ML20033B180
| ML20033B180 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/06/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20033B178 | List: |
| References | |
| NUDOCS 8111300519 | |
| Download: ML20033B180 (2) | |
Text
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NUCLEAR REGULATORY C0.'.1 MISSION 3
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WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAL' REACTOR REGULATION acn 3_ p _ -
MILLSTONE NUCLEAR POWER STATION, UNIT NO. 1 3
ISOLATION CONDENSER SUPPLY LINE 1
WATER HAMMER INCIDENT
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(REVISION I)
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DOCKET NO. 50-245
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- 1. 0' INTRODUCTION On December 19, 1979, a water hammer incident in the isolation condenser system piping resulted in minor concrete damage at containment penetration anchor X-10A. Also, some expansion anchor bolts at other supports of the isolation condenser piping system were pulled slightly out of the concrete by tiie water hammer loads.
In response to a letter from the Director of the Office of IE-Region I, dated January 14,1980 (Ref.1), the licensee provided information regarding the water hammer events in the steam line between the reactor.
vessel and the isolation condenser and the subsequent damage assessments, evaluations including piping and support stress analyses and repairs. The licensee responses are, identified as references 2 throdgh 7.
We reviewed these licensee responses and transnitted the Safety Evaluation Report to NNEC0 by NRC letter date of June 3,1981 (Ref. 8). Based on the mo'st recent information provided by NNECO (Ref. 9), we have revised nur con-clusions in accordance with the following evaluation.
2.0 EVALUATION The fluid forces due to water hamner in the isolation condenser supply and return line were developed by the licensee. The pipe stresses and support /
anchor ' reactions were computed from the water-hammer fluid loads using the ADLPIPE computer code.
In order to maintain the piping stresses for water-hammer loadings within the acceptable limits outlined in the Millstone Nuclear Power Station Unit 1 FSAR, Section 12.0, " Structural Design", some additional pipe restraints were required. The licensee completed the required design and installation of these additional restraints prior to 1
resuming plant operation following the extended refueling outage (10-4-80 to 6-1 7-81 ).
In addition, the licensee has redesigned and repaired the con-tainment penetration anchor X-10A at elevation 80'-9".
8111300519 811106 PDR ADOCK 05000245 p
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,..The isolation condenser piping, pipe restraints and containment penetration
(( anchor X-10A were' all. redesigned for the following loading conditions:
1.
Normal Operating Loads + DBE 2.
Normal Operating Loads + HEPB 3.
Normal Operating; Loads + Water Hammer
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3;.
l where Normal Operating Loads = PRESSURE + DEAD WEIGHT + THERMAL
. 7--
HEPB = High Energy Pipe Break Load of the steam' supply line to the
.m,
~ isolation condenser at the specified location postulated in the licensee's analysis.
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3.0, CONCLUSION.
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W6 have concluded ttiat the~above loading combinationsare acceptable and there is reasonable. assurance that the Millstone Unit 1 isolation con-denser supply line will withstand the effect of water-hammer loads.
However one design. area.does not comply with NRC I&E Bulletin. 79-02
'which requires a factor of safety.of at least four for expansion anchor
' bolts under all design conditions. A factor of two instead of' four was
'calcualted for load condition 2 above. The licensee has stated (Ref. 9) that the original pipe break loads utilized in the design of containment penet. ration anchor X-10A were calculated conservatively and consistent with the technology of the time.
The licensee expects that a new more rigorous mechanistic evaluation of discrete pipe break location consistent with current technology will result in a safety factor of at least 4 We concur that t_his reevaluation should be completed as soon as practical to confirm the adequacy of safety margins. The results of the analytical evaluation of the containment penetration anchor X-10A should be submitted to NRC as soon as they are available.
4.0 REFERENCES
l.
B. H. Grier letter to Northeast Nuclear Energy Company',
dated January 14, 1980.
- 2.. W. G. Counsil letter to B. H.' Grier, dated March 31, 1980.
3.
.W. G. Counsil letter to B. H. Grier, dated April 7,1980.
- 4. 'W. G. Counsil letter to B. H. Grier, dated May 8, 1980.
5.
W. G. Counsil letter to B. H. Grier, dated July 31, 1980.
6.
W. G. Counsil letter to B. H. Grier, dated October 31, 1980.
7.
W. G. Counsil letter to B. H. Grier, dated February 26, 1981.
8.
D. M. Crutchfield letter to W. G. Counsil, dated June 3,1981.
9.
W. G Counsil letter to D. Crutchfield, dated June 12, 1981.
Dated:
November 6,1981
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