ML20137V787
| ML20137V787 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 11/20/1985 |
| From: | Larson C NORTHERN STATES POWER CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 8512100083 | |
| Download: ML20137V787 (2) | |
Text
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i Northem States Power Compa, ny p
414 Nicollet Mall (gg
_l Minneapoks, Minnesota 55401 3
i Telephone (612) 330 5500 OS 7
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November 20, 1985 14 "
r!LQ J G Keppler, Administrator Region III U S Nuc1 car Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 In our letter of September 16, 1985 we committed to provide definitions of scope, objectives, and hardware for the proof of principle test on the snubber manifold system of the steam generator upper lateral supports.
The following information is provided in response to that commitment.
Objectives The objective of this tesc program is to provide additional assurances that the snubber manifolding configuration provides a system that ensures equal distribution of loads to each snubber. We believe the test will indicate, 1) that the manifold system will levelize the loads in the snubbers, even when the snubbers have varying lock up velocities, and 2) that af ter the bank has locked up, loads are equalized between the individual snubbers, even with different snubber bleed rates. This eliminates the potential for overloading of a snubber in the snubber bank.
Hardware The hardware will consist of four surrogate snubbers mounted in a single test rig.
The test rig will force all four snubbers to have the same movement during load testing.
Four interconnected valve blocks, identical to those installed at Prairie Island, will be mounted on each of the four surrogate snubbers. The spring tension of the main poppets will be varied to give a range of individual closure velocities for the tensile direction. The bleed ports on two adjacent valve blocks, one being an end of manifold valve block, will be instrumented for load.
The bank of snubbers will be instrumented for velocity and load as a group.
8512100083 Q N h e2 ADOCK PDR 1~ [O [ t 0 PDR P
MOV351985
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J G Keppler, Reg III
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November 20, 1985 "E"
Nodhem States Power Company Original plans called for the use of four valve blocks to be removed from Unit 2 during the recent outage. However, all eight valve blocks were reinstalled during the outage.
In2tcad, four valve blocks are being purchased from Bergen Paterson for this test program. These valves will be identical to those originally supplied by Bergen Paterson.
Bergen Paterson is presently determining the schedule for the manufacture of these valves. Depending on that schedule, the delivery of these valves may become the critical item for determining when the test can be performed.
Scope The scope of the test includes ramping the snubber bank to lock up in tension and compression. The velocity of the snubber bank will be increased in tension until all four snubbers have locked. The data will be evaluated to verify that, even with the individual snubber lock up velocities set differently, the snubbers resist load equally. The snubber bank will also be ramped up to lock up velocity in compression, and the load increased to attain an internal pressure of 8950 PSI in each snubber (the equivalent of 3600 kip load for the steam generator snubber bank). The bleed ports on two adjacent snubbers will be blocked, the load will be held constant and individual snubber load versus bleed rate versus time will be recorded.
This data will be evaluated to verify that the snubbers are not overloaded. Preliminary acceptance criteria is that all snubbers carry equal loads with a tolerance of +/- 10% of the average load per snubber or the minimum difference which can be read on the test setup, whichever is larger.
So as to avoid any delays in the test schedule we ask that you review the information provided and return any comments to us by the first week of December.
If you have any questions related to this information please call.
ws p~o n C E Larson Vice President Nuclear Generation c: NRR Project Manager, NRC Resident Inspector, NRC G Charnoff
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