JPS6195280A - Upper shielding body for fast breeder reactor - 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 an upper shield for a liquid metal cooled fast breeder reactor.

[Technical background of the invention and its problems] Figure 4 shows a tank-type fast breeder reactor, and in the figure, reference numeral 1 indicates the entire inside of the reactor vessel. The reactor vessel 1 is surrounded on the outside by a protective vessel 2 in case of coolant leakage, and the upper cylinder mouth is shielded by an upper shield (roof slab) 3. Further, the lower peripheral portion of the upper shield 3 is housed in a bit to a formed by a surrounding reinforced concrete wall 5 via a cylindrical skirt 4. A reactor core 6 is provided in the reactor vessel 1, and a secondary coolant bomb 7, an intermediate heat exchanger 8 having a secondary coolant inlet 8a and an outlet 8b, a core upper i structure 9, and a primary coolant liquid sodium 10 is accommodated, liquid sodium 1
An inert gas such as argon gas is sealed between the liquid level at 0 and the upper shield 3 as a cover gas. Note that reference numeral 11 is a motor that drives the primary cold ready-to-read material pump 7;
13 are a secondary coolant inflow pipe and a secondary coolant outflow pipe connected to the intermediate heat exchanger 8, respectively. Also iv issue 14
. . are suction holes of the above-mentioned sub-cooling pump 7, and these suction holes 14-- are surrounded by an outer cylinder 15. Roughly speaking, reference numeral 16 is a core support body that supports the reactor core 6, 17 is a high-pressure blemish provided below the reactor core 6, and 18 is a core support frame that surrounds the reactor core 6. -Then, the discharge port of the secondary coolant pump 7 and the high pressure plenum 17 are communicated with each other by a pressure impulse pipe 19, and the outer cylinder 15 and the core support frame 18 are connected to the upper blenum 20a and the lower plenum 20a within the reactor vessel 1.
It is supported by a partition wall 20 that divides the space into 0b and 0b.

The upper shielding body 3 is provided with a circular opening 21 in the center and through holes 22 around it, and a rotary plug 23 is provided in the opening 21, and each through hole 22 is provided in the opening 21. The above-mentioned secondary coolant bomb 7, intermediate heat exchanger 8, etc. are fitted and supported on the mounts, respectively. In addition to the core upper mechanism 9, the rotary plug 23 supports a fuel exchanger and a fuel exchange drive device (none of which are shown) that drives the core upper mechanism 9. Control rod (
A control rod drive rock (not shown) is supported for inserting and withdrawing the control rod (not shown).

In the above configuration, the liquid sodium 10 in the high-pressure blemish 17 flows through the reactor core 6 from below to above, and is heated by nuclear reaction heat in the reactor core 6. The liquid sodium 10 flowing from the core 6 into the upper blemish 2Oa flows into the intermediate heat exchanger 8 through the inlet 8a, where it exchanges heat with the secondary coolant circulating outside the reactor vessel 1. Thereafter, it flows out into the lower blenheim 2Ob below the partition wall 20 through the outlet 8b. The heat from the secondary coolant generates steam, which becomes the driving source for the power generation turbine.

On the other hand, the liquid sodium 10 in the lower brenum 2Ob is supplied to the inlet 15a and the suction hole 1 provided at the lower end of the outer cylinder 15.
4 into the primary coolant pump 7.
The high pressure plenum below the reactor core 6 is pressurized through the impulse pipe 19 again.

It will be sent into the 17th.

Incidentally, the reactor vessel 1 and the protective vessel 2 that surrounds it from the outside are directly suspended on the upper shield 3 that shields the upper opening of the reactor vessel 1, and the upper shield 3 is equipped with liquid 0-body sodium 10. Primary coolant pump 7 for pumping into the reactor core 6
, an intermediate heat exchanger 8 , a rotating plug 23 , and other heavy structures are installed, so the upper shield 3 is designed to have the strength to support these heavy structures and to protect against radiation from inside the reactor vessel 1. In order to shield radiation such as neutrons,
It consists of a single concrete structure surrounded by iron beams.

However, due to the high temperature inside the reactor vessel 1, a significant temperature difference occurs between the top and bottom surfaces of the upper shield 3, which causes the upper shield 3 to thermally deform, causing the on-board structure to tilt, causing the reactor vessel 1 to ．． There is a risk that the upper shield 3 may interfere with structures inside the upper shield 3 or cracks may occur in the upper shield 3 itself.

In order to prevent such a situation, conventionally a cooling structure 26 and a heat insulating structure 27 are incorporated in the lower part of the upper shield 3 as shown in FIG.

Naturally, the heat insulating structure 27 must have a high heat insulating effect, so heat shield plates made of stainless steel #I board or the like are laminated in multiple layers, and the liquid sodium that has entered between each heat shield plate is The distance between each heat shield plate is set at 10M or more so that the heat shield plate does not act as a heat conduction medium and impair the heat insulation effect.

However, according to the above structure, radiant heat is transmitted through between the heat shielding plates, so not only a sufficient insulation effect is not achieved, but also the thickness of the insulation structure 27 is not sufficient, and the thickness of the insulation structure 27 is insufficient.
0. - Long-term nuclear reactors.

There was a risk that liquid sodium would enter the inside of the heat insulating structure 27 during the life period, further deteriorating the heat insulating effect. Further, in the above-mentioned structure 4, it is necessary to use a large number of thermal Aμ plates in order to prevent the occurrence of thermal stress in the upper shielding body 3, which has the disadvantage of increasing manufacturing costs.

Recently, wire mesh has been used as a heat shielding plate instead of a fully bent thin plate, and radiant heat is blocked between the gaps.4. It is also done to sandwich thin insulation sheets one by one in order to prevent radiation ripening. ! The insulation sheet to be cut is not thick enough □1. Moreover, there was a risk that liquid sodium would seep in over the years, further reducing the insulation effect.

[Object of the invention] The present invention was made based on the above circumstances, and
The purpose is to provide an inexpensive upper shield for a fast breeder reactor that suppresses the temperature rise on the lower surface side of the shield body through its high heat insulation effect, and whose heat insulation effect is less likely to deteriorate even when JVI body sodium deposits occur. It's about doing.

[Summary of the Invention] To achieve the above object, the present invention provides a shielding body that closes the upper opening of a reactor vessel and faces a coolant contained in the reactor vessel from above via a cover gas; A heat insulating structure consisting of a plurality of heat shield plates made of thin metal plates and wire meshes stacked alternately and attached to the lower surface of the shield body is perpendicular to the lower surface of the heat shield body! It is characterized by comprising a vapor deposition prevention film made of a thin metal plate, which is disposed over the entire length of the structure, has a ventilation hole at the upper end, and covers the heat insulating structure from the lower surface side.

[Embodiment of the Invention] Hereinafter, an embodiment in which the present invention is applied to a liquid metal cooled tank type fast breeder reactor will be described with reference to FIGS. 1 to 3.

Figure 1 shows the schematic configuration of a tank-type fast breeder reactor.
The same parts as in FIG. 4 are given the same reference numerals. That is, in the figure, reference numeral 1 is a nuclear reactor vessel.

The reactor vessel 1 is surrounded on the outside by a protection vessel 2 in case of coolant leakage, and the upper opening is shielded by an upper shield (roof slab>30).

Further, the lower peripheral portion of the upper shield 30 has a cylindrical skirt 4.
A bit formed by the surrounding reinforced concrete wall 5 through! -5a is stored inside.

A reactor core 6 is provided inside the reactor vessel 1, and a secondary coolant pump 7, an intermediate heat exchanger 8 having a secondary coolant inlet 8a and an outlet 8b, an upper part of the core [W49 and a primary coolant] liquid sodium 10 is contained therein, and an inert gas such as argon gas is sealed as a cover gas between the liquid level of the liquid sodium 10 and the upper shield 30.

Note that reference numeral 11 is a motor that drives the primary coolant pump 7.
12 and 13 are a secondary coolant inflow pipe i and a secondary coolant outflow pipe connected to the intermediate heat exchanger 8, respectively. Ma"
Reference numerals 14 are suction holes of the secondary coolant bomb 7, and these suction holes 14 are surrounded by an outer cylinder 15. Further, reference numeral 16 denotes a core support that supports the core 6;
17 is a high-pressure plenum provided below the core 6, and 18 is a core support frame surrounding the core 6. The discharge port of the secondary coolant pump 7 and the high-pressure plenum 77 are communicated by a pressure impulse pipe 19, and the outer cylinder '15 and the core support frame 18 are connected to the upper plenum 20a and the upper plenum 20a in the reactor vessel 1.
N 71i t L 2011 k, 'knee compartment'
TZZR! i! 201-J: Supported by v. The upper shield 30 has a circular opening 21 in the center.
In addition, through holes 22 are provided around the openings 21, and rotary plugs 23 are provided in the openings 21.
The above-mentioned secondary coolant bomb 7, intermediate heat exchanger 8, etc. are fitted and supported in .

A cooling structure 32 is provided at a lower portion within the shielding body 31 of the upper shielding body 30 . Further, heat insulating structures 33 and 34 are provided on the lower surface of the shielding body 31 and the lower surface of the rotary plug 23, respectively. These cooling structures □ and 32 and heat insulating structures 33 and 34 are for preventing heat rising from the core 6' from reaching the shielding body 31 and the rotating plug 23.

2 and 3 show the cooling structure 32 and the heat insulation 9.
It shows the peripheral part of the 1M body 33, and the cooling structure 32 is
As shown in FIG. 2, the lower surface has a large number of orifices 35, and these orifices 35 eject cooling gas such as nitrogen gas or air downward, and the jet of cooling gas is directed to the lower surface of the shielding body 31. By touching the shield body 31, the temperature rise is prevented, and thermal deformation due to the difference in salinity between the upper and lower surfaces of the shield body 31 is prevented. In addition, the code 36 is a cold FAt
An air supply pipe 37 supplies cooling gas to the cooling structure 32, and an exhaust pipe 37 discharges gas inside the cooling structure 32.

As shown in FIG. 3, the heat insulating structure 33 is made by alternately laminating heat shielding plates 38 made of a large number of stainless flI thin plates and stainless steel gold plates 1!39... , a plurality of support pipes 40 having threaded portions on the lower outer periphery, which are welded to the lower surface of the shielding body 31, and each support pipe 4.
The shield body 31 is attached to the lower surface of the shield body 31 by a nut 41 that is screwed into the threaded portion of the shield body 31.

Note that the nuts 41 are fixed to the support tubes 40 by spot welding or the like as necessary to prevent loosening. The wire mesh 39 is used to prevent adjacent heat shielding plates 38 from coming into contact with each other and causing heat conduction. Radiant heat directed from the surface of the liquid sodium 10 toward the shielding body 31 is shielded by the plurality of heat shielding plates 38 . In addition, the heat shield plate 38... and the wire mesh 3
9... are made to be bent in advance so that they can sufficiently absorb the expansion and contraction caused by temperature changes.

Further, the area from the bottom surface of the heat insulating structure 33 to the vertical wall surface of the shielding body 31 is covered with a vapor deposition prevention film 42 made of a stainless steel W4 thin plate. The vapor deposition prevention film 42 prevents sodium vapor that evaporates from the liquid surface of the liquid sodium 10 from entering the inside of the heat insulating structure 33 and prevents the heat shielding plate 3
This is to prevent heat conduction paths from being formed due to condensed sodium adhering between the heat insulating structures 33 and to prevent deterioration of the heat insulating performance of the heat insulating structure 33. A breathing hole 43 is provided in the upper part of the vapor deposition prevention film 42 between the shielding body 31 and the rotary plug 23 . This breathing hole 43 eliminates the pressure difference between the inside and outside of the vapor deposition prevention 1f142,
This is to prevent deformation or damage to the vapor deposition prevention film 42 due to the difference in internal and external pressure.

Note that the heat insulating structure 3 provided on the lower surface of the rotating plug 23
4 also has the same configuration as the heat insulating structure 33 of the shielding body 31111, and a vapor deposition prevention film similar to that on the shielding body 31 side is provided as necessary.

In the above configuration, the liquid sodium 10 in the high-pressure plenum 17 flows through the reactor core 6 from below to above, and is heated by the heat of nuclear reaction in the reactor core 6. Then the reactor core 6
Liquid sodium 1 flowing into the upper plenum 20a from
0 flows into the intermediate heat exchanger 8 through the inlet 8a, where it exchanges heat with the secondary coolant circulating outside the reactor vessel 1, and then flows through the outlet 8b into the lower plenum below the partition wall 20. Flows into 2Ob. The heat from the secondary coolant generates steam, which becomes the driving source for the power generation turbine. On the other hand, the liquid I/Rium 10 in the lower Blenheim 2Ob is outside rt! Inlet 1 provided at the lower end of i15
The coolant flows into the primary coolant bomb 7 through 5a and the suction hole 14, is pressurized by the pump 7, and is again sent into the high-pressure plenum 17 below the reactor core 6 through the pressure guiding pipe 19.

In addition, the radiant heat from the liquid sodium 10 is transmitted to the heat insulating structure 33 through the cover gas, but the heat insulating structure 33
The amount of heat that is further transferred to the shield body 31 can be expressed by the following equation.

Here, q; heat flux in the adiabatic Bt body 33 (kcal, ' td
hr) σ: Stefan Holtzmann constant (kcal/mhr 'to') n: Number of heat shields 1i38 ε; emissivity; thermal conductivity of heat shield plate 38 (kcal,'rrLh
r'c) At/A: Ratio of the total cross-sectional area of the metal parts passing through the heat shield plate 38 to the total area of the lower surface of the upper shield 30 2: Thickness of the heat insulation structure 33 m) t: Heat shield plate 38 Plate thickness (m) kg; Cover gas thermal conductivity (kcal/m hr'
c) T1: Temperature of the lower surface of the heat insulating structure 33 (K) ■,: Temperature of the upper surface of the heat insulating structure 33 (i.e. temperature of the lower surface of the shielding body 31) ('K) As described above, the heat insulating structure 33 is connected to the heat shielding plate 38 and wire mesh 39 are alternately layered, radiant heat is shielded by the heat shield plate 38,
Heat conduction between adjacent heat shield plates 38 is prevented by the wire mesh 39. Therefore, the heat insulating effect of the heat insulating tP4 structure 33 is enhanced, and by reducing the number of heat plates 38, the whole heat insulating structure 33 can be made lighter. As a result, the total cross-sectional area of the metal parts that pass through the heat insulating structure 33, such as the support pipe 38 that supports the heat insulating wIi structure 33, can be reduced, and A1. 'A can be made smaller. Therefore, according to the relationship in the above equation, the value of q can be made smaller.

Further, the vapor of the liquid sodium 10 adheres to the outer surface of the vapor deposition prevention film 42 and is prevented from entering the inside of the heat insulating structure 33. Even more prevents vapor deposition! 42 is provided with a breathing hole 43,
Since the pressure inside and outside of the vapor deposition prevention film 42 is maintained at the same pressure, deformation and damage of the vapor deposition prevention film 11!42 due to the difference in pressure between the inside and outside are reliably prevented. Moreover, the above-mentioned breathing hole 43 is connected to the vapor deposition prevention film 42.
Since it is provided at the upper end, it is difficult for the vapor of the liquid sodium 10 to rise up to the breathing hole 43, so that the amount of sodium vapor that enters the heat insulating structure 33 through the breathing hole 43 can be suppressed to the smallest amount. can. Especially in the above embodiment, the breathing hole 43! ! f By locating it in the gap between the main body 31 and the rotary plug 23, the breathing hole 4
As the sodium vapor rises toward 3, it adheres to the shield body 31 and the side mold of the rotating plug 23 and condenses as it rises in the gap, and only the gas whose sodium concentration has sufficiently decreased reaches the breathing hole 43. Therefore, the effect of further reducing the amount of sodium vapor infiltrating from the breathing hole 43 can be obtained. In addition, a heat shielding plate 38 that constitutes the heat insulating structure 33
The wire mesh 39 is made to be bent in advance and can sufficiently absorb expansion and contraction caused by temperature changes.
! The entire lower surface of the shielding body 31 can be covered with a single heat shielding plate 38 or wire mesh 39, making it possible to simplify the manufacturing process and reduce manufacturing costs. The cost can be further reduced.

Furthermore, the vapor deposition/prevention film 42 has a thin plate structure and is easily deformed by heat, so it can also be manufactured as a single piece at low cost.

[R11(7)5FJP! ]
. □As described in detail above, according to the present invention, the temperature rise on the lower surface side of the shield body can be suppressed due to the high heat insulation effect of the shield structure formed by alternately laminating heat shield plates and wire mesh. In addition, since the vapor deposition prevention film prevents sodium vapor from entering the heat shield structure, the insulation effect will decrease, and deformation and damage due to the pressure difference between the inside and outside of the vapor deposition prevention film itself will be prevented. This is prevented by eliminating the pressure difference at the breathing hole. In addition, since the above-mentioned i@slight is provided at the upper end of the vapor deposition prevention film, the gas rising from the liquid level of the monolithic sodium reaches the breathing hole, where the concentration of thorium is sufficiently reduced, thereby improving the insulation performance. The amount of sulphate vapor that causes deterioration that enters through the breathing holes can be suppressed to a very small amount. Further, by reducing the number of heat shielding plates, manufacturing costs can be kept low, and other excellent effects can be obtained.

[Brief Description of the Drawings] Figures 1 to 3 show an embodiment of the present invention.
Figure 1 is a schematic sectional view of a tank-type fast breeder reactor, Figures 2 and 3 are sectional views showing an enlarged part of the upper shield, and Figures 4 and 5 are conventional examples. , FIG. 4 is a schematic sectional view of a tank-type fast breeder reactor, and FIG. 5 is an enlarged sectional view of a part of the upper shield. DESCRIPTION OF SYMBOLS 1... Reactor vessel, 10... Coolant, 30... Upper shielding body, 31... Shielding main body, 38. ... Heat shielding plate, 39 ... Wire mesh, 42 ... Vapor deposition prevention film, 43 ...
Breathing hole. Applicant's agent Patent attorney Takehiko Suzue 12 Figure 1 Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) A shield body that closes the upper opening of the reactor vessel and faces the coolant contained in the reactor vessel from above via a cover gas, and a plurality of thin metal heat shield plates and wire mesh are laminated alternately. A heat insulating structure is attached to the lower surface of the shielding body, and the heat insulating structure is disposed from the lower surface of the shielding body to a vertical wall and has a ventilation hole at the upper end, and covers the heat insulating structure from the lower surface side. 1. An upper shield for a fast breeder reactor, comprising a vapor deposition prevention film made of a thin metal plate. (2) The upper shield for a fast breeder reactor according to claim 1, wherein the heat shield plate and the wire mesh are made of stainless steel. (3) The upper shield for a fast breeder reactor according to claim 1, wherein the breathing hole is located in a gap between the shield body and the rotating plug.