ML18081A830
| ML18081A830 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 11/28/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18081A829 | List: |
| References | |
| NUDOCS 8001030334 | |
| Download: ML18081A830 (4) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555
- Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REGARDING THE FUEL HANDLING ACCIDENT INSIDE CONTAINMENT SALEM NUCLEAR GENERATING STATION UNIT 1 PUBLIC SERVICE GAS AND ELECTRIC COMPANY DOCKET NO. 50-272 Introduction By letter dated January 18, 1977, the s.taff requested the Public Service Gas and Electric Company (the licensee) to evaluate the previously unevalu-ated potential consequences of a postulated Fuel Handling Accident Inside Containment (FHAIC) at Salem 1. The licensee submitted, in a letter dated March 30, 1977, an evaluation of the FHAIC.
The licensee stated that the potential consequenc-es of this postulated.accident are 0.3 Rem thyroid and 0.005 Rem whole body at the Exclusion Area Boundary (EAB) and 0.03 Rem thy-roid and 0.0005 Rem whole body at the Low Population Zone Boundary {LPZB).
The licensee concluded that these doses are well within the guidelines of 10 CFR Part 100.
Evaluation We have completed our review of the licensee's March 30, 1977, submittal which addresses the potential consequences of an accident involving spent fuel handling inside containment.
We have performed an independent analy-sis of the FHAIC.
Our assumptions and the resulting potential consequences at the EAB are given in Table 1. The calculated potential consequences of the postul~ted fuel handling accident inside containment are appropriately w.ithin the guidelines of 10 CFR Part 100 and are, therefore, acceptable.
Appropriately within the guidelines of 10 CFR Part 100 has been defined as less than 100 Rem to the thyroid. This is based on the probability of this event relative to other events which are evaluated against 10 CFR Part 100 exposure guidelines. Whole body doses were also examined, but they are not controlling due to decay of the short-lived radioisotopes prior to fuel hand-ling. The potential consequences of this postulated accident at the LoW Popu-lation Zone Boundary are less than those given for the EAB In Table 1.
. 1/
~recent study-h~s indi'ca~d that dropping a spent fuel assembly 1 nto the. core during refuel 1 ng operations may potentially cause damage to r:iore fu71 pins than has been assumed for evaluating the Fuel Handling Accident Inside Containment. This study has indica-ted that up to all of the fuel pins in two spent fuel assemblies th:-one dropped and the one hit, may be damaged because of the e~
brittlement of fuel cladding material from radiation in the core.
1 J. N. Singh, "Fuel Assembly Handling Accident Analysis," EG&G Idaho Technical Report RE-A-78~227, October 1978.
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J, 1- -
--* The probability of the postulated fuel handling accident inside containment is small.
Not only have there been several hunarea reactor-years of plant operating experience with only a few acci-dents 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 estimated by the study was basea on the assumption that a spent fuel assembly falls about 14 feet directly onto one other assembly in the core; an impact which re-sults in the greatest energy available for crushing the fuel pins in both assemblies. This type of impact is unlikely because tne falling assembly would be subjected to drag forces in the water which shoula cause the assembly to skew out of a vertical fall path.
Based on the above, we have concluded that the likelihood of a spent fuel assembly falling into the core and damaging all the fuel pins in two assemblies is sufficiently small that refueling inside containment is not a safety concern which requires immediate remedial action.
We have, however, conservatively calculateci the potential radiological consequences of a fuel assembly drop onto the reactor core with the rupture of all the fuel pins in two fuel assemblies.
We have also assumed for this postulated accident that the source tenn for both spent fuel assemblies is that given in Regulatory Guide 1.25. This is conservative because (1) these two assemblies should not have the power peaking factor and clad gap activity recommended in Regulatory Guide 1.25 and (2) the pool decontamination factor for inorganic iodine should be greater than that recommended in Regulatory Guide 1.25. The calculated potential radiological consequences at the ex-clusion area boundary for the complete rupture of fuel pins in two assemblies are twice the values given in Table 1. These conserva-tively calculated potential consequences, due to the lower probability of two assembly failures, have been judged against and found less than the guidelines of 10 CFR Part 100.
Consequently, we have concluaed that the potential consequences of this postulated accident are acceptable.
Environmental Considerations The environmental impacts of an accident involving the handling of spent fuel inside containment have been addressed in Section 7.1 of the Fi rial Environmental Statement (FES) dated Apri 1, 1973, for the operation of Salem 1.
Conclusion The staff has evaluated the licensee's analysis of the postulated FHAIC.
After performing an independent analysis of the radiological consequences of a FHAIC to any individual located at the nearest ex-clusion area boundary, the staff concludes that the doses for one assembly failure are appropriately within the guideline values of 10 CFR Part 100 and for failure of two assemblies within the guide-line values of 10 CFR Part 100 and are, therefore, acceptable.
Table I ASSUMPTIONS FOR AND POTENTIAL CONSEQUENCES OF THE POSTULATED FUEL HANDLING ACCIDENTS AT THE EXCLUSION AREA BOUNDARY FOR SALEM NUCLEAR GENERATING STATION UNIT 1 Assumptions:
Guidance in Regulatory Guide 1.25 Power Level Fuel Exposure Time rower Peaking Factor Equivalent Number of Assem-blies damaged Number of Assemblies in core Charcoal Filters available Decay time before moving fuel 0-2 hours X/Q Value, Ex-clusion Area Boundary (ground level release)
Exclusion Area Boundary (EAB)
Consequences from Accidents Inside Containment 3570 Mwt 3 years 1.72 1
193 None 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />
-4 2.4 x 10 sec/m3 Doses, Rem Thyroid Whole Body 71 0.3