Blackness coefficients, effective diffusion parameters, and control rod worths for thermal reactors

Technical Report · Sat Sep 01 04:00:00 EDT 1984

DOI:https://doi.org/10.2172/6330966· OSTI ID:6330966

Bretscher, M M

Simple diffusion theory cannot be used to evaluate control rod worths in thermal reactors because of the strongly absorbing character of the control material. However, good results can be obtained from a diffusion calculation by representing the absorber slab by means of a suitable pair of internal boundary conditions, ..cap alpha.. and ..beta.., which are ratios of neutron flux to neutron current. Methods for calculating ..cap alpha.. and ..beta.. in the P/sub 1/, P/sub 3/, and P/sub 5/ approximations, with and without scattering, are presented. By appropriately weighting the fine-group blackness coefficients, broad group values, <..cap alpha..> and <..beta..>, are obtained. The technique is applied to the calculation of control rod worths of Cd, Ag-In-Cd, and Hf control elements. Results are found to compare very favorably with detailed Monte Carlo calculations. For control elements whose geometry does not permit a thin slab treatment, other methods are needed for determining the effective diffusion parameters. One such method is briefly discussed and applied to the calculation of control rod worths in the Ford Nuclear Reactor at the University of Michigan. Calculated and measured worths are found to be in good agreement.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6330966
• Report Number(s): ANL/RERTR/TM-5; ON: DE85002646
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
220100 -- Nuclear Reactor Technology-- Theory &amp; Calculation
220400* -- Nuclear Reactor Technology-- Control Systems
CONTROL ROD WORTHS
MATHEMATICAL MODELS
P1-APPROXIMATION
P3-APPROXIMATION
REACTORS
SPHERICAL HARMONICS METHOD
THERMAL REACTORS