ML19257A646
| ML19257A646 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 12/12/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19257A644 | List: |
| References | |
| NUDOCS 8001070106 | |
| Download: ML19257A646 (8) | |
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.p WASHINGTON, D. C. 20555 k'..v SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TC AMENDMENT N0. 23 TO FACILITY OPERATING LICENSE NO. DPR-66 DUQUESNE LIGHT COMPANY OHIO EDIS0N COMPANY PENNSYLVANIA POWER COMPANY BEAVER VALLEY POWER STATION, UNIT NO. 1 DOCET NO. 50-334 Introducti on By letter dated January 17, 1977, the staff requested the Duquesne Light Company (the licensee) to evaluate the previously unevaluated potential consequences of a postulated Fuel Handling Accident Inside Containment (FHAIC) at Beaver Valley Power Station Unit 1 (Beaver Valley 1). The licensee's response, dated March 22, 1977 as supplemented April 11, and June 23,1977 did not provide adequate assurance that the consequences of a FHAIC at Beaver Valley 1 would be within the exposure guidelines of 10 CFR Part 100.
Additional information was requested by the staff './ letter dated April 27, 1977. On November 17, 1977, the licensee resubmitted the evaluation for a FHAIC. The licensee included in the submittal proposed facility r:odifications and changes to' the Technical Specifications to assure that the exposure guidelines of 10 CFR Part 100 are met folicwing a FHAIC coincident with the Cesign Basis Earthquake (DBE) for Beaver Valley 1.
The licensee states that the totential consequences of a postulated Fuel Handling Accident (FHA) inside either the containment or fuel building would be 27 rem to the thyroid at the Exclusion Area Boundary (EAB).
The licensee concluded that this dose is well within the 10 CFR Part 100 guidelines.
The licensee proposes to delete the Fuel Building Emergency Exhaust System (FBEES) ar.d use the existing Supplementary leak Collection and Release System (SLCRS) during all modes of fuel building ventilation. The licensee states that the reasons for the proposal are:
1.
With the plant in operation, the FBEES does not operate, and the fuel building is exhausted directly to the SLCRS. A high radiation sigra' '- the fuel building will cause this exhaust to be diverted thrcug -he SLCRS filters.
1692 130 o""g m p y,-sM, w
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2.
The mcde of operation of the SLCRS would be identical during a FHA in either the containment or the fuel building.
3.
There is less equipment maintenance.
4.
Possible exposure from the FBEES to personnel working in the containc.ent is eliminated.
Although this change requires the reevaluation of the potential consequences of a FHA in the fuel building, the potential conseque.ces of this accident are 7
identical to the values for the postulated FHAIC. Therefore, the staff's evaluation given below will be applicable to both the FriA inside containment and the fuel building.
Evaluation We have completed our review of the licensee's March 22, April 22, June 23, and November 17, 1977 submittals. The November 17, 1977 submittal addressed the potential consequences of the facility modifications and included Technical Specifications changes proposed by the licensee.
We have reviewed the licensee's proposed modifications to the Beaver Valley 1 facility. The licensee proposes to line up the existing Containment Purge Supply and Exhaust System (CPSES) from the external containment isolation valve to the seismically supported (45 inch x 36 inch) Supplenantal Leak Collection and Release System (SLCRS) duct with new seismically supported 42 inch duct and dampers. The SLCRS duct can be lined up to exhaust thrcugh the redundant seismically qualified main filter banks and redundant seisnically qualified exhaust fans. The new 42 inch diameter duct includes a seismically qualified damper between the proposed seisnic and existing non-seismic supported duct to the SLCRS duct and will be closed during refueling and open when the CPSES is operating nornally. The seisnically supported branch duct will also include seismically qualified damper, which will be open during refueling in the containment and closed when the CPSES is operating normally. We conclude that this modification will maintain the integrity of the seismically supported SLCRS, and assure that any release of effluent from the containment will be filtered.
1697 131 The licensee also proposes to deactivate the FSEES and use the existing SLCRS exhaust system in the fuel building during all modes of fuel building ventilation systen exhausting.
The deactivation of the FBEES entails permanently sealing the penetrations to the containment and cutting the ductwork of the FBEES. We are in agreement with the licensee that this modification will eliminate the possibility of radia-tion exposure from the FBEES to personnel working in the containment since the FBEES discharges to the containment and reduces the equipment maintainance required of the licensee. Use of the SLCRS during all modes of fuel building exhausting will ensure that any radioactive effluent released following a F.HA inside the fuel building would be filtered prior to discharge to the atmosphere.
We conclude that the proposed modifications to the CPSES, SLCRS, and FBEES would reduce the potential consequences of a postulated FHA in either the containment or fuel building and are acceptable.
We have also reviewed the proposed changes to the Technical Specification which requires operation of the SLCRS during refueling operations (Mode 6).
This change will require that the seismically qualified SLCRS be lined up and operating during fuel handling, to exhaust air from the containment or fuel building through at least one train of the redundant SLCRS HEPA filters and charcoal absorbers. Based on this we conclude that the changes to the Technical Specifications are acceptable.
We have reviewed the proposed change to Table 3.6-1 (Containment Isolation Valves) of the Technical Specifications for Beaver Valley 1.
This change would reduce the required maximum closure tine of the containment isolation valves on the containment purge exhaust line from 15 seconds to 8 seconds.
The change would also require that the insice and outside containment isolation valves en the containment purge supply lire will close in a maximum of 11 and 8 seconds, respectively. This would reduce the ccntribution of the valve closure time of the containment isolation time to the tcral time for monitors to detect radioactivity released in an accident, to activate, and finally to fully close the containment isolation valves. This would also reduce the total allcwable detection-to-closure time to less than the minimum time it would take for the radioactivity, released from the damaged spent fuel as a puff, to reach the in-board containment purge isolation valves. Compliance with this Technical Speci-fication will ensure that no FHAIC activity will be released to the atmosphere.
However, since the purge exhaust ductwork irside the containment containing the radiation monitors is non-seismic we have made dose calculations assuning the ductwork and ronitors are damaged during a seismic event.
In such an event we have assumed there is no containment isolat'Or.
The change to Tacle 3.6-1 also 1692 132 00hbh & _"
includes deleting the Diluted Fuel Building Exhaust valve and the fuel building exhaust valve. These are the valves for the containment penetrations associated with the FEEES. With the deactiviation of the FBEES, these penetrations will be perranently capped and the ductwork to the penetrations will be cut.
This pro-posed change is consistent with the removal of the FBEES.
Based on this, we conclude that the changes to Table 3.6-1 of the Beaver Valley 1 Technical Speci-fications are acceptable.
We have reviewed the proposed changes to the Technical Specifications which would extend the decay time before core alterations or movement of fuel from 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> to 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br />. Because these changes allow for a longer decay of radioactive isotopes, the potential consequences of a postulated fuel handling accident inside either the containrent or fuel building will be reduced.
Therefore, we conclude that the proposed changes to Technical Specifications to extend the decay tire from 100 to 150 hours0.00174 days <br />0.0417 hours <br />2.480159e-4 weeks <br />5.7075e-5 months <br /> are acceptable.
We have reviewed the proposed change to Technical Specification 3.9.9 (Containment Purge and Exhaust Isolation System) which will add Mode 5 (cold shutdown) to the LCO for the Containment Purge and Exhaust Isolation System (CPEIS).
This change will require the operability of the CPEIS during refueling and cold shutdown. This change will ensure that the containment vent and purge penetrations of the containment which are open curing refueling will be automatically closed upon detection of high radiation levels within containment. This will act to keep any radioactive effluent f om being released to the atmosphere unfiltered.
We conclude that the proposed change to Technical Specification 3.9.9 is acceptable.
Based on the above facility modifications and proposed changes to Technical Specifications which the licensee has agreed to, we have performed an independent analysis of the FHAIC. Our assunptions and the resulting potential consequences at the Exclusion Area Boundary (EAS) are given in Table 1.
The calculated potential consequences of the postulated fuel handling accident either inside containment or inside the fuel building are appropriately within the guidelines of 10 CFR Part 100 (defined as less than 100 rem to the thyroid) and, therefore, are acceptable.
This is based on the likelihood of this event relative to other events which are evaluated against 10 CFR Part 100 exposure due to decay of the 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 1.
1692 133 A recent study
- has indicated that dropping a spent fuel assembly into the core during refueling operations may potentially cause damage to more ft.el pins than has been assumed for evaluating the FHAIC. 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 embrittlenent of fuel cladding material from radiation in the core.
The probability of the postulated fuel handling accident inside containnent 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 potent 1cl damage to spent fuel estirated 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 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 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 tern for both spent fuel assenblies 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 reccamended in Regulatory Guide 1.25 and (2) the pool decontamination factor for inorganic iodine should be greater than that recomended 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 fcund less than the guidelines of 10 CFR Part 100. Consequently, we have concluded that the potential consequences of this postulated accident are acceptable also.
- J. N. Singh, " Fuel Assenbly Handling A:cident Analysis," EGlG Idaho Technici c port PE-A-78-227, October 1977.
e 1692 134 The results of this analysis warranted an investiga:icn of a similar accident in the spent fuel pool.
For this, a crcp of 2-1/2 feet was postulated and the analysis perfomed in the sare canner as previously described. Results indicate that in this scenario echanical damage to the missile or target would be minimal. Calculations indicated that no fuel pins in either fuel assembly would be ruptured.
Sumary The staff has evaluated the licensee's analysis of the ;ostulated FHAIC.
Based on the above considerations, we conclude that the changes to the Techni-cal Specifications and the facility modifications to the CPSES, SLCRS and FBEES proposed by the licensee for Beaver Valley 1 are acceptable. After perfoming 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 are also appropriately within the guidelines values of 10 CFR Part 100 and both are, therefore, acceptable.
Environmental Consideration The environmental impacts of an accident involving the handlinq of spent fuel inside containment have been addressed in Section 7.1 of che Final Environmental Statement (FES) dated July 1973 for the operation of-Beaver Valley 1.
We have detemined that the amendment does not authorize a change in effluent types or total amounts nor an increase in ocwer level and will not result in any significant environmental ir'act.
Having made this detemination, we have further concit.ded -hat the amendment involves an action which is insignificant fro-tne standooint of environmental impact and, pursuant to 10 CFR {51.5(d) F;, that an environmental impact statement or negative declaration and environ-mental impact appraisal need not be prepared in connection with the issuance of this amendment.
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Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the anendment does not involve a significant increase in the probability or consequences of accicents previously considered and does not involve a significant decrease in a safety margin, the amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendrent will not be inimical to the comon defense and security or to the health and safety of the public.
Date:
December 12, 1979 1692 136
Taole 1 ASSUMPTIONS FOR AND POTENTIAL CONSECUENCES OF THE POSTULATED FUEL HANDLING ACCIDENT AT THE EXCLUSION AREA BOUNDARY FOR BEAVER VALLEY POWER STATION, UNIT NO. 1 Assumptions:
Guidance in Regulatory Guide 1.25 Power Level 2766 Mwt Fuel Exposure Time 3 years Power Peaking Factor 1.65
. Equivalent Number of Assem-olies camaged 1
Number of Assemblies in core 157 Overall Iodine Filter 85 percent Efficiency Decay time before moving fuel 150 nours 0-2 hours X/Q Value, Ex-clusion Area Bouncary
-3 3
(ground level release) 1.4 x 10 sec/m Doses, Rem Thyroid Whole Bocy Exclusion Area Souncary Consequences the from Fuel Hanc-ling Accicents Insice Con-tainment or Fuel Builcing 06 1.1 1692 137