Bubble worth variation in molten fuel assemblies due to neutron streaming and application of Trombay criticality formula

Journal Article · Mon Nov 01 04:00:00 EST 1982 · Nucl. Sci. Eng.; (United States)

OSTI ID:5870603

Kumar, A

In the considerations of recriticality of molten fuel assemblies, the presence of bubbles in the fuel plays an important role. In such a situation, there are two opposing contributions to reactivity from (a) the phenomenon of neutron streaming in bubbles (negative contribution) and (b) the phenomenon of changing neutron self-multiplication in the fuel (positive contribution). It is not possible to accurately calculate the individual reactivity contributions of the two phenomena using multidimensional transport theory or Monte Carlo codes. A simple diffusion theory expression given by Nicholson and Goldsmith for estimating reactivity contribution due to neutron streaming alone has been used extensively. As a part of the present contribution, first an attempt has been made to improve the applicability of the Nicholson-Goldsmith work by expressing extrapolation length in terms of the root-mean-square free path in the assembly. It is found that the application of the Trombay criticality formula, particularly its ''modified Wigner rational variant,'' leads to an expression for bubble reactivity worth, due to neutron streaming alone, that yields the closest agreement with the bubble worth values computed from the two-dimensional transport theory code TWOTRAN and the Monte Carlo code KENO.

• Research Organization: Bhabha Atomic Research Centre, Neutron Physics Division, Trombay, Bombay 400 085
• OSTI ID: 5870603
• Journal Information: Nucl. Sci. Eng.; (United States), Journal Name: Nucl. Sci. Eng.; (United States) Vol. 82:3; ISSN NSENA
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220300* -- Nuclear Reactor Technology-- Fuel Elements
BUBBLES
COMPUTER CODES
CRITICALITY
DIFFUSION
FUEL ASSEMBLIES
MONTE CARLO METHOD
RADIATION STREAMING
REACTIVITY WORTHS
TRANSPORT THEORY
TWO-DIMENSIONAL CALCULATIONS