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Title: RIA Limits Based On Commercial PWR Core Response To RIA

Reactivity insertion accident (RIA) limits have been under intense review by regulators since 1993 with respect to what should be the proper limit as a function of burnup. Some national regulators have imposed new lower limits while in the United States the limits are still under review. The data being evaluated with respect to RIA limits come from specialized test reactors. However, the use of test reactor data needs to be balanced against the response of a commercial PWR core in setting reasonable limits to insure the health and safety of the public without unnecessary restrictions on core design and operation. The energy deposition limits for a RIA were set in the 1970's based on testing in CDC (SPERT), TREAT, PBF and NSRR test reactors. The US limits given in radially averaged enthalpy are 170 cal/gm for fuel cladding failure and 280 cal/gm for coolability. Testing conducted in the 1990's in the CABRI, NSRR and IGR test reactors have demonstrated that the cladding failure threshold is reduced with burnup, with the primary impact due to hydrogen pickup for in-reactor corrosion. Based on a review of this data very low enthalpy limits have been proposed. In reviewing proposed limits from RIL-0401(1)more » it was observed that much of the data used to anchor the low allowable energy deposition levels was from recent NSRR tests which do not represent commercial PWR reactor conditions. The particular characteristics of the NSRR test compared to commercial PWR reactor characteristics are: - Short pulse width: 4.5 ms vs > 8 ms; - Low temperature conditions: < 100 deg. F vs 532 deg. F. - Low pressure environment: atmospheric vs {approx} 2200 psi. A review of the historical RIA database indicates that some of the key NSRR data used to support the RIL was atypical compared to the overall RIA database. Based on this detailed review of the RIA database and the response of commercial PWR core, the following view points are proposed. - The Failure limit should reflect local fuel enthalpy and the condition of the fuel, i.e. burnup and expected oxide levels as a function of enthalpy. Limits based on cladding oxide needs to take into account that in many core designs the highest oxide will generally be on high burnup rods on the core periphery which have low reactivity, and lower peaking factors. Otherwise excessively low limits based generally on oxide could restrict use of fuel from the spent fuel pool. (authors)« less
Authors:
; ;  [1]
  1. Westinghouse Electric Company, 4350 Northern Pike, Monroeville, PA 15146-2886 and 5801 Bluff Road, Columbia, SC 29250 (United States)
Publication Date:
OSTI Identifier:
21016432
Resource Type:
Conference
Resource Relation:
Conference: 2006 International congress on advances in nuclear power plants - ICAPP'06, Reno - Nevada (United States), 4-8 Jun 2006; Other Information: Country of input: France; 15 refs; Related Information: In: Proceedings of the 2006 international congress on advances in nuclear power plants - ICAPP'06, 2734 pages.
Publisher:
American Nuclear Society - ANS, La Grange Park (United States)
Research Org:
American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
Country of Publication:
United States
Language:
English
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; BURNUP; CLADDING; CORROSION; DESIGN; ENTHALPY; FAILURES; HYDROGEN; OXIDES; PWR TYPE REACTORS; REACTIVITY INSERTIONS; SPENT FUELS; TEMPERATURE RANGE 0065-0273 K; TEST REACTORS