ML20085N536

Safety Evaluation Supporting Amend 80 to License NPF-47

ML20085N536
Person / Time
Site:	River Bend
Issue date:	06/19/1995
From:	Office of Nuclear Reactor Regulation
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ML20085N538	List: ML20085N536 ML20087M121
References
NUDOCS 9506300234
Download: ML20085N536 (6)

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S UNITED STATES 5 )*.'t E

NUCLEAR REGULATORY COMMISSION j

f WASHINGTON, D.C. 20555 4 001 f- [l

• s SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT 80 TO FACILITY OPERATING LICENSEE NO. NPF-47 ENTERGY OPERATIONS. INC.

RIVER BEND STATION. UNIT 1 DOCKET NO. 50-458

1.0 INTRODUCTION

By letter dated February 22, 1994, Entergy Operations, Inc. (E0I), (the licensee), requested an amendment to facility Operating License No. NPF-47 for the River Bend Station (RBS).

The proposed amendment revises Technical Specifications (TSs) 3.6.1.5, " Main Steam - Positive Leakage Control System,"

and 3.6.1.10, " Penetration Valve Leakage Control System," adding an ACTION to each that permits operating for 7 days with both trains of each system inoperable.

In addition, the allowed outage time with one train of the penetration valve leakage control system inoperable is increased from 7 days to 30 days. By letter dated May 19, 1995, the licensee supplemented the request by providing information on the long-term operation of the Automatic Depressurization System by use of a recent installation of a diesel driven air compressor. The use of the alternate air supply in lieu of nitrogen gas bottles is an improvement and does not change the initial proposed no significant hazards consideration determination.

2.0 DISCUSSION TS 3.6.1.10 specifies two Penetration Valve Leakage Control System (PVLCS) subsystems shall be OPERABLE when in OPERATIONAL CONDITIONS 1, 2 AND 3.

The ACTION for one PVLCS subsystem inoperable is to restore the inoperable subsystem to OPERABLE status within seven days or be in HOT SHUTDOWN within the following 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

TS 3.6.1.5 specifies two Main Steam Leakage Control System (MS-PLCS) subsystems shall be OPERABLE when in OPERATIONAL CONDITIONS 1, 2 AND 3.

The ACTION for one MS-PLCS subsystem inoperable is to restore the inoperable subsystem to OPERABLE status within 30 days or be in HOT SHUTDOWN within the following 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and COLD SHUTDOWN within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Based on NUREG-1434, E01 is requesting a line item improvement that would extend the allowed outage time (A0T) for PVLCS from 7 days to 30 days and would add the associated allowed outage time of 7 days for two subsystems inoperable. The proposed ACTION times are consistent with the Completion Times of Specifications LC0 3.6.1.8 and 3.6.1.9 of NUREG-1434, " Standard Technical Specification General Electric Plants, BWR/6" for similar systems.

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. j 3.0 EVALUATION PVLCS System As described in USAR Section 9.3.6 the PVLCS supplements the isolation i

function of primary containment isolation valves (PCIVs) in process lines that also penetrate the secondary containment. These penetrations are sealed by air from the PVLCS to prevent fission products leaking past the isolation valves and bypassing the secondary containment after.a Design Basis Accident (DBA) loss-of-coolant accident (LOCA).

The PVLCS consists of two independent, manually initiated subsystems, either.

i of which is capable of preventing fission product leakage from the containment post LOCA.

Each subsystem is comprised of an air compressor, an accumulator, and injection valve, and three injection headers with separate isolation valves.

This system has additional headers, which serve the Main Steam Positive Leakage Control System and safety / relief valve (S/RV) actuator air i

' accumulators.

The analyses described in USAR Section 15.6.5 provides the evaluation of l

offsite dose consequences during accident conditions. During the first i

25 minutes following an accident, the isolation valves on' lines that penetrate primary containment and also penetrate secondary containment are assumed to

-l leak fission products directly to the environment, without being processed by j

the Standby Gas Treatment System. The system is manually initiated 20 minutes i

following an accident. The analyses take credit for manually initiating PVLCS after 25 minutes and do not assume any further secondary containment bypass i

leakage.

Each process line has two PCIVs and an additional isolation valve outside of the outboard PCIV.

Each valve is provided sealing air from its associated division of PVLCS.

The analysis conducted for the design basis of the PVLCS contains the j

following conservatisms:

The leakage from the valves is assumed to be from open systems inside containment and outside secondary containment. Many of the systems are closed both inside and outside.

i Regulatory Guide 1.3 requires 100% noble gases and 25% halogens be assumed to be released with the majority of the offsite dose being

- t contributed by iodine. At TMI-2 the iodine release was only 0.004%, a factor of 6250 reduction.

As a result, the actual offsite effects of the DBA event are expected to be greatly reduced from those evaluated.

MS-PLCS System As described in USAR Section 6.7 the MS-PLCS supplements the isolation function of the MSIVs by providing a positive pressure air seal for the t

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. fission products that could leak through the closed main steam isolation valve (MSIVs) after a DBA LOCA.

The MS-PLCS consists of two independent subsystems:

an inboard subsystem, which is connected between the inboard and outboard MSIVs; and an outboard 1

subsystem, which is connected to the double disk of main steamline shutoff valves and the valve stem packing glands of the outboard MSIVs at a positive air pressure with respect to reactor vessel pressure following system actuation. The MS-PLCS is supplied with compressed air by two separate and redundant compressed air supply subsystems that are integral components of the PVLCS.

Each subsystem receives power from a separate division of the emergency power supply. The MS-PLCS is manually initiated approximately 20 minutes following a DBA LOCA, and is designed to control and minimize leakage through the MSIVs for up to 30 days.

Justification for Increasina the MSIV-LCS Outaae Time The MSIV-PLCS was installed to prevent a direct leakage path through the MSIVs to the atmosphere following a design basis LOCA.

Such a release could exceed 10 CFR Part 100 radiological release limits. The radiological analysis assumes no credit for maintaining the integrity of the secondary plant system.

If the secondary system maintains its integrity, the main steam piping and main condenser still provide the capability to process MSIV leakage following a LOCA.

The main steam and main condenser systems provide fission product attenuation by providing hold-up and plate-out of fission products that may leak through the MSIVs. Therefore, in addition to the design basis LOCA, a postulated failure of the secondary system to maintain its intayity would also have to be assumed in order to have a direct leakage p nh through the MSIVs given no operable MSIV-LCS. Therefore, with one LCS inoperable two methods of leakage treatment are still available, and with both LCSs inoperable a single diverse (non-seismic Category I) treatment path is likely to be available.

The combination of both these events (LOCA and secondary system integrity loss) occurring simultaneously is deemed acceptably low to justify a 7-day outage time for both LCS trains and a 30-day outage time for a single train.

Automatic Depressurization System Support i

In addition to the sealing air pressure the second function of the compressors is to provide a long term safety-related backup air supply to the Safety Relief Valve (SRV) and Automatic Depressurization System (ADS) accumulators.

USAR Section 5.2.2.4.1 states that the primary source of air for the SRV and ADS accumulators is from the non-nuclear safety main steam air compressors.

Backup to this system is the safety-related PVLCS compressors. The ADS system accumulators have sufficient capacity to depressurize the reactor in the event i

of a design basis small break LOCA and loss of high pressure injection as described in Section 5.2.2.4 of the USAR.

This analysis does not depend on the leakage control compressors to initially depressurize the reactor. The leakage control system is manually placed in service approximately 20 minutes following a LOCA event.

The compressors themselves are automatically sequenced on the electrical distribution system at 10 minutes, after an interruption of electrical power, for long-term operability of the ADS valves.

. In the RBS analysis for Station Blackout (SBO) an evaluation of the actual capacity of the S/RV's was conducted.

This analysis determined for the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> coping criteria RBS has determined that 31 S/RV actuations will be required during the first 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The majority of the actuations will be needed during the earlier portion of the event. The seven ADS valves have a total of 28 to 35 actuations available to control reactor pressure vessel (RPV) pressure. When the nine remaining non-ADS valves are considered a minimum of 37 cycles are available.

In addition, operator guidance for addressing the SB0 event, is available to control RPV pressure by continuous S/RV opening, and conserving accumulator supply. The license, in the original submittal, noted that the operator guidance included providing bottled gas, if necessary, for long-term operation of the ADS. The staff has accepted the use of nitrogen gas bottles at other facilities to recharge the ADS accumulator. The licensee, by letter dated May 19, 1995, has provided an improved alternative to the nitrogen gas bottles for long-term operation by use of the ongoing installation of a diesel driven air compressor originally intended for backup to the instrument air and service air systems. This installation will now include connections to the Safety and Relief Valve System air accumulators, isolation provisions to prevent a failure in the instrument air system from affecting the safety related systems, and operator guidance in the Technical Requirements Manual for assuring air supply to the ADS accumulator for long-term operation. As a result, the actual relieving capacity is in excess of the expected need including that for long-term ADS operation with both PVLCS trains inoperable due to loss of air compressors.

Risk The MS-PLCS and PVLCS are judged to be of low safety significance since both function only to reduce leakage through an isolated containment following an accident. The PVLCS is also judged to be of low safety significance since the valves which it serves are required to meet specific leakage criteria and the j

system mitigates only a fraction of the complete containment leakage following

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an accident. Several studies have documented the minimal impact of increased unfiltered containment leakage, among these are NUREG-1273, Technical Findinas f

and Reaulatory Analysis for Generic Safety Issue II.E.4.3. "Containmen_t Intearity Check." and NUREG/CR-3539, Impact of Containment Buildina leakaae on (W_R Accident Risk.

These documents indicate that leakage rates significantly in excess of the allowed leakage rates would not result in significant increase in risk to the public.

Therefore, a 30 day allowance for one inoperable division and a 7 day allowed outage time for both inoperable divisions are proposed.

Both of these were considered during the development j

of the BWR Standard TS, NUREG-1434, and were accepted for general application for these systems.

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The RBS probabilistic safety assessment (PSA) for a loss of one PVLCS compressor indicated that as an isolation function:

1.

From the level 1 Individual Plant Examination (IPE), the probability of the deterministic DBA LOCA with concurrent loss of offsite power and i

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. worst case loss of one emergency diesel is less than 3E-12 per year.

Therefore, the loss of the PVLCS compressor is an extremely low probability event.

2.

From the Level 2 IPE, the PVLCS compressor was not explicitly modeled.

However, its performance can be bounded by the loss of isolation during a core damage event.

For the Level 1 IPE core damage frequency of 1.55E-5 per year, loss of isolation occurs with a frequency of 4.15E-7 per year. This is a low safety significance and includes events for which no power would be available to the PVLCS compressor even if they were otherwise operable (e.g., station blackout).

Based on this conservatism, the time safety significance of this event should be less than NEI's (was NUMARC) threshold of IE-7 per year for no corrective action needed.

The RBS probabilistic safety assessment (PSA) for a loss of one PVLCS compressor indicated that as a backup to the ADS function, the increase of core damage is insignificant. The increase in fregtency of core damage is 3.76E-10 per year.

This represents a very small increase from the core damage frequency quantified in the RBS IPE. Moreover, the air supply to the SRVs is not credited for compliance to the Station Blackout (SB0) Rule.

The four-hour SB0 coping duration analysis for RBS demonstrates that SRV accumulators have adequate capacity to mitigate this event.

In addition to the above, evaluations performed at RBS have determined the probability of recovering offsite power within various time frames. This work indicated the probabilities are; 89% within one hour, greater then 98% within four hours and greater then 99% in eight hours.

These times indicate for the unlikely event the PVLCS compressors are not available the normal compressors will be available within the time the accumulators are still supplying SRV actuations.

Both Leakaae Control Systems The existing Actions for inoperability of both divisions of the MS-PLCS and PVLCS, by default, requires entry into LC0 3.0.3.

The system's safety function is to limit containment leakage from the main steam isolation valves.

Processing this leakage prior to its release to the environment reduces the consequences of the event.

As presented in the BWR Standard TS NUREG-1434, systems that have an allowed out of service time of 30 days for one division inoperable, typically allow 7 days for instances when both division are out of service.

These out of service times are based on:

1) the safety significance of the system; 2) the probability of an event requiring the safety function of the system; and 3) the relative risks associated with the plant transient and potential challenge of safety systems experienced by requiring a plant shutdown.

4.0 STATE CONSULTATION

In accordance with the Commission's regulations, the Louisiana State official was notified of the proposed issuance of the amendment. The State official had no comment.

5.0 ENVIRONMENTAL CONSIDERATION

The amendment changes a requirement with respect to installation or use of.a facility component located within a restricted area as defined in 10 CFR Part 20. The NRC' staff has determined that the amendment involves no significant increase in the amounts, and no significant changes 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 the amendment involves no significant hazards consideration, and there has been no public comment on such finding (59 FR 11331). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).

Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

6.0 CONCLUSION

The Commission has concluded, based on the considerations discussed above, that:

(1) there is reasonable assurance that the health and safety of the 3

public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to.the common defense and security or to the health and safety of the public.

I Principle Contributors:

Edward Baker, NRR Robert Schaff, NRR Dave Wigginton, NRR Date: June 19, 1995 i

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