ML19242D712
| ML19242D712 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 06/20/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19242D707 | List: |
| References | |
| NUDOCS 7908160566 | |
| Download: ML19242D712 (4) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATICN "CGARDING FUEL HANDLING ACCIDENT IN$1E ccgTAingEni POINT BEACH NUCLEAR PLANT UNITS 1 AND 2 W15CUNSIN ELECTRIC POWER COMPAut DOCKET h05. 50-2co, -3U1 Introduction By letter dated January 18, 1977, the staff requested tne Wisconsin Elec-tric Power Company (the licensee) to evaluate the previously unevaluated potential consequences of a postulated Fuel Hancling Accident Insice Containment (FHAIC) at Point Beach Units 1 and 2 (Point Beccn 1/2). The licensee submitted an evaluation of the FHAIC in a letter cated March 14, 1977. The licensee assumed that the FHAIC occurred 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> af ter plant shutdown and stated that this is the earliest time that fuel handling operations may begi n.
The licensee stated that tne potential consequences of tnis postulated accident are 55 Rem thyroid and 0.028 Rem wnole body at the Exclusion Area Boundary (EAB). The licensee concluded tnat these doses are well within the guidelines of 10 CFR Part 100.
Evaluation We have completed our review of the licensee's March 14, 1977, submi ttal which addresses the potential consequences of an accident involvir j spent fuel handling i nside containment.
We have performed an indepencent analy-sis of the FHAl,.
ne have assumed a minimum decay time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> between plant shutdown and handling of irradiated fuel. This time is shorter tnan that practiced by most operating pressurized water reactors.
Therefore, we nave not requi ud the licensee to adopt a Technical Specification requir-ing a minimum decay time before handling spent fuel. Our remaining assump-tiens and the recciting potential consequences at the EAB are given in Table 1.
The calculated potential consequences of the postulated fuel hand-ling accident inside containment are appropriately within the guidelines of 10 CFR Part 1CO and are. therefore, acceptable.
Appropriately within the guicelines of 10 CFR Par t 100 has been defined as less than 100 Rem to the tny roi d.
This is based on tne probability of this event relative to other events whicn are evaluated against 10 CFR Part 100 exposure guidelines.
Jnole body coses were also examined, but tney are not controlling cue to cecay of the short-lived racioisotopes prior to fuel handling. The poten-tial consequences of this postulated accicent at tne Lcw Population Zone _
Scuncary are less tnan those given for the EAB in Taole 1.
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. A recent study ~1/has indicated that dropping a spent fuel assembly into the core during refueling operations may potentially cause dameg to more fuel pins than has been assumed for evaluatirm the Fuel Handlin3 ircci dent Inside Containment. This study has indicateo that up to all of the fuel pins in two spent fuel assemblies, the one dropped and the one nit, may be damaged because of the embrittlement of fuel claading steridl from radiation in the core.
The probability of the postulated Fue; Handling Accident !nside Contain-ment is small.
Not only have there been several hundred reactor-years of plant operating experience with only a few accidents involving spent fuel being dropped into the core, but none of these accidents has resulted in measurable releases of activity. The potential damage to spent fuel es-timated by the study was based on the assumption that a spent fuel assemoly falls about 14 feet directly onto one other assembly in the core; an impact which results in tne greatest energy available for crushing the fuel pins in both assemblies. This type of irgact is unlikely because the f alling assemoly would be subjected to drag forces in the water which should cause the assembly to skew out of a vertical f all path.
Based on the above, we have concluded that the likelihood of a spent fuel assembly f alling into tne core and damaging all the fuel pins in two as-sem:: lies is sufficiently small that refueling inside containment is not a safety concern which requires immediate remedial action.
We have, however, conservatively calculated tne potential radiological consequences of a fuel assembly dron onto the reactor core with the rup-ture of all the fuel pins in two fuel assemblies.
We have also assumec for this postulated accident that tne source tenn for both spent fuel as-semblies is that given it Regulatory Guide 1.25.
This is conservative because (1) these two -
'molies should not have tne power peaking f actor and clad gap activity assumed in Regulatory Guide 1.25 anc (2) the pool decontaminaticn f actor for inorganic iodine shxid be greater than that assumed i n Regulatory Guide 1.25.
The calculated potential radiological consequences at the exclusion area boundary for the complete rupture of fuel cins in two assemblies are twice the values given in Table 1.
These conser-vatively calculated potential consequences are within the guidelines of 10 CFR Part 100; consequently, we have concluoed tha the potential conse-quences of this costulated accident are acceptable. O.:
In the SE", dated July 15, 1970, the staff indicated that pending resulution of tne dif ferences between the stuf f and the applicant on the assur ions usec fcr the postulated fuel itandling accident in the spent fuel
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J. N. Singn, " Fuel Assembly Handling Accident Analysis, "EG5G Icaho
- ecnnical Report, RE-n-78-227, October 1972.
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7.ne results of this analysis warranted an investigation of a. similar ac :ident in the spent fuel pool.
For this, a drop of 2-1/2 feet was postulated and the analysis performed in the same manner as previcusly descr ibed.
Results indicate that in this scenario damage to the missile or target is minimal. No fuel pins in either fuel assembly were calculatd to be ruptured.
restriction was placed in the Technical Specifications wnich pronioited handling fuel outsice the containment.
In eliminating this Tecnnical Specification restriction on August 10, 1971, the staff failed to docu-ment the basis for its evaluation of this accident. The potential con-sequences for this accident are the same as those for the postulated fuel handling accident insice containment and the numbers given in Table 1 are also appropriate for this postula;ed accident.
Based on this, we have also concluded that the potential consequences of the postulated fuel handling accident in the spent fuel pool are apprcpriately within tne ex-posure guicelines of 10 CFR Part 100 and are, therefore, acceptable.
Environmental Considerations The environmental impacts of an accident involving the handling of spent fuel inside containment have been addressed in Section V.E of the Point Beach 1/2 Environmental Statement (FES) dated May 1972.
Conclusion The staff has evaluated the licensee's analysis of the postulated FHAIC.
Af ter performing an independent analysis of the radiological consequences of an FHAIC to an individual located at any point on the exclusion area boundary, the staff concludes that the coses are appropriately within the guideline valur> of 10 CFR Part 100 and are, therefore, acceptable.
Da te : June 20, 1979
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Table 1 ASSUMPTIONS FOR AND POTENTIAL CONSEOUENCES OF THE POSTULATED FUEL HANDLING ACCIDENTS AT THE EXCLUSION AREA SCU.DARY FOR POINT BEACH NUCLEAR PLANT UNITS 1 AND 2 Assumpti ons :
Guidance in Regulatory Guide 1.25 Power Level 1540 Mwt Fuel Exposure Time 3 years Power Peaking Factor 1.65 Equivalent Numcer of Assem-blies damaged 1
Number of Assemblies in core 121 Charcoal Filters available None Decay tire before moving fuel 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> 0-2 hours X/Q Value, Ex-clusion Area Boundary
-4 (ground level release) 2.6 x 10 sec/m Doses. Rem Thyroid Whole Body Exclusion Area Bouncary (EAB)
Consequences frcm Fuel Hand-iing Accidents Inside Con-tainment 59 0.2 Exclusion Area 30uncary (EAS)
Consequences frca Fuel Hanc-ling Accicents Inside Spent Fuel Pool 59 0.2 b
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