ML20076J243

Forwards Safety & Licensing Portion of Westinghouse Apr 1982 Rept,Providing Addl Info Re Fuel Assembly Failure Effect on Insertion of Control Rods or Core Cooling Geometry

ML20076J243
Person / Time
Site:	Prairie Island
Issue date:	06/07/1983
From:	Musolf D NORTHERN STATES POWER CO.
To:	Office of Nuclear Reactor Regulation
References
TAC-49353, NUDOCS 8306200390
Download: ML20076J243 (2)

Text

W m Northem States Power Company 414 Nicollet Mall Minneapoks, Minnesota 55401 Telephone (612) 330-5500 June 7, 1983 Director Office of Nuclear Reactor Regulation U S Nuclear Regulatory Commission Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Transmittal of Additional Information Related to Fuel Assembly Failure Effect on Insertion of Control Rods or Core Cooling Geometry The purpose of this letter is to transmit for the information of the NRC Staff the Safety and Licensing portion of a Westinghouse report entitled,

" Technical Update of Investigation into Separation of Top Nozzle from Prairie Island Fuel Assembly D-34", issued in April 1982. The report is designated as proprietary class 2 by Westinghouse. The portion included with this letter has been reviewed and reclassified as non-proprietary.

The report indicates that the control rods would still insert and a coolable geometry would be maintained even if the failure occurred while the fuel element was in the core.

un David Musolf Manager - Nuclear Suppo Services DMM/SAF/j s cc: Regional Administrator-III NRR Project Manger, NRC Resident Inspector, NRC G Charnoff

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8306200390 830607 PDR ADOCK 05000282 P PDR

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Safety and Licensing

- 3 Operational and handling concerns with the use of sensitizeq Type 304 stainless steel as a sleeve material have been generically assessed as a safety and licensing issue for all plants. Specifically, cracked bulge joints have been analyzed and detennined not to affect the ability to insert control rods on the basis of the following:

1. Zircaloy thimble tubes remain engaged within the sleeve portion of the top nozzle.

2. Fuel rods maintain grid position and alignment.

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3. Core pins remain engaged within the top nozzle.

4. Holddown springs maintain axial positions.

5. Grids of adjacent fuel assemblies which contain thimble plugs provide additional lateral support.

Assessment of loose parts / debris indicates that each portion remains firmly attached to either the grid or nozzle and that-each is held on the thimble tube by the presence of the grid and nozzle. Any postulated grains of material freed by intergranular corrosion woul'd be too small to affect rod insertion. It is concluded from the above that the inser-tion of control rods is not affected.

Similarly, the ability to maintain coolable geometry in the event of cracked bulge joints has been addressed generically in licensing . It was concluded that coolable geometry was not affected on the basis of:

! 1. No increase in physical deformation caused by postulated events.

2. Lateral loads at sleeve failure can be carried by Zircaloy thimble tubes acting alone, so that alignment is maintained, with no flow blockage.

3. Grid impact loads are absorned primarily by center grids.

4. Postulated loose debris is not significant to affect coolable geometry.

The safety consequence of a dropoed fuel assembly curing handling has b'een adoressed in Safety Analysis Reports and accepteo oy the fluclear Regulatory Commission.