ML16342B283
| ML16342B283 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 03/13/1987 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML16341E121 | List: |
| References | |
| TAC-51501, TAC-51502, TAC-64501, TAC-64502, NUDOCS 8703200027 | |
| Download: ML16342B283 (4) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION DIABLO CANYON NUCLEAR POWER PLANT, UNITS I AND 2 USE OF BRANCH TECHNICAL POSITION MEB 3-1 FOR POSTULATING PIPE BREAK LOCATIONS DOCKET NOS. 50-275 AND 50-323 In a letter dated April 8, 1986 (Reference I) the licensee requested approval to change the criterion for postulating pipe break locations based on stress level from that given in Regulatory Guide 1.46 (Reference
- 2) to the level recommended in Branch Technical Position MEB 3-1 (Reference 3).
Specifically,
'he current criterion for postulating pipe break locations in high energy lines at the Diablo Canyon Nuclear Power Plant, Units I and 2 is that breaks are postulated at all locations where the primary plus secondary stress exceeds 0.8 (S +S ).
S is the allowable stress at maximum temperature and S
is the allowaIIle stress range for expansion stresses as defined in ASME,Section III, Subarticles NC/ND 3611.2 (Reference 4).
Branch Technical Position MEB 3-1 allows a level of 0.8 (l.2Sh+S
) for primary plus secondary stresses before a
break is postulated.
The licensee'is requesting this change as a part of its ongoing snubber reduction program (References 5 and 6).
Use of the higher allowable stresses from Branch Technical Position MEB 3-1 will make this program more successful because fewer new break locations will have to be postulated when compared with the break locations resulting from use of the current criterion in Regulatory Guide 1.46.
This in turn could result in a reduction of the number of snubbers required.
The licensee has stated in the request that all other current pipe break criteria, for example, terminal ends and arbitrary intermediate breaks, will remain unchanged.
In addition, the Diablo Canyon FSAR Update will be revised to incorporate this change upon receipt of NRC approval.
The criteria in Regulatory Guide 1.46 was published in 1973 and was originally implemented by the staff only on piping inside containments.
Branch Technical Position MEB 3-1 was published in 1975 and was originally implemented on piping outside containments.
In 1976, the staff concluded that the criteria in MEB 3-1 are acceptable for piping inside and outside containments and began implementing this on a plant specific basis.
Most of the utilities with facilities which have been reviewed since 1976 have opted to use the criteria in MEB 3-1.
Therefore, the staff has concluded that the use of the criteria for postulating pipe break locations based on stress level in accordance with Branch Technical Position MEB 3-1 instead of Regulatory Guide 1.46 is acceptable.
Accordingly, the licensee's request in Reference I is approved.
The staff requires that this change be included in the next FSAR Update.
PRINCIPAL CONTRIBUTOR:.
H. Brammer (PAEB)
'8703200027 870313 PDR.,
ADOCK 05000275 P
4 e
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REFERENCES:
1.
Letter from J.
D. Shiffer (PG8E) to S.
A. Varga (HRC), "Snubber Reduction Program - Supolemental Information," dated April 8, 1986 (DCL 86-093).
2.
Regulatorv Guide 1.46, "Protection Against Pipe Mhip Inside Containment,"
Nay 1973.
3.
Standard Review Plan 3.6.2, Branch Technical Position MEB 3-1, "Postulated Break and Leakaae Locations in Fluid System Piping Inside and-Outside Containment," July 1981.
4.
ASNE Boiler and Pressure Vessel Code,Section III, "Nuclear Power Plant Components,"
Division 1, Subsection NC and ND, Subparagraphs NC/ND-3611.P, Stress Limits.
5.
Letter from J.
D. Shiffer (PGSE) to J.
B. Martin (HRC), "Diablo Canyon Unit 1 - Snubbers,"
dated May 16, 1984 (DCL 84-183).
6.
Letter from J.
D. Shiffer (PGAE) to S. A. Varga (NRC), "Diablo Canyon Units 1 and 2 - Snubber Reduction Program," dated January 16, 1986 (DCL 86-009).
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