Induced nuclear reactions: processes – systems – and elements – Handling of fission reactor component structure within...
Reexamination Certificate
2002-05-14
2003-09-23
Poon, Peter M. (Department: 3641)
Induced nuclear reactions: processes, systems, and elements
Handling of fission reactor component structure within...
C376S262000
Reexamination Certificate
active
06625245
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods for carrying in and out a reactor vessel to and from a pressurized water reactor (hereinafter abbreviated to a “PWR”). This method of carrying out a reactor vessel is employed when the reactor vessel is to be replaced or decommissioned, for example.
BACKGROUND ART
A reactor vessel is the most important piece of equipment in a nuclear power plant. The service period of a nuclear power plant generally depends on the lifetimes of a reactor vessel and various units of auxiliary equipment installed inside and outside the reactor vessel. Also, when the service period of a nuclear power plant is expired, the nuclear power plant must be dismantled and decommissioned. In such an environment, it is important to prolong the service period of an existing old nuclear power plant that has been operated for relatively long years and is still now in commission.
In an existing old nuclear power plant, the plant has likely been refreshed or rejigged by repair and replacement of equipment other than a reactor vessel and core internals. For further prolongation of the service period, however, there has arisen the necessity of repairing and replacing the reactor vessel and the core internals as well.
In fact, replacement of core internals is already implemented in a boiling water reactor (BWR). Also, replacement of a reactor-vessel upper lid is already implemented in a PWR. From that background, establishing techniques for replacement of a reactor vessel including core internals have been required as one measure of preventive maintenance for an existing old nuclear power plant. In those techniques, it is important to make a plant's “downtime” as short as possible.
As a first type of prior art, methods for carrying out a reactor vessel are disclosed in Japanese Unexamined Patent Application Publication Nos. 8-62368 and 9-145882. However, those prior-art methods are concerned with carrying-out of a reactor pressure vessel of a BWR, and cannot be directly applied to carrying-out of a pressure vessel of a PWR.
Japanese Unexamined Patent Application Publication No. 11-84052 discloses, as a second type of prior art, a method for carrying out core internals of a PWR through a space left around a girder for a polar crane (overhead traveling crane). This prior art can be applied to the carrying-out of core internals, but not to the carrying-out of a reactor vessel. The reasons why the above prior art cannot be applied to carrying-out of a reactor vessel reside in three points as follows:
(1) The reactor vessel cannot pass through the space left around the girder for the polar crane.
(2) The polar crane installed in a reactor containment vessel (hereinafter referred to as a “containment vessel”) does not have a capacity capable of lifting the reactor vessel and an associated radiation shield together.
(3) The reactor vessel including the radiation shield combined therewith cannot be carried out through an equipment carrying-in opening provided in the containment vessel.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a reactor vessel handling method, which is able to carry in and out a reactor vessel of a pressurized water reactor in a short time with high efficiency.
According to one aspect of the present invention, an overhead traveling crane in a reactor containment vessel of a pressurized water reactor is removed, and then a reactor vessel is carried out through an opening provided in a top portion of the reactor containment vessel.
According to another aspect of the present invention, in an area within a reactor containment vessel of a pressurized water reactor where an overhead traveling crane is installed, the overhead traveling crane is operated to move aside for creating a space, through which a reactor vessel is able to pass, and then the reactor vessel is carried out through an opening provided in a top portion of the reactor containment vessel.
According to still another aspect of the present invention, an overhead traveling crane in a reactor containment vessel of a pressurized water reactor is reinforced, a reactor vessel is lifted up to an operating floor by using the reinforced overhead traveling crane, and then the reactor vessel is carried out through an opening provided in a side wall of the reactor containment vessel.
According to still another aspect of the present invention, in a state in which an overhead traveling crane in a reactor containment vessel of a pressurized water reactor is removed, a new reactor vessel is carried in to a predetermined position within the reactor containment vessel through an opening provided in a top portion of the reactor containment vessel.
According to still another aspect of the present invention, in a state in which an overhead traveling crane in a reactor containment vessel of a pressurized water reactor is reinforced, a new reactor vessel is carried in to a predetermined position within the reactor containment vessel through an opening provided in a side wall of the reactor containment vessel.
In a reactor containment vessel, to which any of the above-described methods of the present invention is applied, an opening allowing the reactor vessel to be carried out through the opening is provided in at least one of a top wall and a side wall of the reactor containment vessel.
The present invention set forth above can be applied to carrying-out and -in of a reactor vessel of a PWR when the reactor vessel is to be replaced. The present invention can also be applied to carrying-out of a reactor vessel of a PWR when the reactor vessel is to be decommissioned.
REFERENCES:
patent: 3841495 (1974-10-01), Dronick et al.
patent: 6252922 (2001-06-01), Hasegawa et al.
patent: 04-277196 (1992-10-01), None
patent: 6-102398 (1994-04-01), None
patent: 8-43577 (1996-02-01), None
patent: 8-62368 (1996-03-01), None
patent: 08-262190 (1996-10-01), None
patent: 08-285997 (1996-11-01), None
patent: 9-145882 (1997-06-01), None
patent: 09-310497 (1997-12-01), None
patent: 10-39077 (1998-02-01), None
patent: 10-282283 (1998-10-01), None
patent: 11-84052 (1999-03-01), None
patent: 11-311693 (1999-11-01), None
Kadak, “Low Level Radioactive Waste Disposal. What Should We Do Now?”, [online], Jan, 21, 2000, ANS Public Information, p. 4 of 8, [retrieved on Nov. 12, 2002]. Internet: <URL:ans.org/pi/documents/948952800.html>.
Adachi Takahiro
Aoki Masataka
Ushiroda Kouichi
Matz Daniel
Poon Peter M.
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