ML030590084
| ML030590084 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 02/27/2003 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Moroney B, NRR/DLPM, 415-3974 | |
| Shared Package | |
| ml030660105 | List: |
| References | |
| TAC MB2916, TAC MB3567, TAC MB3954, TAC MB4495, TAC MB4603, TAC MB5465, TAC MB6218, TAC MB6220, TAC MB6221, TAC MB6222, TAC MB6584, TAC MB7182, Y020030008 | |
| Download: ML030590084 (11) | |
Text
ATTACHMENT 1 ACTION PLAN FOR ADDRESSING DAVIS-BESSE LESSONS LEARNED TASK FORCE RECOMMENDATIONS REGARDING STRESS CORROSION CRACKING Last Update: Initial Update (2/27/03)
Lead Division: DLPM Supporting Divisions: DE, DSSA, DIPM, DRIP Supporting Offices: RES, Regions TAC No.
Description MB2916 Non plant-specific activities for Bulletin 2001-01 MB3567 VHP Action Plan (Coordination and Administration)
MB3954 Development of CRDM NUREGs (Bulletin 2001-01)
MB4495 Lead PM Activities for Bulletin 2002-01 MB4603 Non plant-specific activities for Bulletin 2002-01 MB5465 Lead PM Activities for Bulletin 2002-02 MB6218 Inspection TI for Bulletin 2002-02 MB6220 Review of NEI/MRP Crack Growth Rate Report (MRP-55)
MB6221 Development of Alternate (to ASME Code) RPV Head and VHP Inspection Requirements MB6222 Review of NEI/MRP RPV Head and VHP Inspection Plan (MRP-75)
MB6584 RIS: Status of Degradation of RPV Head Penetrations and BACC Programs MB7182 Orders for Interim Inspection Guidelines Milestone Date (T=Target)
(C=Complete)
Lead Support Part I: Reactor Pressure Vessel Head Inspection Requirements 1.
Collect and summarize information available worldwide on Alloy 600, Alloy 690 and other nickel based alloy nozzle cracking for use in evaluation of revised inspection requirements.
[LLTF 3.1.1(1)-High ]
03/04 (T)
RES/DET DE
Milestone Date (T=Target)
(C=Complete)
Lead Support 2.
Critically evaluate existing SCC models with respect to their continuing use in the susceptibility index.
[LLTF 3.1.4(1)-Medium]
05/03 (T)
RES/DET DE 3.
Complete initial evaluation of individual plant inspections in response to Bulletins and Orders. (Staff will continue to review future inspection results).
05/04 (T)
Monitor and provide input to industry efforts to develop revised RPV Head inspection requirements (ASME Code Section XI)
[LLTF 3.3.4(8)-High LLTF 3.3.7(6)-Low]
Note (1)
DE RES/DET DSSA Regions Industry 5.
Participate in meetings and establish communications with appropriate stakeholders (e.g., MRP, ASME)
[LLTF 3.3.4(8)-High]
Ongoing DE RES/DET DLPM DRIP DSSA industry 6.
Make decision to endorse revised ASME Code requirements, when issued, or implement alternative requirements.
[LLTF 3.3.4(8)-High]
Note (1)
DE RES/DET 7.
If alternative, determine appropriate regulatory tool and establish schedule for implementation.
Note (1)
DE DRIP DIPM DSSA RES/DET industry public Part II. Boric Acid Corrosion Control 1.
Collect and summarize information available worldwide on boric acid corrosion of pressure boundary materials for use in evaluation of revised inspection requirements.
[LLTF 3.1.1(1)-High]
10/04 (T)
RES/DET DE
Milestone Date (T=Target)
(C=Complete)
Lead Support 2.
Evaluate individual plant responses to Bulletin 2002-01 regarding Boric Acid Inspection Programs (60-day responses and necessary follow-up) and summarize plant responses on BACC programs in an appropriate public document 04/03 (T)
Participate in meetings and establish communications with appropriate stakeholders (e.g.,MRP, ASME)
Ongoing DE RES/DET DLPM DRIP DSSA industry 4.
Evaluate need to take additional regulatory actions and determine appropriate regulatory tool(s).
04/03 (T)
Develop milestones for additional regulatory actions, as necessary 05/03 (T)
Review and evaluate the adequacy of revised ASME Code Requirements for Pressure Testing/Leakage Evaluation being developed by the ASME Code,Section XI, Task Group on Boric Acid Corrosion.
01/05 (T)
DE RES/DET Part III. Inspection Programs 1.
Develop inspection guidance or revise existing guidance to ensure that VHP nozzles and the RPV head area are periodically reviewed by the NRC during licensee ISI activities.
[LLTF 3.3.4(3)-High]
03/04 (T)
DIPM DE Regions 2.
Develop inspection guidance that provides for timely, periodic inspection of PWR plant BACC programs.
[LLTF 3.3.2(1)-High]
03/04 (T)
DIPM DE Regions
Milestone Date (T=Target)
(C=Complete)
Lead Support 3.
Develop inspection guidance for assessing the adequacy of PWR plant BACC programs (implementation effectiveness, ability to identify leakage, adequacy of evaluation of leaks).
[LLTF 3.2.2(1)-High]
03/04 (T)
DIPM DE RES/DET Regions Notes: (1) Milestone dates will be set when a target date for issuing revised Code requirements is established. However, staff may initiate action to establish alternative inspection requirements, if appropriate, prior to completion of industry activities.
==
Description:==
The reactor vessel head (RVH) degradation found at Davis-Besse, along with other documented incidences of circumferential cracking of vessel head penetration (VHP) nozzles, have prompted the staff to question the adequacy of current RVH and VHP inspection programs that rely on visual examinations as the primary inspection method. Also, the failure to adequately address indications of boric acid leakage at Davis-Besse raised questions as to the efficacy of industry boric acid corrosion control (BACC) programs. Finally, review of the Davis-Besse event identified deficiencies in the NRC inspection programs.
Historical
Background:
In March 2002, while conducting inspections in response to Bulletin 2001-01, the Davis-Besse Nuclear Power Station identified three CRDM nozzles with indications of axial cracking, which were through-wall, and resulted in reactor coolant pressure boundary leakage. During the nozzle repair activities, the licensee removed boric acid deposits from the RVH, and conducted a visual examination of the area, which identified a 7 inch by 4-to-5 inch cavity on the downhill side of nozzle 3, down to the stainless steel cladding. The extent of the damage indicated that it occurred over an extended period and that the licensees programs to inspect the RPV head and to identify and correct boric acid leakage were ineffective.
One of the NRC follow-up actions to the Davis-Besse event was formation of a Lessons Learned Task Force (LLTF). The LLTF conducted an independent evaluation of the NRCs regulatory processes related to assuring reactor vessel head integrity in order to identify and recommend areas of improvement applicable to the NRC and the industry. A report summarizing their findings and recommendations was published on September 30, 2002. The report contains several consolidated lists of recommendations. The LLTF report was reviewed by a Review Team (RT),
consisting of several senior management personnel appointed by the Executive Director for Operations (EDO). The RT issued a report on November 26, 2002, endorsing all but two of the LLTF recommendations, and placing them into four overarching groups. On January 3, 2003, the EDO issued a memo to the Director, NRR, and the Director, RES, tasking them with developing a plan for accomplishing the recommendations. This action plan addresses the recommendations in the Assessment of Stress Corrosion Cracking grouping of the RT report. The LLTF recommendations are listed in the attached Table 1, and have been identified under the appropriate milestone(s).
Proposed Actions: The staff is interacting with all PWR licensees, the American Society of Mechanical Engineers (ASME), the Electric Power Research Institute (EPRI) Materials Reliability Program (MRP), and other external stakeholders in addressing the issues discussed above. This action plan includes milestones aimed at guiding the NRC and industry to effectively manage RVH degradation and BACC. Throughout the implementation of this action plan, the NRC will establish the necessary communications mechanisms to ensure that the NRC, the industry, and all stakeholders are informed and sharing the same information. This will be accomplished through public meetings, technical working groups, ACRS briefings, and web site postings, as appropriate.
The Part I milestones deal with development of improved inspection requirements for the RPV head and VHP nozzles. Interim inspection guidelines (TI-150) have been issued for use by NRC inspectors and are being updated as needed based on inspection results. The first effort in development of new regulatory requirements is for the staff to establish the technical basis for new inspection requirements through ongoing and planned research programs. This will include collecting and evaluating information on VHP nozzle inspection results and evaluating current methodologies for determining leakage probability, nondestructive testing, crack susceptibility, crack growth propagation and failure margins. In parallel with these activities, the staff will monitor and assess the adequacy of revisions to the ASME Boiler and Pressure Vessel Code, which will be based on the inspection program developed by the EPRI MRP. If the revised ASME Code requirements are acceptable, based on the staffs technical evaluations, the NRC will initiate action to endorse them in a revision to 10 CFR 50.55a. If the revised ASME Code requirements cannot be made acceptable to the NRC, then alternate requirements would have to be developed and implemented by the revision to 10 CFR 50.55a. The staff may initiate action to establish alternative inspection requirements, if appropriate, prior to completion of industry activities.
The Part II milestones evaluate whether industry BACC programs are meeting NRC expectations and whether additional inspection guidance should be issued. First, the staff will establish a technical basis for BACC program requirements through ongoing and planned research programs.
This will include evaluation of boric acid corrosion events in past reports and in responses to Bulletin 2002-01, and studies of corrosion rates of reactor pressure boundary materials in boric acid solutions. The staff is also monitoring development of revised ASME Code requirements by the Section XI Task Group on Boric Acid Corrosion. If the staff determines that additional interim guidelines are needed prior to issuance of the revised Code requirements, they will be issued by an appropriate regulatory tool. When the ASME Code requirements are revised, the NRC will initiate action to endorse them, if acceptable. If the revised ASME code requirements cannot be made acceptable to the NRC, then alternate requirements would have to be developed and implemented by an appropriate regulatory tool.
The Part III milestones address the LLTF findings that the NRC inspection guidelines did not provide effective oversight of licensee RPV head inspection and BACC programs. Revised guidelines for these activities will be developed. Throughout the process of establishing new requirements, existing NRC inspection procedures would be evaluated to verify whether they adequately address the revised requirements, and would be updated as needed.
Originating Documents: Memorandum from Travers, W.D. to Collins, S. and Thadani, A. C.,
dated January 3, 2003, Actions Resulting From The Davis-Besse Lessons Learned Task Force Report Recommendations. (ADAMS Accession No. ML023640431)
Memorandum from Paperiello, C.J. to Travers, W.D., dated November 26, 2002, Senior Management Review of the Lessons-Learned Report of the Davis-Besse Nuclear Power Station Reactor Pressure Vessel Head. (ADAMS Accession No. ML023260433)
Memorandum from Howell, A.T. to Kane, W.F., dated September 30, 2002, Degradation of the Davis-Besse Nuclear Power Station Reactor Pressure Vessel Head Lessons-Learned Report.
(ADAMS Accession No. ML022740211)
Regulatory Assessment: The current method for managing PWSCC in the VHP nozzles of U.S.
PWRs is dependent on the implementation of inspection methods intended to provide early detection of degradation of the reactor coolant pressure boundary. Title 10, Section 50.55a(g)(4) of the Code of Federal Regulations requires, in part, that ASME Code Class 1, 2, and 3 components must meet the inservice inspection requirements of Section XI of the ASME Boiler and Pressure Vessel Code throughout the service life of a boiling or pressurized water reactor.
Pursuant to Inspection Category B-P of Table IWB-2500-1 to Section XI of the ASME Boiler and Pressure Vessel Code, licensees are required to perform VT-2 visual examinations of their vessel head penetration nozzles and reactor vessel heads once every refueling outage for the system leak tests, and once an inspection interval for the hydrostatic pressure test.
Based on the experience with the VHP nozzle cracking phenomenon, the VT-2 visual examination methods required by the ASME Code for inspections of VHP nozzles do not provide reasonable assurance that leakage from a through-wall flaw in a nozzle will be detected. The VT-2 visual examination methods specified by the ASME Code are not directed at detecting the very small amounts of boric acid deposits, e.g., on the order of a few grams, that have been associated with VHP nozzle leaks in operating plants. In addition, the location of thermal insulating materials and physical obstructions may prevent the VT-2 visual examination methods from identifying minute amounts of boric acid deposits on the outer surface of the vessel head. Specifically, Paragraph IWA-5242 of Section XI of the ASME Boiler and Pressure Vessel Code does not require licensees to remove thermal insulation materials when performing ASME VT-2 visual examinations of reactor vessel heads. Cleanliness of reactor vessel heads during the examinations, which is critical for visual examination methods to be capable of distinguishing between boric acid residues that result from VHP nozzle leaks and those residues that result from leaks in other reactor coolant system components, is not addressed by the ASME Code.
Based on knowledge obtained from evaluation of the Davis-Besse event, and information provided from PWR licensees in response to Bulletins 2001-01, 2002-01 and 2002-02, the NRC issued an Order to all PWR plants establishing enhanced inspection requirements on an interim basis, which will provide adequate assurance of safe plant operation until permanent requirements are established and promulgated.
Current Status: This is the initial update for this Action Plan, which addresses the Group 1 recommendations of the Davis-Besse Lessons Learned Task Force Review Team regarding Stress Corrosion Cracking.
Potential Problems: The target dates for milestones associated with development of revised inspection requirements are dependent on review of industry proposed inspection guidelines, which are currently being revised. Milestone dates will be established when the revised industry guidelines have been issued.
Proposed Resolution of Potential Problems: Orders have been issued to establish interim inspection guidelines, which will remain in effect until final inspection guidelines are promulgated by appropriate rulemaking.
Schedule Changes Since Last Update: This is the initial update.
Resource Expenditure: As of February 22, 2003, 1717 hours0.0199 days <br />0.477 hours <br />0.00284 weeks <br />6.533185e-4 months <br /> (= 1.2 FTE) have been expended by NRR in FY03 on the TACs listed for this Action Plan. Estimated additional resource expenditures are:
NRR - 8.1 FTE (2.7 FTE in FY03, 1.8 FTE in FY04, 1.8 FTE in FY05 and 1.8 FTE in FY06)
Regions - 1.3 FTE (.2 FTE in FY03,.3 FTE in FY04..4 FTE in FY05 and.4 FTE in FY06)
RES - 1.0 FTE plus $1,580,000 (.5 FTE plus $830,000 in FY03,.5 FTE plus $750,000 in FY04).
TAC No.
TAC Status HOURS MB2916 OPEN 0
MB3567 OPEN 194 MB3954 OPEN 0
MB4495 OPEN 0
MB4603 OPEN 519.4 MB5465 OPEN 560 MB6218 OPEN 57.5 MB6220 OPEN 23 MB6221 OPEN 19.3 MB6222 OPEN 29.5 MB7182 OPEN 314.3 Priority: 2 Contacts:
Brendan Moroney, DLPM, 415-3974 NRR Technical Contacts:
Allen Hiser, EMCB, 415-1034 Edmund Sullivan, EMCB, 415-2796 RES Technical
Contact:
William Cullen, DET/MEB, 415-6754 NRR/DIPM Lead
Contact:
Jeffrey Jacobson, IIPB, 415-2977 NRR/DRIP Lead
Contact:
Terrence Reis, RORP, 415-3281
References:
Orders establishing interim inspection requirements for reactor pressure vessel heads at pressurized water reactors, February 11, 2003.
NRC Bulletin 2002-02, Reactor Pressure Vessel Head and Vessel Head Penetration Nozzle Inspection Programs, August 9, 2002.
NRC Bulletin 2002-01, Reactor Pressure Vessel Head Degradation and Reactor Coolant Pressure Boundary Integrity, March 18, 2002.
Information Notice 2002-11, Recent Experience With Degradation of Reactor Pressure Vessel Head, March 12, 2002.
NRC Bulletin 2001-01, Circumferential Cracking of Reactor Pressure Vessel Head Penetration Nozzles, August 3, 2001.
Information Notice 2001-05, Through-Wall Circumferential Cracking of Reactor Pressure Vessel Head Control Rod Drive Mechanism Penetration Nozzles at Oconee Nuclear Station, Unit 3, April 30, 2001.
Generic Letter 97-01, Degradation of Control Rod Drive Mechanism Nozzle and Other Vessel Closure Head Penetrations, April 1, 1997.
Information Notice 96-11, Ingress of Demineralizer Resins Increases Potential for Stress Corrosion Cracking of Control Rod Drive Mechanism Penetrations, February 14, 1996.
NUREG/CR-6245, Assessment of Pressurized Water Reactor Control Rod Drive Mechanism Nozzle Cracking, October 1994.
Letter from Russell, W. T., (USNRC) to Rasin, W., (Nuclear Management and Resources Council), dated November 19, 1993, Safety Evaluation for Potential Reactor Vessel Head Adaptor Tube Cracking.
Information Notice 90-10, Primary Water Stress Corrosion Cracking of INCONEL 600, February 23, 1990.
Generic Letter 88-05, Boric Acid Corrosion of Carbon Steel Reactor Pressure Boundary Components in PWR Plants, March 17, 1988.
Table 1 LLTF Report Recommendations Included in SCC Action Plan High Priority NUMBER RECOMMENDATION 3.1.1(1)
The NRC should assemble foreign and domestic information concerning Alloy 600 (and other nickel based alloys) nozzle cracking and boric acid corrosion from technical studies, previous related generic communications, industry guidance, and operational events. Following an analysis of nickel based alloy nozzle susceptibility to stress corrosion cracking (SCC), including other susceptible components, and boric acid corrosion of carbon steel, the NRC should propose a course of action and an implementation schedule to address the results.
3.2.2(1)
The NRC should inspect the adequacy of PWR plant boric acid corrosion control programs, including their implementation effectiveness, to determine their acceptability for the identification of boric acid leakage, and their acceptability to ensure that adequate evaluations are performed for identified boric acid leaks.
3.3.2(1)
The NRC should develop inspection guidance for the periodic inspection of PWR plant boric acid corrosion control programs.
3.3.4(3)
The NRC should strengthen its inspection guidance or revise existing guidance, such as IP 71111.08, to ensure that VHP nozzles and the RPV head area are periodically reviewed by the NRC during licensee ISI activities.
Such NRC inspections could be accomplished by direct observation, remote video observation, or by the review of videotapes. General guidance pertaining to boric acid corrosion observations should be included in IP 7111.08 3.3.4(8)
The NRC should encourage ASME Code requirement changes for bare metal inspections of nickel based alloy nozzles for which the code does not require the removal of insulation for inspections. The NRC should also encourage ASME Code requirement changes for the conduct of non-visual NDE inspections of VHP nozzles. Alternatively, the NRC should revise 10 CFR 50.55a to address these areas.
Medium Priority NUMBER RECOMMENDATION 3.1.4(1)
The NRC should determine if it is appropriate to continue using the existing SCC models as predictors of VHP nozzle PWSCC susceptibility given the apparent large uncertainties associated with the models. The NRC should determine whether additional analysis and testing are needed to reduce uncertainties in these models relative to their continued application in regulatory decision making.
Low Priority NUMBER RECOMMENDATION 3.3.7(6)
Determine whether ISI summary reports should be submitted to the NRC, and revise the ASME submission requirement and staff guidance regarding disposition of the reports, as appropriate.