ML20211G651
| ML20211G651 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 06/12/1986 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20211G657 | List: |
| References | |
| NUDOCS 8606200045 | |
| Download: ML20211G651 (3) | |
Text
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SAFETY EVALUATION REPORT RELATED TO REQUEST FOR RELIEF FROM INSERVICE PRESSURE TEST REQUIREMENTS NORTHERN STATES POWER COMPANY MONTICELLO NUCLEAR GENERATING PLANT DOCKET NO. 50-263 INTRODUCTION The Technical Specification for the Monticello Nuclear Generating Plant states that inservice examination of ASME B&PV Code Class 1, 2, and 3 components shall be performed in accordance with Section XI of the Code and appilcable addenda as required by 10 CFR 50.55(g) except where specific written relief has been granted by the Commission. The Examination Program for Unit 1 is based upon the requirea,ents of the 1980 Edition with the addenda:
through the Winter of 1980.
Certain requirements of this Edition and Addenda of Section XI are impractical to perform on older plants because of the plants' design, component geometry, materials of construction or the need for extensive temporary modifications and the resultant substantial radiation exposure to plant personnel.
By letter of May 6,1986, the Northern States Power Company (NSP) requested
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relief from the pressure test requirements of the Code after the replacement or repair and examination of certain sections of pipe in the Class 1 systems.
NSP provided additional-information and justification for the request in a letter dated May 23, 1986.
Requests For Relief Relief is requested from the pressure test requirements o.f IWA 4400 of Section:
XI of the ASME Code, 1980 Edition, Winter 1980 Addenda after repair or replacement of the following Class 1 items:
(a) Safe-end replacement in the Core Spray System (14 x 8 inch OD carbon steel safe-ends).
Also replace 8 inch OD stainless steel pipe with carbon steel pipe.
(b) Replace Control Rod Drive 4 inch stainless steel nozzle cap.
(c) Reroute 2 and 3 inch OD carbon steel Main Steam drain lines.
ASME Code ISI Class 1 Requirements Article IWA-4400 of the ASME Code specifies a 110% of operating pressure hydrostatic test to be performed following repairs by welding on the pressure,
retaining boundary.
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Basis For Relief Request i
Monticello has eight three stage Target Rock safety / relief valves installed on the main steam line.
Conducting the post-repair vessel hydrostatic at 110%
of operating pressure will require the removal of the safety relief valves, installation of covers, and removal of the covers (blind flanges) and The valves must be removed or gagged because replacement following the test.,is set at 1080 psig by the Technical the set point for relief / safety Specifications.
The only gagging device design and procedure available involves the bonnet cap removal, introduces the possibi,11ty of set pressure adjusting ring disruption.
The licensee states that it is neither desirable or prudent to introduce the possibility of setpoint error through the use of a gagging device.
From a review of past exposure history records removal of the safety / relief valves and the associated work required would result in an exposure of eight to ten personremtothestationpersolnnel.
Valve removal and replacement duld require approximately six days to accomplish, three of which will be on the outage critical path.
It will result in additional costs of roughly $600,000.
Licensee's Proposed Alternate Examinations Or Tests The licensee proposes to perform a hydrostatic test at 100% (1000 psig) of operating pressure in lieu of the Code required 110% (1100 psig) of operating pressure.
To supplement this hydrostatic test, the following non-destructive examination will be performed as follows:
(a) Core Spray System safe-end replacement: Visual (VT), penetrant (PT), radiographic (RT), and ultrasonic (UT) examination of butt welds and VT, PT or magnetic particle (MT) examination of socket welds.
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(b) Control Rod Drive Nozzle: VT, PT, RT and UT of weld.
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i (c) Main Steam Drain Lines: VT, PT or MT of socket welds.
EVALUATION The above repaired or replaced, piping cannot be hydrostatically tested to the ASME Code requirements without: removing or modifying the safety / relief valves. As required by the Technical Specifications three of eight three-stage Target Rock pressure relief / safety valves have an opening / closing
-set at 1072/972 pisg.
This is'below the Code required hydrostatic test pressure.
Removing the safety / relief valves would result in excessive
, radiation exposure to the maintenance staff. The staff agrees with the licensee that using an untested design device and procedure for gagging the valves would result in an unacceptable risk of set pressure ring disruption.
The alternati*ve examinations of VT, PT, MT, RT and UT proposed by the licensee are adequate to determine the structural integrity of the repaired and replaced piping and welds.
CONCLUSION Based on the above evaluation, the staff has determined that it is impractical to perform the hydrostatic test at the Code required pressure after the repair and replacement of the piping in the above cited systems. The staff finds that complying with required test pressure during this outage does not provide commensurate gain in the safety of the plant considering the burden that would be placed on the plant if the extra 100 pisg were imposed. The staff concludes that the alternative hydrostatic test plus the additional non-desttnctive examinations give reasonable assurance of the piping pressure boundary integrity.
The staff further concludes that granting relief, for this outage only, were Code requirements are impractical is authorized by law and will not endanger life or property, or the common defense and security and is otherwise in the public interest. Code reouired regular hydrostatic pressure test is reouired during this 10 year inspection interval. Granting relief is recomended.
Principal Contributer:
B. Turovlin i
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