ML17202L298
| ML17202L298 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 07/03/1990 |
| From: | Siegel B Office of Nuclear Reactor Regulation |
| To: | Kovach T COMMONWEALTH EDISON CO. |
| References | |
| IEB-80-11, TAC-63970, TAC-63971, NUDOCS 9007100205 | |
| Download: ML17202L298 (5) | |
Text
J Docket Nos. 50-237 and 50-249 Mr. Thomas J. Kovach UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 July 3, 1990 Nuclear Licensing Manager Commonwealth Edison Company-Suite 300 OPUS West II I 1400 OPUS Place Downers Grove~ Illinois 60515
Dear Mr. Kovach:
SUBJECT:
RESOLUTION ti~ IE BULLETIN 80~11, MASONRY WALLS FOR DRESDEN STATION, UNITS 2 AND 3 (TAC NOS. 63970 AND 63971)
References:
. (a) IE.Bulletin 80-11, dated May 8, 1980.
(b) J. Wojnarowski (CECo) letter to H. Denton (NRC),
dated October 6, 1986.
(c) J. Zwolinski (NRC) letter to D. Farrar (CECo)~
dated December 4, 1986.
(d)
B. Siegel (NRC) letter to T. Kovach (CECo),
(e) dat~d July 20, 1989. -
M. Richter (CECo)* letter*to T. Murley (NRC),
(f) dated September 26, 1989. _'
M. Richter (CECo) letter to T. Murley (NRC),
(g) dated November 30~ 1989.
- M. Richter (CECo) letter to T.
dated June 1990.
~urley (NRC),
(h)
M. Richter (CECo) letter to.T. Murley (NRC),
dated March 5, 1990.
In Reference (a), the staff requested licensees to perform a ~e-evaluation of.
the design adequacy of safety-related masonry walls under postulated loads.
In Reference (b), Commonwealth Edison Company (CECo) submitted documentation supporting the use of the leak-before-break coricept for establishing the acceptabilit¥ of the masonry walls associated with the Reactor Water Cleanup System (RWCS} for Dresden Station, Units 2 and 3.
With Reference (c), the staff issued a safety evaluation for Dresden Station, Units 2 and 3.
- However, the safety evaluation indicated that the concept of leak-before-break was under review as a broad-scope rulemaking issue, and that the adequacy of its appJication to the RWCS pi~ing would be addressed at a later date. The staff informed CECo, in Reference (d), that the leak-before-break approach was not acceptable for the RWCS piping at Dresden Station since the ~iping material was subject to an active degradation mechanism (intergranular stress corrosion cracki~g). Additionally, the staff requested CECo to submit proposed action~
which would resolve the staff's concerns with the masonry wall design for Dresden Station.
In Reference (e), CECo indicated a study was being performed to evaluate the feasibility of demonstrating that the masonry walls can 9007100205 900703
' ~DR ADOCK 0500~~~7 I '.
I
. I)
I
'.: ***~...
- ~
.:f'.
I Mr. Thomas J; Kovach.
July 3, 1990 withstand the consequences of a postulated RWCS full area br~ak. In Reference (f), CECo apprised the staff on the results of the initial phase of the study.
In Reference (g) CECo provided the results of an evaluation performed to demonstrate that the safety-related masonry walls in the vicinity of high energy RWCS piping could* either withstand the pressurization transient resulting from a RWCS pipe break, or that wall failure would not affect*the ability to mitigate the consequences of the pipe break event or the ability to safely.
shut down the plant. The results of this evaluation determined that only one masonry wall (Wall 38 in Unit 3), which s~pports the electrical pull box and c~bling associated with the Uriit 3 RWCS outboard containment isolation valve, could not withstand the calculated peak pipe break pressure. If this wall failed, the operability of this valve could be impacted~ In Reference (h)
CECo stated that the. preferred*design solution, to ensure valve operability. in the event of the wa.ll failure, is to relocate the *electrical pull box and cabling associated with the outboard isolation valve.
In Reference (g), Attachment B, CECo provided a limited risk assessment which utilized the Systematic.Evaluation Program (SEP) methodology for Dresden 2 (NUREG-0823, Integrated Plant Safety Assessment, Dresden Unit 2) to justify
.continued operation until the proposed modification, which is scheduled for the spring 1991 Unit 3 refueling outage, is completed.
In this asses,sment, CECo evaluated the safety significance of a*coiticident RWCS pipe* break and a failure of th~ RWCS outboard containment isolation valve due to an
- overpressu.re failure of Wali 38 *. This evaluation 'was based on the probabilistic methodology of the SEP evaluation for Dresden 2 contained in Appendix D to NUREG-0823 which addressed the probabi.lity of a pipe break *
- outside containment (SEP Topic III-5.B). *The evaluation was adjusted to account for the difference~ between Dresden 2 and 3 (number of pipe segments outside containment involved); The SEP evaluation assumed a pipe break between the inboard and"outboard isolation valves (outside containment) with an assumed single active' f~ilure of the inboard isolation valve which results i.n an uni so lated LOCA.
Th7 frequency of this _combination of events was determined to be 1.8 x 10- /reactor year.
The.staff in NUREG-0823, SEP Topic
- III~S.B, Pipe Break Outside Containment, stated that the importance to risk of pipe breaks between the containment penetration-and the isolation valve outside containment is.low *. The analysis performed by CECo for the Dresden 3 issue does not change this conclusion.
.The staff has evaluated the submittals (References g and h) provided by CECo to resolve the.concerns identified in IE Bulletin 80-11, related to *masonry
. walls and determined the relocation of the electrical pull box and cabling to the RWCS outboard isolation* valve is acceptable.
In addition, based on the
- risk assessment perfo"rmed by CECo, the staff has determined that continued operation of Dresden 3 until this modification is completed during the next refueling outage which is scheduled for spring 1991, is also acceptable.
Mr. thomas July 3, 1990 Please inform the staff when this modification is implemehted or if any significant schedule slippage in implementation should Q~cur.
cc:
See next page S~ncerely,
~! ~:f.
Project Manager Project Directorate III-2 Division of* Reactor Projects - III, IV, V and Special Projects Office of Nuclear Reactor Regulation
. (
Mr. Thomas J. Kovach Commonwealth Edison Company cc:
Michael I. Miller, Esq.
Sidley.and Austin One First National Plaza Chicago, Illinois 60690 Mr. J. Eenigenburg
-Plant Superintendent Dresden Nuclear Power Statiori Rural Route #1 Morris, Illinois 60450.
U. S. Nuclear Regulatory Conunission Resident Inspectors Office.
Dresden Station Rural Route #1 Morris, Illinois 60450 Chairman Board of Supervisors of Grundy County
'Grundy County Courthouse Morris, Illinois 60450 Regional Administrator Nuclear Rt:'gulatory Commission, Region* III 799 Roosevelt Road, Bldg. #4 Glen*Ellyn, Illinois.60137 Il 1 inoi s Department of Nuclear Safety Office of Nuclear Facility Safety*
1035 Outer Park Drive Springfield, Illinois 62704 Robert Ueumann Office of Public Counsel State ~f Illinois Center 100 W. Randqlph Suite 11-300 Chicago, Illinois 60601 Dresden Nuclear Power Station Units 2 and 3
- 9 Mr. Thomas. July 3, 1990 Please inform"the staff when this modification is implemented-or i~ any.
significant schedule slippage in implementation should occur~
j, ** '
l 1)-
- . \\'
- ,*f
~: 'j ~ =-*
~* -..
1 cc:_~ See 11ext page
.,.DISTRIBUTION?
.: __ pocke! tJJe,. *
' NRC & Locil PDRs
~-, CMoore
- -~
- ~. )~OGt
"<:.:*,, 'ACRS '( 10)
WShaf er RI II.
Sincerely,
- Original ~igned by:
Byron L *. Siegel, Pf'.'oject Manager Project* D.i r:ectora ~e
- I I I-2 * * *
. 0-ivision of.Reactor Projects.- I,lL,*
IV, V and Sp~cial P~ojects Office of Nticl~ar.Reactor Regulation PDIII-2 r/f JZwolinski._,.
-BSiegel
- EJordan..
PDIII.:.2 Plant File.
~-
RBarrett _
,-,I'
. ""i.
- ,l '
~, * . ~ '"' I*,.,.._ ~" . '. :*.J :*.- :* l ':: ~ ;* [ !I* ~ ,.* :., - ~1 ~ -.-;:'- '*~~- \\ c/}}