ML20116J734
| ML20116J734 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 11/09/1992 |
| From: | Parker T NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-89-08, GL-89-8, NUDOCS 9211160328 | |
| Download: ML20116J734 (2) | |
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t Northem States Power Company 414 Nicodet Mall Minneapoks. Minnesota tS4011927 Telephone (612) 3345500 November 9, "692 Generic letter 89 08 U S Nuclear Regulatory Commission Attn:
Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLFJJ: GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Update of Response to Generic Letter 89-08 Erosion / Corrosion - Ir.duced Pipe Wall Thinning The purpose of this letter is to update our July 24, 1989 response to G< aeric Letter 89-08, " Erosion / Corrosion - Induced Pipe Wall Thinning", for Prairie Island.
In the July 24, 1989 response to Generic Letter 89-08, we described a number of engineering activities that were underway to mitigate the effects of erosion / corrosion. One of those activities was the aplacement of carbon steel (A-106) oxtraction piping with stainless steel piping.
Following the submittal of the July 24, 1989 response, several materials and methods for replacement of che extraction piping were further evaluated.
It was concluded that A-335 chrome moly steel would be a preferred material for use in replacement of the carbon steel extraction piping.
The decision to use chrome moly steel instead of stainless steel was based on the larger coefficient of expansion for stainless steel and the long suns af piping involved in the replacement effort. Use of stainless steel would have invalved the addition of a new expansion loop and the re-engineering of the piping and the piping supports.
The coefficient of expansion for the A-335 chrome moly steel is similar to the original A-106 carbon steel and would therefore would simplify and reduce the cost of the replaceuent effort.
With respect to the resistance to erosion / corrosion, it is expected that A-335 chrome moly steel will provide protection equivalent to atainless steel.
A portion of the Unit 2 extraction piping was replaced with chrome moly steel during the last Unit 2 refueling outage. Additional extraction piping on both Units 1 and 2 is being replaced during the current dual unit outage.
It is expected that the majority of the carbon steel extraction piping will be replaced by the end of the current outage. Howe 3r, if all of the extraction piping cannot be replaced during this outage, due to schedule constraints, the replacement of the remaining carbon steel extraction piping will be carried over to future outages.
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Noveinber 4, 1992 Pago 2 Please contact us if you have any questions with regard to our respon.e to Generic Letter 89-08.
[ iomas Parker Manager Nuclear Support Services c: Regional Adtninistrator - Region III, NRC Senior Resident Inspector, NRC NRR Project Manager, NRC J E Silberg s
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