ML20246E153
| ML20246E153 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 08/16/1989 |
| From: | Suh G Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20246E158 | List: |
| References | |
| NUDOCS 8908290022 | |
| Download: ML20246E153 (6) | |
Text
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UNITED STATES E
NUCLEAR REGULATORY COMMISSION n
WASHING TON, D. C. 20555 o
August 16, 1989 Docket Nos.: 50-352/353 LICENSEE:
Philadelphia Electric Company FACILITY:
Limerick Generating Station, Unit I and Unit 2
SUBJECT:
SUMMARY
OF' JULY 27, 1989 MEETING ON SEVERE ACCIDENT ISSUES
References:
(1) ' Letter from G. Hunger, Philadelphia Electric Company, to NRC Document Control Desk, dated June 23, 1989.
(2) Letter from R. Clark, NRC, to G. Hunger, Philadelphia Electric Company, dated May 23, 1989.
(3) Letter from G. Suh, NRC, to G. Hunger, Philadelphia Electric Company, dated July 31, 1989.
On July 27, 1989 at the NRC offices in Rockville, Maryland, a meeting'was held between the NRC staff and representatives of the Philadelphia Electric Company and its consultants to discuss severe accident issues related to the Limerick Generating Station. The items discussed at the meeting were identified by the staffinitsreviewofthelicensee'sresponse(Reference 1)tothestaff's request for additional information (Reference 2). Enclosure 1 provides a list of the meeting participar.ts.
For the purpose of keeping a record of the meeting, the meeting was recorded. Copies of the meeting transcript have been placed in the public document room. A summary of some of the meeting highlights are described in the following.
The licensee presented information related to a comparison of the core damage frequencies for each of the accident classes in the original and updated probabilistic risk assessments. The original PRA was completed in 1982. Since then, the PRA has been updated in 1986, 1988, and most recently in June 1989 as presented in Reference 1.
The reasons for changes in core damage frequencies were discussed which included changes in the PRA model, hardware improvements in the plant, and increased credit for certain operator actions. The licensee confirmed that the improvements presented in Table 8 of NUREG-1068, titled
" Review Insights on the Probabilistic Risk Assessment for the Limerick Generating Station," dated August 1984, had been implemented at the plant.
These improvements consisted of improved automatic depressurization system initiation logic following the potential loss of high pressure coolant sources and improved design to achieve alternate methods of HPCI/RCIC room cooling during loss of offsite power events, and were stated in NUREG-1068 to result in a reduction of the core damage frequency estimate by a factor of 2.5.
For other hardware and procedural improvements made to the plant, the change to the estimated values of. plant risk were not available for any specific improvement made to the plant. Licensee representatives stated that the plant PRA model had gone through a number of revisions which made difficult the assignment of an effect from any single change, given the interactive effect between the various changes that had been made.
Models used to develop the release fractions for each of the accident classes and estinates of the offsite consequences were discussed. These models were essentially those used in the development of the 1982 PRA. The methodology y
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used in assessing the risk reduction benefits of various severe accident mitigation design alternatives was summarized. Other topics of discussion
' included the containment event tree, conditional early fatality estimates of the_ dominant accident sequences, the modeling of_the dominant fire sequences, and transient initiator frequencies.
The licensee discussed the process used for the derivation of cost estimates for severe accident mitigation design alternatives. The process included the development of the basic design bases for each alternative; formulation of conceptual designs by engineering teams; review of the design concepts for consistency with the risk reduction analyses effort; and estimation of material quantities, man-hour estimates, and schedu'es.
A discussion was also held of potential mitigation alternatives which have-been considered in the Containment Performance Improvement Program being conducted by the Office of Nuclear Regulatory Research within the NRC. These alternatives are generic items that are being considered for Mark II containment plants, and were not alternatives which had been previously-analyzed by the licensee in Reference 1.
The specific alternatives which were discussed included provisions for an additional standby diesel generator, low pressure backup water supply system, methods for removing drywell spray water from the suppression pool to prevent containment failure, and actions to flood the outer surface of the drywell head. The licensee provided general comments as to the feasibility of these generic items as they related to the Limerick
~
station, but had not performed specific analyses of the benefits.and costs associated with these potential improvements.
During the meeting, several follow-up questions (see Enclosure 2) were identified. These were transmitted to the licensee in Reference 3.
Enclosure 3 provides a copy of the licensee handouts which were distributed at the meeting.
i
.A Gene Y.
h, Project Manager Project Directorate I-2 Division of Reactor Projects I/II
Enclosures:
As stated cc w/encls. 1 & 2:
Licensee / Applicant &
Service List
1
~
Mr. George A. Hunger, Jr.
Limerick Generating Station
~ Philadelphia Electric Company Units 1 & 2 cc:
Troy B. Conner, Jr., Esquire Mr. Ted Ullrich Conner and Wetterhahn Manager - Unit 2 Startup 1747 Pennsylvania Ave., N.W.
Limerick Generating Station Washington, D.
C..
20006 P. O. Box A Sanatoga, Pennsylvania 19464 Mr. Rod Krich S7-1 Philadelphia Electric Company Mr. John Doering 955 Chesterbrook Boulevard Superintendent-Operations Wayne, Pennsylvania 19087-5691 Limerick Generating Station P. O. Box A Mr. Charles W. Elliott Sanatoga, Pennsylvania 19464 Poswistilo Elliott and Elliott 325 N. 10th Street Thomas Gerusky.. Director Easton, Pennsylvania 18042 Bureau of Radiation Protection PA Dept. of Environmental Resources Mr. Graham M. Leitch. Vice President P. O. Box 2063 Limerick Generating Station Harrisburg, Pennsylvania 17120 Post Office Box A Sanatoga, Pennsylvania 19464 Single Point of Contact P. O. Box 11880 Harrisburg, Pennsylvania 17108-1880 Mr. James Linville U.S. Nuclear Regulatory Commission Mr. Philip J. Duca Region I Superintendent-Technical 475 Allendale Road Limerick Generating Station King of Prussia, PA 19406 P. O. Box A Sanatoga, Pennsylvania 19464 Mr. Thomas Kenny Senior Resident Inspector US Nuclear Pegulatory Commission P.'0. Box 596 Pottstown, Pennsylvania 19464 Mr. John S. Kemper l
Senior Vice President-Nuclear Philadelphia Electric Company 2301 Market Street Philadelphia, Pennsylvania 19101 L
4r
. ~
h I
used in assessing th' risk reduction benefits of various severe accident.
e
- mitigation design alternatives was summarized. Other topics of discussion L
included the containment event tree, conditional early fatality estimates of the dominant accident sequences' the modeling-of the dominant fire sequences, and transient initiator frequencies.
The. licensee discussed the process used for the derivation.of cost estimates for severe accident mitigation design alternatives. The process. included the dev_elopment of the basic design bases for each alternative; formulation of conceptual designs by engineering teams; review of the design concepts for consistency with the risk reduction analyses effort; and estimation of material quantitiest man-hour estimates, and schedules.
A discussion was also' held of potential mitigation alternatives which.have-been considered in the Containment Performance Improvement Program being conducted by the Office of Nuclear Regulatory Research within the NRC. These alternatives are generic items that are being considered for Mark II containment plants, and were not alternatives which had been previously analyzed by the licensee in Reference 1.
The specific alternatives which were discussed included provisions for an additional standby diesel generator, low pressure backup water supply system, methods for removing drywell spray water from the suppression. pool.to prevent containment failure, and actions to flood the outer surface of the' drywell head. - The_ licensee provided general comments as to the feasibility of these generic items as they related to the Linerick
-station, but had not performed specific analyses of the benefits and costs associated with these potential. improvements.
During the meeting, several. follow-up questions (see Enclosure 2) were identified.
These were transmitted to the licensee in Reference 3.
Enclosure 3 provides.a copy of the licensee handouts which were distributed at the meeting..
/S/
Gene Y. Suh, Project Manager Project Directorate I-2 Division of Reactor Projects 1/11
Enclosures:
L As stated cc w/encls. 1 & 2:
Licensee / Applicant &
Service List DISTRIBUTION: w/encls. 1-& 2 DocketJJJet PDI-2 Reading
- GSuh/RClark WButler H0'Brien
' Meeting p# ticipants.
SVarga/BBoger TSpeis NRC PDR/LPDR*
'FCongel AThadani LChandler OGC EJordan
-BGrimes ACRS(10)
- w/encls. 1, 2 & 3 PDI-2/PM PDI-2/D GSuh:tr HButler a t 8 /l(,/89 g/489
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ENCLOSURE 1 NRC/PECo MEETING ON SEVERE XECIDENT MITIGATION ISSUES NAME ORGANIZATION R. M. Krich-PEco/ Licensing E. Robert Schmidt NUS Corp.
Robert M. Rader Conner and Wetterhahn
.. Dennis A. Klein' Bechtel James T. Hearn Bechtel J. L. Phillabaum-PEco A. J. Marie PEco P. J. Fulford NUS Corp.
R. J. Barrett NRC/NRR R. L. Palla NRC/NRR E. S. Chelliah NRC/RES/DSR Trevor-Pratt BNL Charles Hinson NRC/NRR John N. Ridgely NRC/RES Charles Ferrell NRC/RES/SAIB.
Brad Hardin NRC/RES Tim Margulies NRC/NRR Ann Hodgdon NRC/0GC Ajit K. Bhattacharyya Comm. of PA/ DER /BRP Sidney Feld NRC/RES Gene Y. Suh NRC/NRR/DRP l.
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1
ENCLOSURE 2 QUESTIONS FROM JULY 27, 1989 NRC MEETING WITH PHILADELPHIA ELECTRIC COMPANY 1.
With regard to the contribution of fire initiated sequences to core damage frequency estimates, do the cables for both trains of safety-related systems have three hour fire ratings?
2.
For the severe accident mitigation design alternatives considered in the June 23, 1989 submittal, what occupational exposure would be incurred in installation and in recurring operation and maintenance? Please provide the bases for the estimates, including work hour estimates, location of the work performed, and applicable radiation dose rates.
3.
Please provide a reference to drawings for the drywell head assembly and.
the associated HVAC systems in the immediate area.
4 In the consideration of mitigation alternatives, one potential alternative would be leaving Unit 2 idle and providing replacement power from other sources.
If Unit 2 was idle, what would be the source (s) of the replacement power, including a description of the type of power source and whether the source would be from inside or outside the utility's system? What would be the environmental impacts which would result from the use of these other sources?
5.
What capacity factor was assumed for Unit 2 in terms of replacement energy costs and what variability was assumed in that factor as a function of plant life?
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