ML20217J697
| ML20217J697 | |
| Person / Time | |
|---|---|
| Site: | Pennsylvania State University |
| Issue date: | 10/18/1999 |
| From: | Pell E PENNSYLVANIA STATE UNIV., UNIVERSITY PARK, PA |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9910250141 | |
| Download: ML20217J697 (3) | |
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PENNSTATE Eva J. Pell (814) 863-9580 Interim (Vice President for Research Fax: (814) 863-9659 interim Dean of the oraduate school E-mail: ejp(@ psu.edu The Pennsylvania state University 3(M old Main October 18,1999 University Park, PA 16802 1904 Nuclear Regulatory Commissions
. Document Control Desk Washington,DC 20555 Re: Reportable Occurrence .- TS 3.2.6 License R-2, Docket No.50-005
Dear Sir or Madame:
This report is being submitted in accordance with Sections 6.5.2 and 6.6.2 of the PSBR Technical Specifications (TS). Initial verbal notifications of this reportable occurrence were made to Tom Dragoun, Region 1 and Al Adams, NRC HQ on October 4,1999 and were confirmed in writing the same day with faxed copies to Marvin Mendonca, Al Adams, and Tom Dragoun and mailed copy to the Document Control Desk.
TS 3.2.6, SCRAM Time, states: "The time form SCRAM initiation to the full insertion of any control rod from a full up position shall be less than 1 second."
~ Description of Event On Friday,. October 1,1999, with the reactor shutdown, a special test was being conducted to measure the drop time for the Transient Rod (TR). During thelest-the TR did not drop freely into the core. The TR was manually inserted. Further operation of the reactor was administratively prohibited. TS 3.1.3, Shutdown Margin, and TS 3.2.1, Reactor Control Rods, were not violated during this event.
There was no indication of unacceptable performance of the TR prior to the test on October 1, 1999. The daily checkouts for the week as well as routine operations had not indicated any
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problems with movement of the TR.
A related event took place on September 29,1997 and was reported in correspondence dated
' October 3,1997 and October 8,1997.
f Since the event of September 27,1997 periodic testing and maintenance of the TR have been a
conducted. The testing has consisted of periodic testing of the drop time with time periods between. tests ranging from days to several weeks. The testing was at biweekly intervals just ,2,0 before this event and we were considering moving to monthly testing based on our test results. o On Monday, . September 27, 1999 we measured a drop time of 929 msec followed by four '
successive drops in the mid to upper 800 msec range. The 929 msec drop time was noticeably longer than our results for the past months. It was decided to clean the TR operating rod and
._ cylinder. Following the cleaning, three successive drop time of about 610 msee were measured.
These times represented the fastest TR drop times in many years.
It was decided to make a measurement of the drop time just before sh~utdown for the weekend and then to measure again on the following Monday to assess whether the weekend shutdowns 9910250141 991018 l v; *. PDR ADOCK 05000005 g PDR. c An Equal opportunity University
o Nuclear Regulatory Commiesion Page 2 October 18,1999 were influencing TR performance. It was during this special measurement on Friday evening, October 1,1999, that the unacceptable performance was observed.
Corrective and Preventative Actions: ;
After the event of September 27,' 1997 numerous different attempts had been undertaken to arrive at an effective maintenance, cleaning, and lubrication process which would provide reasonable assurance of consistent and acceptable TR drop times. These efforts included increasing clearances associated with the operating rod seal at the bottom of the TR cylinder. We had consulted with a tribology expert at the University who advised us to consider mechanical cleaning followed by detergent washing followed by alcohol cleaning followed by lubrication.
Our drop time performance over the past eight months had been consistent and we had not yet ,
l tried his suggestions. When we experienced the Monday drop time of 929 msec we decided to l l -perform the alcohol cleaning and then observe the results. As indicated the drop times were dramatically improved.
At the time of the October 1" event and during subsequent investigations, it was observed that motion of the operating rod within the cylinder was not smooth. It had the feel of an unlubricated cylinder and operating rod. Upon disassembly the interior of the cylinder and the operating rod appeared extremely clean and dry with no evidence of particulate material which might have ;
, impaired motion. Almost no evidence of present or past lubrication was found. These findings, {
l as well as further consultation with the tribology expert, led to the conclusion that the alcohol cleaning without subsequent lubrication had led to the formation of an especially lubricious film which disappeared with usage during the week.
Over the period from October 4* through the 6*, the TR mechanism was examined, partially l disassembled, cleaned, lubricated, reassembled, and tested. The operating rod was mechanically l cleaned, washed with detergent, and given a final cleaning with ethyl alcohol. This was followed l
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by a light lubrication with KRYTOX, a patented Dupont lubricant, which was recommended by our expert for this application. The cylinder was cleaned with acetone followed by an alcohol cleaning and then lubrication with KRYTOX. It was not practical to mechanically clean the cylinder since to do so would require a partial defueling to remove the cylinder from the bridge.
The components were reassembled and exercised to assure a uniform light coating of Nbricant.
The TR was observed to move freely.
Investigations included the air system feeding the TR. No evidence of moisture was found in the.
TR. Opportunities to improve the quality of the air supply were identified during the investigations but do not appear to have had a direct impact on the event. Additional efforts to assure a very dry and clean air supply are being undertaken.
. Following the investigations and the final cleaning and lubrication on October 6*, the TR drop time was measured six times with all times being in the high 600 msec range.
Prior to returning to service, briefings were held with licensed personnel explaining the event, the investigations, the corrective actions, the additional surveillances, and methods of detecting adverse operation. Several demonstration TR drops were performed so the operators would be familiv with the expected performance as well as audible indications as the air is released and the TR drops.
L l The reactor was returned to operation on Wednesday, October 6*. A further drop time measurement was performed later that afternoon with similar results. An administrative L
e Nuclear Regulatory Commission Page 3 October 18,1999 requirement to verify freedom of motion by a TR drop before cach operation and to measure the drop time at the beginning of each day the reactor was operated was put in place.
On Thursday, October 14*, sufficient data had been collected to remove the requirement for I freedom of motion checks before each startup.The daily rod drops remain in effect. As of today, October 18,1999, the average TR drop time since the cleaning and lubrication is 690 msee with a standard deviation of 7 msec. As sufficient information is available the frequency of rod drop measurements will be further modified.
If you have any questions regarding this matter, please call the Director, Dr. Sears at 814-865-6351.
-Sincerely, !
Dr. Eva J. Pell Interim Vice President for Research Interim Dean of the Graduate School RAE:CFS/skt pc: A. Adams L. Burton J. Brenizer T. Dragoun
.T. L. Flinchbaugh M. Mendonca C. F. Sears W. F. Witzig j Subscribed to and sworn before me on the /[O Notary Public in and for Centre County, Pennsylvarir) day of b .1999, l M
z 05hckh,h4 Wy Commesion Exp{es y 12, 2003
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