JPH0250439B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a moderator purification system for a heavy water reactor, and is particularly applicable to a moderator purification system that uses liquid poison in the moderator system and uses a poison-saturated resin as the purification tower resin. The present invention relates to a moderator purification system for heavy water reactors suitable for use in heavy water reactors.

A conventional example of a moderator system for a heavy water reactor is shown in Figure 1.
The moderator system that supplies heavy water, which is a moderator, into the calandria tank 2 includes an overflow tank 6, an overflow pump 7, a heavy water circulation pump 4, a heavy water cooler 8, a D ₂ O ₂ decomposition device 9, a heavy water purification device 11,
It is composed of a poison concentration control system 12 and piping such as a heavy water distribution pipe 13. The heavy water outlet pipe 3 connects the calandria tank 2 and the heavy water cooler 8, and has a heavy water circulation pump 4. The heavy water supply pipe 19 is
The heavy water cooler 8 and the heavy water distribution pipe 13 are connected.
The overflow pipe 5 communicates the calandria tank 2 and the heavy water cooler 8, and has an overflow tank 6 and an overflow pump 7. Purification piping 2
0 connects the D ₂ O ₂ decomposition device 9, the heavy water purification device 11 and the poison concentration control system 12, and both ends are attached to the heavy water supply pipe 19. 1 is an iron body,
10 is a bypass pipe. Most of the heavy water flowing out into the calandria tank 2 from the lower part of the control rod guide pipe 15 passes through the heavy water outlet pipe 3, and a part of it passes through the overflow pipe 5 and enters the heavy water cooler 8.
Most of the heavy water cooled here is from the heavy water supply pipe 1
9 and reaches the inside of the heavy water distribution pipe 13 , further passes through a large number of heavy water inlet pipes 14 , and returns to the calandria tank 2 through the control rod guide pipe 15 . However, some of the heavy water discharged from the heavy water cooler 8 passes through the D ₂ O ₂ decomposition device 9 , the heavy water purification device 11 , and the poison concentration control system 12 . Here, a poison concentration control system and impurity removal in heavy water are performed. The poison concentration control system 12 consists of a poison supply device that stores a highly concentrated poison solution and supplies it to the moderator system, and a poison removal device that reduces the poison concentration in the system.The poison removal device includes a strong basic ion exchange resin. It is used. Poison, such as boron, as a neutron absorber is dissolved in heavy water, which is a moderator.

The heavy water purification device 11 has conventionally been filled with a weakly basic ion exchange resin in order to remove impurities without removing poisons. However, weakly basic ion exchange resins are easily degraded by deuterium peroxide produced by radiolysis of heavy water.
Plans are underway to use strongly basic ion exchange resins that do not easily deteriorate.

When using a strongly basic ion exchange resin, it must be a poison-saturated type, so if the inlet temperature of the heavy water purification equipment changes, such as when starting or stopping the plant, the resin will absorb and desorb poisons, causing damage to the moderator. There is a problem that the concentration of poison changes.

An object of the present invention is to provide a moderator purification system for a heavy water reactor that can reduce changes in the concentration of poison in heavy water moderator water caused by a heavy water purification device.

A feature of the present invention is that the heavy water purification device inlet temperature is maintained at a certain constant temperature between the heavy water cooler outlet temperature and the moderator system minimum temperature.

An embodiment of the present invention will be described below with reference to FIG. The heavy water purification device 11 is filled with a poison saturated strong basic ion exchange resin. In this embodiment, in order to maintain the heavy water flowing into the heavy water purification device 11 at the minimum temperature of the moderator system of 10°C (minimum temperature of the purification device room) even under normal conditions, a regenerative heat exchanger is installed on the upstream side of the purification device. 16, a non-regenerative cooler 17 having a refrigeration device 18 is provided. Regenerative heat exchangers are used to reduce operating costs. A portion of the heavy water discharged from the heavy water cooler 8 passes through the D ₂ O ₂ decomposition device 9 and is cooled to 10° C. in the regenerative heat exchanger 16 and cooler 17, and then is transferred to the heavy water purification device 11.
It is heated by the regenerative heat exchanger 16 and sent to the poison concentration control system 12. In a 60 MWe class heavy water reactor, the purification flow rate is about 20 m ³ /h, so the refrigerator motor capacity required to cool heavy water at 49° C. to 10° C. is about 120 KW, which is not a particular problem.

In this example, even if a failure occurs in the 10°C holding device, the heavy water temperature will rise and the poison will be
Since it is released into the moderator from the poison saturated strong basic ion exchange resin, it has the effect of safely shutting down the nuclear reactor.

In addition, in Figure 2, the constant holding temperature was set as the lowest moderator temperature, which required constant cooling, but by setting the constant holding temperature as the temperature during normal operation of the reactor, the amount of cooling or heating could be reduced. , thermal efficiency can be increased. That is, heavy water purification device 1
The heavy water temperature is measured on the upstream side of the cooler 1, and when the heavy water temperature exceeds a predetermined value, for example, the heavy water temperature during normal operation of the reactor, the refrigeration device 18 is activated to
Cool the heavy water in step 7. As a result, the cooler 17 is operated only when the reactor is started and stopped, thereby increasing thermal efficiency. In this embodiment, only cooling by the heavy water cooler 8 is performed during normal operation of the nuclear reactor.

According to the present invention, the amount of poison adsorbed and desorbed from the purification device due to changes in the poison concentration in the moderator can be minimized, thereby improving poison concentration controllability and reducing the number of times the control rod for output adjustment is driven. There is.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a conventional moderator system for a heavy water reactor, and FIG. 2 is a system diagram of a moderator system for a heavy water reactor according to an embodiment of the present invention. 2...Calandria tank, 3...Heavy water outlet pipe, 8...Heavy water cooler, 11...Heavy water purification device,
14...Heavy water inlet pipe, 16...Regeneration heat exchanger, 1
7...Cooler, 19...Heavy water supply pipe.

Claims (1)

[Claims] 1. A moderator purification system for a heavy water reactor consisting of a pipe whose both ends are connected to a calandria tank filled with heavy water, which is a moderator containing poison, and into which heavy water flows, and a purification device installed in the pipe.
A moderator purification system for a heavy water reactor, characterized in that the purification device is filled with a strong basic resin, and a cooler is provided in the piping upstream of the purification device.