CN-116913570-B - Radioactive purification method for shell-and-tube type vertical heat exchanger

CN116913570BCN 116913570 BCN116913570 BCN 116913570BCN-116913570-B

Abstract

The invention belongs to the technical field of nuclear power plant radiation protection application, and particularly relates to a radioactive purification method for a shell-and-tube type vertical heat exchanger. The radioactive purification evaluation method is established by combining a process for purifying the storage tank medium of the loop coolant temporary storage system and a process for removing the radioactive purification of the shell-and-tube type and vertical heat exchangers, wherein the process for purifying the storage tank medium of the loop coolant temporary storage system analyzes the radioactive volume activity of the storage tank medium of the loop coolant temporary storage system through radioactive chemical sampling, the requirement is limited to be 2.0 multiplied by 10 4 Bq/m 3 , and the process for removing the radioactive purification of the shell-and-tube type and vertical heat exchangers measures the radiation level of the shell-and-vertical heat exchangers, so that the required dose rate is reduced by more than 50 percent. The invention is used for solving the technical problem of purifying and removing radioactivity in equipment after the shell-and-tube type vertical heat exchanger of the nuclear power plant is stopped.

Inventors

XIE WEIPING
ZHANG CHONGSHAN
Di mingle
ZHAO XIHUAN
LI ZHONGHUA
CHEN QUANLI
LIU YUANLIANG
WANG YUANWEI
WEN XIAOFENG
ZHANG XULIANG

Assignees

江苏核电有限公司

Dates

Publication Date: 20260512
Application Date: 20230712

Claims (1)

1. A radioactive purification method for a shell-and-tube vertical heat exchanger is characterized in that the method comprises the following steps: The reactor core is connected with one end of a valve F, the other end of the valve F is respectively connected with one end of a valve G, a shell type and a vertical heat exchanger, the other end of the valve G is respectively connected with one end of a valve J and one end of a valve I, the other end of the valve I is connected with the shell type and the vertical heat exchanger, the other end of the valve J is respectively connected with a temporary storage tank of a loop coolant system and one end of a resin bed D, the other end of the resin bed D is connected with one end of a valve H, the other end of the valve H is connected with the shell type and the vertical heat exchanger, and a pump and a check valve are sequentially arranged between the temporary storage tank of the loop coolant system and the shell type and the vertical heat exchanger; step 1, confirming that a shell-and-tube type vertical heat exchanger is stopped, and providing conditions for implementing the method; step 2, establishing a medium purifying process for a storage tank of a temporary storage system of the primary loop coolant, which comprises the steps of a storage tank of the temporary storage system of the primary loop coolant, a pump, a valve A, a valve B, a resin bed A, a resin bed B, a resin bed C, a valve D, a valve E and a storage tank of the temporary storage system of the primary loop coolant; Step 3, analyzing the radioactive volume activity of the storage tank medium of the primary loop coolant temporary storage system through radioactive chemical sampling, and judging whether the purifying effect reaches the limit value requirement of 2.0 multiplied by 10 4 Bq/m 3 ; Step 3.1, if the purifying effect does not reach the limit value requirement, continuing to purify according to step 2 until the limit value requirement is met; step 3.2, if the purifying effect reaches the limit value requirement, recovering the state of the system equipment, and carrying out the next step; Step 4, establishing a vertical shell type heat exchanger radioactive purification and removal process; step 5, flushing the shell-and-tube type vertical heat exchanger; step 5.1, measuring the radiation level of the shell-type vertical heat exchanger; Step 5.2, a vertical shell-and-tube type heat exchanger flushing process is built, specifically comprising the steps of closing a valve F, a valve G and a valve H, temporarily storing a loop coolant in a system storage tank, pumping, a check valve, a shell-and-tube type heat exchanger, a valve I, a valve J and a loop coolant in a system storage tank; step 5.3, judging whether the flushing effect meets the requirement that the dosage rate of the shell-and-tube type vertical heat exchanger is reduced by 50% by measuring the radiation level of the shell-and-tube type vertical heat exchanger after flushing; step 5.4, if the flushing effect does not reach the limit value requirement, continuing to purify according to step 5.2 until the limit value requirement is met; step 5.5, if the purifying effect reaches the limit value requirement, carrying out the next step; step 6, purifying the shell-and-tube type vertical heat exchanger; Step 6.1, measuring the radiation level of the shell-type vertical heat exchanger; Step 6.2, a vertical shell-and-tube type heat exchanger purification process is built, specifically comprising the steps of closing a valve F, a valve I and a valve G, temporarily storing a loop coolant in a system storage tank, pumping, a check valve, a shell-and-tube type heat exchanger, a valve H, a resin bed D and temporarily storing the loop coolant in the system storage tank; Step 6.3, judging whether the flushing effect meets the requirement that the dosage rate of the shell-and-tube type vertical heat exchanger is reduced by 50% by measuring the radiation level of the shell-and-tube type vertical heat exchanger after flushing; Step 6.4, if the flushing effect does not reach the limit value requirement, continuing to purify according to step 6.2 until the limit value requirement is met; Step 6.5, if the purifying effect reaches the limit value requirement, the purifying work is finished; and 7, recovering the state of the system equipment.

Description

Radioactive purification method for shell-and-tube type vertical heat exchanger Technical Field The invention belongs to the technical field of nuclear power plant radiation protection application, and particularly relates to a radioactive purification method for a shell-and-tube type vertical heat exchanger. Background The shell-and-tube type vertical heat exchanger is mainly used for cooling media of a user system so as to ensure safe and stable operation of the user system. Because of the temperature difference in the heat exchanger area, the shell-and-tube type and vertical heat exchanger used in the primary loop system of the nuclear power plant is easier to deposit radioactive corrosion activation products than other equipment, so that the shell-and-tube type and vertical heat exchanger and the nearby area have higher radiation level. Especially, during the major repair of the nuclear power unit refueling, after the related system of the primary loop of the nuclear power plant is stopped, the medium in the shell-and-tube type vertical heat exchanger is emptied, so that the radiation level of the equipment is further increased, and the irradiated dose of workers for repairing and maintaining the shell-and-tube type vertical heat exchanger and other workers nearby is increased. Nuclear power plants typically shut down shell-and-tube, vertical heat exchanger equipment, and then the radiation level of the equipment is census by radiation protection personnel, and the high radiation level (typically contact dose rate greater than 1 mSv/h) of the equipment is shielded by scaffolding and using lead skin, which causes additional exposure dose to the scaffolding, lead shielded personnel. In addition, the shielding lead can not be increased without limitation due to the bearing requirement of the equipment. How to purify and remove radioactivity in a shell-and-tube heat exchanger after the shell-and-tube heat exchanger is isolated, so as to reduce the radiation level of the shell-and-tube heat exchanger is a problem which needs to be solved by the person skilled in the art. Disclosure of Invention The invention aims to provide a radioactive purification method for a shell-and-tube vertical heat exchanger, which is used for solving the technical problem of purifying and removing radioactivity in equipment after the shell-and-tube vertical heat exchanger of a nuclear power plant is stopped. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a radioactive purifying method for shell-and-tube vertical heat exchanger, 1) Medium purifying process for storage tank of temporary storage system of primary loop coolant Before removing and purifying the shell-and-tube type vertical heat exchanger, the method comprises the steps of taking the medium from the storage tank of the temporary storage system of the loop coolant by a pump, opening a valve A and a valve B, purifying and removing radioactive nuclides in the medium by the storage tank medium of the temporary storage system of the loop coolant through a resin bed A, a resin bed B and a resin bed C, and opening a valve C, a valve D and a valve E to enable the medium of the storage tank of the temporary storage system of the loop coolant to return to the storage tank of the temporary storage system of the loop coolant after the purification; 2) Radioactive flushing and purifying process for vertical tube-type vertical heat exchanger After the medium of the storage tank of the temporary storage system of the loop coolant is purified and meets the requirement, the radioactive purification and removal process of the shell-type and vertical heat exchanger is built by (1) closing a valve F, a valve G and a valve H, the flushing process of the shell-type and vertical heat exchanger is built, in particular, a pump is used for taking the medium from the storage tank of the temporary storage system of the loop coolant, the medium is flushed by the shell-type and vertical heat exchanger through a check valve, a valve I and a valve J are opened, the medium is returned to the storage tank of the temporary storage system of the loop coolant; 3) Establishing a radioactive purification evaluation method The radioactive purification evaluation method is established by combining a process for purifying the storage tank medium of the loop coolant temporary storage system and a process for removing the radioactive purification of the shell-and-tube type and vertical heat exchangers, wherein the process for purifying the storage tank medium of the loop coolant temporary storage system analyzes the radioactive volume activity of the storage tank medium of the loop coolant temporary storage system through radioactive chemical sampling, the requirement is limited to be 2.0 multiplied by 10 4Bq/m3, and the process for removing the radioactive purification of the shell-and-tube type and vertical heat exchangers measures the radiation level of the