ML20150F995
| ML20150F995 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 07/01/1988 |
| From: | Allen C COMMONWEALTH EDISON CO. |
| To: | Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 4852K, CAL, CAL-R111-88-3, CAL-RIII-88-03, CAL-RIII-88-3, NUDOCS 8807190168 | |
| Download: ML20150F995 (3) | |
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r-Commonwealth Edison
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T Address Reply to: Post Omco Box 767
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y/ CNcago, Illinois 60690 0767 July 1, 1988 Mr. A. Bert Davis Regional Administrator U.S. Nuclear Regulatory Commission Region III
-799 Roosevelt Road Glen Ellyn, IL 60137 subject: LaSalle County Station Unit 2 Supplemental Response to Confirmatory Action Letter CAL-RIII-88 NRC Docket No. 50-374 References (a):
A.B. Davis letter to Cordell Reed dated March 17, 1988 transmitting CAL-RIII-88-03 (b):
M.S. Turbak letter to A.B. Davis dated April 15, 1988 transmitting Response to CAL-RIII-88-03 (c):
C.M. Allen letter to US NRC dated May 9, 1988 (d):
E.G. Greenman letter to Cordell Reed transmitting Inspection Report 50-373/88008 and 50-374/88008
Dear Mr. Davis:
The Confirmatory Action Letter (CAL) (Reference (a)) requested that commonwealth Edison (CECO) submit a formal report of our findings and conclusions relating to the LaSalle County Unit 2 event of March 9, 1988 in.
which there was a dual recirculation pump trip and subsequent core performance anomalies. This letter supplements the response to the issues listed in the CAL and the subsequent questions submitted by the Augmented Inspection Team (AIT) (Reference (d)).
In Reference (b), CECO made a commitment to provide your staff with status reports of our involvement with the Boiling Water Reactor Owners Group (BWROG) relating to this event. Specifically, we are determining how to:
(1) demonstrate the adequacy of automatic scram protection and (2) assess the adequacy of existing plant instrumentation to evaluate possible violations of safety limits if regional oscillations were to ever occur. That status report is enclosed. We will continue to provide you status reports as these efforts proceed.
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A.B. Davis July 1, 1988 Additionally the staff indicated an iriterest in changes made to the training simulator as a result of the event. Changes have been made, such that the simulator can now respond in a manner that produces nuclear instrumentation oscillations. This response has been observed by the Station Lead Nuclear Engineer and has been used as a training exercise participated in by the Production Training Center staff.
If you have any additional questions, please address them to this office.
Very truly yours, is "f
C. M. Allen Nuclear Licensing Administrator
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cc:
P. Shemanski (NRR)
L. Phillips (NRR)
Resident Inspector LaSalle M. Ring (RIII)
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4852K
Attachmsnt to Juna 24, 1988 letter to A.B. Davis from C. M. Allen AIT Ouestion 1.a.iii How can the adequacy of automatic scram protection be demonstrated?
Can it be shown by analyses that inherent shutdown mechanisms such as Doppler will limit, the peak, power level
- even under conditions of regional oscillation such that safety limits will not be violated before 118% power APRM scram occurs. What are the limitations of the analysis in terms of fuel design applicability of other factors?
AIT Ouestion 1.d LaSalle 2 has very limited capability to record LpRM traces and other data that would be needed to evaluate possible violation of safety limits if re'gional oscillations were to occur.
Discuss the adequacy of existing instrumentation and recording capability (LPRM alarms, operator observations and automatic recording, etc.) for evaluation of such events as discussed in SIL 380, item 9.
Supplemental Response The BWR Owners' Group (BWROG) formed an Ad Hoc Committee to review the event and NRC concerns and to develop a specific workscope package for resolving the AIT questions and related issues.
By late April 1988 a working subgroup had formulated a workscope which the Ad Koc Committee supported for consideration of the full BUROG.
In the June 8, 1968 full owners' group meeting in St. Louis it was concluded that the proposed workscope should be discussed with the NRC prior to it being funded.
On June 24, 1988 the Ad Hoc Committee met with the NRC to discuss NRC concerns in the above areas and to describe the BWROG proposed path to resolving these concerns.
The proposed workscope and associated analyses were discussed and it was agreed that the analyses would provide useful information concerning the adequacy of existing instrumentation to detect and suppress core oscillations.
The question concerning inherent shutdown mechanisms was discussed in the June 24 meeting and the general difficulties in satisfactory modeling the three dimensional effects, especially thermal-hydraulic effects were presented.
This question was discussed as primarily being associated with question of ATWS power levels during instability, and will be discussed with the Ad Hoc Committee subsequent to General Electric review.
post-event evaluation capability will be discussed at the next Ad Hoc Committee meeting.
Commonwealth Edison will update this response subsequent to completion of a funding vote by the full owners' group which is now scheduled for early to mid-August 1988.
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