ML18043A900
| ML18043A900 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 06/21/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18043A899 | List: |
| References | |
| TASK-15-20, TASK-RR NUDOCS 7908030580 | |
| Download: ML18043A900 (4) | |
Text
.. UNITED STATES
- NUCLEAR REGULATORY COMMISSION WASHINGTON. D. C. 20555.
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
- REGARDING THE. FUEL* HANDLING ACCIDENT* INSIDE** CONTAINMENT PALISADES NUCLEAR GENERATING STATION CONSUMERS POWER COMPANY DOCKET NO.
so~2ss Introduct.i on ENCLOSURE 1
- By letter dated January 14, 1977, the staff requested the Consumers Power Company (the licensee) to evaluate the previously unevaluated potential consequences of a postulated Fuel Handling Accid~nt Inside*Containment (FHAIC) at Palisades.
The licensee submitted, in a letter dated April 6, 1977, an evaluation of the FHAIC.
The licensee stated that the potential
- consequences of this postulated accident are 6.2 Rem Thyroid and 0.03 Rem whole body at the Exclusion Area Boundary (EAB).
The licensee concluded that these doses are well within the guidelines of 10 CFR Part 100..
- Eva 1 uation We have completed our review of the licensee's Aprii 6, 1977, submittal
- which addresses the potential consequences of an accident involving spent fuel handling inside containment.
We have perfonned an independent analysis of the FHAI.C.
Our assumptions and the resulting potential consequences at the EAB are given in Table 1. The calculated potential consequences of the postulated fuel handling* accident inside containment are appropriately within 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 a 1 so examined, but they are not controlling due to decay of the
- short-li~ed r~dioisotopes prior to fuel handling*.
The potential consequences of this postulated accident at the Low Population Zone*
Boundary are less than those given for the EAB in Table 1. The potential thyroid *dose consequences ca 1 cu lated by the staff are 15 times higher than those calculated by the licensee (91 Rem vs 6.2 Rem thyroid}
because the staff used a slightly higher X/Q value (3.4xlo-4 vs 2.6xto-4 SEC/m3) and assumed that all the fuel rods. in the equivalent of an entire assembly failed, as opposed to the licensee's assumption that a single row of fuel rods in the fuel assembly failed.
e ENCLOSURE.1 A recent study (1) has indicated that dropping a spent fuel assembly into the core during refueling operations may potentially cause damage to more fuel pins than has been assumed for evaluating the Fuel Handling
- Accident Inside Containment. This study has indicated that up to all of the fuel pins in two spent.fuel assemblies, the one dropped and the one hit, may be damaged because of the embrittlement of fuel cladding material from radiation in the core.
The probability of the postulated fuel handling accident inside containment 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 estimated by the study was.based on the assumption that a spent fuel assembly falls.about 14 feet directly onto one other assembly in the core;
. an impact which results in the greatest energy available for crushing the fuel pins in both assemblies.. This type of impact is unlikely because the falling assembly would be subjected to drag forces in the water which should 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 a.nd damaging all the fuel pins in two assemblies is sufficiently small that refueling inside containment.
is not*a safety concern which requfres remedial acti~n.
We hav~, however~ conservatively calculated 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 term for both spent fuel.assemblies is that given in Regulatory Guide 1.25. This is conservative because (1} these two assemblies are not expected to have the power peaking factor and clad gap activity reconmended in Regulatory Guide 1.25 and (2} the pool decontamination factor for inorganic iodine should be greater than that reconmended in Regulatory*
Guide 1.25. The calculated potential radiological consequences at the exclusion area boundary for the complete rupture of fuel pins in two assemblies are twice the values given in Table 1. These conservatively 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 concluded that the potential consequences of this postulated accident are acceptable.
(1) J. N. Singh,. "Fuel Assembly Handling Accident AnalysiS", EG&G Idaho Technical Report RE-A-78-227, October 1978.
e ENCLOSURE l Environmental Considerations
- The environmental impacts of an accident involving the handling of spent fuel inside containment have been addressed in Section VI.A of the Final Environmental Statement (FES) dated June, 1972, for the operation of -
- Palisades.
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 exclusion 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 guideline values of 10 CFR Part 100 and ~re, therefore, accept~ble.
Date_:
June 21, 1979
e ENCLOSURE 1 Table 1 ASSUMPTIONS FOR AND POTENTIAL CONSEQUENCES OF THE POSTULATED FUEL HANDLING ACCIDENT AT THE EXCLUSION AREA BOUNDARY FOR PALISADES NUCLEAR GENERATING PLANT Assumptions:
Guidance in Regulatory Guide 1.25 Release is a puff release through the stack with no isolation or effluent filtration.
Power Level.
Fuel Exposure Time Power Peaking Factor Equivalent Number of Assemblies damaged Number of Assemblies in core Charcoal Filtefs available Decay time oefore moving fuel 0-2 hours X/Q Value, Exclusion Area Boundary (ground level release) 2650 Mwt*
3 years 1.65 1
204 None 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> 3.4 x 10-4 sec/m3 Doses~ Rem
- Thyroid Whale Body Exclusion Area Boundary (EAB) 2-hour doses 91 0.4 I.