US-12623182-B2 - Filter for removing radioactive noble gas, filter unit and reactor containment vent system

US12623182B2US 12623182 B2US12623182 B2US 12623182B2US-12623182-B2

Abstract

A radioactive noble gas removal filter, a filter unit, and a nuclear reactor containment vessel vent system with improved durability are provided. The radioactive noble gas removal filter according to the present invention includes a polyimide film including a structural unit represented by general formula (1).

Inventors

Shigenori Matsumoto
Atsuko Ueda
Takahisa MATSUZAKI

Assignees

HITACHI GE VERNOVA NUCLEAR ENERGY, LTD.

Dates

Publication Date: 20260512
Application Date: 20210608
Priority Date: 20200707

Claims (20)

1 . A radioactive noble gas removal filter comprising a polyimide film comprising a structural unit represented by a first formula: wherein, in the first formula, the N 1 and the N 2 each represent nitrogen, the R 1 comprises at least one first aromatic ring, the R 1 and the N 1 form a first imide ring the R 1 and the N 2 form a second imide ring, a first steric structure of the at least one first aromatic ring, is disposed in a first plane, the first steric structure connecting a second steric structure of the first imide ring to a third steric structure of the second imide ring, wherein at least one of the second steric structure or the third steric structure is not coplanar with the first plane in which the first steric structure is disposed, the R 2 comprises at least one second aromatic ring comprising an aromatic ring bonded to the N 2 , the at least one second aromatic ring to which the N 2 is bonded comprises a first carbon atom bonded to the N 2 , the at least one second aromatic ring to which the N 2 is bonded comprises a second carbon atom and a third carbon atom respectively at positions neighboring to the first carbon atom, at least one of the second carbon atom and the third carbon atom has a substituent, the third steric structure of the second imide ring to which the R 2 is bonded and a fourth steric structure of the at least one second aromatic ring to which the N 2 is bonded are not disposed on a same plane, and n represents an integer of one or greater.
2 . The radioactive noble gas removal filter according to claim 1 , wherein the at least one first aromatic ring comprises two or more first aromatic rings, and two of the two or more first aromatic rings are bonded together by at least one selected from the group consisting of sp 3 carbon, a sulfonyl group, a ketone bond, and an ether bond.
3 . The radioactive noble gas removal filter according to claim 1 , wherein the substituent is at least one selected from the group consisting of an alkyl group having a molecular weight of a methyl group or higher, a halogen-substituted alkyl group where at least one hydrogen atom in an alkyl group is substituted with a halogen element, and a halogen element.
4 . The radioactive noble gas removal filter according to claim 1 , wherein the R 2 comprises a first aromatic ring of the at least one first aromatic ring bonded to the N 2 and the at least one second aromatic ring bonded to the first aromatic ring via a bonding group, the first aromatic ring bonded to the at least one second aromatic ring comprises the first carbon atom bonded to the N 2 , and the bonding group is bonded to the second carbon atom at a position neighboring to the first carbon atom.
5 . The radioactive noble gas removal filter according to claim 4 , wherein the bonding group is at least one selected from the group consisting of C, S, and O.
6 . The radioactive noble gas removal filter according to claim 1 , wherein the polyimide film comprising the structural unit represented by the first formula is a polymer of an acid dianhydride represented by a second formula and a diamine represented by a third formula, wherein the second formula is wherein, in the second formula, the R 3 comprises at least one third aromatic ring, and wherein the third formula is H 2 N—R 4 —NH 2 wherein, in the third formula, the R 4 comprises at least one fourth aromatic ring, the at least one fourth aromatic ring comprising one or more fourth carbon atoms, each bonded to an amino group, there are a fifth carbon atom and a sixth carbon atom respectively at positions neighboring to each of the one or more fourth carbon atoms, and at least one of the fifth carbon atom and the sixth carbon atom has a substituent.
7 . The radioactive noble gas removal filter according to claim 1 , wherein the radioactive noble gas removal filter is configured to be disposed on a vent line configured to vent gas in a nuclear reactor containment vessel to an outside to depressurize the nuclear reactor containment vessel.
8 . A filter unit comprising: the radioactive noble gas removal filter according to claim 1 ; and a holding member configured to hold the radioactive noble gas removal filter.
9 . A nuclear reactor containment vessel vent system comprising: a vent line configured to vent gas in a nuclear reactor containment vessel to an outside to depressurize the nuclear reactor containment vessel; and the filter unit according to claim 8 disposed at a part of the vent line.
10 . A filter unit comprising: the radioactive noble gas removal filter according to claim 2 ; and a holding member configured to hold the radioactive noble gas removal filter.
11 . A filter unit comprising: the radioactive noble gas removal filter according to claim 3 ; and a holding member configured to hold the radioactive noble gas removal filter.
12 . A filter unit comprising: the radioactive noble gas removal filter according to claim 4 ; and a holding member configured to hold the radioactive noble gas removal filter.
13 . A filter unit comprising: the radioactive noble gas removal filter according to claim 5 ; and a holding member configured to hold the radioactive noble gas removal filter.
14 . A filter unit comprising: the radioactive noble gas removal filter according to claim 6 ; and a holding member configured to hold the radioactive noble gas removal filter.
15 . A filter unit comprising: the radioactive noble gas removal filter according to claim 7 ; and a holding member configured to hold the radioactive noble gas removal filter.
16 . A nuclear reactor containment vessel vent system comprising: a vent line configured to vent gas in a nuclear reactor containment vessel to an outside to depressurize the nuclear reactor containment vessel; and the filter unit according to claim 10 disposed at a part of the vent line.
17 . A nuclear reactor containment vessel vent system comprising: a vent line configured to vent gas in a nuclear reactor containment vessel to an outside to depressurize the nuclear reactor containment vessel; and the filter unit according to claim 11 disposed at a part of the vent line.
18 . A nuclear reactor containment vessel vent system comprising: a vent line configured to vent gas in a nuclear reactor containment vessel to an outside to depressurize the nuclear reactor containment vessel; and the filter unit according to claim 12 disposed at a part of the vent line.
19 . A nuclear reactor containment vessel vent system comprising: a vent line configured to vent gas in a nuclear reactor containment vessel to an outside to depressurize the nuclear reactor containment vessel; and the filter unit according to claim 13 disposed at a part of the vent line.
20 . A nuclear reactor containment vessel vent system comprising: a vent line configured to vent gas in a nuclear reactor containment vessel to an outside to depressurize the nuclear reactor containment vessel; and the filter unit according to claim 14 disposed at a part of the vent line.

Description

TECHNICAL FIELD The present invention relates to a radioactive noble gas removal filter for removing radioactive noble gas, a filter unit including the same, and a nuclear reactor containment vessel vent system. BACKGROUND ART One of the functions of the nuclear reactor containment vessel installed in a nuclear power plant is that in the unlikely event that a meltdown (hereinafter referred to as a severe accident) occurs in the core placed in the nuclear reactor pressure vessel to release radioactive materials outside the nuclear reactor pressure vessel, the radioactive materials are confined in the nuclear reactor containment vessel to prevent them from leaking outside. Even if a severe accident occurs, if sufficient water is injected afterward and the nuclear reactor containment vessel is cooled, the accident will be resolved. However, in the unlikely event that steam production continues and the cooling of the nuclear reactor containment vessel is insufficient, the nuclear reactor containment vessel will be pressurized. When the nuclear reactor containment vessel is pressurized, the gas in the nuclear reactor containment vessel can be vented to the atmosphere to depressurize the nuclear reactor containment vessel. This operation is called a vent operation. When performing this venting operation, in boiling water reactors, radioactive materials are removed using the pool water of the suppression pool, and the gas in the nuclear reactor containment vessel (hereinafter referred to as “vent gas”) is released to the atmosphere so as to minimize the exposure of the public. In addition, there is a nuclear reactor containment vessel vent system as a system for further removing radioactive materials from this vent gas. Patent Literature 1 describes an example of nuclear reactor containment vessel vent systems. The nuclear reactor containment vessel vent system described in Patent Literature 1 includes a vent line that discharges the gas inside the nuclear reactor containment vessel to the outside to decompress the nuclear reactor containment vessel. The vent system also includes a filter that is located on the end portion of the vent line on the side of the nuclear reactor containment vessel, impermeable to radioactive materials and permeable to steam, and a protective vessel that surrounds the end portion of the vent line and the filter inside the nuclear reactor containment vessel. This vent system further includes an on-off valve for bypass of the vent line installed in the protective container that opens at an operating pressure equal to or lower than the critical pressure of the nuclear reactor containment vessel and closes at a pressure lower than the operating pressure to discharge gas to the outside without passing through the filter, and an activation valve that is installed in the protective container and opened at an operating pressure equal to or lower than the operation pressure of the bypass on-off valve. In this vent system, the vent gas is scrubbed with water in the suppression pool to remove particulate radioactive materials. In addition, particulate radioactive materials that have not been completely removed by scrubbing are further removed by a metal filter. In addition, gaseous radioactive materials such as iodine are removed through an iodine filter by chemical reaction and adsorption. Radioactive noble gases (such as radioactive isotope gases of krypton and radioactive isotope gases of xenon) are then removed using a membrane filter that is permeable to water vapor but impermeable to noble gases. Patent Literature 1 states that a polymer film containing polyimide as a main component (hereinafter referred to as a “polyimide film”) is suitable as such a membrane filter. CITATION LIST Patent Literature Patent Literature 1: JP2018-179693A SUMMARY OF INVENTION Technical Problem A nuclear reactor containment vessel vent system aimed at removing radioactive noble gases using a membrane filter removes the radioactive noble gases by installing a membrane filter permeable to water vapor but impermeable to noble gases on the vent line through which the vent gas passes, as in Patent Literature 1. The amount of water vapor and noble gas that permeate the membrane filter is determined by the membrane area, the partial pressure difference between the gases across the membrane filter, and the permeability of the membrane filter to each gas. A polyimide film has a characteristic that it has excellent heat resistance and has a dense structure, and thus has a lower noble gas permeability than the water vapor permeability, and can selectively release water vapor to the outside. However, a polyimide film is generally obtained by dehydration condensation of two kinds of raw materials, an acid dianhydride and a diamine, to produce the polyimide constituting the film material, so that there is a possibility that hydrolysis reaction by water molecules is reversibly induced. In particular, polyimide, which is used fo