ML20247B361

Safety Evaluation Supporting Amend 112 to License DPR-54

ML20247B361
Person / Time
Site:	Rancho Seco
Issue date:	07/17/1989
From:	Knighton G Office of Nuclear Reactor Regulation
To:
Shared Package
ML20247B302	List: ML20247B296 ML20247B346 ML20247B361
References
NUDOCS 8907240101
Download: ML20247B361 (5)

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SAFETY EVALUATION BY THE.0FFICE.0F. NUCLEAR REACTOR REGULATION SUPPORTING. AMENDMENT NO.112TO. FACILITY.0PERATING LICENSE.DPR 54 3ANCH0.SEC0 NUCLEAR. GENERATING. STATION,. UNIT.1 DOCKET.NO. 50-312

1.0 INTRODUCTION

By letters dated February 28, 1986, May 14, 1987, and August 31, 1988, the Sacramento Municipal Utility District, the licensee for the Rancho Seco Nuclear Generating Station, proposed Technical Specification (TS) changes to Appendix A of Operating License DPR-54 for Rancho Seco. The proposed changes were requested to revise the Rancho Seco TS Table 3.6-1, " Safety Features Containment Isolation Valves" to add 12 new valves into the table and to increase the valve closure time to 25 seconds for all valves listed in the table, including new valves.

The current TS Table 3.7-1 lists 7 safety features containment isolation valves with required maximum valve closure times ranging from 3 to 22 seconds. The proposed amendment adds 12 valves to the table, each with a 25-second closure time, and increases the valve closure time to 25 seconds for 23 selected valves.

The remaining 12 valves (out of 35 valves currently listed in the table) have not changed the maximum allowable closure time in the proposed amendment. All of these safety features isolation valves offer a direct pathway from the containment to the environment.

2.0 EVALUATION In this evaluation, the staff grouped 35 isolation valves (23 selected valves from the current table plus 12 newly added valves) as follows:

1. Reactor Building Purge Valves (4 valves) 2 .. Valves with no automatic isolation features (remote-manual operation) and normally in closed position (10 valves)

3. Valves with automatic isolation features and normally in either closed or open position (21 valves)

E .1 Reactor Buildino. Inlet.and Outlet. Purge Valves.(SFV-53503, SFV-53504, 3FV-53604, and.5FV-53605)

These four reactor building inlet and outlet purge valves are administratively locked closed. The Rancho Seco TS Section 3.6.7 states that the purge valves should be closed with their respective breakers de-energized, except during cold shutdow or refueling. It further states that the valve position should be veri'ied at leas; monthly. Therefore, the valve closing time for these purge valves are only relevant to a postulated fuel handling accident during refuelint op ration.

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The staff reevaluated the offsite radiological consequences due to the. increased ostulated fuel handling accident.

valve In the Rancho closureSeco timeSafety (25 seconds)

Evaluationfollowing Report a p(SER) dated June 1973, the staff previously evaluated a postulated fuel handling accident using assumptions stated in Section 15.3 of the SER. In this evaluation, the staff calculated i the incremental offsite doses attributable to the delayed valve closure time j (25 seconds) using the same assumptions used in the previous analysis. The SER does.not state the valve closure time used previously and therefore, the staff assumed that the zero valve closure time was used.

The staff's calculated offsite doses resulting from 25 second valve closure time following a postulated fuel handling accident inside containment are presented in the attached Table 1 along with previously calculated offsite doses due to the accident. As shown in the table, the potential overall offsite doses for a postulated fuel handling accident including incremental doses attributable to the delayed valve closure time of 25 seconds are still within the acceptance criteria specified in the Standard Review Plan (SRP)

Section'15.7.4. Therefore, the staff finds that the proposed valve closure time of 25 seconds is acceptable.

2.2 Valves With No Automatic. Isolation. Features.(Remote Manual Operation).and Normally in Closed. Position (10. Valves)

1. HV-53617 Reactor Building Hydrogen Purge Line

2. HV-53618 Reactor Building Hydrogen Purge Line

3. HV-70040 Hydrogen Monitoring Isolation Line

4. HV-70041 Hydrogen Monitoring Isolation Line

5. HV-70042 Hydrogen Monitoring Isolation Line

6. HV-70043 Hydroaen Monitoring Iso 16: ion Line

7. HV-70044 Hydrogen Monitoring Isolation Line

8. HV-70045 Hycrogen Monitoring Isolation Line 1

9. HV-70046 Hydrogen Monitoring Isolation Line I

10. HV-70047 Hydrogen Monitoring Isolation Line The above valves are normally closed, remotely-operated one-inch diameter hand valves. The operation of these valves is administratively controlled An operator is in attendance whenever these valves are operated for the purpose of sampling and surveillance. Otherwise, the valves remain in a closed position. The licensee stated in the proposed amendment that these /alves were installed in 1983 as a part of the Post Accident Sampling System.

Therefore, the potential offsite doses are not relevant to and not affected by

l the increased valve closure time (25 seconds) of these normally closed valves.

The valve closure times are only specified and added to the table since they are qualified and designated as containment isolation valves. Therefore, the staff finds that the increased closure times for these valves are acceptable.

2.3 All Other. Remaining Valves (21. Valves)

These valves are normally in either the closed or open position with automatic isolation features.

In the proposed amendment, the licensee modeled, for the purpose of estimatin5 the mass flow rate expected from the containment to the environment following the receipt of a LOCA signal, all 10 containment penetrations (one 6" RC System Drain, two 4" RS Sump Drain and PC Pump Seal Water Return, one 3" RC System Vent, one 21/2" RS System Letdc.m, four 1" sample lines, and one 3/4" sample line) with their 19 isolation valves (except one 12-inch reactor building pressure equalizer line with two isolation valves) as one large penetration (10-inch) having an equivalent cross sectional area. The licensee estimated average mass flow rates from time zero to 25 seconds to be approximately 2.4 x 104 and 1.8 x 104 ft3 through the 12-inch reactor building pressure equalizer line and one 10-inch modeled line respectively. The staff used the LOCA blowdown mass release rate of 4.9 x 105 lbs for the first 25 seconds as given in the Rancho Seco USAR Table 14.4-4.

The Rancho Seco USAR Figures 1.4.2-31 and 14.2-32 show peak fuel cladding temperature (hot spot) as a function of time after a LOCA for an 8.55 ft2 double-ended break in cold leg pipe at the reactor feed pump discharge. The licensee stated that this break resulted in the highest calculated fuel cladding temperature. According to these figures, the cladding temperature of approximately 2000 F. will be reached at 25 seconds after a LOCA. A maximum hot spot cladding temperature of 2299'F. at 38.5 seconds was calculated by the licensee meeting the NRC Interim Criteria of 2300 F. used in 197? (this limit has since been lowered by 10 CFR 50.46 to the current valve of 2200 F.).

Some of the fuel rods may be expected to experience claddir.g perforation-deformation failure due to the heatup transient (fuel-cladaing temperature excursion) during the first 25 seconds after a LOCA. Therefore, the staff used, in accordance with SRP 6.2.4, an iodine spike of 60 mci /yn (dose equiva-lent iodine-131) in the LOCA blowdown as source term. The source term activity will be immediately available for release through the containment isolation '

valve pathways (one 12" reactor building equilizer line and one 10" modeled line opening) for the first 25 seconds after the rer.eipt of a LOCA signal. No credit was given for removal of fission products in the staff's analyses (containment spray, charcoal absorbers, iodine par';ition, iodine plate-out, etc.).

The staff's calculated offsite doses resulting from 25 second valve closure time following a LOCA are also presented in Table 1 along with previously calculated offsite doses due to the LOCA as shown in the SER Table 15.0. As shown in Table 1, the potential overall offsite doses for a LOCA including mm_--__.__m_._m_m

1 1

-4 incresc9al doses attributable to the delayed valve closure time of 25 seconds are still within the dose reference values specified in 10 CFR Part 100.

Therefore, the staff finds that the proposed valve closure time of 25 seconds is acceptable.

3.0

SUMMARY

Based on our review, we find that calculated offsite doses including incremental doses attributable to the increased valve closure time are still within the exposure reference guidelines of 10 CFR Part 100 and are within the acceptance criteria given in Standard Review Plan Section 15.7.4. Therefore, we find the proposed changes to the Rancho Seco TS concerning the safety features contain-ment isolation valve closure time are acceptable.

4.0 CONTACT.WITH. STATE.0FFICIAL The NRC staff has advised the Chief of the Radiological Health Branch, State Department of Health Services, State of California, of the proposed determination of no significant hazards consideration. No comments were received.

5.0 ENVIRONMENTAL CONSIDERATION

This amendment involves changes in the installation or use of a f acility com-ponent located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 61.22(c)(9). Pursuantto10CFR51.22(b),noenvironmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.

6.0 CONCLUSION

We have concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safet of the public will not be endangered by operation in the proposed manner, 2 (y) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to common defense and security or to the health and safety of the public.

Principal Contributor: J. Lee i

Dated: July 17, 1989 l l

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i Table 1- ,

Potential Offsite' Doses-Due'to Desian Basis' Accidents Exc1'usion Area- -Lov Populat' ion-Accidents Boundary - Zone-

.(rem) _ (rem)-

Thyroid -Whole Body. ' Thyroid.. Whole BodyL

. Fuel Handling 2 34 4.- 2'-

<1 Purge Valves 2 <

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Total .. 36 <5 <3 <2' SRP Criteria Limit 75 6= '75 '6 Y

loss of-Coolant 1 267- '.8 48 'l Delayed Valve' Closures - 22 <1 3 - <1.'

Total. 289 <9 51 .<2-10 CFR 100 Limit 300 25 300- 25 2SER Tab'le 15.'0 225 second valve closure time

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