ML020780206

Handouts/Slides for Briefing of the Committee to Review Generic Requirements on Reactor Pressure Vessel Head Degradation

ML020780206
Person / Time
Site:	Davis Besse
Issue date:	03/18/2002
From:	NRC/CRGR
To:
References
Download: ML020780206 (8)

Text

REACTOR PRESSURE VESSEL HEAD DEGRADATION Briefing of the Committee to Review Generic Requirements March 18, 2002

DAVIS-BESSE FINDINGS High susceptibility plant per Bulletin 2001-01 Inspected nozzles with UT 5 nozzles with cracks - 3 were leakers Anomalous UT signal from nozzles 2 and 3 Elected to repair all 5 nozzles Terminated repair of nozzle 3 prematurely Cleaned reactor pressure vessel head Degraded areas on surface by nozzles 1, 2, and 3 - all of which had through-wall flaws DAVIS-BESSE FINDINGS (contd)

Boric acid-like-material covering reactor pressure vessel head near leaking nozzles for several cycles Largest degraded area near nozzle 3 Length: approximately 7-inches Width: approximately 4 to 5-inches at widest point Depth: approximately 6-inches Root cause investigation is on-going Either the deposits on the top of the head, the leaking penetration, or both could contribute to the degradation GENERIC TECHNICAL ACTIVITIES Issued letter to industry on March 11, 2002 requesting Assessment of inspection techniques for plants that have inspected per Bulletin 2001-01 Justification for continued operation for plants that have not inspected Risk assessment Industry provided preliminary results on March 13, 2002 and will provide detailed results on March 19, 2002 Visual exam of 100% of head?

If not 100%, can external corrosion be ruled out?

If UT or other approach was used during most recent inspection, was it capable of detecting cavity?

Plans for Spring 02 outages?

BULLETIN - REQUESTED INFORMATION Summary of the RPV head inspection and maintenance programs Evaluation of the ability of inspection and maintenance programs to identify degradation Description of any conditions that could have lead to degradation and the corrective actions taken to address such conditions Plans, basis, and schedule for future inspections of the RPV head and VHP nozzles Basis for continued operation until the inspections can be performed Results of inspection Boric acid corrosion prevention program for ensuring integrity of reactor coolant pressure boundary CRGR QUESTIONS Problem Statement and Requested Information Anticipated Schedule for NRC Use of Information Initial step in assessing the prevalence and severity Initial assessment within 30-days of receipt of information Request does not Impose New Requirements Burden Justification Significant degradation of reactor pressure vessel head Effectiveness of prior inspection and maintenance practices Risk associated with significant RPV head degradation and the potential for a LOCA CONCLUSIONS Bulletin necessary to verify compliance with existing regulations