ML20140B682
| ML20140B682 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/27/1985 |
| From: | Larson C NORTHERN STATES POWER CO. |
| To: | Harrison J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 8601270092 | |
| Download: ML20140B682 (2) | |
Text
Northern States Power Company 414 Nicoilet Mall Minneapoks. Mir,nesota 55401 Telephone (612) 330 5500 December 27, 1985
%t 4')
't' l
J J Harrison, Chief g!
4[
Engineering Branch LJ US Nuclear Regulatory Commission FILE Q -
Region III 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 October 18, 1985, concerning Inspection Reports No.
50-282/85015 (DRS) and 50-306/85012 (DRS), NSP committed to have Westinghouse conduct a review of the steam generator upper support (SGUS) snubber design specifications and design load calculations.
Westinghouse has completed their evaluation which compared pertinent design requirements originally specified for Prairie Island Unit I and 2 steam generator upper lateral support hydraulic snubbers to current Westinghouse criteria. This effort was acc<,mplished by a review of Pioneer Service and Engineering Company specification 287, Revision 3, and Westinghouse specification G-952835, Revision O.
Criteria which were deemed critical to plant safety by virtue of their effect on the structural integrity / function of the snubbers and reactor coolant loop were identified.
In general, the Pioneer specification was found to be comparable to the Westinghouse specification in the areas of quality assurance, non-destruc-tive examinatf.on and fabrication. Operational criteria (i.e., drag force and bleed rate), although inappropriately specified, are not a concern based upon a review of the 1972 McDowell Wellman test reports which indicate the units will not adversely restrain the reactor coolant loop.
However, additional investigation is being conducted in the areas of radiation environment, static snubber stiffness characteristics and control valve lock-up velocities as follows:
0601270092 051227 PDR ADOCK 050002G2 O
PDR MS I o t
W O/
e J J H:rrison, Chief December 27, 1985
- E" Northem States Power Company
- 1) The radiation level specified by Pioneer is lower than that generically required by Westinghouse. An in-plant survey in the vicinity of the SG upper support snubbers during normal plant operation showed the radiation levels slightly above Pioneer's specification, but 10 times below Westinghouse specifications.
Determination of the remaining useful life of the " soft" materials (i.e., seals) taken from snubbers which have been in service for 10 years (taken from Unit 2 snubbers) is planned for 1986. This data will be used to establish replacement intervals for this
" soft" material.
- 2) Snubber stiffness should be verified, and the values compared to the inputs used in the reactor coolant loop analysis.
It is our intention to measure snubber stiffness during the Unit I refueling outage scheduled for March, 1986.
- 3) The snubber lock-up velocity should be established to ensure actuation will occur during seismic conditions, but will not occur during plant thermal transients.
(A previous Westinghouse analysis for locked-up SGUS snubbers during plant cooldown shows that piping stresses, primary equipment nozzle loads, and equip-ment support stresses meet their respective allowables.) The control blocks on steam generator snubbers have been changed so that snubbers meet current Westinghouse specifications for lock-up velocity.
Westinghouse has also completed their review of the snubber design load calculation and has determined that the design load is approximately 3 percent higher than Pioneer's original value. This higher value is within the original design specification for the snubbers.
Elease contact us if you have any questions relating to the information we have provided.
a.
C E Larso \\- /
Vice President Nuclear Generation c: Regional Administrator-III, NRC NRC Resident Inspector G Charnoff