of uranium (the amount of adsorbent discarded) tends to increase.

The inventors calculated the position dependency of the saturation rate of the adsorbent in the adsorption layer when MoF ₆ was adsorbed and separated by the adsorption layer in the adsorption tower filled with MgF ₂ as the adsorbent. An example of the calculation result is shown in FIG. The position where the adsorbent position X is 0 is the upstream end of the adsorption layer (UF ₆ gas inflow end). When MoF ₆ that is an impurity contained in the UF ₆ gas flows into the adsorption layer, MoF ₆ is adsorbed by MgF ₂ existing on the upstream side of the adsorption layer, but because the adsorption rate of MoF ₆ by MgF ₂ is slow, It circulates in the adsorption layer and is adsorbed on the downstream side of the adsorption layer. For this reason, the saturation rate of the adsorbent becomes a profile that gradually decreases as the position of the adsorbent moves downstream of the adsorbent layer.

In FIG. 3, each position in the adsorption layer where the concentration of MoF ₆ is 1/10, 1/100, and 1/1000 of the concentration before adsorption is shown. As described above, it is necessary to reduce the concentration of MoF ₆ contained in the UF ₆ gas by about three orders of magnitude by purifying uranium. That is, if the adsorption layer corresponding to the position X at which the concentration of MoF ₆ is 1/1000 of the initial concentration has a length in the flow direction of the UF ₆ gas (gas to be treated), the specification of uranium purification for MoF ₆ is Can be satisfied. As described above, the length of the adsorption layer filled with the adsorbent, which is the minimum necessary for reducing the initial concentration of the gas to be adsorbed and separated to the target concentration, is referred to as the adsorption band length.

On the other hand, on the downstream side of the adsorption layer, the saturation rate of the adsorbent is almost zero (see FIG. 3). This is a phenomenon peculiar to uranium purification, and this phenomenon occurs because the adsorption rate of MoF _{6 on} MgF ₂ is slow, that is, a gas having a low partial pressure of 10 ⁻⁴ KPa handled in uranium purification. Is affected by the slow adsorption rate. When purifying uranium in one adsorption tower, before the adsorption layer in this adsorption tower breaks through (the MoF ₆ concentration at the exit of the adsorption layer exceeds 1/1000 of the MoF ₆ concentration before adsorption), the adsorption tower is The supply of the UF ₆ gas is stopped, and all the adsorbents in the adsorption layer are processed as used adsorbents. However, as shown in FIG. 3, the used adsorbent contains a large amount of adsorbent that is not saturated with FP fluoride (still adsorbent that can adsorb MoF ₆ ), and radioactive waste. As a result, the amount of adsorbent to be processed increases.

When the gas treatment method described in Japanese Patent Application Laid-Open No. 2010-214285 is applied to uranium purification, when the adsorbent in the adsorption layer is replaced, the adsorption of the FP fluoride is unsaturated. The amount can be reduced and the amount of adsorbent treated as radioactive waste can be reduced. However, the adsorption zone length in the flow direction of UF ₆ of the adsorption layer used for uranium purification needs to be long as shown in FIG. For this reason, when the gas treatment method described in JP 2010-214285 A is applied to the purification of uranium, the adsorption zone length in the flow direction of UF ₆ of the adsorption layer in the adsorption tower becomes long, The inventors have found that a new problem arises that the capacity of the uranium refining facility cannot be reduced.

  The inventors have studied various measures for solving this new problem and have come to make the present invention. That is, the inventors have made a plurality of adsorption layers filled with the same kind of adsorbent in order to achieve both reduction in the amount of adsorbent that becomes radioactive waste and reduction in the capacity of the purification equipment. Adsorption towers are connected in series, and the length of the adsorption layer of each adsorption tower in the flow direction of the supplied uranium gas is made shorter than the length of the adsorption zone, and any two adsorption towers among the plurality of adsorption towers In this case, it was concluded that the sum of the lengths of the adsorption layers of the two adsorption towers should be longer than the length of the adsorption zone.

  For example, when three adsorption towers having adsorption layers filled with the same kind of adsorption material are connected in series, when the adsorption layer of the adsorption tower located in the uppermost stream is sufficiently saturated with impurities, the remaining two What is necessary is just to achieve the target concentration of uranium purification in the adsorption tower. For this reason, the total length of the adsorption layers of the three adsorption towers in the uranium gas flow direction may be about 1.5 times the adsorption band length. As a result, the equipment capacity of the uranium refining device can be minimized. In addition, the length of the adsorption layer in the latter two adsorption towers is set to such a length that only the two adsorption towers can sufficiently purify uranium, so that the uranium gas that has passed through the adsorption tower arranged in the uppermost stream is It is sufficient to detect the impurity concentration.

  When uranium gas is allowed to flow through the adsorption towers connected in series and the adsorbent saturation rate at the adsorption tower outlet of the adsorption layer of the adsorption tower located upstream reaches a set saturation ratio (for example, 10% or more), this It is considered that the adsorption by each adsorbent in the adsorption layer in the adsorption tower is sufficiently saturated. Therefore, this adsorption tower is isolated from the flow of uranium gas, and the adsorbent in this adsorption tower is replaced with a new adsorbent.

At the time of the above examination, the inventors have reached a state where the adsorbent in the adsorption layer of the adsorption tower located at the uppermost stream is saturated with the adsorption of impurities as a measure for solving the above new problem. Then, the inventors invented a method for purifying uranium gas by flowing uranium gas in the reverse direction in the adsorption layer of the adsorption tower located at the uppermost stream. In general, the adsorption and desorption of impurities to the adsorbent occurs in the adsorption tower, and if the flow direction of uranium gas in the adsorption layer of the adsorption tower is reversed, the desorption of the adsorbed impurities dominates on the downstream side. As a result, the impurities to be adsorbed flow into the downstream adsorption tower, and the efficiency of removing impurities in the adsorption tower located upstream is deteriorated. However, if the adsorbing MoF ₆ to MgF ₂ is adsorbent, since in comparison with the adsorption rate of MoF ₆ MoF desorption rate of ₆ is very small, MoF ₆ to or adsorbed are not released little de, most upstream Even if uranium gas is allowed to flow in the reverse direction in the adsorption layer of the adsorption tower located at, the desorbed impurities hardly flow into the downstream adsorption tower.

  Further, as another countermeasure, the inventors first supplied uranium gas to a fluidized bed type adsorption tower packed with an adsorbent, and adsorbed impurities contained in the uranium gas to the adsorbent in the fluidized bed type adsorption tower. The idea was to supply the uranium gas discharged from the fluidized bed adsorption tower to the fixed bed adsorption tower filled with the adsorbent. In the fluidized bed type adsorption tower, the adsorbent is stirred inside, so that the saturation rate of the adsorbent in the fluidized bed type adsorption tower can be made uniform. By disposing the adsorbent in the fluidized bed adsorption tower when the saturation rate of the adsorbent in the fluidized bed adsorption tower becomes sufficiently high, the amount of unsaturated adsorbent to be discarded can be reduced. it can.

  Examples of the present invention reflecting the above examination results will be described below.

  A method for purifying uranium according to Example 1, which is a preferred embodiment of the present invention, will be described with reference to FIG. First, the uranium purification apparatus used in the uranium purification method of this example will be described with reference to FIG. The uranium purification apparatus 22 of this embodiment includes adsorption towers 1, 3, 5 and detection units 2, 4, 6. Valve 7, adsorption tower 1, detection section 2, valve 8, adsorption tower 3, detection section 4, valve 9, adsorption tower 5, detection section 6 and valve 10 are arranged in this order from the upstream toward the downstream 16. is set up. The pipe 17 provided with the valve 11 connected to the pipe 16 upstream from the valve 7 is connected to the pipe 16 between the valve 8 and the adsorption tower 3. The pipe 18 provided with the valve 12 and connected to the pipe 16 upstream from the valve 7 is connected to the pipe 16 between the valve 9 and the adsorption tower 5. The pipe 19 provided with the valve 13 is connected to the pipe 16 between the detection unit 2 and the valve 8, and further connected to the pipe 16 downstream from the valve 10. The pipe 20 provided with the valve 14 is connected to the pipe 16 between the detection unit 4 and the valve 9, and further connected to the pipe 16 downstream from the valve 10. The pipe 21 provided with the valve 15 is connected to the pipe 16 between the detection unit 6 and the valve 10, and further connected to the pipe 16 between the valve 7 and the adsorption tower 1.

The adsorption towers 1, 3, and 5 each have an adsorption layer filled with the same type of adsorbent (for example, MgF ₂ that adsorbs MoF ₆ which is an FP fluoride gas contained in the UF ₆ gas). The length of each adsorption layer of the adsorption towers 1, 3 and 5 in the flow direction of the gas to be treated (UF ₆ gas) is shorter than the length of the adsorption zone. In any two adsorption towers, the sum of the lengths of the respective adsorption layers is longer than the length of the adsorption zone.

The detector 2 is arranged in a pair with the adsorption tower 1 and detects FP fluoride gas (for example, MoF ₆ ) contained in the UF ₆ gas exhausted from the adsorption layer of the adsorption tower 1. The detector 4 is arranged in a pair with the adsorption tower 3 and detects FP fluoride gas (for example, MoF ₆ ) contained in the UF ₆ gas exhausted from the adsorption layer of the adsorption tower 3. The detector 6 is arranged in a pair with the adsorption tower 5 and detects FP fluoride gas (for example, MoF ₆ ) contained in the UF ₆ gas exhausted from the adsorption layer of the adsorption tower 5. A small amount of adsorbent (for example, MgF ₂ ) is enclosed in the detection units 2, 4, and 6. These detection units include a load meter (not shown) or a detection unit that measures the weight of the detection unit. A radiation detector (not shown) or both for measuring the radiation dose is provided.

The UF ₆ gas generated by the fluorination treatment of the spent nuclear fuel is supplied to the uranium refining device 22. At this time, the valves 7, 8, 9, and 10 are open, and the valves 12, 13, 14, and 15 are closed. The UF ₆ gas containing FP fluoride gas (for example, MoF ₆ ) passes through the pipe 16, and the valve 7, the adsorption tower 1, the detection section 2, the valve 8, the adsorption tower 3, the detection section 4, the valve 9, and the adsorption tower 5. The detector 6 and the valve 10 flow in this order. As a result, UF ₆ gas is purified. MoF ₆ , which is an FP fluoride gas, is adsorbed from the upstream end of the adsorbent that forms the adsorption layer in the adsorption tower 1 located most upstream among the adsorption towers 1, 3, and 5. The adsorption region of the FP fluoride gas spreads to the downstream end side of the adsorption layer with time.

  Part of the FP fluoride gas that has passed through the adsorption layer of the adsorption tower 1 is adsorbed by the adsorbent of the detection unit 2 in the detection unit 2. As a result, the weight (or radiation dose) increases in the detection unit 2 that has adsorbed the FP fluoride gas. The weight of the detector 2 is measured with a load meter (or the radiation dose of the detector 2 is measured with a radiation detector), and this measured value is input to a control device (not shown), for example. The control device calculates an increase amount of the weight of the detection unit 2 using the measured value of the weight (or calculates an increase amount of the measured value of the radiation dose), and uses the increase amount of the weight (or the radiation dose). The saturation rate of the adsorbent enclosed in the detector 2 is obtained. The control device further calculates the saturation rate of the adsorbent in the adsorption layer of the adsorption tower 1 based on the saturation rate of the adsorbent of the detection unit 2. The saturation rate of each adsorbent of the detectors 2, 4, 6 is referred to as a first saturation rate, and the saturation rate of the adsorbent in each adsorption layer of the adsorption towers 1, 3, 5 is referred to as a second saturation rate.

When the calculated second saturation rate of the adsorption tower 1 reaches the set saturation rate, the control device opens the valve 11 and closes the valves 7 and 8. The set saturation rate is a value of the saturation rate when all the adsorbents in the adsorption layer of the adsorption tower 1 have adsorbed FP fluoride gas (for example, MoF ₆ ) and are unable to adsorb the FP fluoride gas. It is. Before the second saturation rate of the adsorption tower 1 reaches the set saturation rate, the FP fluoride gas (for example, MoF ₆ ) contained in the UF ₆ gas discharged from the adsorption layer of the adsorption tower 1 is absorbed by the adsorption tower 3. Adsorbed in layers.

By such valve control, the adsorption tower 1 and the detection unit 2 are isolated from the flow of UF ₆ gas. The UF ₆ gas including MoF ₆ supplied to the uranium purification apparatus 22 flows through the pipe 17 in the order of the adsorption tower 3, the detection section 4, the adsorption tower 5 and the detection section 6 and is purified. When the supply of UF ₆ gas to the adsorption tower 1 and the detector 2 is stopped, the adsorbent in the adsorption layer of the adsorption tower 1 is replaced with a new adsorbent, and the adsorbent in the detector 2 is also a new adsorbent. To be exchanged. The adsorbent taken out from each of the adsorption tower 1 and the detection unit 2 is treated as radioactive waste.

After the replacement of the adsorbents in the adsorption tower 1 and the detection unit 2 is completed, the operator inputs information indicating that the replacement of the adsorbents is completed to the control device. Based on this input information, the control device opens the valves 15 and 13 and closes the valve 10. The UF ₆ gas supplied to the adsorption tower 3 through the pipe 17 is sequentially supplied to the detection unit 4, the adsorption tower 5 and the detection unit 6 through the pipe 16, and further passes through the pipe 21 to the adsorption tower 1 and the detection unit. Led to 2. The UF ₆ gas discharged from the detection unit 2 passes through the pipe 19 and reaches the pipe 16 downstream from the valve 10. UF ₆ gas flows in this way and is purified.

The UF ₆ gas containing the FP fluoride gas is supplied to the adsorption tower 3 located at the most upstream in such a state, and the FP fluoride gas (for example, MoF ₆ ) is supplied to the adsorbent in the adsorption layer of the adsorption tower 3. Adsorbed. When the FP fluoride gas passes through the adsorption layer of the adsorption tower 3, a part of the FP fluoride gas that has passed through the adsorption layer is adsorbed by the adsorbent of the detection unit 4 in the detection unit 4. . As in the case of the detection unit 2, the control device uses the weight of the detection unit 4 measured by the load meter (or the radiation dose of the detection unit 4 measured by the radiation detector) and the weight (or radiation dose). And the second saturation ratio of the adsorbent in the adsorption layer of the adsorption tower 3 is calculated using the calculated increase in weight (or radiation dose). When the second saturation rate reaches the set saturation rate, the control device opens the valves 12 and 13 and closes the valves 9 and 11. Before the second saturation rate of the adsorption tower 3 reaches the set saturation rate, the FP fluoride gas (for example, MoF ₆ ) contained in the UF ₆ gas discharged from the adsorption layer of the adsorption tower 3 is absorbed by the adsorption tower 5. Adsorbed in layers.

By such valve control, the adsorption tower 3 and the detection unit 4 are isolated from the flow of UF ₆ gas. The UF ₆ gas including MoF ₆ supplied to the uranium refining device 22 is supplied to the adsorption tower 5 and the detector 6 through the pipe 18, and further supplied to the adsorption tower 1 and the detector 2 through the pipe 21. And purified. The UF ₆ gas discharged from the detection unit 2 reaches the pipe 16 downstream of the valve 10 through the pipe 19.

When the supply of the UF ₆ gas to the adsorption tower 3 and the detection unit 4 is stopped, the respective adsorbents in the adsorption tower 3 and the detection unit 4 are replaced with new adsorbents. The adsorbent taken out from each of the adsorption tower 3 and the detection unit 4 is processed as radioactive waste.

After the replacement of the adsorbents in the adsorption tower 3 and the detection unit 4 is completed, the control device opens the valves 8 and 14 based on the information that the replacement of the adsorbents input by the operator is completed. The valve 13 is closed. The UF ₆ gas discharged from the detection unit 2 is supplied to the adsorption tower 3 and the detection unit 4, and further passes through the pipe 20 and reaches the pipe 16 downstream from the valve 10. UF ₆ gas flows in this way and is purified.

The UF ₆ gas containing the FP fluoride gas is supplied to the adsorption tower 5 located at the most upstream in this state, and the FP fluoride gas (for example, MoF ₆ ) is used as the adsorbent in the adsorption layer of the adsorption tower 5. Adsorbed. When the FP fluoride gas passes through the adsorption layer of the adsorption tower 5, a part of the FP fluoride gas that has passed through the adsorption layer is adsorbed by the adsorbent of the detection unit 6 in the detection unit 6. . As in the case of the detection unit 2, the control device uses the weight of the detection unit 6 measured by the load meter (or the radiation dose of the detection unit 6 measured by the radiation detector) and the weight (or radiation dose). And the second saturation ratio of the adsorbent in the adsorption layer of the adsorption tower 5 is calculated using the calculated increase in weight (or radiation dose). When the second saturation rate reaches the set saturation rate, the control device opens the valves 7 and 14 and closes the valves 9 and 15. Before the second saturation rate of the adsorption tower 5 reaches the set saturation ratio, the FP fluoride gas (for example, MoF ₆ ) contained in the UF ₆ gas discharged from the adsorption layer of the adsorption tower 5 is absorbed by the adsorption tower 1. Adsorbed in layers.

By such valve control, the adsorption tower 5 and the detection unit 6 are isolated from the flow of the UF ₆ gas. The UF ₆ gas including MoF ₆ supplied to the uranium refining device 22 is sequentially supplied to the adsorption tower 1, the detection unit 2, the adsorption tower 3, and the detection unit 4 through the pipe 16 and purified. The UF ₆ gas discharged from the detector 4 reaches the pipe 16 downstream of the valve 10 through the pipe 14.

When the supply of the UF ₆ gas to the adsorption tower 5 and the detection unit 6 is stopped, the respective adsorbents in the adsorption tower 5 and the detection unit 6 are replaced with new adsorbents. The adsorbent taken out from each of the adsorption tower 5 and the detection unit 6 is processed as radioactive waste.

After the replacement of the adsorbents in the adsorption tower 5 and the detection unit 6 is completed, the control device opens the valves 9 and 10 based on the information that the replacement of the adsorbents input by the operator is completed. The valve 14 is closed. The UF ₆ gas discharged from the detection unit 4 is supplied to the adsorption tower 5 and the detection unit 6 and purified. The UF ₆ gas discharged from the detection unit 6 flows through the pipe 16 through the valve 10. This state is the state described first.

In this embodiment, the length of each adsorption layer of the adsorption towers 1, 3 and 5 in the flow direction of the gas to be treated (UF ₆ gas) is shorter than the length of the adsorption zone. , 5, the sum of the lengths of the respective adsorption layers is longer than the length of the adsorption zone, so that one adsorption tower (for example, adsorption tower 1) located in the uppermost stream is taken. ) Even if the FP fluoride gas flows out of the adsorption layer, the FP fluoride gas is adsorbed on the adsorption layer of the adsorption tower (for example, the adsorption tower 3) disposed downstream of the adsorption tower on the downstream side. Can do. For this reason, FP fluoride gas can be adsorbed until all adsorbents in the adsorption layer of the former adsorption tower located upstream cannot adsorb FP fluoride gas (for example, MoF ₆ ). When the adsorbent is replaced with a new adsorbent, the adsorbent taken out from the adsorption tower contains almost no adsorbent in which FP fluoride gas adsorption is unsaturated. Accordingly, it is possible to reduce the amount of the adsorbent that becomes the radioactive waste discarded from the uranium refining device 22.

Furthermore, in this embodiment, the length of each adsorption layer of the adsorption towers 1, 3, and 5 in the flow direction of the gas to be treated (UF ₆ gas) is shorter than the length of the adsorption zone. It can be made shorter than the length in the flow direction of the gas to be treated of the adsorption layer of the adsorption tower used in the gas treatment method described in 2010-214285. Therefore, the volume of the uranium refining device 22 used in the present embodiment can be made smaller than the equipment capacity when the gas treatment method described in JP 2010-214285 A is applied to uranium refining.

  In this embodiment, a pipe 17 provided with a valve 11, a pipe 18 provided with a valve 12, a pipe 19 provided with a valve 13, a pipe 20 provided with a valve 14, and a pipe 21 provided with a valve 15 are shown in FIG. As shown, each pipe 16 is connected to the adsorption tower 1 and the detection section 2, the adsorption tower 3 and the detection section 4, and any pair of the adsorption tower 5 and the detection section 6 to exchange the adsorbent. Even if separated from 16, uranium can be purified by the remaining two pairs, so that the uranium purification device 22 can continuously purify uranium even when the adsorbent is exchanged.

In this embodiment, it is only necessary to detect the saturation rate of the adsorbent of the adsorption tower located at the uppermost stream in the flow direction of the UF ₆ gas, and the adsorption tower (in particular, Since the gas partial pressure to be detected is higher than when the breakthrough of the adsorption layer is detected at the outlet of the adsorption tower located on the most downstream side, the breakthrough of the adsorption layer is easily detected.

  In this embodiment, the uranium refining device 22 is configured by providing three adsorption towers and three detection units, but the exchange of adsorbents in a pair of adsorption towers and detection units is performed immediately from the adsorption tower in the subsequent stage to the FP hook. If it can be completed before the chemical gas flows out, the uranium refining device 22 may be configured by providing two adsorption towers and two detection units instead of three adsorption towers and detection units.

In the above description of the present embodiment, MoF ₆ that is an FP fluoride gas is adsorbed using MgF ₂ that is the same type of adsorbent for each of the adsorption towers 1, 3, 5 and the detectors 2, 4, ₆ . Said about removing. As described in JP 2006-46967 A, MgF ₂ can adsorb NbF ₆ , TcF ₆ , RuF ₅ , SbF ₅ , and NpF ₆ contained in UF ₆ gas in addition to MoF _6. .

In such a configuration, NbF ₆ , MoF ₆ , TcF ₆ , RuF ₅ , SbF ₅ , and NpF ₆ contained in the UF ₆ gas are adsorbed in the adsorption columns 1, 3, and 5 in the preceding stage, and the adsorption in the subsequent stage is performed. Similarly, in the towers 1, 3 and 5, PuF ₆ and CsF contained in the UF ₆ gas are adsorbed. In such uranium purification, most of the FP fluoride gas contained in the UF ₆ gas can be removed.

  The uranium purification method of Example 2 which is another example of the present invention will be described. In the uranium purification method of the present embodiment, the uranium purification apparatus 22 shown in FIG.

As shown in FIG. 3, the saturation rate of the adsorbent in the adsorption layer of the adsorption tower is lower at the downstream end of the adsorption layer than at the upstream end of the adsorption layer. For this reason, when the saturation rate of the adsorbent existing at the downstream end of the adsorption layer of the adsorption tower reaches a certain value (referred to as the second preset saturation ratio), the adsorption tower is removed from the pipe for introducing the UF ₆ gas. The UF ₆ gas inlet and outlet of the adsorption tower are reversed, that is, the UF ₆ gas inlet of the adsorption tower before removal becomes the outlet, and the UF ₆ gas outlet of the adsorption tower before removal becomes the inlet. Connect to piping. Thereby, since the downstream end part of the adsorption layer having a low saturation rate becomes the upstream end part of the adsorption layer, the FP fluoride gas can be further adsorbed at the upstream end part. The second set saturation rate is a value smaller than the set saturation rate described in the first embodiment (referred to as the first set saturation rate).

As described above, by connecting the adsorption tower with the inlet / outlet connected to the pipe, the portion of the adsorption layer where the adsorption of the FP fluoride is not saturated can be arranged at the upstream end of the adsorption layer. In the state where the FP fluoride gas is not discharged from the adsorption layer, the FP fluoride gas can be adsorbed by utilizing the unsaturated portion. For this reason, the saturation rate of the adsorption tower can be increased. In particular, when the adsorbing MoF ₆ to MgF ₂ filled in the adsorption tower, since the MoF ₆ was once adsorbed to the MgF ₂ is difficult desorption occur from MgF _2, the adsorption column having an adsorption layer filled with MgF ₂ Even if the entrance / exit is reversed, the amount of MoF ₆ that was originally adsorbed at the upstream end of the adsorption layer is desorbed from the adsorption layer is small.

The method for purifying uranium in this example will be described in detail. Each adsorption layer of the adsorption towers 1, 3 and 5 is filled with MgF ₂ which is the same kind of adsorbent. MgF ₂ is also enclosed in the detectors 2, 4, 6.

The UF ₆ gas generated by the fluorination treatment of the spent nuclear fuel is supplied to the uranium refining device 22. At this time, the valves 7, 8, 9, and 10 are open, and the valves 12, 13, 14, and 15 are closed. The UF ₆ gas containing FP fluoride gas (for example, MoF ₆ ) passes through the pipe 16, and the valve 7, the adsorption tower 1, the detection section 2, the valve 8, the adsorption tower 3, the detection section 4, the valve 9, and the adsorption tower 5. The detector 6 and the valve 10 flow in this order. MoF ₆ is adsorbed by MgF ₂ which is an adsorbent in the adsorption tower 1. In this state, the control device calculates the increase amount of the weight (or radiation dose) using the weight of the detection unit 2 (or the radiation dose of the detection unit 2 measured by the radiation detector) measured by the load meter. Then, the second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 1 is calculated using the calculated increase in weight (or radiation dose). When the second saturation rate reaches a second set saturation rate (for example, 10%), the control device opens the valve 11 and closes the valves 7 and 8. The supply of the UF ₆ gas to the adsorption tower 1 is stopped, and the UF ₆ gas is supplied to the adsorption tower 3 through the pipe 17.

The adsorption tower 1 and the detection unit 2 are isolated from the flow of UF ₆ gas in the pipe 16 by closing the valves 7 and 8. In this state, the adsorption tower 1 is once removed from the pipe 16, and as described above, the inlet of the UF ₆ gas and the outlet of the UF ₆ gas in the adsorption tower 1 are reversed, and the pipe 16 is again connected. Connected. This connection inlet and a portion of the UF ₆ gas of the adsorption tower 1 before removing the results in the outlet of the UF ₆ gas after reconnection, an outlet and a portion of the UF ₆ gas of the adsorption tower 1 before removing After reconnection, it becomes the inlet for UF ₆ gas. At this time, the adsorbent enclosed in the detector 2 is also replaced with a new adsorbent.

After the reconnection of the adsorption tower 1 and the replacement of the adsorbent in the detection unit 2 are completed, the control device, based on the information input by the operator that the reconnection and the replacement of the adsorbent have been completed, 8 is opened and the valve 11 is closed. The UF ₆ gas is again supplied to the adsorption tower 1. After the reconnection of the adsorption tower 1, the adsorption layer of the adsorption tower 1 has an adsorbent at the upstream end where the adsorption of FP fluoride is unsaturated. For this reason, MoF ₆ which is FP fluoride gas contained in UF ₆ gas is present on the upstream end side of the adsorption layer of the adsorption tower 1 and adsorbent (MgF ₂ ) in which adsorption of FP fluoride is unsaturated. Can be adsorbed. The UF ₆ gas flows in the order of the adsorption tower 1, the detection section 2, the adsorption tower 3, the detection section 4, the adsorption tower 5 and the detection section 6 and is purified.

The second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 1 calculated based on the weight of the detection unit 2 measured with a load meter (or the radiation dose of the detection unit 2 measured with a radiation detector) is set first. When the saturation rate is reached, the control device opens the valve 11 and closes the valves 7 and 8 as in the first embodiment. The UF ₆ gas is supplied to the adsorption tower 3 through the pipe 17. The adsorption tower 1 and the detection unit 2 are isolated from the flow of the UF ₆ gas, and the adsorption layer of the adsorption tower 1 and the adsorbent in the detection unit 2 are exchanged with a new adsorbent (MgF ₂ ). After these adsorbents are replaced, the control device opens the valves 13 and 15 and closes the valve 10. The UF ₆ gas flows in the order of the adsorption tower 3, the detection section 4, the adsorption tower 5, the detection section 6, the adsorption tower 1 and the detection section 2 and is purified.

The control device calculates the second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 3 based on the weight of the detection unit 4 measured by the load meter (or the radiation dose of the detection unit 4 measured by the radiation detector). To do. When the second saturation rate reaches the second set saturation rate, the control device opens the valves 12 and 13 and closes the valves 9 and 11. The supply of the UF ₆ gas to the adsorption tower 3 is stopped, and the UF ₆ gas is supplied to the adsorption tower 5 through the pipe 18.

The adsorption tower 3 in which the supply of UF ₆ gas is stopped is removed from the pipe 16, and the inlet of the UF ₆ gas and the outlet of the UF ₆ gas in the adsorption tower 3 are reversed as in the above-described adsorption tower 1. Again, it is connected to the pipe 16. This connection inlet and a portion of the UF ₆ gas of the adsorption tower 3 before removing the results in the outlet of the UF ₆ gas after reconnection, an outlet and a portion of the UF ₆ gas of the adsorption tower 3 before removing After reconnection, it becomes the inlet for UF ₆ gas. At this time, the adsorbent enclosed in the detection unit 4 is also replaced with a new adsorbent.

After the reconnection of the adsorption tower 3 and the replacement of the adsorbent in the detection unit 4 are completed, the control device opens the valves 9 and 11 and closes the valves 12 and 13. The UF ₆ gas is again supplied to the adsorption tower 3. After reconnection of the adsorption tower 3, the adsorption of FP fluoride, which is present on the upstream end side of the adsorption layer of the adsorption tower 3, is unsaturated with MoF ₆ that is the FP fluoride gas contained in the UF ₆ gas. It can be adsorbed with an adsorbent (MgF ₂ ). The UF ₆ gas flows in the order of the adsorption tower 3, the detection section 4, the adsorption tower 5, the detection section 6, the adsorption tower 1 and the detection section 2 and is purified.

When the second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 3 reaches the first set saturation rate, the control device opens the valves 12 and 13 and closes the valves 9 and 11 as in the first embodiment. The UF ₆ gas is supplied to the adsorption tower 5 through the pipe 18. The adsorption tower 3 and the detection unit 4 are isolated from the flow of the UF ₆ gas, and the adsorption layer of the adsorption tower 3 and the adsorbent in the detection unit 4 are exchanged with a new adsorbent (MgF ₂ ). After these adsorbents are replaced, the control device opens the valves 8 and 14 and closes the valve 13. The UF ₆ gas flows in the order of the adsorption tower 5, the detection section 6, the adsorption tower 1, the detection section 2, the adsorption tower 3 and the detection section 4 and is purified.

Thereafter, when the second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 5 reaches the second set saturation rate, the control device opens the valve 7 and closes the valves 12 and 15. The supply of the UF ₆ gas to the adsorption tower 5 is stopped, and the UF ₆ gas is supplied to the adsorption tower 1 through the pipe 16. The adsorption tower 5 in which the supply of UF ₆ gas is stopped is removed from the pipe 16, and the inlet of the UF ₆ gas and the outlet of the UF ₆ gas in the adsorption tower 5 are reversed like the above-described adsorption tower 1. Again, it is connected to the pipe 16. This connection inlet and a portion of the UF ₆ gas of the adsorption tower 5 before removing the results in the outlet of the UF ₆ gas after reconnection, an outlet and a portion of the UF ₆ gas of the adsorption tower 3 before removing After reconnection, it becomes the inlet for UF ₆ gas. At this time, the adsorbent enclosed in the detector 6 is also replaced with a new adsorbent.

After the reconnection of the adsorption tower 5 and the replacement of the adsorbent in the detection unit 6 are completed, the control device opens the valves 12 and 15 and closes the valve 7. The UF ₆ gas is again supplied to the adsorption tower 5. After reconnection of the adsorption tower 5, MoF ₆ which is FP fluoride gas contained in the UF ₆ gas is present at the upstream end side of the adsorption layer of the adsorption tower 5, and the adsorption of FP fluoride is unsaturated. It can be adsorbed with an adsorbent (MgF ₂ ). The UF ₆ gas flows in the order of the adsorption tower 5, the detection section 6, the adsorption tower 1, the detection section 2, the adsorption tower 3 and the detection section 4 and is purified.

When the second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 5 reaches the first set saturation rate, the control device opens the valves 7 and 14 and closes the valves 9 and 15 as in the first embodiment. The UF ₆ gas is supplied to the adsorption tower 1 through the pipe 16. The adsorption tower 5 and the detection unit 6 are isolated from the flow of the UF ₆ gas, and the adsorption layer of the adsorption tower 5 and the adsorbent in the detection unit 6 are replaced with a new adsorbent (MgF ₂ ). After these adsorbents are replaced, the control device opens the valves 9 and 10 and closes the valve 14. The UF ₆ gas flows in the order of the adsorption tower 1, the detection section 2, the adsorption tower 3, the detection section 4, the adsorption tower 5 and the detection section 6 and is purified.

  In the present embodiment, each effect produced in the first embodiment can be obtained.

  A method for purifying uranium according to Example 3, which is another example of the present invention, will be described with reference to FIG. In the uranium purification method of this embodiment, a uranium purification apparatus 22A shown in FIG. 4 is used.

The configuration of the uranium purification apparatus 22A will be described with reference to FIG. The uranium purification apparatus 22A includes adsorption towers 23, 24, 25, and 26, detection units 72, 73, 74, and 75, and an annular pipe 27. Valve 30, adsorption tower 23, valve 31, detection section 72, valve 40, adsorption tower 24, valve 41, detection section 73, valve 46, adsorption tower 25, valve 47, detection section 74, valve 52, adsorption tower 26, valve 71 and the detector 75 are provided in the annular pipe 27 in this order in the flow direction of UF ₆ gas (counterclockwise direction in FIG. 4).

The adsorbents filled in the adsorption layers of the adsorption towers 23, 24, 25, and 26 are of the same type and use MgF ₂ . The detectors 72, 73, 74, 75 are also filled with MgF ₂ . The amount of MgF ₂ sealed in each detector is smaller than the amount of MgF ₂ filled in the adsorption layer of each adsorption tower.

The length of each adsorption layer of the adsorption towers 23, 24, 25, 26 in the flow direction of the gas to be treated (UF ₆ gas) is shorter than the length of the adsorption zone, and the adsorption towers 23, 24, 25 , 26, the sum of the lengths of the respective adsorption layers is longer than the length of the adsorption zone. Each detector is provided with a load meter (not shown) that measures the weight of the detector (or a radiation detector that measures the radiation dose of the detector).

  A pipe 29 provided with a valve 28 bypasses the valve 30 and the adsorption tower 23 and is connected to the annular pipe 27. A pipe 39 provided with a valve 38 bypasses the adsorption tower 23 and the valve 31 and is connected to the annular pipe 27. A pipe 43 provided with a valve 42 bypasses the valve 40 and the adsorption tower 24 and is connected to the annular pipe 27. A pipe 45 provided with a valve 44 bypasses the adsorption tower 24 and the valve 41 and is connected to the annular pipe 27. A pipe 49 provided with a valve 48 bypasses the valve 46 and the adsorption tower 25 and is connected to the annular pipe 27. A pipe 51 provided with a valve 50 bypasses the adsorption tower 25 and the valve 47 and is connected to the annular pipe 27. A pipe 54 provided with a valve 53 bypasses the valve 52 and the adsorption tower 26 and is connected to the annular pipe 27. A pipe 56 provided with a valve 55 bypasses the adsorption tower 26 and the valve 71 and is connected to the annular pipe 27.

The UF ₆ gas supply pipe 57 provided with the valve 76 and the UF ₆ gas discharge pipe 61 provided with the valve 80 are connected between the connection point between the annular pipe 27 and the pipe 29 on the upstream side of the valve 30 and the detection unit 75. Connected to the annular pipe 27. The UF ₆ gas supply pipe 58 provided with the valve 77 and the UF ₆ gas discharge pipe 62 provided with the valve 81 are located between the connection point of the annular pipe 27 and the pipe 43 on the upstream side of the valve 40 and the detection unit 72. Connected to the annular pipe 27. The UF ₆ gas supply pipe 59 provided with the valve 78 and the UF ₆ gas discharge pipe 63 provided with the valve 82 are connected between the connection point of the annular pipe 27 and the pipe 49 on the upstream side of the valve 46 and the detection unit 73. Connected to the annular pipe 27. The UF ₆ gas supply pipe 60 provided with the valve 79 and the UF ₆ gas discharge pipe 64 provided with the valve 83 are connected between the connection point of the annular pipe 27 and the pipe 54 on the upstream side of the valve 52 and the detection unit 74. Connected to the annular pipe 27.

The UF ₆ gas supply pipes 57, 58, 59, 60 are connected to a single UF ₆ gas supply pipe (not shown) upstream of the valves 76, 77, 78, 79. The UF ₆ gas exhaust pipes 61, 62, 63, 64 are connected to one UF ₆ gas exhaust pipe (not shown) downstream of the valves 80, 81, 82, 83.

  The uranium purification method of the present embodiment using the uranium purification apparatus 22A will be specifically described.

For example, by opening the valve 76, it supplies the UF ₆ gas into the annular pipe 27 from the UF ₆ gas supply pipe 57. At this time, the valves 30, 31, 40, 41, 46, 47 and 83 are open, and the remaining valves shown in FIG. 4 are all closed. The UF ₆ gas supplied to the annular pipe 27 is sequentially guided to the adsorption tower 23, the detection unit 72, the adsorption tower 24, the detection unit 73, the adsorption tower 25, and the detection unit 74 through the annular pipe 27. The UF ₆ gas discharged from the detection unit 74 is discharged from the annular pipe 27 to the UF ₆ gas discharge pipe 64. Each valve is opened and closed by a control device (not shown).

Adsorbent of the adsorption layer of the adsorption tower 23 which is located most upstream in this state, FP fluoride gas included in the UF ₆ gas (e.g., MoF ₆₎ adsorbs, FP fluoride gas from UF ₆ gas Remove. The control device calculates the amount of increase in the weight (or radiation dose) using the weight of the detector 72 measured by the load meter (or the radiation dose of the detector 72 measured by the radiation detector). The second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 23 is calculated using the increased weight (or radiation dose). When the second saturation rate reaches the second set saturation rate, the control device opens the valves 28 and 38 and closes the valves 30 and 31.

By such valve opening / closing operation, the supply of the UF ₆ gas to the adsorption tower 23 through the valve 30 is stopped, and the UF ₆ gas is supplied to the adsorption tower 23 through the pipe 29. The UF ₆ gas exhausted from the adsorption tower 23 is guided to the detection unit 72 through the pipe 39. As a result, in the adsorption layer of the adsorption tower 23, the flow of UF ₆ gas flowing from the valve 30 toward the valve 31 becomes the flow of UF ₆ gas in the reverse direction from the valve 28 toward the valve 38. By opening the valve 28 and 38, opening and closing operation of the valve closing valve 30, 31, substantially, the outlet of the inlet and UF ₆ gas UF ₆ gas of the adsorption tower that has been removed from the pipe 16 in the second embodiment is reversed Thus, again, the same thing as that connected to the pipe 16 is performed for the adsorption tower 23.

When the supply of UF ₆ gas to the adsorption tower 23 through the valve 30 is stopped, the adsorbent present at the end on the valve 30 side is saturated with the adsorption of FP fluoride in the adsorption layer of the adsorption tower 23. The adsorbent present at the end on the valve 31 side is in an unsaturated state of FP fluoride adsorption. By opening the valves 28 and 38 and closing the valves 30 and 31 as described above, the UF ₆ gas flows from the end of the adsorption tower 23 from the end where the adsorbent in which the adsorption of the FP fluoride is unsaturated is present. Supplied into the adsorption layer. Therefore, the FP fluoride gas contained in the UF ₆ gas is adsorbed by the adsorbent in the adsorption layer in which the adsorption of the FP fluoride is unsaturated in a state where the FP fluoride gas does not flow out to the pipe 39. Is done. That is, the adsorbent in the adsorption layer of the adsorption tower 23 can be effectively used for adsorption of the FP fluoride gas.

  The second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 23 calculated based on the weight of the detection unit 72 measured by the load meter (or the radiation dose of the detection unit 72 measured by the radiation detector) is When the first set saturation rate is reached, the control device closes the valves 28, 38, 76, 79 and opens the valves 77, 52, 71, 80.

The supply of the UF ₆ gas to the adsorption tower 23 and the detection unit 72 is stopped, and the UF ₆ gas is supplied from the UF ₆ gas supply pipe 58 to the annular pipe 27. The UF ₆ gas is sequentially guided to the adsorption tower 24, the detection section 73, the adsorption tower 25, the detection section 74, the adsorption tower 26 and the detection section 75 through the annular pipe 27, and further discharged to the UF ₆ gas discharge pipe 61. The By such a flow of UF ₆ gas, the adsorbent in the adsorption layer of the adsorption tower 24 located at the uppermost stream most adsorbs FP fluoride gas (for example, MoF ₆ ) contained in the UF ₆ gas, Uranium is purified. In the adsorption layer of the adsorption tower 24, UF ₆ gas flows from the valve 40 toward the valve 41.

In the adsorption tower 23 in which the supply of the UF ₆ gas is stopped, the adsorbent in the adsorption layer is replaced with a new adsorbent. Also in the detection unit 72, the adsorbent is replaced with a new adsorbent. The adsorbent taken out from each of the adsorption tower 23 and the detection unit 72 at the time of exchanging the adsorbent is treated as radioactive waste.

The second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 24 calculated based on the weight of the detection unit 73 measured by the load meter (or the radiation dose of the detection unit 73 measured by the radiation detector) is the first. When the two set saturation rate is reached, the control device opens the valves 42 and 44 and closes the valves 40 and 41. By opening and closing the valve, the UF ₆ gas containing the FP fluoride gas is supplied from the pipe 43 to the adsorption tower 24 and the UF ₆ gas discharged from the adsorption tower 24 is supplied to the pipe in the same manner as the adsorption tower 23 described above. 45 is led to the detection unit 73.

  When the second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 24 calculated based on the measured weight (or radiation dose) of the detector 73 reaches the first set saturation rate, the control device 42, 44, 77, 80 are closed and valves 78, 30, 31, 81 are opened.

The supply of the UF ₆ gas to the adsorption tower 24 and the detection unit 73 is stopped, and the UF ₆ gas is supplied from the UF ₆ gas supply pipe 59 to the annular pipe 27. The UF ₆ gas is sequentially guided to the adsorption tower 25, the detection unit 74, the adsorption tower 26, the detection unit 75, the adsorption tower 23, and the detection unit 72 through the annular pipe 27, and further discharged to the UF ₆ gas discharge pipe 62. The By such a flow of UF ₆ gas, the adsorbent in the adsorption layer of the adsorption tower 25 located at the uppermost stream most adsorbs the FP fluoride gas (for example, MoF ₆ ) contained in the UF ₆ gas, Uranium is purified. In the adsorption layer of the adsorption tower 25, UF ₆ gas flows from the valve 46 toward the valve 47.

In the adsorption tower 24 and the detection unit 73 in which the supply of the UF ₆ gas is stopped, the internal adsorbent is replaced with a new adsorbent. During the replacement of the adsorbent, the adsorbent taken out from each of the adsorption tower 24 and the detection unit 73 is processed as radioactive waste.

When the second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 25 calculated based on the measured weight (or radiation dose) of the detection unit 74 reaches the second set saturation rate, the control device displays the valve 48. , 50 and valves 46, 47 are closed. By such valve opening / closing operation, UF ₆ gas containing FP fluoride gas is supplied from the pipe 49 to the adsorption tower 25, and the UF ₆ gas discharged from the adsorption tower 25 passes through the pipe 50 to the detection unit 74. Led.

  When the second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 25 calculated based on the measured weight (or radiation dose) of the detector 74 reaches the first set saturation rate, the control device 48, 50, 78, 81 are closed and valves 79, 40, 41, 82 are opened.

The supply of the UF ₆ gas to the adsorption tower 25 and the detection unit 74 is stopped, and the UF ₆ gas is supplied from the UF ₆ gas supply pipe 60 to the annular pipe 27. The UF ₆ gas is sequentially guided to the adsorption tower 26, the detection section 75, the adsorption tower 23, the detection section 72, the adsorption tower 24 and the detection section 73 through the annular pipe 27, and further discharged to the UF ₆ gas discharge pipe 63. The By such a flow of UF ₆ gas, the adsorbent in the adsorption layer of the adsorption tower 26 located at the uppermost stream most adsorbs the FP fluoride gas (for example, MoF ₆ ) contained in the UF ₆ gas, Uranium is purified. In the adsorption layer of the adsorption tower 26, the UF ₆ gas flows from the valve 52 toward the valve 71. In the adsorption tower 24 and the detection unit 73, the internal adsorbent is replaced with a new adsorbent.

  When the second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 26 calculated based on the measured weight (or radiation dose) of the detection unit 75 reaches the second set saturation rate, the control device controls the valve 53. , 55 are opened and the valves 52, 71 are closed. Thereafter, when the second saturation rate of the adsorbent in the adsorption layer of the adsorption tower 26 calculated based on the measured weight (or radiation dose) of the detection unit 75 reaches the first set saturation rate, the control device The valves 53, 55, 79, 82 are closed, and the valves 76, 46, 47, 83 are opened.

  In the present embodiment, each effect produced in the second embodiment can be obtained.

  The uranium purification method of Example 4 which is another example of the present invention will be described with reference to FIG. In the uranium purification method of this embodiment, a uranium purification apparatus 22B shown in FIG. 5 is used.

The uranium refining device 22B includes an adsorption tower (fixed bed type adsorption tower) 65 and a fluidized bed type adsorption tower 66. The adsorption tower 65 has an adsorption layer filled with an adsorbent (eg, MgF ₂ ) that adsorbs FP fluoride gas (eg, MoF ₆ ). An adsorption layer 67 filled with an adsorbent (for example, MgF ₂ ) that adsorbs FP fluoride gas (for example, MoF ₆ ) is also formed in the fluidized bed type adsorption tower 66. A UF ₆ gas supply pipe 68 is connected to the bottom of the fluidized bed type adsorption tower 66. A pipe 69 connects the fluidized bed type adsorption tower 66 and the adsorption tower 65. A UF ₆ gas discharge pipe 70 is connected to the adsorption tower 65. The adsorption tower 65 and the fluidized bed type adsorption tower 66 are filled with the same kind of adsorbent (for example, MgF ₂ ). The packed amount of the adsorbent is larger in the fluidized bed type adsorption tower 66 than in the adsorption tower 65.

  The uranium purification method of the present embodiment using the uranium purification apparatus 22B will be described.

UF ₆ gas containing FP fluoride gas is supplied to the fluidized bed type adsorption tower 66 through the UF ₆ gas supply pipe 68. The FP fluoride gas contained in the UF ₆ gas is adsorbed by the adsorbent in the adsorption layer 67. In the fluidized bed type adsorption tower 66, the adsorbent in the adsorption layer 67 is always stirred. Therefore, in the fluidized bed type adsorption tower 66, the distribution of the saturation rate of the adsorbent in the adsorption tower as shown in FIG. 3 cannot be achieved, and the saturation rate of the adsorbent is always uniform. Therefore, in this embodiment, as in the first and second embodiments, an operation for reversing the inlet of the UF ₆ gas and the outlet of the UF ₆ gas in the adsorption tower becomes unnecessary. The UF ₆ gas that has passed through the fluidized bed type adsorption tower 66 is supplied to the adsorption tower 65. In this example, uranium is purified in this way.

In the present embodiment, when the saturation rate of the adsorbent in the fluidized bed type adsorption tower 66 reaches the first saturation rate, the adsorbent in the adsorption layer 67 of the fluidized bed type adsorption tower 66 is replaced. During the replacement of the adsorbent, the adsorbent in the fluidized bed type adsorption tower 66 is taken out to the outside, and all the adsorbent present in the adsorption tower 65 is charged into the fluidized bed type adsorption tower 66. The reason for introducing the adsorbent present in the adsorption tower 65 in the fluidized bed adsorption tower 66, most of the FP fluoride gas included in the UF ₆ gas flowing in the UF ₆ gas supply pipe 68 is fluidized bed Since the FP fluoride gas is adsorbed by the adsorbent in the adsorption tower 66 and is not so adsorbed by the adsorbent in the adsorption tower 65, an adsorbent in which adsorption of the FP fluoride is in an unsaturated state is present in the adsorption tower 65. This is because they exist in large quantities.

  The amount of adsorbent to be filled in the fluidized bed type adsorption tower 66 and the amount of the adsorbent to be filled in the fluidized bed type adsorption tower 66 cannot be covered simply by charging the adsorbent from the adsorption tower 65. A new adsorbent is introduced into the fluidized bed adsorption tower 66 by an amount corresponding to the difference in the amount of adsorbent input.

  According to the present embodiment, since uranium is purified in the fluidized bed type adsorption tower 66 filled with the adsorbent, the saturation rate of the adsorbent in the fluidized bed type adsorption tower 66 can be made uniform. For this reason, it is not necessary to change the gas flow direction in the adsorption layer of the adsorption tower as in the first and second embodiments, and the adsorbent having a high saturation rate can be discarded. Therefore, it is possible to reduce the amount of adsorbent that becomes radioactive waste generated from the uranium refining process. Furthermore, since the present embodiment uses the fluidized bed type adsorption tower 66 filled with the adsorbent, the equipment capacity can be reduced.

  In order to continue the adsorption of the FP fluoride gas by the adsorbent in the fluidized bed type adsorption tower 66 when the saturation rate of the adsorbent in the fluidized bed type adsorption tower 66 reaches the first saturation rate, the above-mentioned is performed. Instead of exchanging the adsorbent in the fluidized bed type adsorption tower 66 as described above, the following method may be employed. That is, when the saturation rate of the adsorbent in the fluidized bed type adsorption tower 66 reaches the first saturation rate, among the adsorbents present in the adsorption layer 67 in the fluidized bed type adsorption tower 66, An amount of adsorbent equal to the amount of adsorbent present is removed from the fluid bed adsorber tower 66. Thereafter, all the adsorbent present in the adsorption tower 65 is supplied to the fluidized bed adsorption tower 66. The adsorbent supplied from the adsorption tower 65 to the fluidized bed type adsorption tower 66 and the adsorbent remaining in the fluidized bed type adsorption tower 66 without being taken out are stirred and mixed in the fluidized bed type adsorption tower 66. The adsorption layer of the adsorption tower 66 is filled with a necessary amount of new adsorbent.

By supplying the adsorbent from the adsorption tower 65 to the fluidized bed type adsorption tower 66, the average saturation rate of the adsorbent present in the fluidized bed type adsorption tower 26 can be reduced. Therefore, it is possible to adsorb the FP fluoride gas included in the UF ₆ gas supplied to the fluidized bed adsorption tower 66 by UF ₆ gas supply pipe 68, the adsorbent present in the fluidized bed adsorption tower 26 .

  1, 3, 5, 23, 24, 25, 26, 65 ... adsorption tower, 2, 4, 6, 72, 73, 74, 75 ... detection unit, 7 to 15, 28, 30, 31, 38, 40 to 42, 44, 46 to 48, 50, 52, 53, 55, 71, 76 to 83 ... valves, 22, 22A, 22B ... uranium purifier, 66 ... fluidized bed type adsorption tower.

Claims (14)

It has an adsorption layer filled with the same kind of adsorbent, and has a plurality of adsorption towers connected in series,
The length of the adsorption layer of each of the adsorption towers in the flow direction of the supplied uranium gas is shorter than the length of the adsorption zone. In any two adsorption towers of the plurality of adsorption towers, the 2 The uranium refining apparatus, wherein the sum of the lengths of the adsorption layers of each of the adsorption towers is longer than the length of the adsorption zone.   The uranium refining device according to claim 1, wherein a detection unit that detects a saturation rate of the adsorbent in the adsorption layer of the adsorption tower is disposed downstream of each adsorption tower. It has an adsorption layer filled with the same kind of adsorbent, and comprises a plurality of adsorption towers connected in series, and the length of the adsorption layer of each of the adsorption towers in the flow direction of the supplied uranium gas, It is shorter than the length of the adsorption band, and in any two adsorption towers among the plurality of adsorption towers, the sum of the lengths of the respective adsorption layers of the two adsorption towers is greater than the length of the adsorption band. A uranium purification method for purifying the uranium gas using a uranium purification apparatus that is also long,
The uranium gas is sequentially supplied from the adsorption tower located at the uppermost stream, the saturation rate of the adsorbent in the adsorption layer of the adsorption tower located at the uppermost stream is detected, and the detected saturation rate is equal to or higher than a set saturation rate The uranium gas supply to the adsorption tower located at the uppermost stream is stopped, and the uranium gas is supplied to the other adsorption tower located downstream of the adsorption tower where the supply of the uranium gas is stopped. And a method for purifying uranium.   The method for purifying uranium according to claim 3, wherein the detection of the saturation rate of the adsorbent is performed by a detection unit disposed on the downstream side of each of the adsorption towers.   The method for purifying uranium according to claim 3 or 4, wherein the adsorbent in the adsorption tower where the supply of the uranium gas is stopped is replaced with a new adsorbent.   The method for purifying uranium according to claim 5, wherein the adsorption tower in which the adsorbent is exchanged for the new adsorbent is connected to another adsorbent such that the adsorption tower is located on the most downstream side. It has an adsorption layer filled with the same kind of adsorbent, and comprises a plurality of adsorption towers connected in series, and the length of the adsorption layer of each of the adsorption towers in the flow direction of the supplied uranium gas, It is shorter than the length of the adsorption band, and in any two adsorption towers among the plurality of adsorption towers, the sum of the lengths of the respective adsorption layers of the two adsorption towers is greater than the length of the adsorption band. A uranium purification method for purifying the uranium gas using a uranium purification apparatus that is also long,
The uranium gas is sequentially supplied from the adsorption tower located at the uppermost stream, the saturation rate of the adsorbent in the adsorption layer of the adsorption tower located at the uppermost stream is detected, and the detected saturation rate is the first set saturation A uranium purification method comprising purifying the uranium gas by flowing the uranium gas in the reverse direction in the adsorption layer of the adsorption tower located at the uppermost stream when the ratio becomes equal to or greater than the rate.   When the detected saturation rate reaches a second saturation rate larger than the first set saturation rate in a state where the uranium gas is flowing in the reverse direction, the adsorption to the adsorption tower located at the uppermost stream is performed. The uranium purification method according to claim 7, wherein the uranium gas is supplied to another adsorption tower located downstream of the adsorption tower where the supply of the uranium gas is stopped by stopping the supply of uranium gas.   The method for purifying uranium according to claim 7 or 8, wherein the detection of the saturation rate of the adsorbent is performed by a detection unit disposed on the downstream side of each of the adsorption towers.   The method for purifying uranium according to any one of claims 7 to 9, wherein the adsorbent in the adsorption tower where the supply of the uranium gas is stopped is replaced with a new adsorbent.   The method for purifying uranium according to claim 10, wherein the adsorption tower in which the adsorbent is exchanged for the new adsorbent is connected to another adsorbent so as to be located at the most downstream side.   The detection unit has the same kind of adsorbent as the adsorbent packed in the adsorption tower, measures the weight that increases when the adsorbent of the detection unit adsorbs the impurities, and the increase in the weight The method for purifying uranium according to claim 4 or 9, wherein the saturation rate is determined based on the formula (1).   The detection unit has the same type of adsorbent as the adsorbent packed in the adsorption tower, and measures the radiation dose that increases when the adsorbent of the detection unit adsorbs the impurities. The method for purifying uranium according to claim 4 or 9, wherein the saturation rate is obtained based on an increase amount.   The uranium gas is supplied to the fluidized bed type adsorption tower packed with the adsorbent, and the impurities contained in the uranium gas are adsorbed by the adsorbent in the fluidized bed type adsorption tower, and are discharged from the fluidized bed type adsorption tower. A method for purifying uranium, comprising supplying uranium gas to a fixed adsorption tower filled with the adsorbent.

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