JPH08304587A - Reactor purification device - Google Patents

Abstract

(57) [Summary] [Structure] Impurities brought into the reactor 2 from the water supply device 1 are decomposed in the reactor 2 or are boiled and concentrated as they are, so that they are purified by the reactor water filtration desalination device 8. Ionic impurities in the reactor can be divided into cation and anion species.
The property is detected by the conductivity meter and the pH meter of the sampling device 9, and the powder or fibrous anion and cation exchange resin according to the ratio (equivalent) thereof is added to the precoat tank 1
From 1, the reactor water filtration desalination apparatus 8 is pre-coated to purify the reactor water. [Effect] By reducing the backwashing frequency of the reactor cleaning device to 1/2 or less, it has been possible to halve the relatively high radioactive waste that has purified the reactor water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor cleaning device.

[0002]

2. Description of the Related Art At present, purification of nuclear reactor water is performed by a reactor filtration desalination apparatus within a range of 1 to 7% as a ratio to the feed water flow rate, which varies depending on the plant. As is well known, in a boiling water nuclear power plant, impurities that flow into the reactor from a water supply device or that are generated in the reactor must be accumulated in the reactor without moving to steam except for a very small amount of volatile substances. become. The clad, which is a corrosion product of metal, adheres to a fuel rod having a boiling surface by about 90%, so the concentration in the reactor water is low, but the impurities dissolved in the reactor water in the ionic form are Since it does not adhere to the fuel rods, in order to achieve high purification of the reactor water, the above-mentioned feed water flow rate ratio may be set to a large specification. However, from the viewpoint of the thermal efficiency of the plant, since it is purified by a reactor filtration desalination apparatus, the reactor water must be cooled to about 50 ° C. due to the heat resistance limitation of the ion exchange resin, which is not a good idea. On the other hand, a cation exchange resin and an anion exchange resin to be pre-coated on a reactor water filtration desalination apparatus, which are often powdery or fibrous, have a resin ratio of 1 regardless of the composition of reactor water impurities. : 1 is constant. In actual reactor water, the ionic composition varies depending on the impurities that are mixed in, and cannot be determined in a uniform manner. For example, when starting the plant after the completion of the periodic inspection, CrO, which is an eluate from stainless steel,
₄ ^2- (Chromate ion) is predominant, and the anionic resin is consumed rapidly. As a result, the conductivity of the reactor cleaning apparatus outlet increases due to the anion resin break, and backwashing and reprecoating are performed.

Also, during normal operation, when the resin that should be R-H + due to reverse regeneration of the granular ion exchange resin used in the condensate purification device holds R-Na + and the regenerant. In that case, Na + constantly flows into the reactor water during operation. The load on the cation exchange resin increases, and the backwash reprecoating is performed by ion break. In this way, the supply of cation / anion exchange resin to the existing reactor water filtration desalination equipment is set independently of the ionic composition of the reactor water, so that even ion exchange resin that has not yet been consumed can be used. It will be backwashed and discarded, which will directly increase the amount of radioactive waste and also increase the cost required for operation.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to establish a concrete method for reducing the backwashing frequency of a reactor decontamination apparatus filter desalination apparatus, and to reduce radioactive waste in a nuclear power plant.

[0005]

In order to achieve the above object, the present invention calculates cation conductivity and anion conductivity based on plant data of conductivity and pH, which are indicators of ionic composition of reactor water. Provided is a system for precoating a reactor water filtration desalination apparatus with a powder or fibrous ion exchange resin suitable for the ratio.

In addition, by evaluating the water collection life of the pre-coated ion exchange resin, it is possible to rationalize operational management such as backwash preparation.

[0007]

According to the present invention, the ion exchange resin used in the reactor cleaning device operated to maintain the high purity of the reactor water is characterized by the characteristics of the ionic impurities mixed in the reactor, that is,
Since cationic coating or anionic species or their ratio is pre-measured and pre-coated, the resin for ion exchange is optimally performed, and it becomes possible to increase the amount of water collected per pre-coat, which results in radioactive waste. It is possible to reduce the increase in objects.

[0008]

EXAMPLE An example of the present invention will be described with reference to FIG. In the feed water supplied from the water supply device 1 to the reactor 2, ionic impurities mixed from the condensate purification device, the condensate storage tank, or the like, or deteriorated substances from the ion exchange resin used in the condensate purification device, etc. including. These impurities are concentrated by boiling in the reactor 2. There is a reactor cleaning device 4 branched from a reactor recirculation device 3 in order to clean concentrated reactor water and maintain its purity.

In the reactor cleaning device 4, after the temperature of the coolant is lowered by the regenerative heat exchanger 5 and the non-regenerative heat exchanger 6,
The system is such that the reactor water pressurized by the pump 7 and purified by the reactor water filtration / desalination device 8 is heated again by the non-regenerative heat exchanger 6 and then supplied to the reactor through the water supply device 1. According to the present invention, the cation conductivity and the anion conductivity of the reactor water are calculated from the conductivity meter and the pH meter provided in the sampling device 9 for sampling the inlet and outlet water of the reactor water filtration desalination device 8. Needless to say, cation conductivity is a contribution of conductivity by cations, and when the ionic species is unknown, Na + ions are considered as impurities. Further, anion conductivity is a contribution of conductivity by anions, and when the ionic species is unknown, SO ₄ − ions are considered as impurities.
There are two reasons for selecting Na + and SO ₄ --as the representative ion species. That is, the first is NU
REG / CR5115 “A Review of boiling water reactor chem
Fox JM et al. are investigating the source of impurities in primary reactors of BWR reactors in the United States as "istry", and it is found that the ion exchange resins used in condensate purification devices
0%, condenser seawater leakage has become about 20%, etc., SO ₄ as decomposition products of ion exchange resins - and that the seawater components Na + is typical ion, Second Conductivity Is given by the number 1,

[0010]

[Equation 1]

The equivalent electric conductivity is H + (349.
50-8 except 7S / cm ・ eq) and OH- (200S / cm ・ eq)
This is because they are almost the same in the range of 0 S / cm · eq (at 25 ° C). For example, in the Chemical Handbook (Maruzen), the anion species is Cl-
_{: 76.3, SO 4 -: 80.0} , CrO 4 -: 85, the cationic species _{Na +: 50.1, NH 4 +} : 73.5, Fe
³ +: 68.4, and the like.

The calculation flow is shown in FIG.

Here, the charge balance equation

[0014]

[Equation 2] [H +] + [A +] = [OH-] + [B-] (Equation 2) [A +] [B-]: A, B ion concentration

[0015]

[Formula 3] Kw = [H +] · [OH-] (Formula 3) Kw: Ionic product of water (10 ^{−14 at} 25 ° C.) If each ion concentration is obtained from this, powder or fibrous form corresponding to it The ratio of the ion exchange resin is mixed in the precoat tank 11, and the condensate filtration desalination apparatus is precoated. As a matter of course, the flow-through exchange capacity of the powder or fibrous ion exchange resin is obtained in advance, and the ion exchange resin amount (equivalent ratio) is determined by the ratio of the anion resin and the cation resin to the anions and cations of the reactor water. Multiply by the ratio. Generally, the flow-through exchange capacity is 90% of the neutral salt exchange capacity of the new resin and 60% of the neutral salt exchange capacity of the cation new resin.
Is a guide, but it should be measured in advance.

The cation conductivity and the anion conductivity in Example 1 are determined by measuring the conductivity after passing through the column containing the cation resin in the sampling device 9 as the anion conductivity and the conductivity after passing through the anion resin through the column. Good as a rate. Alternatively, the sampling device 9 may be provided with an ion line or an off-line ion chromatograph, and the ratio of the cation and anion resin to be precoated may be determined by direct quantification of the ion concentration.

FIG. 3 shows one of the embodiments according to the present invention.
Here, the anion / cation resin amount ratio is determined based on the water quality measured by the sampling device 9 in the same manner as described in FIG. 1, but in the resin supply method, the so-called body feed method (BNES 6th Internati
onal Conference on water chemistry of Nuclear Rea
ctor Systems 1992 “Performance Improvement of Prec
oat Type CondensateFilter "Maeda K. et al.) The reactor water filtration desalination unit 8 is pre-coated with 0.5 kg (resin) / m ² (filtration area) of about half of the normal size in advance. , The rest is precoat tank 11 or 12
It is injected into the inlet of the reactor water filtration desalination device 8 more. The ion exchange resin to be precoated here may be a mixture of anion resin and cation resin calculated in advance, or the cation resin may be put in the precoat tank 11 and the anion resin may be fed separately in the precoat tank 12.

[0018]

According to the present invention, an appropriate filter aid (ion exchange resin) is provided according to the properties of the reactor water, so that the water sampling life is as long as the conventional precoat ratio anion: cation = 1: 1.
Since it can be 1: 8 or 8: 1 as compared with 1, it can be extended more than twice. This is the amount of waste generated by the ion exchange resin of relatively high radioactivity, which is obtained by directly treating the reactor water.
It can be reduced to / 2 or less.

[Brief description of drawings]

FIG. 1 is a block diagram of a water purification system for a nuclear power plant.

FIG. 2 is a flowchart for calculating an impurity concentration from the reactor water conductivity.

FIG. 3 is a block diagram of a body feed method according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Water supply device, 2 ... Reactor, 4 ... Reactor cleaning device, 5 ...
Regeneration heat exchanger, 6 ... Non-regeneration heat exchanger, 8 ... Reactor water filtration desalination apparatus, 9 ... Sampling apparatus, 11 ... Precoat tank.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location G21F 9/12 512 G21F 9/12 512G (72) Inventor Toshihiko Fukumoto 3-chome, Hitachi-cho, Ibaraki Prefecture 2-1 Hitachi Engineering Co., Ltd.

Claims (4)

[Claims] 1. A reactor cleaning apparatus comprising a reactor water filter desalting apparatus for a boiling water reactor and a precoat tank for supplying powdery or fibrous cation exchange resin or anion exchange resin to the filter desalination apparatus. , Reactor water conductivity and pH
An apparatus for purifying a nuclear reactor, characterized in that a cation exchange resin and an anion exchange resin, which are proportional to the ratio of cation conductivity and anion conductivity, are pre-coated on a reactor water filtration desalination apparatus. 2. The nuclear reactor purification device according to claim 1, wherein a quantitative value of each component by an ion chromatograph is used as a method of calculating the ratio of the cation conductivity and the anion conductivity. 3. The method for coating powdered or fibrous cation exchange resin and anion exchange resin on a reactor water filtration desalination apparatus according to claim 1, wherein the reactor water purification desalination apparatus inlet is cleaned. A reactor cleaning device that injects the ion-exchange resin in a calculated ratio directly into the device piping. 4. The reactor cleaning apparatus according to claim 1, wherein the cation conductivity and the anion conductivity of the reactor are calculated from the process conductivity and the pH to predict the water sampling life of the ion exchange resin.