ML15238A508
| ML15238A508 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 12/24/1981 |
| From: | Stolz J Office of Nuclear Reactor Regulation |
| To: | Parker W DUKE POWER CO. |
| References | |
| NUDOCS 8201250456 | |
| Download: ML15238A508 (3) | |
Text
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NSIC EBlackwood 0CABER 2 4 Docket rile ORB#4 Rdg OELD NRC PDR PWagner AEOD L PDR RIngram IE-3 TERA HOrnstein ACRS-10 Dockets Nos.
50-269, 50-270 Gray File and 50-287 LRubenstein LPhillipsD DEisen hut Mr. William 0. Parker, Jr.
Vice President -
Steam Production Duke Power Company P. 0. Box 33189 422 South Church Street Charlotte, North Carolina 28242
Dear Mr. Parker:
Reference:
Letter from W. 0. Parker, Jr. (Duke Power Company) to J. P. O'Reilly (NRC) dated July 24, 1981, Docket No.1 50-269
SUBJECT:
REQUEST FOR LPMS REPORT AND NEUTRON NOISE DATA Your analysis of the Oconee-1 broken thermal shield bolts event des cribed in the reference letter indicates that the event poses no threat to public health and safety. However, the information you have provided has led to a staff concern about a loose thermal shield and also about the failure of the Oconee-if loose parts monitoring system (LP14S) to detect the broken bolts..
The large number of broken and loose thermal shield bolts discovered by inspection implies that most or all of the thermal shield bolts could be broken resulting in a loose, thermal shield., In addition, as was learned in the October 9, 1981 meeting of Duke/B&W/NRC at the NRC.
Bethesda Office, a change in neutron noise level ob served midway in the last fuel cycle of Oconee 1 was attributed to a broadening of the 23 Hz,;noise associated with bore barrel shell mode vibration.
A loose OOEL
- o thermal shield or core badrrel would cause reduction in natural fre 13 quency of the structure and, therefore, make it more susceptible to 00 flow-induced 'Vibration resulting in significantly higher cyclic stress.
0.1 This could lead to failure of vessel internals such as the core barrel, thermal shield or even the core support mechanism.
A displaced or 6a) vibrating thermnal shield or core barrel would also affect the calibra 01-A tion and proper operability of the nuclear instrumentation inclu~ding 0IE olu reactor trip settings.
There could be other safety implications from a loose thermal shield or core barrel that were not considered in the M
design analysis.\\
Our concern regarding the effectiveness of the LPM1S relates!'to all Oconee Units.
Your analysis indicates dependence on the LPMS for d6-,
Mr. William 0. Parker, Jr.
-2 tection of broken thermal shield bolts, but does not explain why it failed to do so previously. An undetected loose part in the primary system could cause component damage and material wear by frequent impacting with other parts in the system. It 66u1d also cause partial flow blockage with attendent boiling problem. Other safety concerns about loose parts include increased potential for control rod jamming and for accumulation of radioactive crud in the primary system.
To address our concerns, you are requested to submit the following items for staff review:
- 1. The LPMS signals from the Oconee-2 startup transient flow test:
This will allow detailed analysis that helps detect loose parts which only impact when flow is disturbed.
- 2. The neutron noise data obtained from Oconee Units 1, 2 and 3:
Besides the neutron noise level change observed.in Unit 1, it was stated in the October 9, 1981 meeting that a neutron noise level change was also observed in Unit 2, and consultants had been hired to record and analyze neutron noise at the Oconee Units. These data and analyses will be evaluated for evidence of core barrel or thermal shield vibration.
- 3.
The analysis or evidence to.support your contention in the reference letter that a loose thermal shield or thermal shield bolts will be detected by the LPMS.
- 4.
The Oconee loose part monitoring program report in accordance with Regulatory Guide 1.133, Rev. 1. Theereport should include at least a description of LPMS hardware, implementation, plant personnel training, and in particular, the LPMS calibrations and operational procedure.
Since this request for information involves only the Oconee Nuclear Station, fewer than ten respondents are affected and, therefore, 0MB clearance is not required under P. L.96-511.
If you have any questions on this subject, please contact your NRC Project Manager.
Sincerely, I0RIGIVAI SIGNlWD BL JOHN Fo STVIg..
John F. Stolz, Chief Operating Reactors Branch #4 Division of Licensing cc:
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N-RC FORM 318 {10-80) NRCM O240 OFFICIAL RE CO RD COPY usaPo: 198-335-960
Duke Power-Company cc w/enclosure(s):
Mr. William L. Porter Duke Power Company P. 0. Box 33189 422 South Church Street Office of Intergovernmental Relations Charlotte, North Carolina 28242 116 West Jones Street Raleigh, North Carolina 27603 Oconee County Library 501 West Southbroad Street Walhalla, South Carolina 29691 Honorable James M. Phinney County Supervisor of Oconee County Walhalla, South Carolina 29621 Regional Radiation Representative EPA Region IV 345 Courtland Street, N.E.
Atlanta, Georgia 30308 William T. Orders Senior Resident Inspector U.S. Nuclear Regulatory Commission Route 2, Box 610 Seneca, South Carolina 29678 Mr. Robert B. Borsum Babcock & Wilcox Nuclear Power Generation Division Suite 220, 7910 Woodmont Avenue Bethesda, Maryland 20814 Manager, LIS NUS Corporation 2536 Countryside Boulevard Clearwater, Florida 33515 J. Michael McGarry, III, Esq.
DeBevoise & Liberman 1200 17th Street, N.W.
Washington, D. C. 20036