ML20211P390

SER Supporting Util 860825 Request for Rev to Relief Request I-00007 Seeking Relief from Surface Exam for Welds within Flued Heads & Guard Pipes

ML20211P390
Person / Time
Site:	Grand Gulf
Issue date:	12/12/1986
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20211P385	List: ML20211P378 ML20211P390
References
TAC-62277, NUDOCS 8612190066
Download: ML20211P390 (6)

Text

. s p2 rahq kg UNITED STATES NUCLEAR REGULATORY COMMISSION

, 5 '; E WASHINGTON, D. C. 20555

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ENCLOSURE 1 SAFETY EVALUATION REPORT BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO A REQUEST FOR RELIEF FROM CERTAIN INSERVICE INSPECTION REQUIREMENTS MISSISSIPPI POWER AND LIGHT COMPANY GRAND GULF NUCLEAR STATION UNIT 1 l

l INTRODUCTION The Technical Specification for the Grand GJ1f Nuclear Station Unit 1 (GGNS-1) states that inservice examination of ASME Code Class 1, 2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and cpplicable Addenda as required by 10 CFR 50.55a(g) except where specific written relief has been granted by the Convuission. Some plants were designed in conformance to early editions of this Code Section, consequently certain requirements of later editions and addenda of Section XI are impractical to perform because of the plants' design, component geometry, and materials of construction. Regulation 10 CFR 50.55a(g)(6)(1) authorizes the Commission to grant relief from those requirements upon making the necessary findings.

By letter dated July 22, 1986, the NRC staff transmitted its Safety Evaluation l

Report (SER) in regard to the licensee's Inservice Inspection Plan for the first 10-year interval and relief requests from certain inspection requirements.

In that SER we had concluded that some of the relief requests should be granted and some conditionally granted. With respect to Relief Request No. I-00007, the staff granted relief provided that the Code-required surface examination was perfomed.

By letter dated August 25, 1986, Mississippi Power and Light Company (MP&L)

I submitted a revision to Relief Request No. I-00007 requesting relief from surface examination for welds within the flued heads and guard pipes which MP&L had determined to be impractical to perform at Grand Gulf Nuclear Station Unit 1.

EVALUATION The staff's evaluation of the revised Relief Request No. I-0007 is given herein, using the same format as that used in its previous SER (staff letter dated July 22, 1986, Attachment 2, pages 26-30).

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Relief Request No. I-00007, Piping Welds Within Guard Pipes, Category B-J, Items B9.11 and 89.21. (Revised August 25, 1986)

Components ASME Section III Class 1 pressure retainino circumferential welds located in FeedwaterLoopsAandB(B21),MainSteam(B21),MainSteamDrain(B21),

Reactor Core Isolation Cooling (E51), Residual Heat Removal (E12) and Reactor Water Clean-up (G33) piping. These welds are located on system piping inside guard pipes, which extend beyond the containment. The applicable welds are listed on Table 1.

Code Requirement Circumferential Welds Item B9.11. For circumferential welds in pipe of nominal pipe size 4 inch and greater, surface plus volumetric examination shall be performed in accordance with Figure IWB-2500-8 over essentially 100%

of the weld length during each inspection interval. The examinations shall include the following:

(a) All terminal ends in each pipe or branch run connected to vessels.

(b) All terminal ends and joints in each pipe or branch run connected to other components where the stress levels exceed the following limits under loads associated with specific seismic events and operational conditions.

(1) primary plus secondary stress intensity of 2.4Sm for ferritic steel and austenitic steel, and (2) cumulative usage factor U of 0.4.

(c) All dissimilar metal welds between combinations of (1) carbon or low alloy steels to high alloy steels, (2) carbon or low alloy steels to high nickel alloys, and (3) high alloy steels to high nickel alloys.

(d) Additional piping welds so that the total equals 25% of the circumferential joints in the reactor coolant piping system. This total does not include welds excluded by IWB-1220. These additional welds may be located in one loop (one loop is currently defined for BWR plants in the 1977 Edition).

> Circumferential Welds. Item B9.21.

For circumferential welds in pipe of nominal pipe size less than 4 inches, surface examinations shall be performed in accordance with Figure IWB-2500-8 over essentially 100% of the weld length during each inspection interval. The examinations shali include the following:

(a) All terminal ends in cach pipe or branch run connected to vessels.

(b) All terminal ends and joints in each pipe or branch run connected to other components where the stress levels exceed the following limits under loads associated with specific seismic events and operational conditions.

(1) primary plus secondary stress intensity of 2.4Sm for ferritic steel and austenitic steel, and (2) cumulative usage factor U of 0.4.

(c) All dissimilar metal welds between combinations of (1) carbon or low alloy steels to high alloy steeh, (2) carbon or low alloy steels to high nickel alloys, and (3) high alloys steels to high nickel alloys.

(d) Additional piping welds so that the total equals 25% of the circumferential joints in the reactor coolant piping system. This total does not include welds excluded by IWB-1220. These additional welds may be located in one loop (one loop is currently defined for BWR plants in the 1977 Edition).

Code Relief Request Relief is requested to permit ultrasonic and surface examination of only the accessible areas of the welds, for the piping welds listed in Table 1.

Proposed Alternative Examination The length of each weld accessible through the 4" x 6" access ports will be ultrasonically and surface examined in accordance with ASME Section XI, Table IWB-2500-1. Examination Category B-J. Should signs of weld deterioration or discrepancies be noted during regular inspections, evaluation of the conditions will be made. The percentage of each weld examined will be recorded during the inservice examination.

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i Table 1 i

REQUEST FOR RELIEF NO. I-00007 i

i Item System Weld Ib. ISO Ih. Pipe Component Limi ted Type Class Reason for 1

No. h. Size Area Scan Limita tions 1 821 G12-C1-A MS-11-9 28" Pipe to Pipe 53% T 1 Guard Pipe 2 821 G12-Al-A MS-11-3 28" Pipe to Pipe 53%- T 1 Guard Pipe 3 8 21 G12-DI-A MS-11-12 28" Pipe to Pipe 53% T 1 Guard Pipe 4 821 G12-81-A NS-11-6 28" Pipe to Pipe 53% T 1 Guard Pipe 5 821 W2 FW-11-1 24" Pipe to Pipe 50% T 1 Gaard Pipe

! 6 821 W18 Fil-11-7 24" Pipe to Pipe 50% T 1 Guard Pipe

! 7 821 W9 SD-11-2 3" Pipe to Pipe 50% T 1 Cuard Pipe ,

8 E12 W47 All-11-1 20" Pipe to Pipe 50% T 1 Guard Pipe 9 ESI W12 RI-8-9 6" Pipe to Pipe 50% T 1 Cuard Pipe l 10 E51 W7 RI-11-3 10" Pipe to Pipe 50% T 1 Guard Pipe 1

11 E51 W18 CU-11-3 6" Pipe to Pipe 50% T' 1 Guard Pipe I

e i

o Licensee's Basis for Requesting Relief The circumferential welds joining the flued head and the process pipe are encapsuled by the portion of the guard pipe which protrudes beyond the l containment. To comply with the inservice inspection requirements of ASME i Section XI, two 4 x 6 inch elliptical access ports spaced 180 degrees apart are provided for access to the welds. After fabrication and installation of the process pipe, guard pipe and the flued head, it was determined that the entire length of the weld is not accessible through the two access ports.

Approximately 50% of the weld is accessible for inservice inspection.

Exemption is requested for the inservice inspection of inaccessible portions of welds located inside guard pipes for the following reasons:

1. All but two of these lines were designed to high energy pipe break criteria. The exceptions are Q1E12G012W47 and Q1E51G001W12 which are classified as moderate energy pipes.

2. These welds were designed and fabricated in accordance with ASME Section III, Class I requirements and were examined by radiographic and liquid penetrant techniques.

3. These welds have satisfactorily passed both liquid penetrant and ultrasonic examination in accordance with ASME Section XI, Class 1 requirements.

4. Class 1 isolation valves in the process pipe on both sides of the quard l

pipes are capable of completely isolating each pipe in the event of a pipe failure.

5. The guard pipes have been designed and constructed in accordance with ASME Section III, Class 2 requirements and were hydrostatically tested in accordance with ASME Section III, Class 2 requirements.

6. The guard pipes are open to the drywell environment; thus, any leakage due to weld failure will t,e contained within the drywell. The guard pipes will prevent any leakage from escaping to the Containment Building.

7. The process pipes inside the guard pipes were hydrostatically tested in accordance with ASME Section III, Class I requirements.

8. The process piping inside each guard pipe assembly will be subject to periodic pressure tests in accordance with ASME Section XI, Table IWB-2500-1, Category B-P, requirements.

Evaluation The welds for which relief is requested are circumferential welds encapsulated in guard pipes which protrude beyond the containment wall. Two 4 x 6 inch elliptical access ports spaced 180 apart were provided in the guard pipes to perinit examination of the circumferential welds. However, with currently available ultrasonic equipment, only about 50% of the length of each weld can be volumetrically examined through the access ports. Surface exami-nation is equally restricted so that only 50% of the weld can be examined.

The process piping for which relief is requested was designed to ASME Section III, and the circumferential welds were radiographed and liquid penetrant checked during construction. The sections of process piping within the guard pipes can be completely isolated by Class 1 valves on both sides of the guard pipes. The guard pipes are hydrostatically tested Class 2 piping designed to divert any leakage from the process pipes to the drywell. j The circumferential welds in the process pipe will be volumetrically and surface examined over about 50% of the weld length in accordance with Section XI.

In addition, the process pipe weld inside the guard pipe will be visually examined during system pressure tests. ,

Conclusions and Recomendations Based on the above evaluation, it is concluded that for the welds discussed above, adherence to the Code requirements is impractical. To perform the code required examinations, the containment penetrations, including the guard pipe and the process pipe, would have to be removed, redesigned, refrabricated and reinstalled. It is further concluded that the proposed examinations will provide necessary assurance of structural reliability during this interval. Therefore, relief is recommended as .

requested.

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CONCLUSION  ;

l Based on its review of revised Relief Request No. I-00007, the staff concludes  ;

, that relief granted from the examination and testing requirements and alternate methods imposed through this SER give reasonable assurance of maintaining the l piping pressure boundary integrity. The staff has determined that the Code requirements are impractical and, pursuant to 10 CFR 50.55a(g)(6)(1), the i

granting of the requested relief is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the l public interest considering the burden that could result if the requirements were imposed on the facility.

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