ML20138K906

Safety Evaluation Supporting Amends 122 & 86 to Licenses NPF-39 & NPF-85,respectively

ML20138K906
Person / Time
Site:	Limerick
Issue date:	02/11/1997
From:	NRC (Affiliation Not Assigned)
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ML20138K895	List: ML20138K892 ML20138K906
References
NUDOCS 9702190203
Download: ML20138K906 (7)

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NUCLEAR REGULATORY COMMISSION 2

WASHINGTON, D.C. so66EHlooi Y49.....

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS 122 AND 86 TO FACILITY OPERATING LICENSE NOS. NPF-39 AND NPE-81 PHILADELPHIA ELECTRIC COMPANY LIMERICK GENERATING STATION. UNITS 1 AND 2 DOCKET NOS. 50-352 AND 50-353

1.0 INTRODUCTION

By letter dated September 27, 1996, the Philadelphia Electric Company (the licensee) submitted a request for changes to the Limerick Generating Station (LGS), Units 1 and 2, Technical Specifications (TSs). The requested changes would increase the maximum allowable inleakage rate into the reactor enclosure secondary containment (RESC) to 2500 cfm from 1250 cfm. This change would also result in (1) an increase the RESC pressure drawdown time, and (2) a reduction of air residence time in the Standby Gas Treatment System (SGTS) charcoal adsorber bed.

Specifically, the licensee made these requests:

1.

Amend the allowable inleakage rate specified in the TS Section 4.6.5.1.1.c, to 2500 cfm from 1250 cfm and revisc TS Bases Section 3/4.6.5 accordingly.

2.

Amend the allowable RESC pressure drawdown time specified in the TS Sections 4.6.5.1.1.g and 4.6.5.1.1.c, to 916 seconds (15 minutes and 16 seconds) from 126 seconds (2 minutes and 6 seconds) and revise TS Bases 3/4.6.1.4 accordingly.

3.

Change the system Flow rate for charcoal adsorber bypass leakage testing in the TS Sections 4.6.5.1.1.b, 4.6.5.1.1.e, and 4.6.5.1.1.f and in TS Bases Section 3/4 6.5, to 5764 cfm (2500 cfm from each unit plus 764 cfm from common refueling area) from 3264 cfm (1250 cfm from each unit plus 764 cfm from common refueling area).

4.

Add a sentence in Bases Section 3/4.6.5, "The laboratory analysis performed on the SGTS charcoal adsorber samplers will be tested at a air flow velocity of 66 feet per minute based on corresponding 5764 cfm flow through the SGTS charcoal adsorber" deleting "This flow rate corresponds to the maximum overall three zone inleakage rate of 3264 cfm."

9702190203 970211 DR ADOCK 050003 2

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', l 2.0 EVALUATION The SGTS is common to both Units 1 and 2 and consists of the two redundant SGTS filter trains and two 100 percent capacity fans.

Each fan has a controllable capacity of 500 cfm to 8400 cfm. Air flow varies in response to secondary containment differential pressure controls, which modulate the fan inlet vanes and control dampers in the run-around bypass and discharge ducts provided for each fan.

Each filter train consists of, among other things, a vertical 8-inch deep charcoal adsorber bed. The licensee stated in the submittal that it is becoming difficult to maintain the RESC at an inleakage rate of less than 1250 cfm due to normal wear and tear on secondary containment doors, seals, gaskets, and penetrations. Changing the RESC post drawdown maximum inleakage rate to 2500 cfm per unit will not require any modifications to the SGTS or any supporting system.

The staff has reviewed the licensee's analysis and finds that its offsite and control room operator radiological consequence assessments meet the relevant dose acceptance criteria.

The staff has performed independent assessments of the offsite and control room operator radiological consequences resulting from a postulated LOCA.

The staff used an increased RESC inleakage rate of 2500 cfm and an increased RESC pressure drawdown time of 15 minutes and 30 seconds in its evaluation.

In Amendment No. 106 to the Limerick Unit No. 1 TS and Amendment 53 to the Limerick Unit No. 2 TS dated January 24, 1996, and February 16, 1995, respectively, the staff assessed the offsite and control room radiological consequences of a loss of coolant accident (LOCA) for increased allowable Maim Steam Isolation Valve (MSIV) leak rate and deletion of the MSIV leakage control system.

In those assessments, the staff considered the following sources and radioactivity transport paths to the environment following a postulated LOCA:

(1) containment leakage (2) main steam isolation valve leakage (3) post-LOCA leakage from engineered safety features (ESF) outside containment In this evaluation for the increased RESC inleakage rate and increased RESC drawdown time, the staff recalculated the offsite and control room radiological consequences resulting only from containment leakage (pathway 1 above) and post-LOCA leakage from ESF outside containment (pathway 3 above) since the dose contribution from MSIV leakage (pathway 2 above) is not affected by increased RESC inleakage and remains the same. The procedures used in the staff's recalculation of offsite and control room radiological consequences were based en (1) the current TID-14844 source team which are l

consistent with the guidelines provided in the applicable Standard Review Plan (SRP) (NUREG-0800) and Regulatory Guides, and (2) assumptions and parameters used in the previous radiological consequence assessments, except for the increased RESC inleakage rate and the increased RESC pressure draw downtime.

'. In its analysis, the licensee has taken a deviation to technical position C.3.1 in Regulatory Guide 1.52, " Post Accident ESF Atmosphere Cleanup System l

Air Filtration and Adsorption Units," Revision 2, dated March 1978. The l

technical position states, among other things, that the charcoal adsorber l

system should be designed for an average atmosphere residence time of 0.25 seconds per 2 inches of adsorbent bed.

This guidance corresponds to a total of 1.0 second for the 8-inch deep adsorber bed in the Limerick SGTS.

i Increasing the secondary containment inleakage rate to 2500 cfm could result in a 3-zone total inleakage rate of 5764 cfm (i.e., 2500 cfm each unit and 764 cfm from the common refueling area). At this inlp kage rats, ine atmosphere residence time in the charcoal adsorbcr bed is reduced to 0.68 seconds. The current atmosphere residence time for the existing adsorber bed for a 3-zone inleakage rate of 3264 cfm (i.e.,1250 cfm from each unit and 764 cfm from the common refueling area) is 1.1 seconds. The proposed residence time of 0.68 seconds represents an air velocity through the charcoal adsorber bed of approximately 66 feet per minute (fpm).

To justify this deviation, the licensee proposed to revise the existing LGS procedures to require the laboratory analysis for carbon samples to be performed at an air velocity of 66 fpm (0.68 atmosphere residence time) to

)

meet surveillance requirements specified in Limerick TS Section 4.6.5.1.1.

The corresponding Limerick TS Bases Section 3/4.6.5, " Secondary Containment,"

will also be revised to state this change. The staff finds the justification provided by the licensee to be acceptable.

The recalculated offsite doses resulting from a postulated LOCA and the parameters and assumptions used in recalculation are given in Tables 1 and 2 of this Safety Evaluation (SE), respectively. The staff finds that recalculated offsite doses still meet the dose guidelines set forth in 10 CFR Part 100. The recalculated control room operator doses following a postulated LOCA, along with the parameters and assumptions used, are listed in the Table 3 of this SE. The staff also finds that the recalculated whole-body and equivalent organ doses (thyroid) are still within the guidelines of Standard Review Plan (SRP) Section 6.4 and therefore, within the acceptance criteria specified in General Design Criterion (GDC) 19 of Appendix A to 10 CFR Part 50.

Based on the above evaluation and the calculated radiological consequences shown in Tables 1 and 3, the staff concludes that the proposed RESC Inleakage rate of 2500 cfm and RESC pressure drawdown time of 15 minutes and 30 seconds are acceptable.

l The staff further concludes that the existing distances to the exclusion area l

and to the low population zone boundaries of the Limerick Generating Station, in conjunction with the engineered safety features provided in the Limerick i

Generating Station, are still sufficient to provide reasonable assurance that the radiological consequences of a postulated LOCA will be within the dose guidelines set forth in 10 CFR Part 100 and the control room operator dose acceptance criteria specified in GDC-19 of Appendix A to 10 CFR Part 50. This

?

-4 conclusion is based on the staff review of the applicant's analysis and on the independent analysis by the staff which confirms that the calculated total doses are within these guidelines.

TABLE 1 Radiological Consequences of Loss-of-Coolant Accident (rem)

EAB LPZ Thyroid Whole Body Thyroid Whole Body Containment Leakage 19.6 2.7 5.4 1.7 Emergency Core Cooling 29.5 4.3 8.2 1.8 System (ECCS) Component leakage MSIV leakage (D 17.0 15.8 38.0 6.4 Total 66.1 22.8 51.6 9.9 (1) From Amendment No. 106 to the Limerick Unit No. 1 TS and Amendment 53 to the Limerick Unit No. 2 TS dated January 24, 1996 and February 16, 1995, respectively l

1

1 l TABLE 2 Assumptions Used to Evaluate the loss-of-Coolant Accident l

Parameter Value Power level 3527 Mwt t

Frattion of core inventory released roble gases 100%

iodine 50%

Iodine initial plate-out fraction 50%

Iodine chemical species Elemental 91%

Particulate 5%

Organic 4%

Suppression pool decontamination factor Noble gas 1

Organic iodine 1

Elemental iodine 10 Particulate 10 Iodine dose conversion factors ICRP-30 Iodine deposition factor (MSIV) 10 MSIV leakrate 200 SCFH Iodine partition factor for ECCS leak 10 ECCS leak rate 5 gpm Standby gas treatment system Filter efficiency 99%

3 Flow rate 2500 ft / min)

Drawdown time 930 seconds l

Primary containment free volume 4.0E+5 ft )

3 Secondary containment free volume 1.8E+6 ft )

3 l

Secondary containment mixing efficiency 50 percent l

Breathing rates Regulatory f uide 1.3

7 a

. 2 TABLE 3 Assumptions and Estimates of the Radiological Consequences to Control Room Operators following a LOCA 3

Control room free volume 1.26E+5 ft 4

Recirculation Rates Filtered Intake 525 CFM Unfiltered Intake 0.0 Filtered Recirculation 2475 CFM Filter Efficacy 95%

(2 inch charcoal)

Unfiltered control room infiltration rate (assumed) 50 CFM Duration of accident 30 days Breathing rate of operators in control room for the course of the accident 3.47 x 10 m /sec 3

Meteorology (wind speeds for all sectors 0 - 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> 3.46 x 10 sec/m 3

8 - 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 2.04 x 10 sec/m 3

24 - 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> 1.30 x 10 sec/m 3

96 - 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> 5.71 x 10'5 sec/m 3

Iodine protection factor 38.5 Iodine Dose Conversion Factors

• ICRP-30 Control Room Operator Occupational Factors 0 - 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> 1

8 - 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 1

24 - 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> 0.6 96 - 720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br /> 0.4 Doses to control room Thyroid dose

• Whole body dose **

operators (rem)

(rem) 20

<1

• unweighted dose equivalent

• • unweighted dose equivalent (red bone marrow) due to immersion in an infinite cloud

Based on the foregoing evaluation, the staff finds the proposed changes to the TS, and associated bases, acceptable.

3.0 STATE CONSULTATION

,3 i

In accordance with the Commission's regulations, the Pennsylvania State l

official was notified of the proposed issuance of the amendments. The State official had no comments.

4.0 ENVIRONMENTAL CONSIDERATION

The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change the 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 coment on such finding (61 FR 64392). Accordingly, the amendments meet 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 amendments.

5.0 CONCLUSION

The Comission 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 Comission's regulations, and (3) the issuance of the amendments will not be inimical to the comon defense and security or to the health and safety of the public.

Principal Contributors:

J. Lee R. Goel Date: February 11, 1997 i