ML20127A975
| ML20127A975 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 06/14/1985 |
| From: | Miosi A COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 0243K, 243K, 5000457, NUDOCS 8506210314 | |
| Download: ML20127A975 (3) | |
Text
,
9 ihfi-Commonwealth Edison r-One First National Plazl, Chicago, Ilknois Address Reply to: Post Othee Box 767 Chicago, Illinois 60690 June 14, 1985 Mr. James G. Keppler Regional Administrator U.S. Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, IL. 60137
Subject:
Byron Station Unit 2 Braidwood Station Units 1 and 2 10 CFR 50.55(e) 30 Day Report High Energy Line Break (HELB) in Auxiliary Building NRC Docket Nos. 50-455 and 50-456/457 Reference (a):
B. J. Youngblood letter to D. L. Farrar dated May 20, 1985
Dear Mr. Keppler:
On May 16, 1985, Commonwealth Edison Company notified Mr. W. L.
Forney of your office of a deficiency reportable pursuant to 10 CFR 50.55(e) regarding environmental effects on high energy line breaks associated with steam generator blowdown and auxiliary steam in the auxiliary building. This deficiency was assigned number 85-03 for Byron Unit 2 and number 85-05 for Braidwood for your tracking purposes.
This letter provides information to fulfill the thirty day reporting requirement, and is considered to be a final report. For Byron Unit 1, this matter was reported under 10 CFR 50.72 requirements.
DESCRIPTION OF DEFICIENCY Certain postulated high energy line breaks (KLBs) in the auxiliary building were evaluated for potential environmental effects on safety-related equipment using information which has been shown to be inaccurate. Two high energy systems were identified:
- 1) The steam generator blowdown (SD) system was originally assumed to be operating at a blowdown rate of 15 gpm which was the original design per Westinghouse guidelines. Reviews being performed in conjunction with flooding calculations in 1984 revealed that due to steam generator water chemistry requirements, the normal blowdown rate would be in the 60-90 gpm range. The resultant changes in valve settings could increase the postulated break flow, thereby changing the predicted environmental temperatures in a large general area of the auxiliary building.
8506210314 850614 PDR ADOCK 05000455 JUN 171985 S
PDR I
I 3 2 9
m
~
d J. G. Keppler June 14, 1985
- 2) As a result of the situation described above, a review was made of all auxiliary building HELBs to determine if additional breaks might adversely affect environmental qualification conditions. Auxiliary steam (AS) system breaks in the radwaste area were identified as a potential problem. These breaks are in non-safety-related areas and, when originally reviewed were assumed to affect only auxiliary building non-safety areas and the turbine building. Upon review, flow paths were identified which could allow steam to enter safety-related areas.
When these cases were identified, initial review indicated that, due to the large areas and limited amount of steam available, the effects on the environment would be relatively small and of very short duration.
Analysis was initiated to resolve the problem, but this was ultimately unsuccessful because of the complexity of the situation and the need to allow 30 minutes for operator action to isolate the break.
ANALYSIS OF SAFETY ItPLICATIONS In the event of a full rupture of a steam generator blowdown line or an auxiliary steam line in the radwaste area, some safety-related equipment designed only for mild environment could, within 30 minutes, be exposed to a harsh (high temperature and humidity) environment in excess of existing equipment qualification. This could potentially cause a loss of function of this equipment.
CORRECTIVE ACTION TAKEN As a permanent resolution, a temperature monitoring system will be installed which will automatically isolate the SD and AS Systems in the event of a high temperature in the HELB areas. The monitors will be a redundant Class 1E System which would provide signals to close the valves and also alarm in the Control Room. Because the SO System is a closed system inside containment, it contains only one fall closed automatic Category I isolation valve on each line which penetrates containment.
Tr.
provide redundancy in the event of a valve failure, operating instructions will be developed to require isolation of manual valves on these lines upon actuation of the Control Room alarm. These manual valves are accessible and in an area not affected by the HELB in question. The AS System is a Category II system and the only isolation valve which will stop flow to the auxiliary building is a fail closed Category II valve in the turbine building. Redundancy will be provided for this valve by operating instructions which will require closure of a manual valve after receipt of the Control Room alarm.
7 u
J. G. Keppler June 14, 1985 Installation of the above described temperature monitoring and associated operating instructions will be in place at Byron Unit 2 and Braidwood Units 1 and 2 prior to fuel load. Details of this modification will be provided to mR for review as requested in Reference (a). Because of the pending tRR review in this matter, we consider this letter to be a final 10 CFR 50.55(e) report.
Please address any questions that you or your staff may have concerning this matter to this office.
Very truly yours, h;gfce.Y Anthony'D. Miosi Nuclear Licensing Administrator
/klj cc: NRC Resident Inspector-Byron NRC Resident Inspector-Braidwood Director-of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC. 20555 0243K f
t l