ML20117C662
| ML20117C662 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Hatch |
| Issue date: | 07/11/1984 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20114F930 | List:
|
| References | |
| FOIA-84-616 NUDOCS 8505090484 | |
| Download: ML20117C662 (3) | |
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Safety Evaluation for Operation With
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Missing Pipe Restraints for High Energy Lines Outside Containment Hatch Unit 2 Introduction On June,23, 1983, the Georgia Power Company report by Licensee Event Report 50-336/263-46 that eight pipe whip restraints were missing in the Edwin I.
Hatch Nuclear Plant Unit 2.
S more comprehensive discussion of the circumstances of the event, and the justification for' plant operation in the present plant configuration were submitted on June 28, 1983.
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Descript1on Eight pipe whip restraints were discovered to be missing from installation during a review of postulated break locations and mitigation protection in the main steam pipe chase. The need for these restraints was identified in the Hatch 2 FSAR Sections 15A and 15A-A, but their existence was not indicated in the engineering drawings. -The individual locations, system working conditions and the nearest break location stress condition are listed as follows:
No. of Pipe Break Locat.
Restraints System Size Schedule Material Tem).
Pressure Stress
- TU7 (PSI)"
1 RCIC 4"
120 CS 546 1000 53.6 1
RWCU 6"
80 SS 532 1191/1030 30.9 1
RWCU 4"
80 SS 532 1191/1030 31.6 3
CRD 3"
80 CS 150 1029 NA 2
AS 10" 40 CS 450 175 89.8,60.6 SS= stainless steel CS= carbon steel
- in percentage of the stress at which NRC Standard Review Plan, Section 3.G.2 requires a break to be postulated.
The restraints in the RCIC and the RWCU Systems were required to protect the containment outboard isolation valves from postulated breaks downstream of those valves. The restraints in the CRD System were required to protect cable
-trays.
The Auxiliary Steam System supplies steam to the reactor building for heating purposes.
The need of restraints for the AS system was not described in the FSAR, although three of them were shown in Fig.15A-29. All missing restraints are located ou.tside of the containment, and are at intermediate break locations in those systems.
In a letter from L. T. Gucova to NRC, Region II dated June 28, 1983 and in subsequent discussions with the licensee, Georgia Power Company proposed the following action.
850509o4s4 841002 NFI
-616 PDR
Short-Term Plan 1.
Proceed expeditiously on design and procurement of the missing RWCU and RCIC restraints. During operation these locations are in inaccessible areas of the plant.
2.
Proceed expeditiously to postulate pipe break locations, design and procure whip restraints for the rerouted CRD return line to the Reactor Water Cleanup System.
3.
Isolate the auxiliary steam line in the reactor building so that no failures need be postulated while this line is isolated.
4.
Prior to start-up, perform a volumetric examination of several austenitic welds at the RWCU break location to insure that the welds are free of unacceptable indications.
Long-Term Plan In accordance with the intent of the FSAR and the requirements to maintain isolation capabilities, the design of pipe whip restraints for the RCIC steam, RWCU pump suction / discharge and the CRD return line is in progress.
The design considers the use of energy absorbing material and/or wire ropes to mechanistically address the dynamic effects of the pipe break. The analysis follows the Bechtel Topical Report, BN-TOP-2 in conjunction with the FSAR design criteria. The installation of all restraints will be tompleted at the first shutdown of sufficient duration or at the latest by December 31, 1983.
Evaluation 1.
The auxiliary steam system originally was classified as a moderate energy line in accordance with the guidance provided by the December 1972 Giambusso letter.
FSAR Section 15.A.A. subsequently reclassified it as a high energy line operating for less than 1% of the plant operating time. This line supplies heating steam to the reactor building and has no safety related function.
Isolation of this line in the reactor building as proposed by the licensee will remove the steam
-loads from this line.
2.
The postulated break locations near the missing restraint locations in the RCIC and the RWCU systems all have stress levels well below the SRP
.3.2.2 criterion. The RCIC system lines are made of ferritic material and therefore not susceptible to IGSCC found in sensitized austenitic material in BWR plants. Thus, plus the fact that both systems are c
l equipped with numerous leak detectors indicate that an early warning of system leak will alert operators before a break could occur.
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3.
The RWCU lines are made of austenitic material. However,the licensee
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will volumetrically examine welds in the break location to determine that they are free of unacceptable indications for the short term period of operation.
4.
Pipe whip restraints for Hatch-2 are not used in any way for normal (non-accidentoperation).
Conclusion Based on the above evaluation, we have concluded that Hatch 2 may be safely operated without the missing restraints until the long-tenn plan has been implemented.
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