ML023580127

FENOC Meeting Handouts for Meetings with Individual Commissioners Regarding Davis-Besse Nuclear Power Station Reactor Pressure Vessel Head Issues

ML023580127
Person / Time
Site:	Davis Besse
Issue date:	04/07/2002
From:	FirstEnergy Nuclear Operating Co
To:	Office of Nuclear Reactor Regulation
References
Download: ML023580127 (10)

Text

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• Degradation of CRDM Nozzle and Other Vessel Closure 4/00 llead Penetrations" 12RFO video 1/93 9/RQ B& W issues "Safetv and visual Eialuation for 4/96 intspection of NRC audit of DI B& W Design Reactor IORFO visual 4/98 head boric acid corrosion inspection II RFO visual control program Vesselflead CRDM Nozzle of head inspection of per GL 89-05 I Cracking" head T

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DB provides NRC letter NRC Information Notice ACRS subcommittee 2/27/02 w'ilh commitments on operation D notifies 2002-11 on "Recent Experience wilh DB oii 2 NRC of first until 13 RFU on Feb 16, 2002 indtion with Degradation of Reactor head degradation offir irndication of pressure !!

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"* Visual inspections since 1988

"* Commitment to start refueling outage early

"* Compensatory measures until start of refueling outage

"* Most comprehensive inspection of reactor head in industry to date

- Hairline axial cracks found in 5 nozzles

"* Formation of FENOC Investigation Team

" Complete weld repairs on 3 nozzles 11'!

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Addressing the Problem

"* Special team formed to investigate root cause includes Framatome, EPRI, INPO, Oconee, MRP and other industry, experts

"* Team to create, repair plan

"* Safety Assessment submitted to NRC April 8 Plant operated safely during this condition

"* Repair plan to be submitted during April

"* Contingency plan available w New head previously ordered for i

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!qW qW TV Tw imp %WIVIV(1p MMUp (11 ry M(W (Wry ry! ry ry -tv q, 1 ry rv rv r; rj ry r; r1l ril FENOC Root Cause Summary

"* Probable Cause Through wall cracking of CRDM nozzle, resulting in boric acid corrosion of Reactor Pressure Vessel (RPV) head low-alloy steel.

"* Contributing Causes Failure to clean boric acid from RPV head Design of RPV service structure limited access for cleaning and inspections {)

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Deferral of modification to install portals to service structure to allow cleanings and inspections ,

- Deferral of head cleaning and inspecti,

FENOC Root Cause Summary (continued)

• Causal Factors Acceptance of boric acid accumulation on RPV head from CRDM flange leakage Failure to recognize symptoms of leakage collected from Containment Building monitors Harsh environmental conditions

-Boric acid corrosion control program targeted CRDM flange leakage