ML18142A279
| ML18142A279 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 01/28/1985 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Harold Denton, Varga S Office of Nuclear Reactor Regulation |
| References | |
| 761B, NUDOCS 8502010183 | |
| Download: ML18142A279 (4) | |
Text
L e
e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261
- w. L. STEWART VICE PRESIDENT NUCLEAR OPERATIONS January 28, 1985 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation Attn:
Mr. Steven A. Varga, Chief Operating Reactors Branch No. 1 Division of Licensing U, S. Nuclear Regulatory Commission Washington, D. C. 20555 Gentlemen:
VIRGINIA POWER Serial No. 761B NO/JDH:acm Docket No. 50-281 License No. DPR-37 SURRY POWER STATION UNIT NO. 2 PROPOSED TECHNICAL SPECIFICATION CHANGE -
SUPPLEMENT Attached is historic, failure analysis and inspection information regarding seven snubbers associated with our proposed Technical Specification change submitted January 4, 1985 (Serial No. 761).
This information was given to the NRC Surry Resident Inspector on January 18, 1985.
In addition, we have completed the limited inspection we committed to conduct in our January 9, 1985, supplement (Serial No. 761A) to the proposed Technical Specification change.
Unit 2 containment was entered on January 22, 1985 for snubber inspection in accordance with Surry Power Station Special Test 2-ST-161A, "Snubber Inspection at Power."
A total of sixty-eight snubbers were inspected, comprising about 33% of the total nonaccessible snubbers.
Results were satisfactory.
If you have any further questions or require additional information, please contact us immediately.
Attachment cc:
Mr. J, P. O'Reilly Regional Administrator Mr. D. J. Burke NRC Resident Inspector Surry Power Station Mr. C. Price Department of Health 109 Governor Street Richmond, Virginia 23219 Mr. John Olshinski
.NRC Region _U.
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e UNIT 2 SNUBBER EVALUATION In response to the additional information requested to support the Company's request to defer the currently scheduled Unit 2 snubber inspection outage, the failures from the November outage have been evaluated.
The seven snubbers listed as failed were:
1-RC-HSS-122 1-RC-HSS-123 1-RC-HSS-124 1-RC-HSS-125 2-SHP-HSS-6A 2-SHP-HSS-8 2-SHP-HSS-12 6
11 Bore Pathon Snubbers on Pressurizer (Comm.on Reservoir) 2~" "A" Main Steam Line 6
11 "A" Main Steam Line 8
11 "A" Main Steam Line The noted failures were attributed to seal problems on the pressurizer snubbers, and fitting problems on the main steam snubbers.
Failure Analysis Each of the inoperable snubbers were referred to Engineering and Construction for evaluation.
In each case, the review found that no physica*l damage would have resulted from the conditions identified.
The four pressurizer snubbers are connected to a common reservoir.
All four*
were, therefore, declared inoperable as a result of low fluid level.
It is important to note that one seal failure could have caused the fluid leak and resulting failure of four snubbers.
Therefore, despite the counting of this event as four failures for T.S. inspection interval, this can be considered statistically as only one failure.
Had this been counted as one failure, the inspection interval would have been 124 days, not requiring a request for relief at this time.
Mo~e importantly, however, is that it has been determined that these snubbers are not required, and may be replaced with a fixed restraint.
North Anna does not have these snubbers.
We currently plan to delete these snubbers during the upcoming refueling outage.
2-SHP-HSS-8 was found to have no fluid in the remote reservoir, due to a leak in the fitting at the reservoir.
The snubber and the tubing below the fitting were full of fluid.
Engineering Mechanics determined that no damage could have been caused by thermal and turbine trip loads.
2-SHP-HSS-6A was found to be empty of fluid.
Calculations indicated that calculated loads were low enough that the other snubber in the pair has sufficient capacity to carry the total combined turbine trip and seismic loads for both snubbers.
2-SHP-HSS-12 was found to have no fluid in the remote reservoir, due to a leak in the fitting at the reservoir.
The snubber and the tubing below the fitting were found to be full of fluid.
Engineering Mechanics has determined that no damage could have been caused by thermal and turbine trip loads.
L 2
Prior History shows the previous inspection history for these snubbers.
No indication of impending failure could be drawn from trending the "as found" levels.
The three main steam snubbers were functionally tested and rebuilt during the April 1984 inspection.
The pressurizer snubbers were not tested or rebuilt during the April outage.
All seven snubbers were rebuilt or replaced during the November outage.
Future Inspections The Technical Specification inspection intervals are based on a statistical approach, considering the previous failure history and the low probability of a
design basis seismic event.
As noted above, the fact that the four pressurizer snubbers are tied to a common reservoir results in one failure counting as four.
In addition, one of the main steam snubbers appears to be redundant from the perspective of seismic and trip loadings.
Therefore, a failure of that snubber (2-SHP-HSS-6A) during a seismic event would not have resulted in any physical damage under any condition.
Since all 7 affected snubbers were rebuilt or replaced during the last outage, all known problems were corrected.
No further problems are expected at this time.
A good statistical argument exists to support a 124 day inspection interval as requested.
In addition, the proposed at power visual inspection of low-dose and "no-climbing" snubbers will provide further assurance of satisfactory snubber condition.
In particular, the pressurizer snubbers will be included in the at power inspection.
Duririg the upcoming outage, it is planned to delete the four pressurizer snubbers, and to eliminate all common reservoirs.
r I
I ATTACHMENT 2
AS FOUND INSPECTION (Reservoir fluid levels in percent)
Snubber Date 2/15/79 8/2/80 4/22/81 9/6/81 11/12/81 5/17/82 12/12/82 4/18/83 7/14/83 4/84 l-RC-HSS-122' 90%
80%
85%
50%
2 75%
70% 3 50%
60%
>80%
95%
l-RC-HSS-123' 90%
80%
85%
50% 2 75%
70% 3 50%
60%
>80%
95%
l-RC-HSS-124' 90%
80%
85%
50% 2 75%
70% 3 50%
60%
>80%
- 95.
l-RC-HSS-125 1 90%
80%
85%
50% 2 75%
70%)
50%
60%
>BO%
95%
l-SHP-HSS-6A 90%
60%
90%
90%
90%
80%
80%
. 95%
90%
50% 4 l-SHP-"HSS-8 90%
100%
100%
100%
100%
100%
100%
90%
100%
100%
l-SIIP-IISS-12 90%
75%
95%
80%
75%
100%
100%
95%
100%
100%
Notes
- 1. Snubbers connected to common reservoir
- 2. Leaks observed on, sight glass. and ~eals.
- 3. Leaks observed on fittings.
- 4. Leak observed on valve block.