JPS59447B2 - Fuji Yung Gas Seisei Houhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is particularly applicable to non-radioactive gases such as methane, hydrogen, oxygen, nitrogen, argon, carbon dioxide, carbon monoxide and water, as well as cesium, in helium, which is a coolant for nuclear reactors. This invention relates to a method for effectively purifying radioactive substances such as iodine, krypton, and xenon.

Conventional methods for purifying helium containing these impure gases include oxidizing hydrogen and carbon monoxide from steel dioxide, adsorbing and removing moisture and carbon dioxide using molecular sieves, adsorbing and removing radioactive substances using activated carbon, and then using liquid Activated carbon cooled with nitrogen removes residual radioactive material.
It was straining.

However, in this conventional method, the remaining impurity gas due to the reduced purification capacity of the pre-trap cannot be treated in the post-trap, so the life of each trap and the filler in each trap, namely steel dioxide, activated carbon, and molecular sieve, is extremely short. Each trap had to be replaced frequently, which shortened the refining operation time and was uneconomical.

In addition, the regeneration of the filler in the trap, that is, the activated carbon and molecular sieve, requires a complicated system and various equipment such as a heater, as it uses a gas sweep method that uses internal combustion exhaust.
Furthermore, since a high-temperature gas other than helium is introduced into the trap from the outside, the helium atmosphere is disturbed by the residual gas, making it impossible to purify helium to a high degree of purity.

Further, hydrogen is oxidized using steel dioxide, but if this method is used, the steel dioxide trap itself tends to be damaged due to an increase in temperature, and carbon dioxide gas and water are generated.

Removal of these gases is technically very difficult, and furthermore, all of the exhaust gases contain radioactive gases, resulting in significant drawbacks such as poor secondary treatment efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to provide a practically useful method for purifying impure gas in helium containing radioactive substances, which eliminates the above-mentioned drawbacks of the conventional methods and significantly extends the life of each trap.

Hereinafter, the method of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram of an apparatus for implementing the method of the present invention, and in the same figure, a coolant purification system 20 for implementing the method of the present invention is sent from a reactor cooling system 1 to a coolant purification system 20 containing impure gas. Helium 3 is first introduced into a pre-charcoal trap 4 filled with activated carbon, and the metallic and non-volatile fission product gas, ie, iodine, in the impure gas-containing helium is adsorbed and removed.

The pre-charcoal trap 4 has a structure in which each trap can be replaced without being regenerated to prevent environmental pollution.

To prevent leakage of radiation, this pre-charcoal trap is wrapped in a shield 5 made of lead, for example, and this shield has a structure that allows it to be transported when being replaced.

The impure gas-containing helium 3 from which iodine has been removed is introduced into a molecular sieve trap 6c filled with a molecular sieve, where water and carbon dioxide are adsorbed and removed.

Next, the impure gas-containing helium 3 that has passed through the molecular sieve trap 6 is introduced into the cold charcoal trap 7, which is filled with activated carbon and cooled with liquid nitrogen 8.
Methane and carbon monoxide are removed.

Note that the remaining radioactive gas is almost completely removed here.

The cold charcoal trap 1 is shielded with a shielding material such as lead if necessary, and has a structure that allows replacement of each trap.

The impure gas-containing helium 3 that has passed through the cold charcoal trap is introduced into the titanium sponge trap 9 (the titanium sponge filled inside the trap 9 is fed into the heater 100).
By increasing the temperature, hydrogen and tritium are adsorbed and removed.

This titanium sponge trap, like the pre-charcoal trap 4, has a structure that allows each trap to be replaced in order to prevent environmental pollution due to radioactive gas.

The impure gas-containing helium 3 passes through each of the traps described above and is returned to the reactor cooling system 10 as a purifying agent helium 11.

In the illustrated case, a molecular sieve trap 6, a cold charcoal trap 70, and a heater 12 are provided, and the molecular sieve trap 6 and cold charcoal trap 7 are connected to an exhaust header 13, respectively.

In this way, the molecular sieve trap 6 and the cold charcoal trap 7 are heated by the heater 12 and evacuated by the exhaust header 13, thereby regenerating the filler in each trap.

At this time, the liquid nitrogen 8 in the cold charcoal trap 7
It is preferable to once take out the filler to the outside, regenerate the filler, and then return it to the trap.

A heat exchanger 14 is provided between the molecular sieve trap 6 and the cold charcoal trap 7, and this heat exchanger increases the thermal efficiency of O when the impure gas-containing helium 3 flows from the molecular sieve trap 6 to the cold charcoal trap 7. act.

In the illustrated case, the impure gas-containing helium discharged from the cold charcoal trap 7 passes through the heat exchanger 14 and further passes through the preheater 15 to flow into the titanium sponge 9.

This preheater 15 rapidly heats the helium 3 containing impure gas within the titanium sponge 9 in order to efficiently purify it.

In the present invention, impurity gas in helium can be efficiently purified and removed by combining the traps as described above.

In addition, to increase the safety of the device, the cooler is air-cooled and a titanium sponge trap (this is equipped with a preheater).

Among radioactive substances, the release of radioactive iodine and tritium into the environment is optimal for preventing damage.

Therefore, a pre-charcoal trap is provided as the first trap to collect radioactive iodine, and a final trap closure and a titanium sponge trap are provided to collect tritium, and these traps are not regenerated but treated as solid waste.

Molecular sieve trap, charcoal trap (Even if it is difficult, in order to reduce the amount of radioactive material, we do not use the usual air purging method with N2 gas, but vacuum regenerate each trap by heating it to a higher temperature than the operating temperature.

This regeneration gas is processed in the exhaust system. If the combination order of each trap is different, efficient purification and removal of impure gas cannot be performed.

For example, if the first stage is a titanium trap, as in the prior art, a large number of impurity gases will be adsorbed, resulting in a shortened lifetime and the need for regeneration.

Referring to the table shown below, specific examples of each trap used in the present invention are shown.

Further, FIG. 2 shows the relationship between the impurity concentration in the primary system of an actual material irradiation test (38 cycles) and the date and time of measurement.

As is clear from FIG. 2, the impurity concentration of the water at the inlet of the purification system decreases with the passage of time.

Therefore, it can be seen that helium is being purified.

According to the present invention, as described above, post-treatment of each trap can be carried out sufficiently by the heater and exhaust header equipped with the trap, so that the life of each trap and the life of the filler can be extended, and the radioactive gases adsorbed can be can be completely handled by replacing the trap.

Furthermore, by heating the titanium sponge, hydrogen and tritium are adsorbed and removed, making it possible to efficiently purify a large amount of helium containing impure gas.

In this case, damage to the trough upper body caused by the high heat generated when hydrogen is removed using carbon dioxide steel can be avoided by using the titanium sponge.

Furthermore, since a high-temperature evacuation method using external heat is adopted, the helium atmosphere within each trap does not collapse, further increasing efficiency.

In addition, the impure gas-containing helium introduced into the titanium sponge trap via the preheater can be trapped in a much larger capacity than the conventional titanium sponge trap, which further increases purification efficiency and eliminates waste gas containing radioactive gas and radioactive waste gas. It has great effects such as being able to perform secondary treatment separately from the exhaust gas that does not contain oxygen.

It should be noted that the arrangement of the traps in the method of the present invention is not limited to the above embodiment, and it goes without saying that the traps may be connected in parallel depending on the amount and concentration of impurity gas.

Further, if the temperature of the pre-charcoal trap or molecular sieve trap is lowered through a heat exchanger or by using liquefied carbon dioxide, the performance can be easily improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus for carrying out the method of the invention;
FIG. 2 is a graph showing the relationship between impurity concentration and measurement date and time. 4... Pre-charcoal trap, 6...
・Molecular sheep trap, 7...Cold charcoal trap, 8...Liquid nitrogen, 9...
...Titanium sponge trap, 10,12...
...Heater, 13...Exhaust header, 14...
...Heat exchanger, 15...Preheater.

Claims (1)

[Claims] 1. Metallic and non-volatile fission product gases are removed by a pre-charcoal trap, then moisture and carbon dioxide are removed by a molecular sieve trap with a heater and connected to the exhaust header, and then the heater and liquid nitrogen are removed through a heat exchanger. Oxygen, nitrogen, methane and carbon monoxide are removed by a cold charcoal trap connected to the exhaust header containing the hydrogen by a titanium sponge trap with a titanium sponge and a heater that heats this titanium sponge through a heat exchanger and a preheater. and a method for purifying impure gas in helium containing radioactive substances, characterized by removing tritium.