JPS59126293A - Relaxation device for horizontal pipe temperature distribution of fast breeder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a horizontal pipe temperature distribution relaxation device for a fast breeder reactor.

[Technical Background of the Invention] FIG. 1 shows a liquid metal cooled fast breeder reactor, and in the figure, reference numeral 1 indicates a reactor vessel.

A reactor core 3 supported by a core support plate 2 is disposed within the reactor vessel 1 . A fixed plug 4 is inserted into the upper opening of the reactor vessel 1, and a rotary plug 5 is inserted into a through hole formed in the fixed plug 4. This rotary plug 5 has an eccentric through hole bored therein.
A core upper mechanism 6 is inserted into this through hole. A reactor vessel inlet nozzle pipe 7 is opened at the lower side of the reactor vessel 1, and a reactor vessel outlet nozzle pipe 8 is opened at the upper side.

In the liquid metal cooled fast breeder reactor configured as described above, the reactor vessel 1 contains a liquid metal 9 made of, for example, liquid metal sodium, and the reactor vessel 1 includes reactor vessel inlet nozzle piping. The relatively low temperature liquid metal 9 flowing in from the reactor core 3 obtains thermal energy through nuclear fission, and then flows out from the reactor vessel outlet nozzle pipe 8.

[Problems with the Background Art] However, in the liquid metal cooled fast breeder reactor configured as described above, when the reactor is tripped, for example, the liquid metal in the upper reactor plenum will flow as indicated by the broken line a in FIG. As shown in Figure 1, due to the difference in density due to the temperature difference in the liquid metal, it is divided into two parts: a hot upper region w,b and a cold lower region C, and due to the difference in buoyancy between them, the two form a layer without mixing. In this layered state, it flows out through the so-called hot leg piping, such as the furnace vessel outlet nozzle piping 8.

That is, generally after a reactor trip, the coolant flow rate is supplied by pony motor operation, so that the rated flow rate is approximately 1
0%, but the flow rate in the hot leg piping is also about 10%, and considering the volume of the upper furnace plenum, the liquid metal that forms a layer for a considerable period of time enters the hot leg piping such as the furnace vessel outlet nozzle piping 8. There will be an influx. In such a case, non-uniform temperature distribution occurs along the circumferential direction of the hot-leg piping, which may damage the hot-leg piping.

For example, in a power-generating fast reactor, the rated coolant conditions are - furnace outlet temperature is 530'C and furnace inlet temperature is approximately 40'C.
The temperature is around 0°C, and stainless steel, for example, is used for cooling system piping and equipment. However, the lower limit of creep occurrence for this stainless steel is 425℃, and hot leg piping and equipment are used within the temperature range where creep occurs.In such hot leg piping and equipment, it is necessary to prevent the occurrence and progression of creep. Therefore, it is required to eliminate tensile stress, compressive stress, shear stress, residual stress, etc. as much as possible, as well as to eliminate as much as possible the causes of these stresses, such as thermal shock.

[Object of the invention] The present invention has been made in response to such conventional circumstances,
Eliminate non-uniform temperature distribution in the circumferential direction of hot leg piping caused by stratification of liquid metal during a reactor trip,
The present invention aims to provide a horizontal piping temperature distribution relaxation device for a fast breeder reactor that can maintain the integrity of hot leg piping.

[Summary of the Invention] In other words, the present invention provides a heating means for heating the lower part of a horizontal piping of a primary liquid metal system that circulates liquid metal in a nuclear reactor vessel, and a heating means for heating the lower part of the horizontal piping for circulating liquid metal in a nuclear reactor vessel, and measuring the temperature of the upper and lower parts of the horizontal piping, respectively. temperature measuring means, and a liquid that inputs temperature signals indicating the temperatures at the upper and lower parts of the horizontal piping from these temperature measuring means, and activates the heating means when the difference between the two exceeds a predetermined constant value. This is a horizontal piping temperature distribution relaxation device for a fast breeder reactor characterized by comprising a metal temperature control device.

[Embodiment of the Invention] The details of the present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 2 shows the primary liquid metal system of a liquid metal cooled fast breeder reactor, and in the figure, reference numeral 20 indicates the primary liquid metal system. This primary liquid metal system 20 is provided to transfer the nuclear energy generated in the nuclear reactor to the intermediate heat exchanger 21 via liquid metal, and the primary system piping that circulates the liquid metal in the nuclear reactor. 22 is provided with a primary system pump 23, an intermediate heat exchanger 21, and a check valve 24 from the upstream side.

In the example shown in this figure, the C reactor vessel 1 and the primary system pump 23 are connected by hot leg piping consisting of two horizontal piping 25.26 and two vertical piping 27.28. In the example shown in this figure, there are two horizontal pipes 29 and 30 between the primary pump 23 and the intermediate heat exchanger 21.
and two vertical pipes 31 and 32 by hot leg piping.

Figure 3 and M4 are horizontal piping 25.26 shown in Figure 2.
．． 29.30 shows the horizontal piping 25, and in the figure, the reference numeral 25 indicates the horizontal piping.

A heat insulating material 33 is disposed surrounding the horizontal pipe 25, and a switch 3 (not shown) is connected to a power source (not shown) passing through the heat insulating material 33 near the bottom of the horizontal pipe 25 and running almost parallel to the horizontal pipe 25.
4, and a strip heater 35 is provided. Note that the outer periphery of the heater 35 is surrounded by an insulating sheath 39.

Temperature measuring means 36 and 37 each consisting of a thermometer are arranged in contact with the lower and upper outer peripheries of the horizontal pipe 25, respectively.
is thermally isolated from the heater 35.

In FIG. 3, reference numeral 38 indicates a liquid metal temperature control device, and this liquid metal temperature control device 38 includes temperature measuring means 36.
Temperature signals $1 and S2 are inputted from 37 respectively, and when the difference between the two exceeds a certain value set in advance in this liquid metal temperature control II device 38, a switch 34 disposed in the heater 35 is activated. Turn on and operate the heater 35.

Note that the constant value preset in the liquid metal temperature control device 38 is determined to be approximately equal to the temperature difference between the upper pipe temperature and the lower pipe temperature of the horizontal pipe 25 when the stratification phenomenon occurs in the horizontal pipe 25.

In the horizontal pipe 25 formed as described above, when the reactor trips, due to the stratification phenomenon of the liquid metal inside the reactor vessel 1, as shown in FIG. As shown in , low-temperature liquid/body metal flows into the upper side of the horizontal pipe 25, as shown by symbol e, high-temperature liquid metal flows in a layered manner, but this low-temperature liquid metal d
The temperature of the liquid metal e and the temperature of the high-temperature liquid metal e are always measured by the temperature measuring means 36 and 37, and when the difference between the two exceeds a predetermined value due to the occurrence of a stratification phenomenon, the liquid metal temperature control is started. The switch 34 of the heater 35 is turned on by the device 38, and the heater 35 is activated.

Therefore, due to the stratification phenomenon, the low temperature liquid metal d flowing in the lower part of the horizontal pipe 25 is heated by the heater 35, and its temperature rises to almost the same temperature as the high temperature liquid metal e flowing in the upper part of the horizontal pipe 25. , it is possible to completely eliminate the uneven temperature distribution in the circumferential direction that conventionally occurred in hot leg piping such as the horizontal piping 25, and significantly reduce the thermal shock given to various equipment, piping, etc. installed on the downstream side. can be reduced to

Note that when the temperatures of the liquid metal flowing in the upper and lower parts of the horizontal pipe 25 are approximately equal, the temperature measuring means 36
．． The difference between the temperature signals 81 and S2 input from 37 to the liquid metal temperature control device 38 becomes within a predetermined constant value, and the liquid metal temperature control device 38 controls the temperature of the heater 3.
The switch 34 disposed at the terminal 5 is turned OFF and F, and the operation of the heater 35 is stopped.

[Effects of the Invention] As described above, according to the horizontal pipe temperature distribution relaxation device for a fast breeder reactor of the present invention, for example, when a nuclear reactor is tripped, d
Temperature uneven distribution in the circumferential direction of the hot leg piping due to the stratification phenomenon in 3 °C can be completely eliminated after the piping is implemented according to the present invention, resulting in safer liquid metal cooling with improved integrity of the hot leg piping. It is possible to provide a type fast breeder reactor.

In addition, in the embodiment described above, an example was described in which the heater 35 is disposed at the lower part of the horizontal pipe 25 and the lower part of the horizontal pipe 25 is heated by this heater 35. Since a preheater is provided to heat the hot leg piping at the time of starting up the furnace, etc., it goes without saying that the heater provided at the bottom of the hot leg piping may be used as the heating heater 35. .

In this case, the heating heater and the preheating heater can be shared, so equipment costs can be reduced.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view showing a conventional liquid metal cooled fast breeder reactor, Figure 2 is a piping system diagram showing the liquid metal system of a fast breeder reactor, and Figure 3 is a horizontal cross-sectional view of a fast breeder reactor according to the present invention. A vertical cross-sectional view showing one embodiment of the piping temperature distribution relaxation device, FIG. 4 is Iv of FIG. 3.
It is a cross-sectional view along the line -■. 1......Reactor vessel 25...
・・・・・・Horizontal piping 33・・・・・・・・・・・・
Heat insulating material 35... Heater 36.37.
・・Temperature measurement means 38 ・・・・Liquid metal temperature control device representative Satoshi Suyama - Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1) A heating means for heating the lower part of the horizontal piping of the primary liquid metal system that circulates the liquid metal in the reactor vessel, a temperature measuring means for measuring the temperature of the upper and lower parts of the horizontal piping, respectively; and a liquid metal temperature control device that receives temperature signals from the temperature measuring means that indicate the temperatures at the upper and lower portions of the horizontal pipe, respectively, and operates the heating means when the difference between the two exceeds a predetermined constant value. A horizontal piping temperature distribution relaxation device for a fast breeder reactor, characterized by: