US 11,837,372 B2
Methods for protection of nuclear reactors from thermal hydraulic/neutronic core instability
John A. Blaisdell, Suffield, CT (US); Edward M. Chu, San Jose, CA (US); Camilla S. Rotander, Enkoping (SE); and Gurikar V. Kumar, San Jose, CA (US)
Assigned to Westinghouse Electric Company LLC, Cranberry Township, PA (US)
Filed by Westinghouse Electric Company LLC, Cranberry Township, PA (US)
Filed on Dec. 28, 2020, as Appl. No. 17/134,983.
Application 17/134,983 is a continuation of application No. 13/798,418, filed on Mar. 13, 2013, abandoned.
Claims priority of provisional application 61/611,618, filed on Mar. 16, 2012.
Prior Publication US 2021/0225538 A1, Jul. 22, 2021
Int. Cl. G21D 3/00 (2006.01); G21C 17/112 (2006.01); G21D 3/04 (2006.01)
CPC G21D 3/001 (2013.01) [G21C 17/112 (2013.01); G21D 3/04 (2013.01); G21D 3/005 (2019.01); Y02E 30/30 (2013.01)] 4 Claims
OG exemplary drawing
 
1. A method for protecting a nuclear reactor core from fuel damage due to thermal hydraulic instability in an extended operating domain for an extended power uprate, comprising:
generating a power-flow operating map, comprising:
establishing a natural circulation curve;
establishing a Maximum Extended Load Line Limit Analysis (MELLLA) control rod line; and
establishing a higher MELLLA+ control rod line positioned above the MELLLA control rod line;
forming a MELLLA+ domain above the MELLLA control rod line, up to the higher MELLLA+ control rod line;
identifying a predetermined core flow rate;
calculating by a thermal hydraulic code simulator a thermal hydraulic stability limit for core flow rates less than or equal to the predetermined core flow rate;
determining a power level that corresponds to the thermal hydraulic stability limit at different core flow rates that are less than or equal to the predetermined core flow rate;
providing an Average Power Range Monitor (APRM) flow-biased scram line;
lowering the APRM flow-biased scram line to below the thermal hydraulic stability limit based on the core flow rate being less than or equal to the predetermined core flow rate; and
when operating in the MELLLA+ domain, actuating an APRM-based trip system based on a core flow decrease resulting from a flow decrease transient and power increases above the power level to provide an automatic anticipatory scram or a selected rod insertion trip to cause a power reduction.