View source for Information Notice 1993-83, Potential Loss of Spent Fuel Pool Cooling After a Loss-of-Coolant Accident or a Loss of Offsite Power

{{Adams
| number = ML031070131
| issue date = 08/24/1995
| title = Potential Loss of Spent Fuel Pool Cooling After a Loss-of-Coolant Accident or a Loss of Offsite Power
| author name = Crutchfield D
| author affiliation = NRC/NRR
| addressee name = 
| addressee affiliation = 
| docket = 05000003, 05000010, 05000029, 05000133, 05000155, 05000171, 05000206, 05000213, 05000219, 05000220, 05000237, 05000244, 05000245, 05000247, 05000249, 05000250, 05000251, 05000254, 05000255, 05000259, 05000260, 05000261, 05000263, 05000265, 05000266, 05000267, 05000269, 05000270, 05000271, 05000272, 05000275, 05000277, 05000278, 05000280, 05000281, 05000282, 05000285, 05000286, 05000287, 05000289, 05000293, 05000295, 05000296, 05000298, 05000301, 05000302, 05000304, 05000305, 05000306, 05000309, 05000311, 05000312, 05000313, 05000315, 05000316, 05000317, 05000318, 05000320, 05000321, 05000322, 05000323, 05000324, 05000325, 05000327, 05000328, 05000329, 05000330, 05000331, 05000333, 05000334, 05000335, 05000336, 05000338, 05000339, 05000341, 05000344, 05000346, 05000348, 05000352, 05000353, 05000354, 05000361, 05000362, 05000364, 05000366, 05000368, 05000369, 05000370, 05000373, 05000374, 05000382, 05000387, 05000388, 05000389, 05000390, 05000391, 05000395, 05000397, 05000400, 05000409, 05000410, 05000412, 05000413, 05000414, 05000416, 05000423, 05000424, 05000425, 05000437, 05000438, 05000439, 05000440, 05000441, 05000443, 05000444, 05000445, 05000446, 05000454, 05000455, 05000456, 05000457, 05000458, 05000461, 05000482, 05000483, 05000498, 05000499, 05000508, 05000528, 05000529, 05000530
| license number = 
| contact person = 
| document report number = IN-93-083, Suppl 1, NUDOCS 9508180256
| document type = NRC Information Notice
| page count = 12
}}
{{#Wiki_filter:V

I

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 August 24, 1995 NRC INFORMATION NOTICE 93-83, SUPPLEMENT 1:    POTENTIAL LOSS OF SPENT FUEL POOL

COOLING AFTER A LOSS-OF-COOLANT

ACCIDENT OR A LOSS OF OFFSITE

POWER

==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 NRC staff findings regarding the risk associated

with the potential loss of spent fuel pool (SFP) cooling. It is expected that

recipients will review this information notice for applicability to their

facilities and consider any appropriate actions. However, suggestions

contained in this information notice are not NRC requirements; therefore, no

specific action or written response is required.

Background

The staff has been evaluating a report made under Part 21, "Reporting of

Defects and Noncompliance," of Title 10 of the Code of Federal Regulations

(10 CFR), which two engineers, who formerly worked under contract for the

Pennsylvania Power and Light Company, filed on November 27, 1992. In the

report, the two engineers contended that the design of the Susquehanna Steam

Electric Station (SSES) failed to meet numerous regulatory requirements with

respect to a postulated sustained loss of the cooling function for the SFP

that mechanistically results from a loss-of-coolant accident (LOCA) or a loss

of offsite power (LOOP). The report provided a series of detailed technical

and regulatory arguments to support this assertion. It also postulated that

subsequent boiling of the SFP would cause failure of equipment necessary to

mitigate the accident or to safely reach a shutdown condition because of the

adverse environmental conditions created by SFP boiling within the reactor

building. As a result of these equipment failures, severe offsite

consequences would result.

Units 1 and 2 at SSES are boiling water reactors with Mark II containments

designed by General Electric Company. The SFP and associated systems for each

unit are located in each unit's reactor building. The surface of the SFPs is

on the common refueling floor, which spans the uppermost level of the two

reactor buildings. The two SFPs communicate through a common cask storage pit

when the path is not isolated by gates. The SFP cooling system for each unit

at the SSES consists of three parallel heat exchangers and three pumps. Water

9508180256                                                               X

5   Ath

IN 93-83, Supp. 1 August 24, 1995 the SFP is normally

to make up for evaporation and small leakage losses from

supplied by the condensate transfer system.

for adding SFP makeup

The normal SFP cooling system and the normal system used                     events.

water are not designed to remain functional after        design-basis

designed    to    operate after

However, the residual heat removal (RHR) system is                   operation     of valves

these events and can be aligned to cool the SFP       by   manual

water    system    is   also   designed

in the reactor building. The emergency service                         water    to   the SFP

to operate after these events and can be aligned        to  provide

operation     of  valves     in the   reactor

to make up for evaporative losses by manual

building.

==Description of Circumstances==
a loss of SFP

The staff completed an assessment of safety with regard to Part 21 report were

cooling and determined that the concerns     identified     in  the

an engineering

of low safety significance for SSES. The assessment included          loss    of SFP

from   or  mitigate     a

evaluation of the capability to recover                                  sustained     loss of

the  frequency      of  a

cooling, and a quantitative estimation of                                       This

SFP cooling based on the findings of the     engineering      evaluation.

which is

assessment is documented in a final safety evaluation report,on the draft

available for public review. The    staff  considered      comments

report, from

safety evaluation report from the authors of the Part 21                   and from the

Pennsylvania Power and Light Company    (the  licensee     for  SSES),
                                             for  inclusion     in   the   final safety

Advisory Committee on Reactor Safeguards                             Power    and Light

evaluation report. The report was     issued  to  Pennsylvania

Company, Docket Nos. 50-387 and   50-388,  on  June    19,   1995.

for SSES

While the staff was evaluating the Part 21 report, the licensee from a loss of

initiated several actions to improve the capability to recover                     to operate

SFP cooling. These actions included the following: (1) committing   increase     the

with the two SFPs cross-connected through the cask pit to committing to conduct

redundancy of cooling systems  for the  combined    SFPs;     (2)
                                                                        reliability of the

testing and analyses that support assumptions regarding theanalyses that

SFP cooling assist mode of the RHR system; (3) completing                installation of

support modifications and procedural changes; (4) completing       conditions; and

instrumentation to improve the capability to monitor SFP                   that improve the

(5) completing changes to off-normal and emergency procedures

reliability of recovery from a loss-of-SFP-cooling event.

assessment

The staff used both deterministic and probabilistic safety                        a loss  of

safety  implications    of   events    involving

techniques to evaluate the                                              evaluation of     the

SFP cooling. Because the staff did not consider a detailed                     of risk,   the

effects of SFP boiling necessary, based on an initial assessment                         base

SFP boiling and

staff elected to quantitatively estimate the frequency of

decisions regarding further evaluations on that estimate.

to recover

The staff's deterministic engineering evaluation of the capability     features     of SSES

from or mitigate a loss of SFP cooling identified important            characteristics

for modeling in the probabilistic safety assessment. These                      and outage

included the following: (1) on the basis of licensee commitments          after a loss of

management procedures, the time to the onset of pool boiling

IN 93-83, Supp. 1 August 24, 1995 maintain the

cooling will exceed 25 hours; (2) natural circulation flow will         [30'F]    with the

temperature difference between the two pools less than 17C allowing a single

pools cross-connected through the common cask pit, thereby                    pool to

fuel pool cooling system of adequate capacity aligned to either errors, which

prevent boiling in both pools; (3) equipment failures and           human

are explicitly modeled in the safety assessment, are the cooling   significant failure

assist mode

modes for the normal SFP cooling system; and (4) the SFP                    or   both pools

of the RHR system will provide a reliable means of cooling            one

alignment       is   available.

when access to the reactor building for manual system

of reaching a

The safety assessment quantitatively estimated the frequency water vapor to

near-boiling condition, which could add significant         heat   and

The

the reactor building atmosphere, on the basis of the above information.    to  improve    the

staff estimated that the actions the licensee has        implemented

have  reduced      the   near-boiling

capability to recover from a loss of SFP cooling

frequency from 7.OE-5 per plant-year to 2.OE-5 per plant-year.

LOOP,
The dominant sequences for near-boiling frequency involve an extended                    The

but sequences involving a LOCA or a shorter LOOP        are  also   significant.

the  reliance      of  the    normal

dominance of sequences involving a LOOP reflects                           the limited

SFP cooling system on offsite sources of electrical power and of the RHR

availability of the RHR system for fuel pool      cooling    because

Sequences

system's primary reactor vessel decay heat removal function. because the RHR

involving a LOCA were identified as significant       specifically

pool

system in the affected unit is assumed to be unavailable for fuel

cooling.

each unit at

Despite the relatively small fraction of an operating cycle that        occurring      during

SSES was assumed to be in a refueling outage,-     the  sequences

refueling outage periods that were examined     dominated     the  near-boiling

shorter

frequency. Two factors contributed to this result: the relatively        the   practice     of

time to reach boiling after a loss of SFP     cooling   because     of

and  the  practice     of   removing      systems

conducting full-core off-loads at SSES                                           removal

associated with the outage unit that contribute to SFP decay heat

capability from service for maintenance    during   refueling     outages.

and separate

To address generic concerns identified through the Part 21 report           a  special

concerns related to spent fuel storage    pools   identified     during

Bulletin 94-01, inspection at a permanently shutdown reactor facility (see NRC at Dresden

"Potential Fuel Pool Draindown Caused by Inadequate Practicesbegun implementing

Unit 1," dated April 14, 1994), the staff has developed and                   actions:
  a generic action plan. The generic plan includes the following            storage     pool

(1) a search and analysis of information    regarding     spent   fuel

operation   and  design    of  spent     fuel    storage

issues, (2) an assessment of the                                      the assessment

pools at selected reactor facilities, (3) an evaluation of                of an

findings for safety concerns,  and  (4) selection     and  execution

based  on the   safety   significance       of the findings.

appropriate course of action                                                 that were

During these assessments, the staff will examine those features             risk from loss- identified at SSES as important to the acceptably low level of

of-SFP-cooling events.

K>~/                             K.)   IN 93-83, Supp. 1 August 24, 1995 Discussion

The functional capability to protect the reactor coolant pressure boundary, to

mitigate the effects of potential design-basis events, and to shut down the

reactor and maintain it in a safe shutdown condition are important safety

attributes. Nuclear power plants are designed so that the potential for loss

of the capability to perform any of these functions is remote. Adverse

environmental conditions, which may affect many components simultaneously, have the potential to disable the redundant equipment that provides this

capability.

The staff conducted a licensing-basis review for SSES, which is documented in

Appendix A to the final safety evaluation report, and concluded that a loss of

SFP cooling initiated by a seismic event (seismically induced LOOP) was

considered in originally granting the facility's license. The staff concluded

that, with the exception of seismically induced design-basis events, the

development of an adverse environment in the reactor building as a result of a

loss of SFP cooling is outside the licensing basis for SSES. However, it also

concluded that the licensing basis with regard to SFP cooling at other

facilities may vary widely from that of SSES. Therefore, the conclusion that

the development of an adverse environment in the reactor building as a result

of a loss of SFP cooling is outside the licensing basis at SSES may not be

valid at other facilities.

The staff performed a safety assessment to evaluate the frequency of near- boiling events in the SFPs at SSES and found that the potential for such an

event was acceptably remote at SSES. After analyzing the safety assessment

results, the staff concluded that the potential for reaching a near-boiling

condition in the SFP was remote principally because of the diverse installed

systems available for fuel pool cooling and the administrative controls that

ensured an extended period for recovery of cooling before the onset of

boiling.

IN 93-83, Supp. 1 August 24, 1995 written response.

This information notice requires no specific action or   this notice, please

If you have any questions regarding the information inthe   appropriate Office

contact one of the technical contacts listed below or

of Nuclear Reactor Regulation (NRR) project manager.

Dennis M. Crutchfield,     ector

Division of Reactor Program  Management

Office of Nuclear Reactor  Regulation

Technical contacts:  Steven Jones, NRR

(301) 415-2833 Joseph Shea, NRR

(301) 415-1428 David Skeen, NRR

(301) 415-1174 Attachment:

===List of Recently Issued NRC Information Notices===
A+1 4          ~#        f?/.eV(         QJckt7&

"'A'tachment

IN 93-83, Supp. 1 August 24, 1995 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information                                    Date of

Notice No.              Subject                Issuance    Issued to

95-33           Switchgear Fire and            08/23/95    All holders of OLs or CPs

Partial Loss of Offsite                    for nuclear power reactors.

Power at Waterford

Generating Station, Unit 3
95-10,          Potential for Loss of          08/11/95    All holders of OLs or CPs

Supp. 2        Automatic Engineered                        for nuclear power reactors.

Safety Features Actuation

95-32          Thermo-Lag 330-1 Flame          08/10/95    All holders of OLs or CPs

Spread Test Results                        for nuclear power reactors.

95-31          Motor-Operated Valve            08/09/95    All holders of OLs or CPs

Failure Caused by Stem                     for nuclear power reactors.

Protector Pipe Inter- ference

95-30           Susceptibility of Low-         08/03/95    All holders of OLs or CPs

Pressure Coolant Injection                 for nuclear power reactors.

and Core Spray Injection

Valves to Pressure Locking

94-66,          Overspeed of Turbine-          06/16/95    All holders of OLs or CPs

Supp. 1         Driven Pumps Caused by                      for nuclear power reactors.

Binding in Stems of

Governor Valves

95-29           Oversight of Design and         06/07/95    All holders of OLs or CPs

Fabrication Activities                      for nuclear power reactors.

for Metal Components Used

in Spent Fuel Dry Storage

Systems

95-28           Emplacement of Support         06/05/95    All holders of OLs or CPs

Pads for Spent Fuel Dry                    for nuclear power reactors.

Storage Installations at

Reactor Sites

OL = Operating License

CP = Construction Permit

~       i                           k)
                                                                     IN 93-83, Supp. 1 August 24, 1995 This information notice requires no specific action or written response.

If you have any questions regarding 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.

orig /s/'d by DMCrutchfield

Dennis M. Crutchfield, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts:     Steven Jones, NRR

(301) 415-2833 Joseph Shea, NRR

(301) 415-1428 David Skeen, NRR

(301) 415-1174 Attachment:
    List of Recently Issued NRC Information Notices

DOCUMENT NAME:      9383SP1.IN

See nrevious concurrence

OFFICE     lSPLB      l lPECB         l  l               TECH ED I        PL     I

NAME         SJones*         DSkeen*       JShea*        RSanders*     GHubbard*
DATE         03/03/95        02/14/95      02/20/95      02/09/95      03/02/95     l

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IN 93-83, Supp. I

August xx, 1995 This information notice requires no specific action or written response.

If you have any questions regarding 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.

Dennis M. Crutchfield, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts:                 Steven Jones, NRR

(301) 415-2833 Joseph Shea, NRR

(301) 415-1428 David Skeen, NRR

(301) 415-1174 Attachment:
    List of Recently Issued NRC Information Notices

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DATE            03/03/95                 02/14/95      02/20/95      02/09/95      03/02/95         l

OFFICE          C:SPLB         l         D:DSS         SC:PECB   I   PECB  I       C:PECB    I

NAME            CMcCracken*               GHolahan*    RDennig*      RKiessel*     AChaffee*
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NAME            DMCrutchfield

4A1 DATE            08/ /95

===OFFICIAL RECORD COPY===

IN 93-83, Supp. 1 August xx, 1995 This information notice requires no specific action or written response.

If you have any questions regarding 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.

Dennis M. Crutchfield, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts:    Steven Jones, NRR

(301) 415-2833 Joseph Shea, NRR

(301) 415-1428 David Skeen, NRR

(301) 415-1174 Attachment:
    List of Recently Issued NRC Information Notices

DOCUMENT NAME      G:\DLS\iN95-KX--SFP    X

See Drevious concurrence

OFFICE =    SPLB     Il    OECB      I    DRPE     l    TECH ED I     SC:SPL     l   l

NAME        SJones*        DSkeen*        JShea*        RSanders*      GHubbard*
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DATE        07/ /95

===OFFICIAL RECORD COPY===

IN 93-83, Supp. I

June xx, 1995 This information notice requires no specific action or written response.

If you have any questions regarding .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.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts:   Steven Jones, NRR

(301) 415-2833 Joseph Shea, NRR

(301) 415-1428 David Skeen, NRR

(301) 415-1174 Attachment:
    List of Recently Issued NRC Information Notices

DOCUMENT NAME     G:\DLS\IN95-XX.SFP

See nrevious concurrence

OFFICE      SPLB     lIOECB        l    DRPE   Z      TECH ED l      SC:SPLB  l

NAME        SJones*       DSkeen*        JShea*       RSanders*      GHubbard*
DATE        03/03/95      02/14/95       02/20/95     02/09/95       03/02/95 OFFICE

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06/   /95 DATE        03/03/95 OFFICE      D:DOPS     I

NAME        BKGrimes

DATE        06/ /95

===OFFICIAL RECORD COPY===

IN 93-83, Supp. 1 March xx, 1995 This information notice requires no specific action or written response.

If you have any questions regarding 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.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts:   Steven Jones, NRR

(301) 415-2833 Joseph Shea, NRR

(301) 415-1428 David Skeen, NRR

(301) 415-1174 Attachment:
    List of Recently Issued NRC Information Notices

DOCUMENT NAME:    G:\DLS\IN95-XX.SFP

See Drevious concurrence

OFFICE      SPLB          OECB      lDRPE             TECH ED       SC:SPLB

NAME        SJones*       DSkeen*       JShea*        RSanders*      GHubbard*
  DATE       03/03/95      02/14/95      02/20/95      02/09/95       03/02/95 OFFICE     C:SPLB        D:DSSA        SC:OECB       OECB          C:OECB

NAME       CMcCracken*   GHolahan       RDennig      RKiessel      AChaffee

DATE       03/03/95                  102/    /95     02/   /95      02/   /95 OFFICE     D:DOPS     I

NAME       BKGrimes

DATE       02/ /95

===OFFICIAL RECORD COPY===

K-,                               K)
                                                                       IN 93-83, Supp. 1 February xx, 1995 This information notice requires no specific action or written response.

If you have any questions regarding 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.

Brian K. Grimes, Director

Division of Project Support

Office of Nuclear Reactor Regulation

Technical contacts:       Steven Jones, NRR

(301) 415-2833 Joseph Shea, NRR

(301) 415-1428 David Skeen, NRR

(301) 415-1174 Attachment:
    List of Recently Issued NRC Information Notices

DOCUMENT NAME:       G:\DLS\IN95-XX.SFP

OFFICE      SPLB              OECB          DR4           TECH ED       SC:SPLB

RSandersta GHubbaid/    7 NAME        SJones    '       DSkeerfS      J    S

DATE        07/ 2/O5          02//q/95      02    /95     02/a1/95      0-
                                                                          O/  /95 OFFICE      C:ISPL)                         SC:OE         OECB I lIC:OECI

ED:DSSA         l

NAME       CMkra     e nL    GHolahan      RDennig       RKiessel      AChaffee

DATE            ?//95         02/  /95      02/   /95     02/  /95      02/   /95 OFFICE      D:DOPS         I

NAME       BKGrimes

DATE       02/ /95 OFFICIAL RECORD COPY}}

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