Information Notice 1997-14, Assessment of Spent Fuel Pool Cooling

Assessment of Spent Fuel Pool Cooling
	ML031050356
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000268, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	03/28/1997
From:	Martin T; Office of Nuclear Reactor Regulation
To:	;
References
	IN-97-014, NUDOCS 9703270253
	Download: ML031050356 (11)
	v • d • e

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UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 March 28, 1997 NRC INFORMATION NOTICE 97-14: ASSESSMENT OF SPENT FUEL POOL COOLING

Addressees

All holders of operating licenses or construction permits for nuclear power reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert

addressees to results of an assessment performed by the Office for Analysis and Evaluation

of Operational Data (AEOD) on operating experience involving spent .jel pool (SFP) cooling

and inventory control. The AEOD assessment is detailed in NUREG-1275, Volume 12,

"Assessment of Spent Fuel Cooling," February 1997. It is expected that recipients will review

the information for applicability to their facilities and consider actions, as appropriate, to avoid

similar problems. However, suggestions contained in this information notice are not NRC

requirements; therefore, no specific action or written response is required.

Description of Circumstances

NRC's Executive Director for Operations directed AEOD to independently assess the

likelihood and consequences of an extended loss of SFP cooling or inventory. The

assessment focused on the collection and analysis of operating experience involving SFP

cooling and inventory control and comprised of six major tasks:

(1) Develop generic configurations delineating SFP cooling and inventory control

equipment for a boiling-water reactor (BWR) and a pressurized-water reactor (PWR).

(2) Review and assess more than 12 years of operating experience for domestic and

foreign reactors.

(3) Visit six sites to gain an understanding of the physical configurations, practices, and

operating procedures for the licensees' SFPs.

(4) Review applicable SFP regulations and the NRC Standard Review Plan

(NUREG-0800) for the acceptance criteria and the applicable regulatory guides.

(5) Perform independent assessments of electrical systems, instrumentation, heat loads, and radiation levels associated with the SFP.

(6) Estimate near-boiling frequencies utilizing probabilistic techniques.

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IN 97-14 March 28, 1997 The findings and conclusions of the AEOD assessment are summarized below.

The loss of SFP coolant inventory in excess of 1 foot has occurred 10 times over the

last 12 years at a rate of about once every 100 reactor-years. Loss of SFP cooling

with a temperature increase in excess of 11 OC [20 OF] has occurred 4 times in the

last 12 years at a rate of approximately 3 times every 1000 reactor-years. The

consequences of these actual events have not been severe; however, some events

resulted in loss of several feet of SFP coolant level and have continued for more than

24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The primary cause of these events has been human error, most preva- lently, valve mispositionings. These errors are discussed in greater detail in

NUREG-1275, Volume 12.

The relative risk due to loss of spent fuel pool cooling is low in comparison with the

risk of events not involving SFPs. The review determined that the likelihood and

consequences of SFP loss-of-cooling events are highly dependent on human

performance (e.g., valve manipulations, crane manipulations, spent fuel handling

equipr,lent manipulations) and individual plant design features.

The efforts by utilities to reduce outage durations have resulted in full core off-loads

early in outages. This increased fuel pool heat load reduces the time available to

recover from a loss-of-SFP-cooling should such an event occur early in the outage.

On a plant specific basis the following observations are provided:

Failures of reactor cavity seals or gate seals or ineffective antisiphon devices could

potentially cause loss of SFP coolant inventory, which could potentially result in

uncovering the fuel or endangering makeup capability.

Ineffective configuration control was the most frequent cause of SFP loss-of-inventory

events and loss-of-cooling events.

At multi-unit sites with common pools, there is the potential for SFP boiling conditions

to affect safe-shutdown equipment for the operating unit, particularly during full core

off-loads.

Improved procedures and training which recognize the time frames over which SFP

events can proceed, the heat load and possibility of loss of inventory, could enhance

control room operator response to loss-of-inventory and loss-of-cooling SFP events.

Insufficient control room instrumentation and non-safety-related power supplies to SFP

instrumentation may hinder operator response to SFP events.

1-.)

IN 97-14 March 28, 1997 Discussion

The AEOD assessment found large variations in the designs and capabilities of SFPs and

related systems at individual nuclear plants. The AEOD assessment identified that the

frequency of loss-of-inventory events was relatively high compared to loss-of-cooling events, and prompt off-loads will lead to reduced time to boil if cooling is lost. A loss of SFP

inventory in combination with higher heat loads reduces the time to respond to SFP events.

Thus, the emphasis of the findings were on instrumentation to quickly alert the operators and

effective procedures and training to facilitate prompt operator response. The operating

experience review determined that loss-of-SFP-cooling events are infrequent and the

consequences of actual events have been small. The risk assessment indicates that the SFP

events are not a dominant contributor to overall plant risk. However, human error initiators

and operator actions required to mitigate an error are subject to large uncertainties, and there

are large variations in design vulnerabilities among plants. In summary the following areas

need emphasis:

(1) Procedures and training to detect and respond to SFP loss-of-inventory and loss-of- cooling events, including those caused by loss of offsite power are needed and should

address configuration controls that can prevent and/or mitigate such events. They

should be consistent with the time frames over which SFP events can proceed at the

specific plant, recognizing the plant-specific heat load and the possibility of loss of

inventory because of cavity seal or gate failures.

(2) Reliable instrumentation is necessary to monitor SFP temperature and level and SFP

area radiation, including periods following a loss of offsite power, in order to detect

SFP loss-of-inventory events and loss-of-cooling events in a timely manner.

(3) Testing, maintenance, and configuration control of plant features such as reactor

cavity seals, gate seals, or antisiphon devices need to be examined for those plants

where failures could potentially cause loss of SFP coolant inventory sufficient to

endanger makeup capability or result in fuel uncovery.

This information notice requires no specific action or written response. If you have any

questions about the information in this notice, please contact one of the technical contacts

listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Jose G. Ibarra, AEOD Stephen Koenick, NRR

(301) 415-6345 (301) 415-2841 E-mail: jgi@nrc.gov E-mail: ssk2@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

Attachment

IN 97-14 March 28, 1997 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

97-13 Deficient Conditions 03/24/97 All holders of OLs

Associated with Pro- or CPs for nuclear

tective Coatings at power reactors

Nuclear Power Plants

97-12 Potential Armature 03/24/97 All holders of OLs

Binding in General or CPs for nuclear

Electric Type HGA power reactors

Relays

92-27, Thermally Induced 03/21/97 All holders of OLs

Supp. 1 Accelerated Aging or CPs for nuclear

and Failure of ITE/ power reactors

Gould A.C. Relays

Used in Safety-Related

Applications

97-11 Cement Erosion from 03/21/97 All holders of OLs

Containment Subfounda- or CPs for nuclear

tions at Nuclear Power power reactors

Plants

97-10 Liner Plate Corrosion 03/13/97 All holders of OLs

in Concrete Containments or CPs for power

reactors

97-09 Inadequate Main Steam 03/12/97 All holders of OLs

Safety Valve (MSSV) or CPs for nuclear

Setpoints and Perform- power reactors

ance Issues Associated

with Long MSSV Inlet

Piping

OL = Operating License

CP = Construction Permit