ML19210E848
| ML19210E848 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 11/14/1979 |
| From: | Groce R Maine Yankee |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-79-02, IEB-79-2, NUDOCS 7912130086 | |
| Download: ML19210E848 (3) | |
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O 617-3GG -0011 ENGIN EERif4G OF F10E WSTUORO, f.*ALSA CHL 3E T TS 01 M t
._ fra O B.4.1.1 KEY 79-132 tbvember 14, 1979 United States Nuclear Regulatory Commission Office of Inspection and Enforcement Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 Attention:
Mr. Boyce H. Grier, Director
References:
(a)
License Ib. DPR-36 (Docket tb. 50-309)
(b)
USNRC Letter to MYMC dated March 8,1979 I&E Bulletin 79-02 (c)
USNRC Intter to MYAR' dated June 21, 1979 I&E Bulletin 79-02, Pavision 1 (d) M'BUC Intter to USNRC dated July 5,1979 (e) M'iAPC Letter to USNRC dated October 11, 1979
Dear Sir:
Subject:
Second Suplemantary Response to I&E Bulletin 79-02, Pavisica 1 At the reauest of I&E we submit the following breakdown of expansion anchor bolts tested in various systems:
Table 1 System Number Tested Reactor Coolant 10 HPSI 3
Chemical Volu.n & Control 3
RHR 3
Seal H O System 2
2 Second Cmponent Cooling 27 Primary Component Cooling 12 Containment Spray 15 Totals 75 1543 117 ro1uso osc G
United States Nuclear Pegulatory Cc.nmission November 14, 1979 Attention:
Mr. Boyce H. Grier, Diredor Page 2 The folloving list identifies the total nu2er of anchor bolts we estimate exist at Maine Yankee:
a Table 2 FP Drawing Title Estimated Total Anchor Bolts Containment Annuluis Piping 209 Containment Spray Piping 81 Secondary Component Cooling Piping 118 Pressure Spray Safety & Quench Tank Piping 60 Residua.1 Heat Removal 112 Primary Component Cooling 475 Safety Injection Piping 37 Steam Generator Feedwater Piping 26 Chemical Volum Containmnt Piping 788
'Ibtal Anchor Bolts 1906 The sampling philosophy we followed in our test effort at Maine Yankee is the same one we used at both Vermont Yankee and Yankee Rowe.
This sampling plan was derived from evidence that failures are not related to the systems which the anchors are supporting, but are related to the lack of adherence to installation procedures by the individuals installing anchors.
Thus, failures tend to be more area related than system related.
Failures we found in other plants tended to occur in discrete areas.
If several systems were located in that area, each system would have anchor bolts exhibiting failures at about the same rate. We, therefore, looked for a statistical approach based on a large population of features without a known failure rate. The Poisson Methodology was selected, and to assure ourselves of its validity, we employed the services of a consultant knavledgeable in industrial statistics who independently verified the theory.
Application of the theory results in random sampling of anchor bolts in nuders larger than 60 out of a large total population.
If no failures are found sampling is complete and a 95% confidence of 5% or less defects is assured.
If failures are found, sampling continues to approximately 90.
Taelve failures in a sample of ninety requires 100% inspection.
One failure in ninety gives 95 % confidence of 5% or less defects. Defects nuntering between 1 and 12 require some additional decision to be made.
The important fact is that the random sample of 75 anchor bolts tested at Maine Yankee without failures affords better than a 95% confidence that 5% or less cbfective anchors exists in the remaining pog21ation.
1543 113
United States Nuclear Regulatory Ccanission November 14, 1979 Attention:
Mr. Boyce H. Grier, Director Page 3 We trust this provides you with sufficient information to fully describe our sampling program on expansion anchor bolts at bhine Yankee and its results.
If additional information is required, please contact us.
Very truly yours, MAINE YANKEE A'IQ4IC PGER CQ4PANY
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Robert H. Groce Senior Engineer - Licensing RIG /kaf 1543 114 a
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