Fuel assembly for a boiling water reactor
A fuel assembly for a boiling water reactor contains a plurality of fuel rods maintained laterally by spacers and surrounded by a fuel assembly case. The outer walls of a spacer are provided with projecting elements that maintain a minimum space between the outer surface of the spacer and the fuel assembly case, the opening span of a spacer being smaller than the internal width of the fuel assembly case. The fuel assembly is characterized in that the spacer is maintained in an off-center position by a force acting laterally thereon such that an external space located between an outer surface of the spacer associated with the outer surface of a central cell and the fuel assembly case is narrower than an internal gap opposite the external space and oriented towards the center or towards a control element disposed at the center.
1. A fuel assembly, comprising:
a fuel element case for a boiling water reactor;
a spacer for laterally holding a bundle of fuel rods, said fuel element case surrounding said spacer, said spacer including two inner edge webs and two outer edge webs, said two inner edge webs being adjacent an interspace for a control element;
an inner gap formed between said two inner web edges and said fuel element case, said inner gap extending substantially along said two inner web edges;
an outer gap formed between said two outer web edges and said fuel element case, said outer gap extending substantially along said outer web edges;
spring elements extending away from said two inner edge webs and into said inner gap, said spring elements supported against said fuel element case, said spring elements holding said spacer held in an off-center position such that said outer gap is narrower than said inner gap; and
studs projecting from said outer edge webs and into said outer gap, said studs ensuring that said outer gap maintains a minimum dimension.
2. The fuel assembly according to claim 1 wherein said spring elements include a first spring element and a second spring element, and said inner gap extends at least from said first spring element to said second spring element.
3. The fuel assembly according to claim 1 , wherein said spacer has a corner, and at least one of said spring elements is disposed adjacent said corner of said spacer.
4. The fuel assembly according to claim 1 , wherein said fuel element case has inner sides, and said spring elements press said spacer away from said inner sides of said fuel element case with a force extending transversely with respect to a corresponding one of said inner edge webs.
5. The fuel assembly according to claim 1 , further comprising a control element disposed in the interspace.
6. The fuel assembly according to claim 1 , wherein each of said inner web edges has a total length, and said inner gap extends along said total length of said inner web edges.
7. A core cell for a boiling water reactor, the core cell having four fuel elements, and a control element disposed between said four fuel elements, each one of said four fuel elements comprising:
a fuel element case for a boiling water reactor;
a spacer for laterally holding a bundle of fuel rods, said fuel element case surrounding said spacer, said spacer including two inner edge webs and two outer edge webs, said two inner edge webs being adjacent the control element, said two outer edge webs being remote from the control element;
an inner gap formed between said two inner web edges and said fuel element case, said inner gap extending substantially along said two inner web edges;
an outer gap formed between said two outer web edges and said fuel element case, said outer gap extending substantially along said outer web edges;
spring elements extending away from said two inner edge webs and into said inner gap, said spring elements supported against said fuel element case, said spring elements holding said spacer held in an off-center position such that said outer gap is narrower than said inner gap; and
studs projecting from said outer edge webs and into said outer gap, said studs ensuring that said outer gap maintains a minimum dimension.