Thomas E Robbins

US Patent:

42933803, Oct 6, 1981

Filed:

Nov 25, 1977

Appl. No.:

5/854970

Inventors:

Thomas R. Robbins - Crofton MD

International Classification:

G21C 700

US Classification:

376209

Abstract:

An improved reactor and fuel assembly design is disclosed wherein a liquid moderated thermal reactor is initially run with all or a portion of its fuel assemblies in an undermoderated boiling water mode to take advantage of increased conversion ratio at lower H/fuel ratios, and after a suitable period of operation, the neutron spectrum for all or a portion of the undermoderated boiling assemblies is shifted to lower energies to increase reactivity by converting a number of fuel assemblies to a nearer optimum moderated pressurized or non-boiling mode. The increased reactivity allows for continued operation of the modified assembly. The improved reactor and fuel assembly design results in improved fuel utilization and neutron economy and reduced control requirements for the reactor. The design may be augmented by reducing the number of fuel rods comprising the assembly after a suitable period of operation, as disclosed in the applicants copending application filed Nov. 1, 1977, Ser. No. 847,524.

US Patent:

42552362, Mar 10, 1981

Filed:

Nov 1, 1977

Appl. No.:

5/847524

Inventors:

Thomas R. Robbins - Crofton MD

International Classification:

G21C 700
G21C 730
G21C 1920

US Classification:

176 20SS

Abstract:

An improved reactor and fuel assembly design is disclosed wherein a light water reactor is initially run with undermoderated fuel assemblies to take advantage of increased conversion ratio, and after a suitable period of operation, the neutron spectrum for the undermoderated assemblies is shifted to lower energies to increase reactivity by withdrawing a number of fuel rods from the assemblies. The increased reactivity allows for continued operation of the modified assembly, and the fuel rods which are removed are used to construct similar assemblies which are also capable of continued operation. The improved reactor and fuel assembly design results in improved fuel utilization and neutron economy and reduced control requirements for the reactor.