Information Notice 2011-02, Operator Performance Issues Involving Reactivity Management at Nuclear Power Plants

Operator Performance Issues Involving Reactivity Management at Nuclear Power Plants

ML101810282
Person / Time
Issue date:	01/31/2011
Revision:	0
From:	Blount T B Division of Policy and Rulemaking
To:
Beaulieu, D P, NRR/DPR, 415-3243
References
IN-11-002
Download: ML101810282 (6)

ML101810282 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, DC 20555-001 January 31, 2011 NRC INFORMATION NOTICE 2011-02: OPERATOR PERFORMANCE ISSUES INVOLVING REACTIVITY MANAGEMENT AT NUCLEAR POWER PLANTS

ADDRESSEES

All holders of operating licenses for nuclear power reactors under the provisions of Title 10 of the Code of Federal Regulations (10 CFR) Part 50, "Domestic Licensing of Production and Utilization Facilities," except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reacto

PURPOSE

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform addressees of events involving deficiencies with reactivity management planning and implementatio The NRC expects recipients to review the information for applicability to their facilities and to consider actions, as appropriate, to avoid similar problem Suggestions contained in this IN are not NRC requirements; therefore, no specific action or written response is require DESCRIPTION OF CIRCUMSTANCES Callaway Plant During a Callaway Plant shutdown in October 2003, the control room operators did not effectively control core reactivity during low-power operation The event began on the morning of October 20, 2003, when the Callaway Plant experienced an inverter failure on a safety-related bus that put the unit in a 24-hour technical specification action to restore the inverter or be in Mode 3 (hot standby) within the next 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> The next morning, because the inverter had not yet been restored, operators initiated a plant shutdown at approximately 10 percent per hou With the main turbine on line and with turbine bypass valves closed, operators attempted to stabilize the plant at approximately 8-percent powe Per procedure, operators opened the turbine drain valves, which increased main steam flow, reducing reactor coolant temperature and adding positive reactivit At the same time, negative reactivity was being inserted by xenon buildup, decreasing reactor powe The net effect was that reactor coolant temperature decreased by approximately 10 degrees Fahrenheit over a half-hour perio Operators did not withdraw control rods or dilute boron concentration to stabilize reactor power or reactor coolant temperatur As a result of the lowering reactor coolant temperature, pressurizer level lowered enough to cause letdown to isolat In addition, reactor coolant temperature decreased below the technical specification required minimum temperature while critical for several minute In response to the lowering reactor coolant temperature, the IN 2011-02