UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
March 3, 2006
NRC INFORMATION NOTICE 2006-06:
LOSS OF OFFSITE POWER AND STATION
BLACKOUT ARE MORE PROBABLE DURING
SUMMER PERIOD
ADDRESSEES
All holders of operating licensees for nuclear power reactors, except those who have
permanently ceased operations and have certified that fuel has been permanently removed
from the reactor vessel.
PURPOSE
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to inform
addressees about the recent Office of Nuclear Regulatory Research (RES) study that
confirmed an increased frequency of loss-of-offsite power (LOOP) and station blackout (SBO)
events during the summer period (i.e., May through September). Recipients are expected to
review the information for applicability to their facilities and consider appropriate actions to
address similar problems. However, suggestions contained in this information notice are not
NRC requirements and no specific action or written response is required.
DESCRIPTION OF CIRCUMSTANCES
NUREG-1784, Operating Experience Assessment - Effects of Grid Events on Nuclear Power
Plant Performance, dated December 2003 (Agencywide Documents Access and Management
System (ADAMS) Accession No. ML033530400), showed that switchyard and grid-related
LOOP events occurred mostly during the summer months.
A new report on RES-sponsored work by the Idaho National Laboratory entitled
NUREG/CR-6890, Re-evaluation of Station Blackout Risk at Nuclear Power Plants, was
published in December 2005 (ADAMS Accession Nos. ML060200477, ML060200479, and
ML060200510). The new report confirmed the earlier observations and showed the following
seasonal risk insights:
The SBO risk increased by a factor of two during the summer period between
1997 and 2004 because 22 summer and 2 non-summer LOOP events occurred
during this period.
The overall LOOP frequency is more than twice as high during the summer
period when compared to the annual average.
The probability of LOOP after a reactor trip is greater during the summer period.
All four categories of LOOP (plant, switchyard, grid, and weather-centered
events) had higher frequencies during the summer period.
DISCUSSION
An insight from the new study is that plant-specific LOOP frequencies can change significantly
with seasonal conditions. The changes in the probability of a LOOP or an SBO by season can
affect assumptions used in plant-specific risk assessments (either quantitative or qualitative)
required by Title 10 of the Code of Federal Regulations, Section 50.65, the Maintenance Rule.
The risk assessments for individual plants in different regions of the country and at different
times of the year could also be affected based on regional uniqueness resulting from seasonal
generating and transmission limitations.
CONTACT
This information notice requires no specific action or written response. Please direct any
questions about this matter to the technical contacts listed below or the Office of Nuclear
Reactor Regulation (NRR) project manager.
/RA/
Christopher I. Grimes, Director
Division of Policy and Rulemaking
Office of Nuclear Reactor Regulation
Technical Contacts:
Thomas Koshy, NRR
George Morris, NRR
301-415-1176
301-415-4074 E-mail: txk@nrc.gov
E-mail: gwm2@nrc.gov
Dale Rasmuson, RES
301-415-7571 E-mail: dmr@nrc.gov
NRR Project Manager: Carla Roquecruz, NRR
301-415-1455 E-mail: cpr1@nrc.gov
Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.
ML053200013
OFFICE
EEEB:DE
Tech Editor
BC:EEEB:DE
RES
BC:APLA:DRA
D:DE
NAME
TKoshy*
P.Kleene*
RVJenkins*
DRasmuson*
MRubin*
MMayfield*
DATE
11/21/2005
11/14/2005
11/27/2005
12/12/2005
02/01/2006
02/13/2006 OFFICE
IOEB:DIRS
BC:IOEB:DIRS
LA:PGCB:DPR
PM:PGCB:DPR
BC:PGCB:DPR
D:DPR
NAME
CRoqueCruz*
MJRoss-Lee*
CHawes*
DBeaulieu*
CJackson*
CIGrimes
DATE
02/14/2006
02/16/2006
03/02/2006
03/02/2006
03/03/2006
03/03/2006
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- Information Notice 2006-02, Use of Galvanized Supports and Cable Trays with Meggitt Si 2400 Stainless Steel Jacketed Electrical Cables (19 January 2006, Topic: Safe Shutdown, Fire Barrier)
- Information Notice 2006-03, Motor Starter Failures Due to Mechanical Interlock Binding (25 January 2006, Topic: Stroke time)
- Information Notice 2006-04, Design Deficiency in Pressurizer Heaters for Pwrs (13 February 2006)
- Information Notice 2006-04, Design Deficiency in Pressurizer Heaters for PWRs (13 February 2006)
- Information Notice 2006-05, Possible Defect in Bussman KWN-R and KTN-R Fuses (3 March 2006)
- Information Notice 2006-06, Loss of Offsite Power and Station Blackout Are More Probable During Summer Period (3 March 2006, Topic: Loss of Offsite Power)
- Information Notice 2006-07, Inappropriate Use of a Single Parameter Limit as a Nuclear Criticality Safety Limit at Fuel Cycle Facilities (31 March 2006)
- Information Notice 2006-07, Inappropriate Use of a Single Parameter Limit As a Nuclear Criticality Safety Limit at Fuel Cycle Facilities (31 March 2006)
- Information Notice 2006-07, Inappropriate Use of a Single Parameter Limit as a Nuclear Criticality Safety limit at Fuel Cycle Facilities (31 March 2006)
- Information Notice 2006-08, Secondary Piping Rupture At Mihama Power Station in Japan (16 March 2006, Topic: Safe Shutdown, Flow Accelerated Corrosion, Feedwater Heater)
- Information Notice 2006-08, Secondary Piping Rupture at Mihama Power Station in Japan (16 March 2006, Topic: Safe Shutdown, Flow Accelerated Corrosion, Feedwater Heater)
- Information Notice 2006-09, Performance of NRC-Licensed Individuals While on Duty With Respect to Control Room Attentiveness (11 April 2006, Topic: Inattentive)
- Information Notice 2006-09, Performance of NRC-Licensed Individuals While on Duty with Respect to Control Room Attentiveness (11 April 2006, Topic: Inattentive)
- Information Notice 2006-10, Use of Concentration Control For Criticality Safety (23 April 2006)
- Information Notice 2006-10, Use of Concentration Control for Criticality Safety (23 April 2006)
- Information Notice 2006-11, Applicability of Patient Intervention in Determining Medical Events for Gamma Stereotactic Radiosurgery and Other Therapy Procedures (12 June 2006, Topic: Brachytherapy)
- Information Notice 2006-12, Exercising Due Diligence When Transferring Radioactive Material (6 July 2006)
- Information Notice 2006-13, Ground-Water Contamination Due To Undetected Leakage of Radioactive Water (10 July 2006, Topic: Time of Discovery)
- Information Notice 2006-13, E-mail from M. Mclaughlin on NRC, Regarding NRC Information Notice 2006-13: Groundwater Contamination (13 July 2006, Topic: Boric Acid, Time of Discovery)
- Information Notice 2006-14, Potentially Defective External Lead-Wire Connections in Barton Pressure Transmitters (25 September 2006, Topic: Functionality Assessment, Operability Determination)
- Information Notice 2006-15, Vibration-Induced Degradation and Failure of Safety-Related Valves (27 July 2006, Topic: Enforcement Discretion, Through-Wall Leak, Unidentified leakage, Power Uprate)
- Information Notice 2006-17, Recent Operating Experience of Service Water Systems Due to External Conditions (31 July 2006, Topic: Significance Determination Process, Frazil ice, Biofouling)
- Information Notice 2006-18, Significant Loss of Safety-related Electrical Power at Forsmark, Unit 1, in Sweden (10 August 2007)
- Information Notice 2006-19, Leaking Fuel Element Causes False Indication of Steam Dryer Leakage in Boiling Water Reactors (24 August 2006)
- Information Notice 2006-20, Foreign Material Found in the Emergency Core Cooling System (16 October 2006)
- Information Notice 2006-21, Operating Experience Regarding Entrainment of Air Into Emergency Core Cooling and Containment Spray Systems (21 September 2006, Topic: Unanalyzed Condition)
- Information Notice 2006-22, New Ultra-Low-Sulfur Diesel Fuel Oil Could Adversely Impact Diesel Engine Performance (12 October 2006)
- Information Notice 2006-24, Recent Operating Experience Associated with Pressurizer and Main Steam Safety/Relief Valve Lift Setpoints (14 November 2006, Topic: Corrosion bonding)
- Information Notice 2006-26, Failure of Magnesium Rotors in Motor-Operated Valve Actuators (20 November 2006)
- Information Notice 2006-27, Circumferential Cracking in the Stainless Steel Pressurizer Heater Sleeves of Pressurized Water Reactors (11 December 2006, Topic: Boric Acid, Intergranular Stress Corrosion Cracking, Stress corrosion cracking, Through Wall Leak, Unidentified leakage, Operational leakage)
- Information Notice 2006-28, Siren System Failures Due to Erroneous Siren System Signal (22 December 2006, Topic: Tone Alert Radio, Siren)
- Information Notice 2006-29, Potential Common Cause Failure of Motor-operated Valves as a Result of Stem Nut Wear (14 December 2006)
- Information Notice 2006-29, Potential Common Cause Failure of Motor-operated Valves As a Result of Stem Nut Wear (14 December 2006)
- Information Notice 2006-30, Summary of Fitness-for-Duty Program Performance Reports for Calendar Year 2004 and 2005 (21 December 2006, Topic: Time of Discovery, Fitness for Duty, Blind Performance Test)
- Information Notice 2006-31, Inadequate Fault Interrupting Rating of Breakers (26 December 2006)
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