ML20249B372
| ML20249B372 | |
| Person / Time | |
|---|---|
| Issue date: | 06/16/1998 |
| From: | Carpenter C, Lund A NRC (Affiliation Not Assigned), NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Hackett E, Sullivan E NRC (Affiliation Not Assigned), NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| References | |
| NUDOCS 9806220373 | |
| Download: ML20249B372 (3) | |
Text
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WASHINGTON. D.C. 30006-0001 June 16,1998 MEMORANDUM TO: Edmund J. Sullivan, Acting Chief
' Materials and Chemical Engineering Branch Division of Engineering Office of Nuclear Reactor Regulation Edwin M. Hackett, Acting Chief Electrical, Materials and Mechanical Engineering Branch Division of Engineering Technology Office of Nuclear Regulatory Research FROM:
C. E. Carpenter, Jr., Materials Engineer
' - /'
Materials and Chemical Engineering Branch
- Division of Engineering Office of Nuclear Reactor Regulation l
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l A. Louise Lund, Materials Engineer 3
Electrical, Materials and Mechanical Engi ring ra c Division of Engineering Technology Office of Nuclear Regulatory Research
SUBJECT:
TRIP
SUMMARY
FOR JUNE 4,1998, MEETING WITH EPRI REGARDING COOPERATIVE RESEARCH ON WELDABILITY OF IRRADIATED BWR INTERNAL COMPONENTS On Thursday, June 4,1998, we met with several representatives of the Electric Power Research institute (EPRI) and the BWR Vessel and Intemals Project (BWRVIP) Repair subcommittee at the EPRI NDE Center in Charlotte, NC, to discuss a cooperative research initiative involving the weldability of irradiated intemal components of BWRs. The BWRVIP had previously provided to the staff, by letter dated October 27,1997, the EPRI proprietary report "Weldability of Irradiated LWR Structural Components (BWRVIP-45)," which describes the work previously done by the industry to address this issue. At high fluences, helium is generated in reactor base materials due to the transmutation of nickel and boron through neutron absorption. Industry experience has shown that, in highly irradiated metals, inferior welds can be produced due to the helium thermally-induced growth of pre-existing helium bubbles which then cause cracks and inclusions in the weld.
Participating in this discussion were Robert Thomas and Ken Wolfe of EPRI, Bruce McLeod of
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the BWRVIP, Robin Dyle of inservice Engineering, and Lew Willertz from PP&L.
3 The Memorandum of Understanding (MOU) between the NRC and EPRI on cooperative nuclear safety research was discussed first, and was referred to frequently throughout the meeting, in order to ensure that all proposed actions were in accordance with this agreement. The meeting
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' E. J. Sullivan, et al. then focused on the scope of the proposed undertaking, and what actions needed to be
. accomplished in the near term to facilitate the research.
' Agreement was reached that the research scope would not focus on fluence calculations or boron concentration, as these factors are extremely difficult to accurately quantify. Rather, the concem would be the helium ('He) concentration in the areas of concem. To this end, the.
research would concentrate primarily on techniques and tooling for measuring 'He, methods of benchmarking present 'He concentrations, and determining possible methods of mitigating 'He deposition. Also to be examined would be the probable boundaries within the vessel beyond which 'He concentrations could be reasonably expected to be sufficiently low that welding in these regions would not constitute a problem. The jet pump riser brace area was se!ected as an area of initial focus since it does not lend itself well to conventional mechanical repair l
techniques. Initially, the feasibility of welding in this location will be assessed and then welding techniques will need to be developed and tested.
Tne EPRI and BWRV!P representatives stated that the short term material issue was to
- determine that, even if crecidag of welds occurred due to excess 'He concentrations, that there would not be a safety concem, that these welds would still be capable of performing their intended safety function. The staff stated that an appropriate technical analysis would need to be performed to assure that welds that cracked, especially if due to high 'He concentrations, j
were still capable of performing their intended safety function. The staff agreed that the long term material properties needs to be accurately characterized in order to determine what effects weld repairs will have.
The next agenda item was determining what actions needed to be performed in th's near term and who was to perform them. The EPRI and BWRVIP representatives agreed to contact organizations, both domestic and foreign, that may have experience with performing welding on highly irradiated steels in order to obtain information on the processes used and experience gained. The staff agreed to also contact other agencies and organizations to ascertain if the information could be provided to the staff. EPRI will contact organizations that may be able to provide or develop technology for performing in situ determination of 'He concentrations.
Further, EPRI and the BWRVIP will contact their members to find volunteers who may have samples of highly irradiated steels available to both test for material characteristics and to
. perform welding experiments on.
l l
Finally, the meeting concluded with an agreement to expedite the information gathering portion and to have a telephone conference call in July 1998 to discuss the status of efforts to date.
Tim staff will meet with the BWRVIP and EPRI representatives again in the late summer,1998, i
. time frame.
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1 E. J. Sullivan, et al. then focused on the scope of the proposed undertaking, and what actions needed to be accomplished in the near term to facilitate the research.
Agreement was reached that the research scope would not focus on fluence calculations or boron concentration, as these factors are extremely difficult to accurately quantify. Rather, the concern would be the helium ('He) concentration in the areas of concern. To this end, the research would concentrate primarily on techniques and tooling for measuring 'He, methods of benchmarking present 'He concentrations, and determining possible methods of mitigating 'He deposition. Also to be examined would be the probable boundaries within the vessel beyond which 'He concentrations could be reasonably expected to be sufficiently low that welding in these regions would not constitute a problem. The jet pump riser brace area was selected as an
{
area of initial focus since it does not lend itself well to conventional mechanical repair techniques, initially, the feasibility of welding in this location will be assessed and then welding techniques will need to be developed and tested.
The EPRI and BWRVIP representatives stated that the short term material issue was to determine that, even if cracking of welds occurred due to excess 'He concentrations, that there would not be a safety concern, that these welds would still be capable of performing their intended safety function. The staff stated that an appropriate technical analysis would need to be performed to assure that welds that cracked, especially if due to high 'He concentrations, were still capable of performing their intended safety function. The staff agreed that the long term material properties needs to be accurately characterized in order to determir,e what effects weld repairs will have.
The next agenda item was determining what actions needed to be performed in the near term and who was to perform them. The CPRI and BWRVIP representatives agreed to contact organizations, both domestic and foreign, that may have experience with performing welding on highly irradiated steels in order to obtain information on the processes used and experience gained. The staff agreed to also contact other agencies and organizations to ascertain if the information could be provided to the staff. EPRI will contact organizations that may be able to provide or develop technology for performing in situ determination of 'He concentrations.
Further, EPRI and the BWRVIP will contact their members to find volunteers who may have samples of highly irradiated steels available to both test for material characteristics and to perform welding experiments on.
l l
Finally, the meeting concluded with an agreement to expedite the information gathering portion
- and to have a telephone conference cal! in July 1998 to discuss the status of efforts to date.
The staff will meet with the BWRVIP and EPRI representatives again in the late summer,1998, l
time frame.
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