ML17157C023

Safety Evaluation Supporting Amends 123 & 90 to Licenses NPF-14 & NPF-22,respectively

ML17157C023
Person / Time
Site:	Susquehanna
Issue date:	10/03/1992
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML17157C022	List: ML17157C020 ML17157C023
References
NUDOCS 9210130275
Download: ML17157C023 (8)

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II UNITED STATES UCLEAR REGULATORY COMMISS WASHINGTON, O. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.123TO FACILITY OPERATING LICENSE NO. NPF-14 AMENDMENT NO. 90 TO FACILITY OPERATING LICENSE NO. NPF-22 PENNSYLVANIA POWER 8c LIGHT COMPANY ALLEGHENY ELECTRIC COOPERATIVE INC.

SUS UEHANNA STEAM ELECTRIC STATION UNITS 1

ANO 2

'OCKET NOS.

50-387 AND 388

1. 0 INTRODUCTION By letter dated January 9,

1991, as supplemented by letters dated August 19,

1991, June 22,

1992, and August 3,

1992, the Pennsylvania Power and Light Company and Allegheny Electric Cooperative, Inc. (the licensees) submitted a

request for changes to the Susquehanna Steam Electric Station (SSES),

Units 1

and 2, Technical Specifications (TS).

The requested changes would make changes to the technical specifications to prevent inadvertent isolation of the Reactor Water Cleanup (RWCU) system due to high seasonal temperatures while still providing timely leak detection capability.

The August 9,

1991, June 22,

1992, and August 3, 1992, letters provided clarifying information that did not change the initial proposed no significant hazards consideration determination.

Ambient and differential temperature conditions are monitored in the RWCU penetration room to provide indication of leakage from the Reactor Coolant Pressure Boundary (RCPB).

Control room annunciation and automatic system isolation will occur if the temperatures exceed predetermined setpoints.

The purpose of this leak detection and isolation function is to prevent the release of radioactive material outside the primary containment boundary.

However, a leak rate basis was not specifically defined for the temperature setpoints that currently exist in the Technical Specifications for RWCU isolation.

At Susquehanna, the RWCU system is currently subject to inadvertent isolation due to high ambient temperatures that occur during the summer months.

Inadvertent isolation of the RWCU system can result in operational problems due to chemistry excursions that subsequently occur in the reactor coolant system (RCS),

and such RWCU system transients can cause leaks in the RWCU pump seals.

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On July 12,

1991, a temporary waiver of compliance was granted by the staff that allowed the licensee to increase the RWCU penetration room ambient temperature isolation setpoint from 118.3 'F to 131 'F.

The waiver was in effect until October 15,

1991, and was intended to prevent inadvertent isolation of the RWCU system as a result of high outdoor temperatures during the summer months.

2. 0 EVALUATION The existing Technical Specifications for Susquehanna require that the RWCU system be isolated if the ambient room temperature exceeds 118.3 'F, or if the differential temperature exceeds 35.3 'F.

These temperature limits were originally established to isolate RCS leakage outside containment that could occur due to a breach in the RWCU system.

However, a rigorous basis was not established for these initial temperature isolation setpoints.

In addition, sufficient margin was not included in these setpoints to account for seasonal temperature vari ations that can occur or for normal operational occurrences such as a loss of heating, ventilation, and air conditioning (HVAC).

Consequently, the RWCU system is subject to spurious isolation during the summer months due to high ambient temperatures, and could be subject to spurious isolation due to high differential temperatures during winter months if loss of HVAC were to occur.

In its submittal, PPEL requested that the RWCU penetration room high ambient temperature isolation setpoint be changed to 131 'F, with an allowable value of 137 'F; and that the differential temperature isolation setpoint be changed to less than or equal to 40.5 F, with an allowable value of less than or equal to 43.5 'F.

Also, the licensee requested that the allowable value for high differential temperature isolation in the RWCU pump rooms and heat exchanger rooms be changed to less than or equal to 72 'F.

2. 1 Isolation Temperature Bases PPEL established the following criteria for selecting the RWCU penetration room isolation temperature trip setpoints:

a.

Leak detection temperature trip setpoints are selected to detect and isolate a leak that is normally less than 25 gpm and below the flow rate corresponding to the critical crack size for the system piping.

b.

Leak detection isolation temperature trip setpoints are set below fire suppression systems actuation setpoints.

c.

Leak detection isolation temperature trip setpoints are set high enough to avoid inadvertent isolation caused by normal temperature transients or abnormal transients caused by non-leak conditions (such as loss of ventilation).

d.

Leak detection isolation temperature trip setpoints are set using worst-case conditions (high temperature - winter conditions; differential temperature - summer conditions).

e.

Leak detection isolation temperature trip setpoints are set to include allowance for instrument tolerance and instrument drift.

f.

Leak detection isolation temperature trip setpoints are established such that the leak will be detected and isolated within a reasonable time (<24 hours).

g.

Leak detection isolation temperature trip setpoints are established such that the radiological release that occurs prior to system isolation will not exceed the control room and offsite dose limitations that are stated in the regulations.

2.2 RWCU Penetration Room Temperature Isolation Requirements The licensee has analytically determined the temperature response spectra in the RWCU penetration room for various plant conditions, including winter operation, summer operation, loss of ventilation, and for postulated RWCU system leakage rates of 5 gpm and 25 gpm.

Applying the criteria stated in Section 3. 1 above, the licensee established allowable values and isolation setpoints for the high ambient and high differential temperature isolation functions.

Although RWCU leak rates of 5 gpm were analyzed, the licensee determined that such a small leak rate could not serve as a basis for RWCU isolation because the leak could not be detected within a reasonably short period of time without subjecting the RWCU system to spurious isolation due to seasonal temperature variations.

RWCU Penetration Room Hi h Ambient Isolation Tem eratu e

Allowable Value and

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. Based on the analyses that were performed, the licensee determined that the appropriate temperatures for the TS required Allowable Value and Trip Setpoint for RWCU penetration room high ambient temperature isolation should be less than or equal to 137 'F and 131 'F, respectively.

The existing TS requires these values to be less than or equal to 125.3 'F and 118.3 'F, respectively.

Assuming winter conditions with HVAC operating (worst case),

the licensee's analysis for a 25 gpm leak in the RWCU penetration room indicated that the trip setpoint of 131 'F would satisfy the selection criteria.

Based on its

analysis, the licensee determined that a 25 gpm leak would cause RWCU penetration room temperatures to exceed 131 F within 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.

Also, recognizing that the RWCU penetration room temperatures occasionally approached 115 'F during the summer months, the calculated Trip Setpoint provided a margin of about 15 'F for any unexpected spurious temperature fluctuations that may occur.

Upon a loss of HVAC, the licensee calculated that the temperatures in the RWCU penetration rooms would reach 138 'F within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> assuming summer ambient temperature conditions of ll5 'F in the RWCU penetration room.

However, due to TS requirements (TS 3.6.5) and operational restrictions stated in the Emergency Operating Procedures, the plant is required to be shutdown within ten hours following a loss of reactor building HYAC.

The licensee's analysis indicated that the RWCU penetration room temperature would approach 131 'F four hours after HVAC is lost and the temperature would reach approximately 134 'F 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> after HVAC is lost.

Therefore, the selected RWCU penetration room Trip Setpoint would allow a minimum of about 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> for plant personnel to respond to a loss of reactor building HVAC before RWCU is isolated on high ambient temperature.

RWCU Penetration Room Hi h Differential Isolation Tem erature Allowable Value and Tri Set oint Based on the analyses that were performed, the licensee determined that the appropriate temperatures for the TS required Allowable Value and Trip Setpoint for RWCU penetration room high differential temperature isolation should be less than or equal to 43.5 'F and 40.5 'F, respectively.

The existing TS Allowable Value and Trip Setpoint for the RWCU penetration room high differential temperature isolation function is 44.3 F and 35.3 'F, respectively.

Assuming the minimum initial differential temperature under summer conditions (worst case),

the licensee's analysis for a 25 gpm leak in the RWCU penetration room indicated that the penetration room differential temperature trip setpoint of 40.5 'F would satisfy the selection criteria.

Recognizing that both loss of HVAC air flow during summer conditions and loss of heating capability under winter conditions created extreme RWCU penetration room differential temperature conditions, the Trip Setpoint provided a margin of about 10 'F for any unexpected spurious temperature fluctuations that may occur between HVAC inlet and RWCU ambient conditions.

RWCU Pum Rooms and He t Exch n er Roo s

i h Differential Isolation Tem erature - Allowable Value Based on its analyses, the licensee concluded that the allowable value for high differential temperature isolation in the RWCU pump rooms and heat exchanger rooms should be changed to less than or equal to 72 'F from the existing value of less than or equal to 78 'F.

This value is more conservative than the existing TS value.

2.3 Radiological Considerations The licensee analyzed the consequences of a coolant leak outside primary containment in calculation SE-B-NA-078.

Fifty gpm of reactor grade water was assumed to leak into secondary containment at a concentration of 4.0 pCi/gm Dose Equivalent Iodine-131 (maximum allowable coolant concentration of iodine for SSES operation).

No credit for removal, holdup, or decay was taken; and the leak was isolated after 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.

The licensee's analysis concluded that the resultant offsite and control room doses fell far below 10 CFR Part 100 offsite dose limits and 10 CFR Part 50, Appendix A, General Design Criteria (GDC) 19 control room dose limits.

The licensee also analyzed the consequences of a reactor steam leak in calculation FX-C-DAM-010.

In this case, a 50 gpm water equivalent steam leak was assumed to occur over a 24-hour period.

Again, no credit for removal, holdup, or decay was taken.

The licensee's analysis concluded that the resultant offsite and control room doses fell far below 10 CFR Part 100 offsite dose limits and 10 CFR Part 50, Appendix A, GDC-19 control room dose limits.

2.4 Miscellaneous Considerations In addition to the analyses that were performed, the licensee provided the following additional information in support of the requested changes to the Technical Specifications:

a.

Although the SSES Final Safety Analysis Report (FSAR) does not specifically analyze a 25 gpm RCS leak outside containment, other accidents which result in coolant leakage outside containment are analyzed in FSAR Section 15.6.2 (Instrument Line Break) and FSAR Section 15.6.4 (Steam System Piping Break Outside Containment).

The 25 gpm RWCU leak rate that is assumed is bounded by the analysis in FSAR Section 15.6.4.

b.

FSAR Table 5.2-10 shows that a leak rate of 25 gpm is less than those leak rates associated with the onset of unstable pipe rupture.

c.

The effects of the new design basis leak rate on equipment, procedures, and personnel were assessed and found to be minimal.

d.

All areas with steam leak detection circuitry have their temperatures (and differential temperatures) available in the main control room for monitoring.

e.

The alarm response procedures identify specific actions required including observation, confirmation, isolation, and repair of leaks.

Visual observation of a steam leak, or rising room temperatures, or the occurrence of a pre-isolation temperature alarm in the main control room would invoke operator action without attempting to quantify the leak rate, or waiting for the temperature to reach the isolation setpoint.

f.

All equipment required to function within the environmental zone of the leak is included in the equipment qualification program.

The equipment is qualified for the effects of a high energy line break HELB.

2.5 Staff Findings Since temperature isolation setpoints are based on analysis and a large degree of uncertainty exists, the staff position is that the leakage detection system initiate system isolation when the area temperature conditions exceed the threshold for spurious isolation.

Factor s to be consider ed when establishing the threshold for spurious isolation include seasonal temperature variations assuming a loss of normal room ventilation or heating for short periods of time and temperatures that will be reached in the protected area during accident conditions.

The isolation leakage rate under the most conservative initial conditions should normally be less than 25 gpm.

The requested temperature changes for the TS Allowable Values and Trip Setpoints for RWCU isolation satisfy the criteria established by the licensee and discussed in Section 3. 1 of this Safety Evaluation (SE),

and also provide for RWCU isolation when penetration room temperatures exceed the threshold for spurious isolation as discussed above.

The temperature limits that have been established by the licensee will minimize spurious isolations of the RWCU system while ensuring that system leakage will be isolated within a reasonably short period of time.

Also, the staff noted that the requested changes to the Allowable Values for high differential temperature isolation in the RWCU penetration

rooms, pump rooms and heat exchanger rooms was conservative.

The licensee has analyzed the radiological consequences of an RCS leak outside primary containment and has determined that the resultant offsite and control room doses fall far short of 10 CFR Part 100 offsite dose limits and 10 CFR Part 50, Appendix A, GDC-. 19 control room dose limits.

The licensee has also determined that a 25 gpm RWCU leak rate is bounded by the analysis contained in FSAR Section 15.6.4 (Steam System Piping Break Outside Containment).

The staff agrees with these determinations.

The licensee has determined that all equipment required to function within the environmental zone of the leak is included in the equipment qualification program and that a 25 gpm leak rate from the RWCU system will not result in a catastrophic pipe fa'ilure.

Also, as discussed in Section 3.4 of this SE, the licensee has established operational controls to ensure that RCS leakage outside primary containment is identified in a short period of time and that appropriate corrective actions will be taken.

These elements are necessary to provide added assurance that the reactor coolant pressure boundary (RCPB) will be adequately maintained and to ensure that safety related equipment will remain operable.

The staff has reviewed the licensee's request and based on the considerations stated

above, the staff has found that the proposed RWCU penetration room ambient temperature setpoint of 131 'F and differential temperature setpoint of 40.5 'F are acceptable.

2.6 Summary Based on the considerations and findings discussed in this SE, the staff has determined that the requested changes to the RWCU isolation temperature values are acceptable and satisfy the requirements stated by GDC 30, and the guidance of Regulatory Guide 1.45 and Section 5.2.5 of the Standard Review Plan.

The established values will prevent inadvertent isolation of the RWCU system due to high seasonal temperatures while still providing timely leak detection capability.

The increase in isolation temperature setpoints will still limit the offsite doses due to leaks outside containment to a small fraction of 10 CFR Part 100 limits and is within 10 CFR Part 50, Appendix A, GDC 19 control room dose limits.

~TNT CUN ULT Tl In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed issuance of the amendments.

The State official had no comments.

4.0 ENVIRONM NTAL CONSIDERATION The amendments change a requirement with respect to installation or use of a facility component located within the r estricted area as defined in 10 CFR Part 20.

The NRC staff has determined that the amendments involve 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 the amendments involve no significant hazards consideration, and there has been no public comment on such finding (57 FR 39713).

Accordingly, the amendments meet 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 amendments.

5.5

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The Commission has concluded, based on the considerations discussed

above, that:

(1) there is reasonable assurance that the health and safety of the 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 amendments will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributors:

James E. Tatum James J. Raleigh

, Date:

October 3, 1992