ML20206G814
| ML20206G814 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 03/26/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20206G807 | List: |
| References | |
| NUDOCS 8704150164 | |
| Download: ML20206G814 (6) | |
Text
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- g UNITED STATES
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- j WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO REQUESTS FOR RELIEF FROM INSERVICE INSPECTION REQUIREMENTS SECONO TEN YEAR INSPECTION INTERVAL BOSTON EDISON COMPANY PILGRIM NUCLEAR POWER STATION DOCKET NO. 50-293
1.0 INTRODUCTION
Technical Specification 4.6.G for the Pilgrim Nuclear Power Station states that the inservice examination of ASME Code Class 1, 2, and 3 components (including supports) shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable addenda as required by 10 CFR 55a(g) except where specific written relief has been granted by the Commission. The plant was designed, and constructed in accordance with the code in effect on the date of the order of the components, consequently certg requirements of later editions and addenda of Section XI are impractical to perform because of the plant's design, component geometry, material of con-struction or the need for extensive temporary modifications and the resultant substantial exposure to plant personnel.
Regulation 10 CFR 55a(g)(6)(1) authorizes the Commission to grant relief from those requirements upon making the necessary findings. On August 13, 1985 tha NRC issued a Safety Evaluation (SE).
During the review of the ISI program and relief requests some areas were identified as in possible need of relief requests.
These possible additional relief requests were left as open items in the SE.
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A request for additional information (RAI) was forwarded to the licensee by letter dated January 6,1986 and by telephone conversation on August 1,1986 i
a request was made for clarification of certain items in the licensee's response of April 15, 1986. The ifcensee responded to the requests of January 6, 1986 by letter dated April 15, 1986 and to our request of August 1, I
1986 by letter of December 12, 1986 which contained a complete revision of
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the ISI program and revisions of PRR-1, 3, 4, 6, 8, 9 and 10.
This SE addresses only PRR8 and PRR9.
2.0 RELIEF REQUESTS l
i 2.1 Relief Request No. PRR-8 Rev. 1 Pressure Retaining Nozzle Welds In Vessels.
Category C-B Item C2.21 2.1.1 Code Requirement 1
Section XI ASME,B&PV Code, 1980 Edition through Winter 1986 Addenda requires a surface and volumetric examination of the nozzle-to-shell welds in each inspection interval.
2.1.2 Code Relief Request Request relief from the surface and volumetric examination of the four 16 inch diameter nozzles of the two RHR System heat exchangers. Only two of the nozzles are required to be examined.
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3 2.1.3 Proposed Alternate Examination A surface examination of the reinforcing plate welds to the nozzles and vessel will be conducted in lieu of the volumetric examinations of the nozzle to vessel weld required by IWC-2500-1, 2.1.4 Licensee's Basis For Requesting Relief There are two 16" diameter nozzles in the Class 2 portion of each of the two RHR System heat exchangers that are fabricated with reinforcement saddles.
These saddles are fillet welded over the actual pressure retaining nozzle-to-shell weld.
This type of fabrication precludes any type of volumetric or surface examination of the primary pressure retaining weld.
The design does however have additional strength at the joint and results in lower stresses at the internal weld.
2.1.5 Evaluation The welds required to be examined are completely covered by a reinforcing ring that prevents access and therefore any volumetic or surface examination as required by the ASME Code.
The ring or saddle is welded to the shell and to the nozzle with fillet welds.
The welds cannot be examined without removing the saddle or ring reinforcement by grinding out the filletwelds attaching the saddle to shell and nozzle.
This is impractical.
Visual examination for leakage during system pressure and hydrostatic tests required by the code will provide assurance that an adequate level of safety is maintained.
Later editions of the code require surface examinations of the welds on the reinforcing rings or saddles.
The Itcensee has committed to performing these extra examinations.
4 2.1.6 Conclusion Based of the above evaluation, the staff concludes, that for the welds discussed above the Code requirements are impractical.
It is further i
i concluded that the alternate examinations discussed above will provide the necessary added assurance of structural reliability.
Therefore, relief is granted, as requested, from performing volumetric and surface examinations of two saddle reinforced nozzle-to-vessel welds on each RHR System heat exchanger, provided that; (a) the proposed alternate surface examination is performed on the rein-forcing ring (saddle) welds that make the nozzle-to-vessel welds in-accessible.
J (b) Visual examination of the saddle welds for leakage is performed during periodic system pressure and hydrostatic tests in accordance with Subsection IWC-5000 requirements.
i 2.2 Relief Request No. PRR-9 Rev.1. Full Penetration Welds Of Nozzles In Vessels.
Category B-D. Items 83.90 And 83.100 i
2.2.1 code Requirement t
The nozzle-to-vessel weld and the nozzle inside radius section, including adjacent areas of the nozzle and vessel, of all reactor vessel nozzles shall be volumetrically examined in accordance with appitcable portion of Figure IWB-2500-7.
Item No. B3.90 requires that volumetric examination of each I
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5 nozzle-to-vessel weld be conducted.
Item B3.100 requires that a volumetric examination of nozzle inner radius section be conducted. These examinations are required to be completed each inspection period.
2.2.2 Code Relief Request I
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Relief is requested from the Code examination of 100% of required volume for 21 nozzle-to-vessel welds located within the biological shield wall.
Relief is requested from the above mentioned code requirements (Item B3.100) for nozzle N18.
2.2.3 Proposed Alternate Examination The reactor nozzle-to-vessel welds and the nozzle inner radius on Nozzle N1B will be volumetrically examined to the maximum extent practicable.
I 2.2.4 Licensee's Basis For Requestina Relief Relief is requested from the above mentioned code requirements (Item B3.90) on the basis that 100% accessibility is not permitted due to the reactor vessel i
insulation / biological shield configuration. Accessibility for the examination of all nozzle-to-vessel welds was not provided for in the original plant design which occurred prior to the issuance of ASME B&PV Code,Section XI requirements.
Relief is requested from the above mentioned code requirements (Item B3.100) for nozzle N1B due to a thermocouple pad which is installed on the nozzle in the area of the required examination.
The pad interferes with examination of a portion of the nozzle inner radius section.
6 2.2.5 Evaluation j
The licensee estimates that for 14 of the 21 nozzle welds affected by accessibility limitations, between 69.08% and 72.73% of the composite required volume has been and will be examined.
In addition the pressure retaining boundary in the vessel is required to be visually examined during i
periodic system leakage tests and hydrostatic tests required under Category l
l 8-P.
The historical record of examinations for the remaining 7 nozzles did I
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not provide sufficient detail to calculate the percentage of the code required volume which was examined.
2.2.6 Conclusion Based on the above evaluation, it is concluded that for the nozzle inside radius section of Nozzle N18 and the 21 nozzle welds discussed above, j
adherence to the Code requirements is impractical.
It is further concluded that the proposed alternate examinations will provide reasonable assurance of
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the structural integrity of the nozzles.
Therefore, relief is granted as requested provided:
l (a) the volumetric examinations are performed to the maximum extent possible; and I
I (b) the Code required system pressure tests are performed in accordance I
with IWB-5000, j
Principal Contributor:
B. Turovlin Dated: March 26, 1987 2
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