ML17338A847
| ML17338A847 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 05/30/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17338A846 | List: |
| References | |
| NUDOCS 7907130141 | |
| Download: ML17338A847 (8) | |
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UNITEDSTATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 Encl osure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATIOtI REGARDING FUEL HANDLING ACCIDENT INSIDE CONTAINMENT FLORIDA POWER AND LIGHT COMPANY TURKEY POINT NUCLEAR GENERATING STATION UNIT NOS.
3 AND 4 DOCKET NOS. 50-250, 50-251 Introduction By letter dated March 21, 1977, Florida Power and Light Company, (the licensee) submitted an evaluation of a postulated Fuel Handling Accident Inside Containment (FHAIC) at the Turkey Point Plant Unit Nos.
3 and 4.
In the evalu'ation. the licensee assumed that the FHAIC occurred 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> after plant shutdown on the basis that this is the earliest time that fuel handling operations may begin.
The licensee stated that the potential consequences of this postulated accident are 46 Rem thyroid and 0.2 Rem'.whole body at the Exclusion Area Boundary (EAB).
The licensee concluded that these doses are well below the guidelines of 10 CFR Part 100.
1 Evaluation We have completed 'our review of the licensee's March 21, 1977, submittal which addresses the potential consequences of an accident involving spent fuel handling inside containment.
We have also performed an independent analysis of the FHAIC.
In our evaluation we have assumed a minimum decay time of 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br /> between plant shutdown and handling of irradiated fuel.
This time is shorter than that practiced by most operating pressurized water reactors.
Therefore, we will not require the licensee to modify the Technical Specifications to require a minimum decay time before handling spent fuel.
Our remaining assumptions and the resulting potential consequences at the EAB are given in Table'.l.
Our.evaluation supports that of the licensee in that the calculated poten-tial consequences of the postulated fuel handling accident inside contain-ment 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 also examined, but they are not controlling due Ro decay of short-lived radioisotopes 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 l.
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A recent study-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 assem-blies.
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.
Ba'sed on the above evaluation
, 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 1's not a safety concern which requires immediate remedial action...
We'-. have, however, conservatively calculated the potential'adiological 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 should not have the power peaking factor and clad gap aMivity recommended in Regulatory Guide 1.25 and (2) the pool decontamin-ati'on factor for inorganic iodine is expected to be greater than that recommended in Regulatory Guide 1.25.
The calculated potential radiological co'nsequences 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 proba-bil.ity 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.
I J.
N. Singh, "Fuel Assembly Handling'Accident Analysis,"
EG&G Idaho Technical Report RE-A-78-227, October 1978.
Environmental Consideration The environmental impacts of an accident involving the handling of spent fuel inside containment have not changed from those given in Section V.E of the Turkey Point 3/4 Environmental Statement (FES) dated July 1972.
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 appro-priately 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 are, therefore, acceptable.
Date:
jl
Table 1
ASSUMPTIONS FOR AND POTENTIAL CONSEQUENCES OF THE POSTULATED FUEL HANDLING ACCIDENTS AT THE EXCLUSION AREA BOUNDARY FOR TURKEY POINT PLANT UNITS 3 AND 4 Assumptions:
Guidance in Regulatory Gui de 1.25 Power Level Fuel Exposure Time Power Peaking Factor Equivalent Number of Assem-b1 i es damaged Number of Assemblies in core Charcoal Filters avail able Decay time before moving fuel 0-2 hours X/0 Yalue, Ex-clusion Area Boundary (ground level release) 2244 Mwt 3 years 1.65 157 Hone 50 hours5.787037e-4 days <br />0.0139 hours <br />8.267196e-5 weeks <br />1.9025e-5 months <br />
-5 3
5.5 x 10 sec/m
- Doses, Rem Thvroi d
~Mhol e Bod Exclusion Area Boundary Consequences from Acci dents Inside Containment 16 0.07