JP2005221491A - Supercritical water-cooled nuclear reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To elevate a cooling water temperature in a reactor core outlet, by bringing cooling water for a fuel assembly into a downflow in a peripheral part of a supercritical water cooled nuclear reactor. <P>SOLUTION: The cooling water of a low temperature flows from a cold leg 3 into a reactor pressure vessel 1. One portion of the cooling water is passed through a downcomer 2 to reach a lower dome 12. The remainder of the cooling water is passed through an upper dome 5, goes down through a control rod cluster guide tube 7, goes down further through the fuel assembly 9 in the peripheral part, and reaches to the lower dome 12. The cooling water joined in the lower dome 12 flows from a core lower part 11 into the fuel assembly 10 in the central part, and heated to be discharged thereafter to a core upper part 8. Two flows of high temperature cooling water discharged from the respective fuel assemblies in the central part are mixed therein to flow toward a turbine through a hot leg 4, after outgoing from the reactor pressure vessel 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a supercritical water-cooled nuclear reactor.

  The supercritical water-cooled nuclear reactor is a nuclear reactor using high-temperature and high-pressure supercritical water as a coolant, and the concept is already known (for example, see Non-Patent Document 1). Unlike conventional light water reactors, boiling does not occur in the core, so that the coolant can be heated to a higher temperature and the power generation efficiency is greatly increased.

  The supercritical water-cooled nuclear reactor is a once-through direct cycle, and after the cooling water supplied from the feed water pump is heated in the core, the whole amount goes to the turbine. Since the core is composed of a plurality of fuel assemblies, the cooling water from each fuel assembly is mixed in the upper part of the core. Increasing the temperature of the cooling water at the top of the core after mixing increases the thermal efficiency. Further, when the coolant temperature at the upper part of the core is increased, the temperature difference between the upper part and the lower part of the core is increased, so that the core flow rate is reduced and the equipment and the building are downsized. As described above, in the supercritical water-cooled nuclear reactor, the performance of the nuclear reactor can be improved by increasing the cooling water temperature at the upper part of the core.

  However, if the output varies depending on the fuel assembly, a difference occurs in the coolant temperature at the fuel assembly outlet. Since the maximum temperature is a constraint in order to maintain the soundness of the nuclear reactor, if a temperature difference occurs at the outlet of the fuel assembly, the cooling water temperature after mixing becomes low.

  In particular, due to the characteristics of the nuclear reactor, the output of the fuel assemblies around the core is not so high, the cooling water temperature at the outlet of such fuel assemblies is lowered, and the performance of the reactor is lowered.

  There are several technologies related to supercritical pressure water-cooled reactors proposed so far (see, for example, Patent Documents 1 to 11). As a method for increasing the reactor outlet temperature, supercritical pressure light water-cooled fast reactors are used. There is only a method of cooling the blanket fuel assembly (see, for example, Patent Document 3). This method can be applied only to fast reactors and not to thermal neutron reactors without blanket fuel assemblies.

JP 08-313664 A JP 2000-056081 A JP 2001-004774 A JP 2001-091689 A JP 2002-031694 A JP 2002-156492 A Japanese Patent Laid-Open No. 2002-341079 JP 2003-050292 A JP 2003-063801 A JP 2003-129881 A JP 2003-294878 A Yoshiaki Oka, “Concept of Supercritical Pressure Light Water Reactor”, Nuclear Industry, Vol.38, November, Page 71-77 (1992)

  Therefore, there is a demand for means that minimizes the difference in the outlet temperature of the fuel assembly and raises the cooling water temperature as much as possible after mixing in the upper part of the core.

  In order to solve the above problems, in the present invention, the cooling water in the fuel rod passages of the fuel assemblies in the peripheral part of the core is used as a downward flow, and the cooling in the fuel rod passages of the central fuel assemblies Use water as an upward flow. This prevents the cooling water flowing out from the peripheral fuel assembly having a low output from being discharged to the upper part of the core. Since only the cooling water flowing out from the central fuel assembly is mixed in the upper part of the core, the cooling water temperature after mixing can be kept high.

  According to the present invention, the supercritical pressure water-cooled nuclear reactor does not discharge low-temperature cooling water flowing out from the low-power fuel assembly at the periphery of the core to the upper part of the core, and after mixing at the upper part of the core. The cooling water temperature can be kept high. As a result, the thermal efficiency is increased and the core flow rate is reduced, whereby the equipment and the building can be downsized, and the performance of the supercritical water-cooled nuclear reactor is improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view showing a vertical cross section of a reactor pressure vessel according to an embodiment of the present invention. Cooling water having a temperature lower than that of the cold leg 3 flows into the reactor pressure vessel 1. A part of the cooling water passes through the downcomer 2 and reaches the lower dome 12. The rest of the cooling water passes through the upper dome 5, descends the control rod cluster guide pipe 7, further descends the peripheral fuel assembly 9, and reaches the lower dome 12. The cooling water merged at the lower dome 12 flows into the fuel assembly 10 at the central portion from the lower core portion 11, is heated, and then discharged to the upper core portion 8. Here, the high-temperature cooling water discharged from the fuel assemblies in the central portion is mixed and exits the reactor pressure vessel 1 and passes through the hot leg 4 toward the turbine.

  FIG. 2 is a view showing a vertical cross section and a horizontal cross section in the upper portion of the peripheral fuel assembly according to the embodiment of the present invention. The control rod cluster guide tube 7 in FIG. 1 is doubled. The control rod cluster guide tube outer tube 13 and the control rod cluster guide tube inner tube 14 are connected to the control rod cluster guide tube outer flow path 15 and the control rod cluster guide tube. An inner flow path 16 is created. The cooling water descending the control rod cluster guide tube outer passage 15 passes through the inter-fuel rod passage connection pipe 22 and is led to the inter-fuel rod passage and becomes a downward flow. The cooling water descending the control rod cluster guide tube inner flow path 16 is guided to the water rod 21 and becomes a downward flow. The control rod cluster includes a plurality of control rods 19, and each control rod 19 is inserted into a control rod guide tube 20 in the water rod 21. Although the distribution of the flow rate between the fuel rods and the flow rate of the water rod 21 needs to be set in the core design, it is set by the control rod cluster guide tube outer channel orifice 17 and the control rod cluster guide tube inner channel orifice 18. Is possible.

  FIG. 3 is a view showing a vertical section and a horizontal section in the upper part of the fuel assembly in the center. The control rod cluster guide tube 7 in FIG. 1 is a single tube in this case, and there is a single control rod cluster guide tube flow path 23. This is connected to the water rod 21, and the cooling water in the water rod can be made to flow downward. In addition, the cooling water of the fuel rod passage 26 formed in the gap between the fuel rods 25 is guided from the lower dome 12 and becomes an upward flow.

  In the embodiment shown above, the cooling water is led from the upper dome through the control rod guide tube to the upper part of the peripheral fuel assembly, but can also be led directly from the downcomer.

  Further, it is possible to provide a structure in which an ascending flow path is provided from the lower dome to the periphery of the core, and cooling water is sent from there to the upper part of the fuel assembly in the periphery.

  Further, the cooling water of the lower dome can rise between the fuel assemblies and reach the upper part of the peripheral fuel assembly.

  In the embodiment shown above, the cooling water in the water rod is in a downward flow in all the fuel assemblies in the central part and the peripheral part of the core, but the cooling water in the water rod of the fuel assembly in the central part. Is not necessarily downflow.

  In the embodiment shown above, the control rod cluster guide tube connected to the peripheral fuel assembly is a double tube, and the control rod cluster is included therein, so that the structure is complicated. Therefore, if the combustion reactivity can be compensated by means other than the control rod by increasing the flammable poison in the fuel, the control rod is not required in the peripheral fuel assembly. In this case, the structure of the control rod guide tube is simplified.

The figure which shows the vertical cross section of a nuclear reactor pressure vessel. The figure which shows the vertical cross section and the horizontal cross section in the upper part of the fuel assembly of a peripheral part. The figure which shows the vertical cross section and horizontal cross section in the upper part of the fuel assembly of a center part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reactor pressure vessel 2 Downcomer 3 Cold leg 4 Hot leg 5 Upper dome 6 Control rod drive 7 Control rod cluster guide tube 8 Upper core 9 Peripheral fuel assembly 10 Central fuel assembly 11 Lower core 12 Lower dome 13 Control rod cluster guide tube outer tube 14 Control rod cluster guide tube inner tube 15 Control rod cluster guide tube outer channel 16 Control rod cluster guide tube inner channel 17 Control rod cluster guide tube outer channel orifice 18 Control rod cluster guide tube inner channel Orifice 19 Control rod 20 Control rod guide tube 21 Water rod 22 Fuel rod flow passage connection tube 23 Control rod cluster guide tube passage 24 Control rod cluster guide tube passage orifice 25 Fuel rod 26 Fuel rod passage

Claims (4)

  The cooling water in the flow path between fuel rods of the fuel assembly in the peripheral part of the core is a downward flow, and the cooling water in the flow path between fuel rods of the fuel assembly in the center is an upward flow Critical pressure water cooled reactor.   2. The supercritical water-cooled nuclear reactor according to claim 1, wherein the cooling water in the water rods of the peripheral and central fuel assemblies is a downward flow.   3. The supercritical water cooling reactor according to claim 1, wherein the cooling water is guided from the upper dome of the reactor pressure vessel to the upper end of the fuel assembly through the control rod cluster guide tube. Reactor.   The supercritical water-cooled nuclear reactor according to claim 1, 2, or 3, wherein the fuel assemblies in the peripheral portion where the cooling water in the flow path between the fuel rods becomes a downward flow have no control rod. Supercritical water-cooled nuclear reactor.

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