ML20154E914
| ML20154E914 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 09/02/1988 |
| From: | Bliss H COMMONWEALTH EDISON CO. |
| To: | Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 5074K, NUDOCS 8809190186 | |
| Download: ML20154E914 (4) | |
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one First Netone! Ptars. CMago, lagos h J CONHRenW90Nh h Address Reply to. Poet Omco som 77 i
CW,ago,lanos 606fs0 0767 i
September 2, 1988 i
Mr. A. Bert Davis Regional Administrator U. S. Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn. IL 60137
SUBJECT:
Braidwood Station Unit 1 Clarification of Response to Inspection Report No.
50-456/88-013 HRC_DocktLNodO _AM REIERENCE: (a) W. L. Torney letter to C. Reed dated June 15, 1988 (b) H. E. Bliss letter to A. B. Davis dated July 15, 1988 Pett Mr. Davis:
During a conference call on July 29, 1988 held with Mr.
W.L. Torney of your staff and Commonwealth Edison. it was determined that additional information was required to supplement reference (b).
Enclosed is the response that provides that information and supports idison's response to reference (a).
Should you or your staff have any questions please call this office.
M M4 H. E liss Nuclea Licensing Manager
/klj encl.
cc:
NRC Resident Inspector - Braidwood NRC Document Control Desk 5074K r,t'. U\\
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e etas SEP 6 198
i CLARIFICATION OF l
COMM0!NEALM EDISON COMPANY RE SEONS E_T0J N S PIC11.0lLREP ORLsM18.8011 Braidwood entered the quarterly incore-excore calibration procedure with high expectations for success based on the MIDS cleaning performed in January, 1988 and adequate performance of the system in March, 1988.
When sticking problems were encountered, recent precedence had indicated there was no apparent basis for considering them to be significant.
Based on this previous experience, exercising the MIDS was expected to free up the sticking 1
thimbles.
Therefore assuming that a timely resolut. ion of the problemwouldbeachieved,thesurveillanceconditionsthathadbeen entered (nominal 76% power) were maintained.
At that time.
Braidwood believed that this was an acceptable. ccnservative position, based on it's view of the Technical Specification and the 1
situation at hand.
The following is a brief chronology of the moveable incore detection system (HIDS) thimble cicaning and the incore-excore i
j calibration surveillance, j
12/86 NUS cleaned and lubricated all 58 thimbles.
[
t 05/27/87 Unit 1 Initial Criticality achieved.
No apparent
]
problems with 58 thimbles operable.
l I
10/30/87 Performed full core flux map.
Used 52 thimbles.
l Thought to have drive problems.
(In retrospect this was i
probably the beginning of the thimble sticking problems).
i 12/05/f' Ai'dit.ional 7 full core flux maps taken.
Operable tnimbl@s ranged from 52 to 55.
Developed plan to clean thimbles during surveillance outage (16 thimbles l
identified that were in the most need of cleaning).
12/31/87 50 t.5.imbles operable.
l 01/88 Cleaned the celected 16 thimbles.
l 1
l 03/20/88 Exercised MIDS at NOT/NOP.
No thimble sticking problems encountered.
03/20/88 Unit 1 critical.
4 03/21/88 Unit 1 > 15% power, i
l 03/23/88 Unit I shutdown.
04/24/88 Unit 1 critical following outage.
l 05/10/88 Surveillance conditions established at 75% power.
[
i Commenced quarterly incore-excore calibration l
l surveillance.
I
.o
, Encountered sticking problems on numerous thimbles.
As few as 39 thimbles operable.
Initiated comprehensive test / exercise program to free thimbles.
(Surveillance condition (nominal 76% power) maintained while pursuing MIDS problems.
Management believed that, based on previous success with exercising the thimbles, the MIDS would be freed up in a timely manner and the surveillance procedure could be continued.)
05/13/88 System maintenance and troubleshooting began in parallel with MIDS exercise program.
05/23/88 NRC identifies concern relative to MIDS Surveillance.
05/24/88 Reactor power reduced to 74%.
05/27/88 Westinghouse installed and tested the Thimble Obstruction Removal System I.
This system proved to be ineffective.
05/31/88 Technical Specification change requested to reduce percentage of incore detector thimbles from 75% to 65%.
06/02/88 May 31, 1988 Technical Specification change request not accepted by NRC.
Submitted Technical Specification change request to extend the incore-excore calibration check monthly surveillance interval from 31 to 41 days.
06/02/88 NRR approved Technical Specification monthly survel11ance interval change.
06/10/88 June 2, 1988 Technical Specification change request acceptance issued by NRC.
06/11/88 Unit 1 Shutdown.
06/13/88 Westinghouse installed and tested the Thimble Obstruction Removal System II.
System effective in removing thimble bloctage.
06/14/88 Unit 1 Critical.
06/15/88 Satisfactorily completed the monthly incore-excore calibration check surveillance.
06/28/88 Satisfactorily completed quarterly incore-excore calibration surveillance.
- In reviewing this chronology in retrospect, the more prudent management action would have been to reduce power to less than 75%
when the sticking problems had not been resolved after about 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
In reference (a), page 10, the liRC identifies ?lant management personnel as stating that they chose to stay above 75% power
"...as an incentive to operating personnel to correct the MID problem..."
It is Braidwood Station mangement's belief that this statement was tahen out of context from a general discussion on "philosophy" of plant operations between operations management and the Senlor Resident inspector.
It is Braidwood Statien's policy that plant operations be within the boundaries specified in the Technical Specifications and be in adherence to procedures and operating orders.
Pending implementation of the corrective actions committed to in Reference (b), Braidwood will, in a similar situation, reduce power or otherwise place the unit in a mode or condition for which the specification does not apply.
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