JPS59112294A - Device for removing radioactive iodine from nuclear fuel reprocessing plant - 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 The present invention relates to an apparatus for removing radioactive iodine generated in a nuclear fuel reprocessing plant, and particularly to an apparatus suitable for efficiently and economically removing radioactive iodine.

Conventionally, equipment for removing radioactive iodine contained in off-gas treatment systems during the shearing and melting processes of nuclear fuel reprocessing plants has adopted either a wet method using an alkaline absorption liquid or a dry method using an adsorbent impregnated with silver. Ta. However, in the wet method, in the case of the alkaline cleaning method, the removal efficiency was as low as about 10, and there were problems in processing the waste liquid generated in large quantities. On the other hand, the dry method using a silver-impregnated adsorbent requires a large amount of expensive silver, resulting in high costs.

The purpose of the present invention is to place an adsorbent impregnated with a metal other than silver that roughly removes iodine in the front stage of radioactive iodine removal equipment using a wet method or a dry method, thereby further increasing the iodine removal efficiency and making it more economical. The goal is to provide a device that is

For adsorbents for removing iodine, metals other than silver can also be used.
Basic experiments have shown that metals such as lead, copper, and cadmium have relatively excellent removal performance, and have attracted attention as adsorbents that can replace silver. It had not been put into practical use. The present invention reduces the load required for iodine removal in conventional equipment by combining these adsorbents impregnated with metals other than silver with conventional removal equipment, and achieves high removal efficiency and economical radioactive iodine removal equipment Rough 6. It is a duplicate.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. -1,2
U This is an adsorbent that is completely impregnated with metals other than silver.

In the present invention, gas containing radioactive iodine generated in the nuclear fuel reprocessing shearing/composition process passes through the adsorption tower 1 and is adsorbed and removed according to the following reaction formula.

MX+L→IVI I 2 (1) In the formula (1), M represents a metal mesh other than iron such as lead, copper, or cadmium, and X represents a base material such as Zeon-f I-. Table 1 shows an example of the removal efficiency j (11 constant) of the adsorbent completely impregnated with these metals.
Shown below. As is clear from the table, the removal efficiency is generally low at relative humidity other than zero. High humidity (more than 90% in temperature removal) and high iodine concentration (several io
For example, in the case of PbX, the removal efficiency is about 80%.

Table 1 Removal performance of elemental iodine According to the present invention, for example, when PbX is used in the first stage, about 80 parts of iodine is removed, and the iodine concentration sent to the wet or dry removal equipment in the second stage is about 20 parts. Reduced to vine. In this way, if iodine is roughly removed in step 1, step 7 can be obtained, so the iodine load on the subsequent iodine removal equipment is reduced. When combined with the wet method, the effect of improving iodine removal efficiency can be seen. Furthermore, in the case of a dry method using a silver adsorbent, the amount of silver used can be reduced.

After iodine is adsorbed to saturation in step 1, the operation is switched to step 2. Used adsorbents are packed into drums and stored as is. Metals such as lead and copper are relatively inexpensive, so even if they are disposed of it, the cost can be reduced. While the switching operation is being performed in step 2, preparations are made for the next operation.

According to the present invention, when combined with the conventional wet method, the removal efficiency of radioactive iodine in the off-gas treatment system of the nuclear fuel reprocessing process is about five times higher than when lead is used. (The DF of lead is about 5 as described above) It is also possible to reduce the amount of iodine in the iodine-containing waste liquid in the wet method, which has the effect of facilitating the subsequent waste treatment. In addition, when combined with a silver-impregnated adsorbent, it is possible to prevent adverse effects such as a decrease in DF due to changes in the concentration of the silver-impregnated adsorbent in response to sudden changes in the iodine concentration in the off-gas.

For example, the amount of radioactive iodine generated when 600 tons of spent light water reactor fuel is reprocessed per year is about 160 kg. (
After 667 days of combustion at a burnup of 40,000MWD/l, 5
). Comparing the total amount of silver required when all of this iodine is adsorbed by silver (Case A) and when a lead-impregnated adsorbent is placed in the front stage (Case B), stoichiometrically, Case A The island is approximately 193
kg, in case B, silver is about 39 kg and lead is about 80 kg.
kg, it is possible to reduce the amount of silver required by approximately 154 kg,
It is possible to reduce the cost to about 1/4.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of an apparatus for removing radioactive iodine from a nuclear fuel reprocessing facility according to the present invention. 1.2...Adsorption tower, 3...Radioactive iodine removal equipment.

Claims (1)

[Scope of Claims] 1. An apparatus for removing radioactive iodine from a nuclear fuel reprocessing facility, characterized in that a device for roughly removing radioactive iodine is provided upstream of a wet or dry method radioactive iodine removal facility. 2. Lead in equipment that roughly removes radioactive iodine. An apparatus for removing radioactive iodine from a nuclear fuel reprocessing facility according to claim 1, further comprising an adsorbent impregnated with a metal other than silver, such as copper or cadmium.