ML17165A033

Safety Evaluation Supporting Amends 182 & 156 to Licenses NPF-14 & NPF-22,respectively

ML17165A033
Person / Time
Site:	Susquehanna
Issue date:	07/06/1999
From:	NRC (Affiliation Not Assigned)
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ML17165A032	List: ML17165A031 ML17165A033
References
NUDOCS 9907140025
Download: ML17165A033 (12)

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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATIONBYTHE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENTNO.

TO FACILITYOPERATING LICENSE NO. NPF-14 AMENDMENTNO. 156 TO FACILITYOPERATING LICENSE NO. NPF-22 PPttL tNC.

ALLEGHENYELECTRIC COOPERATIVE INC.

SUSQUEHANNA STEAM ELECTRIC STATION UNITS 1 AND 2 DOCKET NOS. 50-387 AND 388

1.0 INTRODUCTION

By letter dated November 26, 1997, which was superseded by letter dated June 1, 1998, PP&L, Inc., (the licensee) submitted a request for changes to the Susquehanna Steam Electric Station (SSES), Units 1 and 2, Technical Specifications (TSs). Additionally, the June 1, 1998, letter was supplemented by letters dated October 30, 1998, March 29, 1999, April20, 1999, and May 28, 1999.

The requested changes would replace the current ultimate heat sink average water temperature limit of 88 'F for all combinations of plant operations with a set of more restrictive values of 85 'F, 87 'F or 88 'F depending on whether either unit has been in mode 3 less than 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, at least 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> but less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, or at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, respectively, with the other unit in mode 1 or 2.

The notice for the November 26, 1997, amendment request was published on May 20, 1998, (63 FR 27764). Although the June 1, 1998, letter superseded the November 26, 1997, letter, it was not necessary to re-notice this amendment request in the Federal Rectister since in both letters the licensee's safety assessment remained the same and the proposed no significant hazards consideration determination did not change. The October 30, 1998, March 29, 1999, April20, 1999, and May 28, 1999, letters provided clarifying information that did not change the initial proposed no significant hazards consideration determination.

2.0 BACKGROUND

The ultim'ate heat sink (UHS) at SSES is a Seismic Category I concrete lined spray pond which is shared between Unit 1 and Unit 2. It is designed to provide sufficient cooling water to the emergency service water (ESW) system and the residual heat removal service water (RHRSW) system at a maximum average UHS water temperature of 97 'F without make-up for 30 days following a design basis loss-of-coolant accident (LOCA) in one unit and simultaneous e9Ora4OmS ei07ae PDR AoaCX OSOOaa87 P

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/(4 shutdown of the other unit. In order to limitthe average UHS water temperature at or below 97'F following a LOCA, the current plant TS Section SR 3.7.1.2 requires the average UHS water temperature be maintained at less than or equal to 88 'F during plant operations in Modes1,2, or 3.

In June 1997, during an engineering review, the licensee identified an error in the decay heat values used to establish the UHS water temperature limitduring plant operations in Modes 1, 2 or 3.

Results of subsequent UHS water temperature analyses incorporating the corrected decay heat values show that there was a need to lower the maximum acceptable UHS water

. temperature from 88 'F to 85 'F during plant operations in Modes 1, 2,or 3 in order to limitthe average UHS water temperature at or below 97'F following a LOCA.

The licensee further revised the UHS water temperature analyses with the decay heat values which take credit for the lower reactor decay heat rate 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> or more after shutdown and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or more after shutdown, compared to the reactor decay heat rate during the first 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> following shutdown.

Results of the revised analyses indicate that the maximum UHS water temperatures which are allowed during plant operations in Modes 1, 2, or 3 vary from 85

'F to 88'F depending upon the length of time one unit has been in Mode 3 while the other unit is in Modes 1 or 2. Therefore, the licensee proposed changes to the TSs for both units to reflect the results of the revised UHS water temperature analyses by replacing the current UHS average water temperature limitof 88 'F with a set of more restrictive values of 85'F, 87 'F or 88 F.

The following evaluation covers the applicable areas of the licensee's submittals (including its responses dated October 30, 1998, and March 29, 1999, to the staff's Request for Additional Information dated September 8, 1998) for which the Plant Systems Branch has the primary review responsibility.

3.0 EVALUATION 3.1 Surveillance Requirements (SRs) Regarding Average UHS Temperature LIMITSDuring Plant Operation Current TS Section SR 3.7.1.2 requires that:

Verifythe average water temperature of the UHS is ~ 88 'F once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

The licensee proposed to replace the above current TS Section SR 3.7.1.2 with the following three subsections:

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a. SR 3.7.1.2.a When both units are in MODE 1 or 2, or either unit has been in MODE 3 for less than twelve (12) hours, verify the average water temperature in the UHS is~ 85 'F once per 24'ours.

b. SR 3.7.1.2.b When either unit has been in MODE 3 for at least twelve (12) hours but not more than twenty-four (24) hours, verify the average water temperature in the UHS is~ 87 'F once per 24'ours.

c. SR 3.7.1.2.c When either unit has been in MODE 3 for at least twenty-four (24) hours, verify the average water temperature in the UHS is~ 88'F once per 24'ours.

The licensee stated that the revised decay heat values used in the UHS water temperature analyses were calculated in accordance with the guidance described in the Nuclear Regulatory Commission (NRC) Branch Technical Position ASB 9-2 and took credit for the lower decay heat generated in a reactor 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> or more after shutdown and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or more after shutdown, compared to the reactor decay heat generated in a reactor during the first 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> following

shutdown, The UHS water temperature analyses were re-performed in accordance with the guidance described in Regulatory Guide 1.27 and with conservative inputs to establish the proposed TS UHS water temperature limits. The licensee identified the conservatisms considered in the analyses.

The following are the more significant conservatisms:

a.

A worst case initial spray pond level (the highest pond level) is assumed to reduce the distance that spray droplets travel through air from the nozzles back to the pond. Thus, heat removed from the spray droplets willbe minimized.

In the response (dated October 30, 1998) to the staff's request for additional information (RAI), the licensee stated that seven resistance temperature detectors (RTDs) are used to monitor spray pond temperature.

Four of these RTDs are in the spray network areas and provide only surface temperatures.

The remaining three RTDs are in a vertical array just outside the ESWS pump house and provide surface, middle and bottom temperature inputs to the average temperature calculation.

Spray pond temperatures from the latter three RTDs are recorded four times a day in the shift surveillance log (This is more restricted than the TS requirement of once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />).

An individual reading is recorded for each of the 3 levels, and an average value is calculated manually.

Same as Footnote 1.

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No heat loss from the spray pond to the environment through the concrete basin is assumed.

c.

No credit is taken for heat loss from ESW/RHRSW system components and piping to the environment.

d.

Allpump energy is assumed to be deposited into the working fluid.

In addition, a measurement error allowance of 0.5'F is included (by increasing the initial UHS water temperature from 85 'F to 85.5 'F) in the calculation.

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~ lt In response to the staff's concerns, the licensee performed an additional analysis using less conservative (more realistic) assumptions to calculate the average UHS water temperatures to demonstrate that adequate margins exist in the above proposed TS temperature limits for the UHS. The licensee revised the above cited conservative assumptions in the following manner:

a.

An average spray pond water level is assumed based on a calculated water level decrease of 6" during the first 44 hours5.092593e-4 days <br />0.0122 hours <br />7.275132e-5 weeks <br />1.6742e-5 months <br /> following a LOCA. The effect of this revised assumption is an increase in the heat removal from the UHS compared to the previous calculation by increasing the effective distance that spray droplets travel through air from the nozzles back to the pond surface.

b.

The heat transferred from the UHS water to the sediment, concrete basin and supporting soil as the UHS water temperature rises is included.

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The heat transferred from the ESW and RHRSW fluid through the wall of the piping to the surrounding soil as the UHS water temperature rises is accounted for.

d.

Estimated power input to the ESW and RHRSW pumps consistent with the manufacture's brake horsepower curves for the respective system pumps is used in the calculation.

Based on the calculations using the revised assumptions described above, the licensee stated that the analytical limitfor the initial UHS water temperature for 2-unit operation is 87.5 'F in order to limitthe average UHS water temperature at or below 97'F following a LOCA. The

'corresponding proposed TS surveillance limitof 85'F willprovide an adequate margin to this

. analytical limit. Similarly, for 1-unit operation with one unit shut down at least 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and for 1-unit operation with one unit shut down at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the analytical limits are 89.5 'F and 90.5 'F, respectively.

The corresponding proposed TS surveillance limits of 87'F and 88 'F, respectively, willprovide adequate margins to these analytical limits, In the October 30, 1998 submittal, the licensee stated that the spray pond temperature monitoring system willprovide an alarm in the control room as well as an alarm in the ESW system pump house whenever the spray pond temperature of 83'F is detected by any of the seven4 RTDs. Plant operating procedures require operator actions to reduce the spray pond temperature whenever a spray pond high temperature alarm is received.

The 2'F margin See Footnote 1.

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between the spray pond alarm setpoint of 83 'F and the TS temperature limitof 85 'F provides sufficient time for operator response.

ln the October 30, 1998 submittal, the licensee stated that a new calculation confirming spray pond temperature measurement uncertainty was performed. The calculation, which took into consideration accuracy of all loop components, repeatability, readability of indicators, calibration accuracy, and drift, as well as biased accuracy for non-independent (shared or common) components, showed an overall uncertainty of+1.97'F. Also, based on its review of the calibration records for the loops used to calculate the average.UHS water temperature for the 10-year period that included the most recent (1996) calibrations, the maximum as-found loop inaccuracy had not exceeded the design accuracy of a 2 'F. Only twice during that period had the as-found inaccuracy for any of these loops been as much as s 1.25 'F. The licensee concludes that the spray pond water temperature measurement uncertainty is bounded by the margin of ~ 2'F design accuracy.

Based on its review of the licensee's rationale and the conservatism described above, the staff finds the above proposed TS temperature limits for the spray pond during plant operation acceptable.

3.2 TS B 3.7.1.c Regarding An OPERABLE UHS Current TS B 3.7.1.c defines an OPERABLE UHS as follows:

The OPERABILITYof the UHS is based on having a minimum water level of 678 feet I inch above mean sea level and a maximum water temperature of 88'F.

The licensee proposed to revise TS B 3.7.1.c to define an OPERABLE UHS in the following manner:

The OPERABILITYof the UHS is based on having a minimum water level at the overflow weir of 678 feet 1 inch above mean sea level and a maximum water temperature of 85 'F; unless either unit is in MODE 3. If a unit enters MODE 3, the time of entrance into this condition determines the appropriate maximum ultimate heat sink fluid temperature.

Ifthe earliest unit to enter MODE 3 has been in that condition for less than twelve (12) hours, the peak temperature to maintain OPERABILITYof the ultimate heat sink remains at 85 'F. If eigher unit has been in MODE 3 for more than twelve (12) hours but less than twenty-four (24) hours, the OPERABILITYtemperature of the ultimate heat sink becomes 87 'F. If either unit has been in MODE 3 for twenty-four (24) hours or more, the OPERABILITY temperature of the ultimate heat sink becomes 88'F.

The staff finds that the above revised definition for UHS OPERABILITYappropriately reflects the UHS temperature limitas established in the proposed TS SR 3.7.1.2. Therefore, the staff finds it acceptable.

Based on its review of the licensee's rationale and the evaluation described above, the staff finds that the design and operation of the UHS at SSES are in accordance with the guidance

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described in RG 1.27. Therefore, the staff concludes that the above cited proposed TS changes are acceptable.

4.0 ST TE CONSULTATION In accordance with the Commission's regulations, the Pennsylvania State officialwas notified of the proposed issuance of the amendments.

The State official had no comments.

5.0 ENVIRONMENTALCONSIDERATION The amendments change. surveillance requirements.

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 (63 FR 27764). Accordingly, the amendments meet eligibilitycriteria 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.

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 public willnot be endangered by operation in the proposed manner, (2) such activities willbe conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments willnot be inimical to the common defense and security or to the health and safety of the public.

Principal Contributor: D. Shum Date:

Ouly 6, 1999

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