JPS6091297A - Method of treating waste liquor of decontaminating agent - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] industrial application field) The present invention relates to a decontamination agent waste liquid treatment method.

Prior Art) Numerous proposals have been made for the decontamination (hereinafter referred to as "decontamination") of conventional reactor primary cooling systems, purification systems, fuel handling and storage systems, radioactive waste processing systems, etc. Chemical decontamination methods include the Single 5tep method and the IVf method.
ulti 5tep method, ]) iluieSolvent
It can be divided into laws. A typical example of such a Multi Step method is the AP-CHrox method. Kneading is the process of depositing cladding (CR, UD; iron, nickel,
The main components are oxides of chromium, manganese and cobalt.
Iron oxides, nickel oxides, etc. are dissolved and removed by passing a trox solution (mainly composed of citric acid and oxalic acid or their organic acid salts).

However, two methods have been conventionally proposed as waste liquid treatment methods in the AP-C1trox method.

1) ■Waste the AP waste liquid and solidify it into concrete, ■-
On the other hand, 1 trox waste liquid is solidified into concrete after neutralization.

11) ■ Mix HP waste liquid and first washing liquid ■ C
Mix the i trox waste liquid and the first washing solution ■ Mix ■ and ■ After neutralization treatment, reduce potassium permanganate with formalin, then add calcium salt,
Forms insoluble citrate and sulfate.

■ Supernatant water and second AP]f, - and C1tr
The volume of the oxidized rinsing liquid is reduced in an evaporator, while the sludge is solidified with cement or asphalt.

However, in the waste liquid treatment methods 1) and II),
Since the 7-carbon and citric acid components in the C1jrox solution remain undecomposed, the volume of solidified waste is large and a large storage space must be secured, and method 11) does not contain harmful substances such as chromium ions. The problem is that the evaporator is not precipitated and can damage the evaporator, leading to corrosion of the can body.

Purpose of the Invention) The present invention was made against the background of the technical problem mentioned above, and it is possible to solve the problem of sludge generation by decomposing or precipitating the main component of the decontamination agent and precipitating the metal ions constituting the cladding. A- and P-based decontamination agents and C1trox that have a low amount of chromium and other harmful substances remaining in the treatment solution, and can be easily used in the treatment process.
The purpose of this invention is to provide a method for treating waste liquid of system decontamination agents.

(Structure of the Invention) That is, the present invention uses a waste liquid of an AP decontamination agent whose main component is alkaline permanganate, and a C1trox decontamination agent whose main components are oxalic acid and citric acid. This is a method for treating a waste liquid of a decontamination agent, characterized in that the following steps (a) to (d) are combined when treating the waste liquid of a decontamination agent.

(a) The first step of mixing and neutralizing the waste liquid of AP-based decontamination agent and the waste liquid of C1trox-based decontamination agent.

(b) A second step in which all acids are added to bring the pH to 7 or less to decompose permanganate and organic acid salts such as oxalic acid and citric acid or kneaded.

(c) Adding an alkali r) At least one metal ion from the group such as manganese, iron, nickel, copper, uranium, and ruthenium contained in the waste liquid to a hydroxide or Sixth step to precipitate as oxide or salt.

(d) (A) Precipitate the chromium ions contained in the waste liquid as a salt by adding a metal salt, or (
B) Add an acid to the filtered P solution to remove the precipitate to bring the pH to 1 to 4. Next, add a reducing agent to reduce the chromium ions contained in the waste fluid, and then add an alkali to bring the pH to 7. A fourth step in which the reduced chromium ions are precipitated as a hydroxide oxide.

The present invention will be described in detail below step by step.

(b) First step AP-based decontamination agents are usually alkaline water bath liquids whose main components are permanganates such as potassium permanganate and alkali metal hydroxides such as sodium hydroxide.
The 1trox decontamination agent is an acidic aqueous solution containing 7-euric acid, citric acid, or their organic acid salts as main components.

Therefore, AP-based decontamination agents and (hereinafter referred to as "AP-based waste fluids" or "Citrox-based waste fluids") waste liquids of J I lox-based decontaminating agents can be prepared by mixing these two types, ■■ and ■. Mixing and neutralization are recommended.

The mixing and neutralization treatment temperature may be from room temperature to 100°C.

Thus, by completely neutralizing the AP-based waste liquid and the CHrox-based waste liquid, permanganate, 0, phosphoric acid, and citric acid, or their organic acid salts, partially react.
Permanganate 1 is directly decomposed and partially becomes manganese dioxide, and part of nouric acid, citric acid, etc. is oxidized and decomposed into carbon dioxide.

1 sip) 2nd step The treated solution (including sediment) after mixing and neutralization in the 1st step is not completely neutralized because the A and P waste solutions themselves are alkaline in composition. It is not practiced and is alkaline.

Therefore, in the second step, an acid such as nitric acid, sulfuric acid, hydrochloric acid, acetic acid, etc., preferably nitric acid, is added to the treatment liquid obtained in the first step (
and adjust the pH to 7 or less, preferably 3 to 7, and adjust the pH to 1.
Preferably it is 5.5 or less. The remaining permanganate, uric acid and citric acid, or their organic salts decompose and generate carbon dioxide, and the chromium component contained in the waste liquid is oxidized to chromium ions with a filtration value. Become. The decomposition reaction caused by the acid addition 1 in the second step of sintering is an exothermic reaction accompanied by carbon shells, but the reaction temperature is room temperature to 100°C and the reaction time is 5 minutes or more. ~12
When carried out with a grip strength of 0 minutes: Yes.

A typical reaction example in the second step is as follows, assuming that nitric acid is used as the acid added.

5H2C204+ 2KMnO4+61('NO3→1
0CO2+2Mn(No3)2+2KNO! ,+8H
205C,,H80,+181(Mn04+54HN
03→30CO2+ 18Mn (No3),, + 1
81 (No3+ 47H205(NH,)2C204+
2KMnO4+6HNO5→10CO2+2Mn(N
O3) 2,02KNO3+1oIJ5+8H20 (c) Third step Second step 8 is a decomposition reaction accompanied by the generation of carbon dioxide, so the completion of foaming is the standard for the end of the decomposition reaction. Therefore, after the completion of foaming, an alkali such as sodium hydroxide, potassium hydroxide, or aqueous ammonia is added to the treatment liquid obtained in the second step (including the precipitate) to adjust the pH to 7 or more, preferably 7 to 1.
3. In addition, the manganese (A
At least one metal ion from the group consisting of iron, nickel, cobalt, uranium and ruthenium (including P-based decontamination agent components) is precipitated as a hydroxide, oxide or salt.

Typical reaction examples in the sixth step are as follows.

+nn2++20H-+ Mn((JH) (whiteness j
) Fe5 + Juro OH- → 1Fe(OH)5 (red-brown precipitate) Co21- + No-, 4-OH- → Co (
(')H)N(Js (blue precipitate) Co2++20H-
1-Co(OH) 2 (pink precipitate) UO2(NtJ3) -1-2NH4OH-+ (NH
4), U3O, (yellowness 2) 2U02 +60H-
+2Na+→Na2U2o7・3H2゜ (yellow precipitate) If, u” + 30T (-+ Ru (OR14 (black precipitate) The chromium ions contained in the solution form chromite ions and the solution does not precipitate.

Therefore, in the fourth step, chromium ions are precipitated by employing the steps (A) and (B) above.

<4th step f￥i (A-) > Nitrate, sulfate, hydrochloride, and acetic acid of lead, calcium, barium, strontium, or magnesium are added to the treatment solution containing the precipitate obtained in the 6th step. Represented by, etc.
By adding an excessive amount of metal salt, preferably barium nitrate, the dissolved chromium ions are precipitated as chromate, filtered, and separated into total precipitate and F solution. .

Representative reaction example 1 is as follows.

2Cr04+Ba(NO3)2→BaCrO4+2K
NO5i(2CrO4+ Pb(CH6COO) 2-
+ PbCrO4+2CH3C(X)K Note that some of the added metal salt ions (lead, calcium, barium, strontium, magnesium, etc.) are dissolved in the liquor obtained in the fourth step (A) as surplus. Therefore, further (C nitric acid, sulfuric acid, hydrochloric acid, acetic acid, etc.) is added to the liquor,
The ions may be precipitated as insoluble salts, and the precipitate may be removed by filtration again to obtain a clear F solution, and the vaginal fluid may be neutralized to obtain the final treatment solution.

<Fourth step (B)> The treated solution containing the precipitate obtained in the sixth step is filtered and separated into the precipitate and P solution. Next, nitric acid, sulfuric acid,
Add an acid such as hydrochloric acid or acetic acid, preferably nitric acid for r) H of 1 to 4, preferably 2 to 3, then add sodium sulfate, sodium sulfate, hydrogen peroxide, sulfuric acid. 1. Adding a reducing agent such as ferrous iron or immediate sulfuric acid gas to reduce the chromium ions dissolved in the waste liquid. Sara(/i
l: Add alkali such as sodium hydroxide, potassium hydroxide, aqueous ammonia, etc. to adjust the pH to 7-11, precipitate the reduced chromium ions as hydroxide or oxide, filter, and separate the precipitate and P solution. do.

A typical reaction example in the fourth step (B) is as follows.

Cr2O7+3803' + 8H →2C%+ 3SO4' + 4H0Cr2O7+
6Pe +14I(” →2Cr+6Fe+7H20 3+ Cr + 30H-→Cr(OHIs (dark green precipitate)
The liquor liquor obtained in the fourth step (13) may be further neutralized to obtain the final treated liquor.

In this way, in the present invention, AP system waste liquid and C1tro
x-type waste liquid can be separated into precipitate and clear final treated liquid, and the volume of the latter can be reduced by a large amount by employing evaporation means such as an ordinary evaporator.

Although the present invention has mainly been described with respect to the decontamination of equipment contaminated with radioactivity, it is not limited to this, but is also applicable to AP systems that occur when cleaning schools such as ordinary boilers and heat exchangers. It goes without saying that this method can also be applied to C1trOX-based waste liquids.

Examples) Hereinafter, the present invention will be concretely explained in detail by listing the actual results.
do.

Example 1 HP-based decontamination agent (composition: 11 um of sodium hydroxide 105 y/l
, potassium permanganate (32 P/l) and C1trO
x-based decontamination agent (composition: 259/l of oxalic acid, 50/l of ammonium citrate, 21/l of ferric nitrate, 11/l of diethylthiourea) at a rate of 130%! /l, 80
! 1 ton of aqueous solution dissolved in
(total of 4F), and these were used as coagulated waste liquid (hereinafter referred to as r
APAP-based waste liquid (referred to as "C1trox-based waste liquid"). This AP-based waste liquid and C1jrnx-based waste liquid are mixed and neutralized (step 1), and then concentrated nitric acid is added to this mixed liquid (p) (5.
5, and a decomposition reaction was carried out at a temperature of 1F and 50℃ for 60 minutes (second
process). After confirming that the carbon dioxide release accompanying the decomposition reaction was completed, the solution was then oxidized with 10N hydroxide.) When a lithium aqueous solution was added and the pH was adjusted to 9.5, manganese ions dissolved in the waste solution were detected. and a precipitate of iron ions was formed (third step).

Treatment solution containing the obtained precipitate 1:8y/101:l++
The chromium ions dissolved in the treatment solution were precipitated as barium chromate by adding 5001111 of the barium nitrate aqueous solution (4th step (A)).

After filtering the obtained treatment solution containing the precipitate and separating it into the precipitate and P solution, 12 ml of concentrated sulfuric acid was added to it to precipitate the excess B)J ion, and then 10N hydroxide) and adjust the pH to 8.0 by adding an aqueous solution of iumium ions.
Further 1 (this treated solution is filtered into L1 precipitate and F solution from door to door)
Ta. This P solution is the final treatment solution, and the analysis results of this treatment solution are shown in Table 1.

Using the final treated solution obtained in Table 1, a 1% eclipse test was conducted according to a conventional method under the same normal pressure and boiling point conditions as the operating conditions of the evaporator. 1 or less, which was confirmed to be within the normally acceptable range.

Example 2 Example 1. After filtering the treatment solution containing the precipitate obtained in the 6th step and separating the P into the precipitate and E solution, add concentrated nitric acid to this P solution.
was added to adjust the pH to 6, then sodium sulfite 2009
1DOml of aqueous solution of 10% of the concentration of sodium chloride was added, the pH was adjusted to 3 with nitric acid, the chromium ion was reduced from hexavalent to hexavalent, and a 1C10 normal sodium hydroxide aqueous solution was added to adjust the pH to 9.5, resulting in the precipitation of chromium hydroxide. Generated [4th step (B)]
.

The treated solution containing the obtained phase and precipitate was filtered and separated into the precipitate and F solution, and the slurry was neutralized to pH 8 with concentrated sulfuric acid and used as the final treatment FT!
I got the liquid. The analysis results of this final treatment solution are shown in Table 2.

Table 2: Effects of the Invention) As described above, according to the present invention, citric acid, citric acid, and their organic acid salts constituting the il C11rox decontamination agent can be decomposed with carbon dioxide. Significant volume reduction can be achieved.

11) Since waste liquid can be separated into precipitate and clear final treated liquid, radioactive substances can be concentrated in the former (precipitate), and radioactive substances can be concentrated in the latter (final liquid). Contamination can be greatly reduced.

111) There are substantially no harmful metal ions (C
Since there is no containment force, even if the volume of vaginal fluid is reduced by the evaporator, the can will not be damaged.

iv) The treatment process itself of the present invention is extremely simple and easy to operate.

vl) Sludge (sediment) generated by waste liquid outlet IC
The amount of is extremely small.

It has numerous advantages such as, and its industrial significance (is extremely dog.

Patent issue i (! II person Mitsubishi Kakoki Co., Ltd. agent)
Patent Attorney Takashi Shirai Continuation of page 1 @ Inventor Sawara 4 City Yozaki City Sakusho

Claims (1)

[Claims] 1. Waste liquid of AP-based decontamination agent whose main component is alkaline permanganate, and waste liquid of CHrox-based decontamination agent whose main components are citric acid and oxalic acid or their organic acid salts. 1 (a decontamination agent waste liquid treatment method characterized by combining the following steps (a) to (d)). (a) AP-based decontamination agent waste liquid and citrox-based decontamination The first step is to mix and neutralize the waste liquid of the agent (the second step is to add an acid to make the pH 7 or less to decompose permanganate, citric acid and oxalic acid, or their organic acid salts) (c) At least one metal ion from the group such as manganese, iron, nickel, cobalt, uranium, and ruthenium is added to the waste liquid to make it pH 7 or higher, and to convert it into hydroxide, The third step is to precipitate it as an oxide or salt. (d) (A) Precipitate the chromium ions contained in the waste liquid as a salt by adding a metal salt, or (B) remove the precipitate by filtration. Add acid to the F solution LpH
1 to 4, then reduce the chromium ions contained in the waste liquid by adding a transition agent, and further add an alkali to adjust the pH to 7 to 11. The reduced chromium ions are converted into hydroxides or oxides. The fourth step is precipitation.