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    NUREGKR-6451BNL-NUREG-52498

    A Safety and RegulatoryAssessment of Generic BWRand PWR PermanentlyShutdown Nuclear Power PlantsManuscript Completed: April 1997DatePublished August 1997

    Prepared byR J. Travis, R E. Davis, E. J. Grove, M. A. Azarm

    Bmkhaven National LaboratoryUpton, NY 11973

    G. J. Menciasky, NRC Program Manager

    Prepared forDivision of Regulatory ApplicationsOffice of Nuclear Regu latory ResearchU.S. Nuclear Regulatory Comm issionWashington, DC 20555-0001NRC Job Code L2590DISCLAIMER

    This report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United Sta tes Government nor any agency thereof, nor any of theiremployees, makes an y warranty, express or implied, or assumes any legal liability or responsi-bility for the accuracy, completeness, or usefulness of any information, apparatus, product, orprocess disclosed, or represents that its use would not infringe privately owned rights. Refer-ence herein to any specific commercial product, process, or service by trade name, trademark,manufacturer, or otherwise does not neccssarily constitute or imply its endorsement, recom-mendation, or favoring by the United States Government or any agency thereof. The viewsand opinions of authors expressed herein do not necessarily state or reflect those of th eUnited S tates Government or any agency thereof.

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    DISCLAIMERPortions of this dormmat may be iDegi%Iein eiectmnic image products. Images areprodud from the best available originaldOr?nmf!XltW

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    ABSTRACT

    An evaluation of the nuclear power plant regulatory basis is pe rformed, as it pertains to those plants thatare permanently shutdown (PSD) and awaiting or undergoing decommissioning. Four spent fuel storageconfigurationsare examined. Recommendations are provided for those operationally based regulationsthat could be partially or totally removed for PSD plants without impacting public health and safety.

    iii JUREG/CR- $51

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    CONTENTSpageABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiEXECUTIVESUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix

    FOREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiiiACRONYMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv1.2 .3 .

    4 .

    5.6 .7 .

    INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SPENT FUE L STORA GE CONFIGURATION INPUT ASSUMPTIONS . . . . . . . . .3.1 Configuration 1 .Hot Fuel in the Spent Fuel Pool . . . . . . . . . . . . . . . . . . . . .3.1.1 Representative Plant and Fuel Pool Data . . . . . . . . . . . . . . . . . . . . . .3.1.2 Accident Initiator and Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.1.3 Critical Decay Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.1.4 Meteorological and P opulation Data . . . . . . . . . . . . . . . . . . . . . . . .3.1.5 Accident Inventory and Source Term . . . . . . . . . . . . . . . . . . . . . . . .3.1.6 Emergency Response and O ther Data Requirements . . . . . . . . . . . . . . .3.2 Configuration 2 - Cold Fuel in the Sp ent Fuel Pool . . . . . . . . . . . . . . . . . . . .3.2.1 Accident Initiator and Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.2.2 Accident Inventory and Source Terms . . . . . . . . . . . . . . . . . . . . . . .3.3 Configuration 3 - All Fuel Stored in an IndependentSpent Fuel Storage Installation (ISFSI) . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3.1 Accident Initiator and Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3.2 Exclusion Area and Meteorology . . . . . . . . . . . . . . . . . . . . . . . . . .3.3.3 Accident Inventory and Source Term . . . . . . . . . . . . . . . . . . . . . . . .3.4 Configuration 4 - All Spent Fuel Removed from the Site . . . . . . . . . . . . . . . . .RESULTS OF THE CONSEQUENCE ANALYSES . . . . . . . . . . . . . . . . . . . . . .4.1 Configuration 1 - Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.2 Configuration 2 - Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.3 Configuration 3 - Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.4 Configuration 4 - Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    REGULATORY ASSESSMENT SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . .SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    1-12-13-13-13-13-23-23-4 3-73-8 3-9 3-93-9

    3-103-103-123-123-124-1 4-14-54-8 4-95-16-17-1

    APPENDIX A PREVIOUS ANALYSES OF SPENT FUEL POOL ACCIDENTSAPPENDIX B DETAILED REGULATORY ASSESSMENT . . . . . . . . . . . . . . . . . . . .. . . . . . . A- 1B- 1

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    FIGURESFigure Page3.1 Spent fuel temperature as a function of time for the representative PWRconfiguration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-53.2 Spent fuel temp erature as a function of time for the representative BWRconfiguration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

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    Table3.1

    3.23.34.14.24.34.44.54.64.74.85.1

    6.1

    TABLESpage

    Spent Fuel Storage Configuration Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . .Configuration 1 Release Fractions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    3-3

    3-8 Configuration 3 Release Fractions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 1Mean PWR Consequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2Mean BWR Consequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3PWR Core Melt Accident Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4Mean Offsite Consequences - Configuration 2 . . . . . . . . . . . . . . . . . . . . . . . 4-6Configuration 2 Estimates of the Committed 50 Year Dose to a Worker . . . . . . . 4-7 Mean Offsite Consequences - Configuration 3 . . . . . . . . . . . . . . . . . . . . . . . 4-9 Activity of the S hort-Lived Isotopes in the Boric Acid Concentration Tanks . . . . . 4-11Activity of the Long-Lived Isotopes in the Boric Acid Concentration Tanks . . . . . 4-11Assessment of Continued Regulatory Applicability for Permanently ShutdownNuclear Power Reactors (Summary) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2 Generic PWR Accident Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

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    EXECUTIVE SUMMARY

    The long -term availability of less expensive power and the inc reasing plant modification and maintenancecosts have caused some utilities to re-examine the economics of nuclear pow er. As a result, severalutilities have opted to permanently shutdo wn their plants. Each licensee of these permanently shutdow n(PSD) plants has submitted plant-specific exemption requests for those regulations that they believe areno longer applicable to their facility. The preparation and subsequent review of these exemption requestsrepresents a large level of effort for both the licensees and the NRC staff. This experience has indicatedthe need for an explicit regulatory treatment of PSD nuclear power plants.This report presents a regulatory assessment for generic BWR and PWR plants that have permanentlyceased operation in support of NRC rulemaking activities in this area.After the reactor vessel is defueled, the traditional accident sequences that dominate the operating plantrisk are no longer applicable. The remaining source of public risk is associated with the accidents thatinvolve the spent fuel. Previous studies have indicated that complete spent fuel pool drainage is anaccident of potential concern. Certa in combinations of spent fuel storage configurations and decay times,could cause freshly discharged fuel assemblies to self heat to a temperature where the self sustainedoxidation of the zircaloy fuel cladding may cause cladding failure.Spent Fuel ConfigurationsThis study has defined four spent fuel configurations which encompass all of the anticipated spent fuelcharacteristics and storag e modes following permanent shu tdown. Spent fuel which (due to a combinationof storage geometry, decay time, and reactor type) can suppo rt rapid zircaloy oxidation is designated asSpent Fuel Sto rage Configuration 1 - "Hot Fuel in the Spent Fuel Pool." Configuration 1 encompassest