DECAY HEAT REMOVAL SYSTEM WITH HYBRID HEAT PIPE HAVING COOLANT AND NEUTRON ABSORBER FOR COOLING NUCLEAR POWER PLANT

• US 20150023461A1
• Filed: 07/18/2014
• Published: 01/22/2015
• Est. Priority Date: 07/18/2013
• Status: Active Grant

• Current Assignee: Ulsan National Institute of Science and Technology
• Original Assignee: UNIST Academy-Industry Research CorporationUNIST
• Inventors: BANG, In Cheol, KIM, Ji Hyun, PARK, Seong Dae, KANG, Sarah, SEO, Han, KIM, Kyoung-Mo, MOON, Sung Bo, SEO, Seok Bin, KIM, In Guk, JEONG, Yeong Shin, HEO, Hyo
• Granted Patent: US 9,865,365 B2
• Time in Patent Office: Days
• US Class Current: 376/299
• CPC Class Codes: G21C 15/18 Emergency cooling arrangements; Removing shut-down heat
• CPC Class Codes: G21C 15/26 by convection, e.g. using chimneys, using divergent channels
• CPC Class Codes: G21C 19/07 Storage racks; Storage pools
• CPC Class Codes: G21C 19/08 Means for heating fuel elements before introduction into the core; Means for heating or cooling fuel elements after removal from the core
• CPC Class Codes: G21C 7/103 Control assemblies containing one or more absorbants as well as other elements, e.g. fuel or moderator elements
• CPC Class Codes: G21C 7/12 Means for moving control elements to desired position dropping rods in an emergency G21C9/02
• CPC Class Codes: Y02E 30/30 Nuclear fission reactors

Abstract

Disclosed is a decay heat removal system for cooling the decay heat of a reactor core and the spent fuel. The decay heat removal system including: a first heat pipe which is placed in an upper plenum of the reactor vessel and arranged in upward and downward directions corresponding to a position of an insertion hole formed on a top of the nuclear fuel assemblies; a control rod drive mechanism which is connected to an upper portion of the first heat pipe and drives the first heat pipe to move up and down so that the first heat pipe can be selectively inserted in a control rod insertion hole of the reactor core arranged in the nuclear reactor vessel; and a second heat pipe which is coupled to and in close contact with a bottom surface of the reactor vessel and removes the decay heat generated in the reactor core.

Claims

1. A decay heat removal system for removing decay heat of a reactor core arranged in a reactor vessel, the decay heat removal system comprising:

a first heat pipe which is placed in an upper plenum of the reactor vessel and arranged in upward and downward directions corresponding to a position of an insertion hole formed on a top of the nuclear reactor vessel;

a control rod drive mechanism which is connected to an upper plenum of the first heat pipe and drives the first heat pipe to move up and down so that the first heat pipe can be selectively inserted in a control rod insertion hole of the reactor core arranged in the nuclear reactor vessel; and

a second heat pipe which is coupled to and in close contact with a bottom surface of the reactor vessel and removes the decay heat generated in the reactor core.

2. The decay heat removal system according to claim 1, wherein the first heat pipe receives the coolant from an upper plenum of the reactor vessel as a heat sink, and performs cooling by absorbing the decay heat generated in the reactor core, and transferring the absorbed heat to the coolant.

3. The decay heat removal system according to claim 1, wherein the temperature of the coolant in an upper plenum, i.e., in a condenser of the first heat pipe is maintained or adjusted by convection of the coolant based on connection between the upper plenum and an in-containment refueling water storage tank, cooling based on a heat pipe heat exchanger additionally installed in the upper plenum, or cooling based on a condenser cooling tank provided on an outer wall of the upper plenum.

4. The decay heat removal system according to claim 1, wherein the first heat pipe performs cooling through a heat exchanging device employing a coolant provided outside the nuclear reactor vessel.

5. The decay heat removal system according to claim 1, wherein a fin is provided in a condenser of the first heat pipe and secure a heat transfer area, which employs air, water, nanofluid, seawater, nitrogen or liquid metal as a coolant for exchanging heat with the first heat pipe.

6. The decay heat removal system according to claim 1, wherein the second heat pipe comprises a first end coupled to in-containment refueling water storage tank, and a second end attached to the bottom surface of the reactor vessel, and performs the cooling by using the coolant stored in the in-containment refueling water storage tank as a condenser, absorbing the decay heat generated in the reactor core and transferring the absorbed heat to the coolant.

7. The decay heat removal system according to claim 1, wherein the first heat pipe or the second heat pipe is provided in the form of a hybrid heat pipe internally provided with both a neutron absorber and a coolant, and not only absorbs a neutron generated in the reactor core inside the reactor vessel but also removes the decay heat.

8. The decay heat removal system according to claim 1, wherein the second heat pipe is made of a flexible material, is curved corresponding to the shape of the bottom surface of the reactor vessel, and closely contacts the bottom surface.

9. The decay heat removal system according to claim 1, wherein the second heat pipe has a bellows-like structure, is curved corresponding to the shape of the bottom surface of the reactor vessel, and closely contacts the bottom surface.

10. The decay heat removal system according to claim 1, wherein a working fluid circulated in the first heat pipe or the second heat pipe comprises one of water (H₂O), a nanofluid, a refrigerant, mercury (Hg), lithium (Li) and FLiBe (LiF—

BeF₂).

11. The decay heat removal system according to claim 10, wherein a wick placed in the first heat pipe or the second heat pipe comprises one of carbon fiber, copper, stainless steel, zirconium alloy, silicon carbide (SiC), and boron carbide (B₄C).

12. The decay heat removal system according to claim 11, wherein a case material forming an outer appearance of the first heat pipe or the second heat pipe comprises one of stainless steel, zirconium alloy, inconel alloy and molybdenum alloy.

13. A decay heat removal system for removing decay heat of spent fuel assemblies, the decay heat removal system comprising:

a plurality of unit storage racks which includes standing heat pipe plates coupled to one another and assembled in the form of a box to internally form space for storing the spent fuel assemblies, in which a working fluid is circulated inside the heat pipe plate and absorbs the decay heat of the spent fuel.

14. The decay heat removal system according to claim 13, wherein the respective unit storage racks are arranged and close to each other in the storage space where a coolant for removing the decay heat of the spent fuel.

15. The decay heat removal system according to claim 13, further comprising a third heat pipe inserted in a control rod insertion hole penetrating a middle of the spent fuel assemblies, and internally circulating a working fluid to absorb the decay heat of spent fuel.

16. The decay heat removal system according to claim 15, wherein the heat pipe plate or the third heat pipe are provided in the form of a hybrid heat pipe internally comprising both a neutron absorber and a coolant.

17. A decay heat removal system for removing decay heat of spent fuel assemblies, the decay heat removal system comprising:

a storage container which is an internal space for storing the spent fuel;

a fourth heat pipe which is horizontally arranged in the form of traversing the internal space of the storage container, and working fluid is circulated inside therein to absorb the decay heat of the spent fuel; and

a fifth heat pipe which is horizontally arranged in the form of traversing the internal space of the storage container, is installed in a direction of intersecting the fourth heat pipe, and, together with the fourth heat pipe, forms a rectangular storage space in which the spent fuel is arranged.

18. The decay heat removal system according to claim 17, wherein the fourth heat pipes and the fifth heat pipes are spaced apart from each other at a distance corresponding to a horizontal length of a storage unit for the spent fuel, and closely contact circumference of the spent fuel.

19. The decay heat removal system according to claim 18, wherein the storage container 51 is supplied with and stores a coolant for removing the decay heat of the nuclear fuel.

20. The decay heat removal system according to claim 17, further comprising a sixth heat pipe inserted in a control rod insertion hole penetrating the middle of the spent fuel assemblies, and internally circulating a working fluid to absorb the decay heat from the inside of the spent fuel assemblies.

21. The decay heat removal system according to claim 20, wherein the fourth heat pipe, the fifth heat pipe and the sixth heat pipe are provided in the form of the hybrid heat pipe internally comprising both a neutron absorber and a coolant, in the spent fuel.

22. The decay heat removal system according to claim 20, wherein the fourth heat pipe, the fifth heat pipe and the sixth heat pipe use seawater as an ultimate heat sink, in which the seawater is circulated inside an independent condenser cooling tank.