Leakage Control System for Spent Fuel Cooling Pool

Abstract

A leakage detection system for spent fuel cooling pools is related to the field of testing and measurement instrumentation and is aimed at monitoring leakages in the storage facilities, mostly in spent fuel cooling pools at NPPs.

In the leakage detection system for spent fuel cooling pools the welded joints in the pool are additionally fenced with a metal guard which are connected via valve installed tubes to the pipeline, which, in turn, is connected on both of its sides to the leakage collector tank via a receiving valve and a return valve. The leakage collector tank is equipped with a level control sensor.

A leakage detection system for spent fuel cooling pools ensures control over airtightness of welded joins in the pool and allows for detection of leaking welded joints without preliminary emptying the pool which enhances the radiation safety of the pool and reduces the maintenance time.

Claims

1. A leakage control system for monitoring leakages in the spent fuel pool which includes the following components: a pipeline, a liquid level gauge connected to a control module; welded joints in the spent fuel cooling pool are additionally fenced with a metal guard connected to the pipeline by means of two tubes with valves; the pipeline is connected on both sides to the leakage collector which is equipped with a liquid level gauge; a control module is connected to all the valves.

2. The leakage control system of claim 1 characterised by an additional compressed air supply unit with a compressed air supply valve; the compressed air supply unit is connected to the pipeline by means of the compressed air supply valve; the compressed air supply unit is designed to supply compressed air via the compressed air supply valve; the pipeline and the compressed air supply valve are integrated in the metal fence around the welded joints as an additional means of leakage detection.

3. The leakage control system of claim 1 characterised by an additional coloured water supply unit with a coloured water supply valve; the coloured water supply unit is connected to the pipeline by means of the coloured water supply valve; the coloured water supply unit is designed to supply coloured water via the coloured water supply valve; the pipeline and the coloured water supply valve are integrated in the metal fence around the welded joints as an additional means of leakage detection.

4. The leakage control system of claim 1 characterised by a receiving valve and a return valve installed in the outlet of the leakage collector.

5. The leakage control system of claim 1 characterised by an additional pump installed between the leakage collector and a return valve.

6. The leakage control system of claim 1 wherein the level control sensor is a pressure sensor.

7. The leakage control system of claim 1 wherein level control sensor is a conductivity sensor.

8. The leakage control system of claim 1 characterised by the control module connected to all the valves in the system and to the pump either via wired or wireless communication.

9. The leakage control system of claim 1 characterised by a compressed air supply unit additionally fitted with compressed air pressure sensor.

Description

BRIEF DESCRIPTION OF FIGURES

[0022] The core idea of the proposed invention is represented in FIGURE where the embodiment of the leakage control system is shown: it includes the metal lining of the cooling pool (6) with the welded joints (1) and surrounded with a concrete wall (shaded area), each welded joint (1) is fenced with a metal guard (2) which are secured against the cooling pool (6) with external welded joints (11) and connected with the valve installed tubes (3) to the pipeline designed with the possibility of discharging potential leakages via a receiving valve (4) to the leakage collector tank (7) which is equipped with a level gauge (5). The leakage water can go back from the leakage collector tank (7) to the cooling pool (6) with the help of the pump (8) via the return valve (9). The system also includes a compressed air supply valve (10) designed to supply either compressed air or coloured water to the system, and equipped also with a compressed air pressure sensor (12). All valves and the pump are connected to the control module (not shown on the FIGURE) via wired and wireless connections, and the control module is designed to control all the valves and the pump.

EMBODIMENTS

[0023] The functioning of the leakage control system for spent fuel cooling pool can be described as follows: In the period when the spent nuclear fuel is stored in the pool (6) the operator uses the control module for regular opening of the valves (3), when one of the valves is open, the rest of the valves are closed, at this point the operator should check the indications of the level control sensor (5) with the return valve (9) closed and with the pump (8) OFF. In case the indications displayed by the level gauge (5) remain without changes, the operator understands that the welded joint (1) which corresponds to the opened valve (3) is free of leakages. In case the level gauge (5) indicates that the level in the leakage collector tank (7) has increased, the operator understands that the welded joint (1) which corresponds to the opened valve (3) is leaking. After that the operator applies the same procedure to check the rest of the welded joints. When the inspection is completed or the leakage collector tank (7) is full, the operator gets the liquid from the leakage collector tank (7) back to the pool by opening the return valve (9) and using the pump (8). Then the operator closes the valves (3) which correspond to those welded joints (1) for which the leakage was detected during the inspection, in order to prevent any radioactive water to penetrate the side walls of the cooling pool. It should be noted that radioactive water which leaked out of the pool (6) through the faulty welded joint (1) is prevented from penetrating the side walls by metal guards (2), this makes it possible to continue using the pool up to the scheduled maintenance, the duration of the maintenance will also be reduced because the location of leakages on the welded joints (1) has already been detected.

[0024] In its preferable embodiment the leakage control system for the spent fuel cooling pool is additionally equipped with a compressed air supply valve (10) designed to supply compressed air, for example, from a compressed air cylinder. In this embodiment the operator supplies the compressed air to the system by opening the compressed air supply valve (10) and all or part of the valves (3), with the receiving valve (4) and the return valve (9) shut off. At this point the compressed air goes through the pipelines and through the open valves (3), gets to the cooling pool (6) through the leaking welded joints (1) and can be identified by slight bubbles which clearly show how airtight each welded joint is, and where exactly the joint is leaking. Use of telemetric facilities makes it possible to detect the leakages without emptying the pool (6). Instead of compressed air in one of the embodiments the coloured water is used, as it provides for the same result.

[0025] Moreover, if an additional pressure sensor (12) for the compressed air is integrated in the compressed air supply unit (10) it will be possible to check the airtightness of external welded joints (11) which secure the metal guards (2) against the cooling pool (6). To do this, the operator should initiate the compressed air supply to the pipeline, for example, with one of the valves (3) open and the rest of the valves (3), receiving valve (4) and return valve (9) closed. If no bubbles appear near the internal surface of the corresponding welded joint (1), the operator should check the indications of the compressed air pressure sensor (12). In case the pressure has dropped, the operator understands that this welded joint securing the metal guard (11) is leaking.

INDUSTRIAL APPLICABILITY

[0026] The system for detection of leakages in the spent fuel cooling pools ensures improved radioactive safety and reliable storage of spent nuclear fuel in the cooling pools, as well as allows reducing the duration of maintenance for the cooling pools, so it can be widely used in nuclear power generation.