ML20205E861
| ML20205E861 | |
| Person / Time | |
|---|---|
| Issue date: | 10/16/1985 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| Shared Package | |
| ML20204J261 | List: |
| References | |
| FOIA-87-714, REF-GTECI-A-43, REF-GTECI-ES, TASK-A-43, TASK-OR NUDOCS 8510250500 | |
| Download: ML20205E861 (3) | |
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@,) vL HEMORANDUM FOR: William J. Oircks Executive Director for Operations FROM: Harold R. Denton, Director Office of Nuclear Reactor Regulation
SUBJECT:
RESOLUTION OF USI A-43 (REF. CRGR MEETING NUMBER 80) s We have reviewed the minutes of CRGR Meeting Number 80 dated September 13, 1985, dealing with USI A-43 and are in agreement with all of their recommended changes which are listed on page 2 of Enclosure 3 to their minutes. In accordance with those recommendations the regulatory analysis sumary section has been augmented to recognize the more recent work on fracture-mechanics resulting in lower estimates of pipe-break frequency. Also the implementation language in RG 1.82, Revision 1, SRP Section 6.2.2, Revision 4 and the generic letter has been revised to clearly reflect our intent to only forward-fit and to treat any plant-specific actions identified in the future as backfits pursuant to 10 CFR 50.109.
Drafts of the revised documents have been reviewed with T. Cox and ELD staff.
Enclosure 1 contains the individual CRGR comerts on recomended changes and the resulting NRR changes. We are therefore ptoceeding with preparation of a Comission Paper, associated letters and natifications needed to conclude technical resolution of USI A-43.
o db f) tor Office of Nuclear Reactor Regul3 tion
Enclosure:
As Stated Above a cc w/ encl:
R. Hernan, NRR T. Cox, CRGR W. Shields, ELD E. Jackel, ELO W. Campbell, RES tVLStello;;EPROGR!h
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ENCLOSURE 1 CRGR COMMENTS AND NRR CHANGES (Ref. CRGR Meeting No. 80, Enclosure 3)
CRGR Corment No.1:
The more recent work on fracture-mechanics resulting in lower estimates of pipe-break frequency should be explicitly recognized and re! "ced in the sumary section of the regulatory analysis.
Response: '
The following paragraph has been added to the consequence analysis section of b the main report body:
"The A-43 pipe break probabilities were calculated from a 1977 data base that included piping failures of all types known at that time, including i
. materials not used in nucitar plant piping (see Appendix C). The estimate l,.
probabilities were 3 x 10-0/Rx yr for large pipes Q 28 inches) to 3 x 10 g/ '
Rx yr for small pipes (2 to 6 inches). The more recent experimental and analytical work, which is based on mechanistic fracture mechanics, results in probabilities of the rupture of large-size ductile piping (unaffected by IGSCC) significantly lower (better by several decades in magnitude) than ;
those employed in the A-43 analyses. Therefore, if pipe failure .
probabilities are extremely low--because of such considerations as leak-before-break, etc.--these calculations would result in very low estimated releases, and backfits would not be supportable on the basis of value/ impact criteria."
CRGR Coment No. 2: ,
Implemcntation wording in the Regulatory Guide and SRP section should be modified to clearly show that the NRC staff use of the new review material l
will be forward-fit only. 3
Response
The implementation wording in R.G. 1.82, Revision 1 and SRP Section 6.2.2 Revtsion 4 has been changed to read as follows:
c "methods desceibed in this guide will be used by the NRC staff in its' evaluation of all:
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- 1) construction permit applications and applications for preliminary l design approval that are docketed af ter -
4
- 2) applications for final design approval, for standardized designs which are intended for referencing in future construction Demit applications, that have not received approval by ;
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- 3) applications for licenses to manufacture that are docketed after i
_ Six (6 months after issuance of the Regulatory Guide)
CRGR Conment No. 3:
The generic letter should clearly state that NRC application of the new guidance to an operating plant, particularly with respect to NRC staff reviews of licensee 10 CFR 50.59 reviews, will be treated by the NRC staff as a e plant-specific backfit action pursuant to 10 CFR 50.109. ;
Response
The generic letter has been modified as follows: .
"Although the staff has concluded that no new requirements need be imposed on licensees and construction permit holders as a result of our concluding analyses dealing with the resolution of USI A-43, we do recommend that RG 1.82, Revision 1 be used as guidance for the conduct of 10 CFR 50.59 reviews i' dealing with the changeout and/or modification of thermal insulation installed '
on primary coolant system piping and components. RG 1.82, Revision 1 provides guidance for estimating potential debris blockage effects. If, as a result '
of NRC staff review of licensee actions associated with the changeout or modification of thermal insulation, the staff decides that Standard Review Plan Section 6.2.2, Revision 4 and/or RG 1.82, Revision 1 should be (or should have been) applied to the rework by the licensee, and the staff seeks to
, impose these criteria, then the NRC will treat such an action as a plant-specific backfit pursuant to 10 CFR 50.109."
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