ML20245L315
| ML20245L315 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 04/25/1989 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| CON-NRC-89-049, CON-NRC-89-49 IEB-79-14, VPNPD-89-252, NUDOCS 8905050379 | |
| Download: ML20245L315 (3) | |
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Wisconsin l Electnc POWER COMPANY 231 W Michigan, RO. Box 2046. Mitwoukee. WI 53204 (414)221 2345 VPNPD-89 2 52 l
NRC-89-049 April 25, 1989 Mr. A.
Bert Davis Regional Administrator, Region III U.S. NUCLEAR REGULATORY COMMISSION l
799 Roosevelt Road Glen Ellyn, Illinois 60137
Dear Mr. Davis:
DOCKETS 50-266 AND 50-301 IE BULLETIN 79-14 SAMPLE PROGRAM POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2
Reference:
WE letter VPNPD-89-145/NRC-89-034 to Mr.
A.
Bert Davis dated 3/10/89.
We understand based on telephone conversations with Mr. Liu of your. staff that the sampling program for integral welded attach-ments (IWA) proposed by WE in the referenced letter is not considered large enough.
During a telephone conversation on April 12, 1989, Mr. Liu suggested that WE review EPRI Final Report NP-5380, Visual Weld Acceptance Criteria, as an example of a sample program that has been accepted by the NRC.
This letter a
will present the basis for our sample size and selection of the l
specific IWA to be evaluated.
Further, it will demonstrate that the sample size determination criteria described in Volume 2 of EPRI Final Report are not appropriate for the evaluation we are performing for Mr. Liu.
In prepar>ng the sample program, we reviewed all IWA supports which required requalification by Bechtel in accordance with our 79-14 program criteria for supports with loads calculated by 79-14 analyses which were higher than the original design loads.
This i
requalification included the use of stress intensification factors l
(SIF) based on engineering judgement.
Mr. Liu had requested that we evaluate a sample of the supports to verify that good engineering judgement was used, j
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- ' NRC Document Control De sk April 25, 1989 Page 2 The total number of supports in this group for which an SIF was not generated and included in the piping analysis by Bechtel was thirty-eight (38).
The specific attachments were of the following types:
1)
Lugs 2)
Elbow lugs 3)
Plate with gusset 4)
Stanchion, lateral restraint 5)
Stanchion, anchor 6)
Three-way support 7)
Elbow stanchion /three-way anchor 8)
Fabricated anchor 9)
Ear lugs The sample of ten (10) selected and proposed by our letter includes supports of Types 1, 3,
5, 6,
7, and 8.
Supports with the highest loads were selected such that the evaluations would bound similar support types with lower loads.
Support Types 2, 4,
and 9 were not chosen since the loads on these supports were small.
Thus, the sample is expected to be " worst case" rather than random.
The total number of supports with integral welded attachments for which an SIF was generated and included in the piping analysis by Bechtel was sixteen (16).
The specific attachments were of the following types:
1)
Stanchion on straight pipe 2)
Stanchion on elbow 3)
Stanchion on tee The sample of five (5) selected and proposed by our letter includes all three types of supports.. As.above, supports with the highest loads were selected so as to bound lower load cases and the sample is biased toward " worst case."
The sample selection criteria were based on engineering judgement to obtain a representative sample of support types and a bounding evaluation.
The sample population is large relative to the total population.
We believe the size of each sample (10 of 38 or 26 percent and 5 of 16 or 31 percent) is sufficient to draw accu-rate conclusions on the reasonableness and appropriateness of the 79-14 program methods and results for IWAs.
The EPRI Report NP-5380, Volume 2, addresses a sampling plan for visual reinspection of structural welds.
The sampling plans are intended to evaluate acceptability of a very large population of structural welds based on a random sample.
For a single plan, only 58 welded connections are required to be reviewed and for a
s...*
NRC Document Control Desk April'25, 1989 Page 3 multiple sample plan, a minimum of only 64 are required.
The welds considered as part of the population include, but are not limited to:
Main building frame members and connecting members; e
e Supports for equipment, components and piping, cable trays and conduits, and HVAC ducts; Miscellaneous steel including bracing and stiffeners; e
embedments; stairways and handrails; doors and door frames; window frames, gratings; covers, etc.
Thus, the total population is in the order of thousands or tens of thousands and the sample population is less than one percent.
The sample size proposed in our program is at least an order of magnitude larger than what would be required by the EPRI document suggested by Mr. Liu.
Wa are puzzled by Mr. Liu's comments that our proposed sample is "a good beginning" but not totally responsive to his concerns.
Prior to his leaving Milwaukee, during the February 14-15, 1989 inspection, our personnel discussed the subjects to be addressed by our letter and received Mr. Liu's concurrence on the scope.
We believe we have provided the information agreed upon to resolve the outstanding issues and to dascribe the proposed program of future evaluations.
Mr. Liu has also stated subsequently that he has technical concerns regarding the Bechtel calculation for support AC-60lR-2-R38 transmitted by our letter; however, we have not received the details of these concerns.
Our sampling program for the IWA evaluations and calculation reviews we committed to is currently underway.
We trust that with the clarifications provided above your staff will concur with our program.
We request that any comments or requests for additional information and clarifications regarding our referenced letter be forwarded to us for formal response.
Very truly yours,
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Fay Vice President Nuclear Power Copies to NRC Resident Inspector NRC Document Control Desk l
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