Induced nuclear reactions: processes – systems – and elements – Fuel component structure – Plural fuel segments or elements
Patent
1998-04-09
1999-09-07
Wasil, Daniel D.
Induced nuclear reactions: processes, systems, and elements
Fuel component structure
Plural fuel segments or elements
376418, 376444, 376451, G21C 317, G21C 332
Patent
active
059498390
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a fuel assembly for a light-water nuclear reactor, and more specifically of boiling-water type.
BACKGROUND OF THE INVENTION
A core in a boiling water reactor comprises a plurality of vertically arranged fuel assemblies. A fuel assembly comprises a bundle of vertical elongated fuel rods which are retained and fixed by a number of spacers arranged in spaced relationship to each other along the bundle. The spacers comprise a number of cells for mutually fixing the fuel rods. The ends of the bundle are retained at the bottom and at the top, by a bottom tie plate and a top tie plate. In certain fuel assemblies, the bundle is divided into four orthogonal sub-bundles and the lower and upper parts, of each sub-bundle are retained by a bottom tie plate and a top tie plate, respectively. The bundle and the sub-bundles, are surrounded by a fuel channel which is normally designed with a square cross section. The fuel assembly comprises a vertical channel containing non-boiling water surrounded by a tubular casing. In the following, the channel including its casing will be referred to as a water channel. The water channel extends through the whole fuel assembly and has a cross section which may be circular or cruciform.
The fuel rods contain a stack of pellets of a nuclear fuel arranged in a cladding tube. During the burnup of the nuclear fuel, fission gases contained inside the fuel rod are released. To prevent the pressure on the cladding from becoming too great, an expansion space for the fission gases is needed, a so-called fission gas plenum. The fission gas plenum is normally arranged above the stack of fuel pellets.
The core is immersed into water which serves both as a coolant and as a neutron moderator. During operation, the water flows from below and upwardly through the fuel assembly, whereby part of the water is transformed into steam. The proportion of steam is highest in the upper part of the fuel assembly. In the following, coolant means the water and the steam which flow through the fuel assembly. When the coolant flows upwardly through the fuel assembly, it is important that it be subjected to as little pressure drop as possible. Because of the high proportion of steam, the pressure drop is higher in the upper part of the fuel assembly than in the lower part thereof. During operation, the pressure drop across a spacer in the upper part of the fuel assembly is about five times higher than the pressure drop across a corresponding spacer in the lower part of the fuel assembly. Therefore, it is of particular importance to design the upper part of the fuel assembly in such a way that there is as low a pressure drop as possible.
A low pressure drop in the upper part of the fuel assembly is favorable for the stability properties of the fuel assembly and reduces the risk of dryout.
A high pressure drop means a high pressure on the fuel channel and may give rise to creeping and subsequently unacceptable deformation of the fuel channel.
SUMMARY OF THE INVENTION
The object of the invention is to provide a fuel assembly which, during operation, has a low pressure drop in its upper part.
A fuel assembly for a boiling water reactor, wherein the fuel assembly during operation is arranged vertically in the core of the reactor. The fuel assembly comprises a plurality of vertical fuel rods arranged in at least one fuel bundle, wherein each one of the fuel rods comprises a stack of fuel pellets surrounded by a cladding tube. A bottom tie plate retains and supports the lower part of the fuel bundle and is arranged at the bottom of the fuel assembly. A number of spacers retain and position the fuel rods in spaced relationship to each other and are arranged axially separated along the fuel rods. A vertical water channel is provided through which water flows upwards through the fuel assembly, and a fuel channel which surrounds the fuel bundle. A top spacer which retains and supports the upper part of the fuel bundle and is arranged above and spaced apart from the stacks
REFERENCES:
patent: 3748230 (1973-07-01), Gerosa et al.
patent: 4914679 (1990-04-01), Tomiyama et al.
patent: 5219519 (1993-06-01), Matzner
patent: 5297177 (1994-03-01), Inagaki et al.
patent: 5331679 (1994-07-01), Hirukawa
patent: 5416812 (1995-05-01), Matzner
patent: 5859886 (1999-01-01), Nylund
Kobayashi et al., Fuel Assembly, Patent Abstracts of Japan, JP 63-315981, vol. 13, No. 157, Apr. 1989.
Asea Brown Boveri AB
Lattig Matthew J.
Wasil Daniel D.
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