Use of gadolinium in PWR cores: the effects on local power and on nodal normalization

Conference · Fri Nov 01 00:00:00 EST 1985 · Trans. Am. Nucl. Soc.; (United States)

OSTI ID:5740358

Rothleder, B M

Past studies have shown that judicious loading of gadolinium (Gd/sub 2/O/sub 3/) as a distributed burnable absorber in pressurized water reactor cores can result in improved power shapes, lower peaking factors, a more negative moderator temperature coefficient, and increased control rod worth. These and other such studies, however, either have not addressed or have not published information about local power behavior and the validity of standard nodal normalization procedures. Gadolinium depletion characteristics suggest that x,y pin (or local) power peaking behavior and validity of nodal normalization prior to imposing feedback be reexamined. As in past studies, a Westinghouse 157-assembly, 17 x 17 lattice core with both borosilicate and axially zoned 2 and 3 wt% Gd/sub 2/O/sub 3/ burnable absorbers was analyzed through first cycle using the ARMP/SIMULATE code system, modified to treat gadolinium. Results are as follows: 1) The x,y pin peaking in gadolinium designs is essentially the same as that in conventional designs, but shows significantly greater radial migration. 2) The maximum feedback-initiated x,y assembly power change in gadolinium designs is twice that in conventional designs, thus increasing any inaccuracy incurred by the super-position of feedback effects on x,y parameters. 3) Axial normalization of nodal codes may require explicit evaluation for gadolinium designs.

• Research Organization: SAIC, McLean, VA
• OSTI ID: 5740358
• Report Number(s): CONF-851115-; TRN: 86-020255
• Journal Information: Trans. Am. Nucl. Soc.; (United States), Vol. 50; Conference: American Nuclear Society winter meeting, San Francisco, CA, USA, 10 Nov 1985
• Country of Publication: United States
• Language: English

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