ML20044B740
| ML20044B740 | |
| Person / Time | |
|---|---|
| Issue date: | 02/25/1993 |
| From: | Taylor J NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | |
| References | |
| GL-92-01, GL-92-1, SECY-93-048, SECY-93-48, NUDOCS 9303030326 | |
| Download: ML20044B740 (7) | |
Text
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POLICY ISSUE February 25, 1993 SEC M 3-048 (InfOrmation)
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The Commissioners From:
James M. Taylor Executive Director for Operations Subiect:
STATUS OF REACTOR PRESSURE VESSEL ISSUES INCLUDING COMPLIANCE WITH 10 CFR PART 50, APPENDICES G AND H l
(WITS 9100165)
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Purpose:
To respond to the Commission's request for a report on the status of licensee reactor vessel surveillance programs with regard to 10 CFR 50, Appendix H,
" Reactor Vessel Material Surveillance Program Req.tirements," as requested in the Staff Requirements Memorandum M910711A, July 19, 1991 I
(Samuel J.
Chilk to James M. Taylor), and, based on the preliminary review of responses to Generic Letter 92-01, provide an update of the status of plants with regard to Appendix G,
" Fracture Toughness Requirements."
Backaround:
During the staff presentation to the Commission on l
Yankee Rowe Embrittlement Issues on July 11, 1991, Commissioner Curtiss requested additional information related to Appendices G and H.
Commissioner Curtiss requested:
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(1) the staff to provide information on whether l
there are facilities other than Yankee Rowe where Upper Shelf Energy (USE) requirements of 10 CFR 50, Appendix G, Section IV.A.1 are not met, and whether, if such cases exist, not only has the analysis authorized under IV.1 been done by the Director of NRR but the licensee has also been required to meet V.C.1 l
as well; 1
1 (2) the staff to ptovide for the record their position on whether the requirements of V.C.
in Appendix G to 10 CFR 50 apply if the Upper 120004 Shelf Energy values sM cified in IV.A.1 are I
g not met; and i
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TO BE MADE
PUBLICLY AVAILABLE i
CONTACT:
Jack R.
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IN 10 WORKING DAYS l
504-279 O W 3 h
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The Commissioners (3) the staff to provide to the Commission a list of any other plants which have not but should i
have requested exemptions from the requirements of 10 CFR 50, Appendix H.
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1 The staff provided complete responses to items-(1)
I and (2) and a partial response to item 3 in SECY-l 91-220, " Yankee Rowe Pressure Vessel Embrittlement Issues," dated July 24, 1991.
The information provided in this paper on Appendix H (Question 1 in Generic Letter 92-01, Revision 1,
" Reactor 1
-Vessel Structural. Integrity, 10.CFR 50.54(f),")
completes the staff response to item 3.
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The integrity of the reactor. pressure vessel is essential in ensuring reactor safety.
The fracture resistance of reactor vessel materials i
decreases with increasing fluence.- This is manifested by an increase in the brittle-to-ductile transition temperature and a reduction in the upper shelf energy.
These changes in fracture i
resistance must be carefully monitored and i
periodically assessed through reactor vessel surveillance programs to ensure that specified margins of safety are satisfied for reactor vessels.
On March 6, 1992, the staff issued i
Generic Letter 92-01, Revision 1, to compile l
information necessary to confirm that licensees and permittees satisfy requirements for ensuring-J reactor vessel integrity.
In the generic letter, the staff requested responses to three questions.
The staff received responses to each question from all licensees and permittees except those for Bellefonte 1 and 2, Perry 2,. San Onofre 1, WNP-1, WNP-3 and Yankee Rowe.
The licensee for Yankee Rowe was not required to respond and the other facilities have deferred licensing activities or are being shut down.
Results of the. staff's preliminary review of the responses are summarized below.
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The Commissioners 1 l
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J Discussion:
Ouestion 1: Reactor Vessel Material Surveillance I
Procrams-j I
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The staff requested information on the~ reactor
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vessel' material surveillance requirements specified in 10 CFR Part 50, Appendix H.
All i
licensees and permittees stated that their reactor vessel surveillance programs satisfy the i
requirements of 10 CFR Part 50, Appendix H, j
" Reactor Vessel Material Surveillance Program Requirements."
The staff performed a preliminary j
review, and agrees with the licensees' responses.
Ouestion 2: Reactor Vessel Material Uoner Shelf l
Enerav j
The staff requested information on the 50 ft-lb minimum upper shelf energy criterion specified in 10 CFR Part 50, Appendix G.
All licensees responded that, based on plant-specific data and evaluations, their reactor vessels satisfy the 50 I
i ft-lb minimum upper shelf energy criterion.
However, if the NRC staff's generic criteria are i
used, fifteen (15) plants would currently have calculated reactor vessel material upper shelf energies less than 50 ft-lbs.
Three'(3) other l
plants would have reactor vessel upper shelf energies less than 50 ft-lbs before the end of their operating licenses.
These plants are listed in the Enclosure.
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During the staff's review, it found that it would need additional information to determine if plant-specific analyses used acceptable methods 'tx) 4 derive reactor vessel upper shelf energies, i
i Typical information required would include the bases for correlation factors used to convert test j
results from longitudinal.tx) transverse specimen orientations and the bases for establishing.
initial upper shelf energies in the absence of unirradiated test data.
The licensees for many 2
boiling water reactor -(BWR) plants lack the initial unirradiated upper shelf energy.and materials data necessary to perform plant-specific analyses..The staff also found differences between the data in some of the responses and previously reported data.
These differences.need to be reconciled.
The staff anticipates that as
The Commissioners
-4 the reviews proceed, some licensees may not be able to adequately demonstrate that their reactor vessel upper shelf energies are above 50 ft-lbs or will remain above 50 ft-lbs until the end of their licenses.
l The NRC staff and-industry met on September 2-3, 1992 to coordinate their efforts on reactor.
pressure vessel integrity'issucs.
During the meeting, the NRC staff suggested that the industry j
perform generic bounding analyses to demonstrate that vessels with upper shelf energies below 50 ft-lbs have safety margins equivalent to those I
required by Appendix G of the American Society of Mechanical Enginears (ASME) Code.
Analyses of this type are required by 10 CFR Part 50, Appendix j
G, to assure reactor vessel integrity if the upper i
shelf energy falls below 50 ft-lbs.
The Babcock.
and Wilcox (B&W) reactor vessel Owners Group and some individual licensees (Zion 1 and 2, Turkey 1
Point 3 and 4, Oyster Creek and Nine Mile Point 1) l had previously begun to perform such analyses.
After the September meeting, the Nuclear Management and Resources Council (NUMARC) began I
coordinating the industry's efforts in this area.
The owners groups representing the licensees of General Electric, Westinghouse and Combustion Engineering reactors also began conducting bounding equivalent margins analyses.
The owners groups have scheduled to submit their final bounding analyses as follows:
Owners GrouD Date Babcock & Wilcox (B&W)
Reactor Vessel Owners Group 1/93 i
Westinghouse Owners Group 3/93 i
Combustion Engineering (CE)
Owners Group 3/93 1
Boiling Water Reactors (BWR)
Owners Group
'4/93 The B&W, BWR, and CE owners groups have already submitted or presented preliminary analyses to the staff.
In addition, the NRC Office of Nuclear Regulatory Research has performed independent l
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The Commissioners analyses to bound the results for the different plant and material types.
The results of these industry and staff analyses indicate that the margins of safety required by Appendix G of the ASME Code can be satisfied using conservative estimates of upper shelf energy based on the staff's generic criteria.
The NRC staff is conducting detailed reviews to resolve differences in the methodologies used to calculate upper shelf energies, discrepancies in the available data, and other issues.
Licensees or permittees for which these concerns exist have the option of requesting that the equivalent margins analyses be reviewed and approved for their facilities.
j Ouestion 3:
Temnerature Effects and Surveillance Data The staff requested information on the consideration of temperature effects and surveillance data in evaluating irradiation embrittlement.
The staff will thoroughly review licensees' responses on the effects of irradiation temperature and the implications of surveillance data on the assessment of reactor pressure vessel fracture toughness and will consider them in evaluating the methods used to calculate upper shelf energies.
FUTURE ACTIONS AND SCHEDULE The staff will confirm the adequacy of the equivalent margin analyses and expects to complete this effort by the middle of 1993.
The staff is performing detailed reviews of the responses to Generic Letter 92-01.
These reviews will include requests for additional information, as indicated in the discussion of Question 2, and detailed evaluations of the upper shelf energies reported for each plant, or the review and approval of equivalent margin analysis as requested by licensees.
The staff will also review the current values of reactor vessel material brittle-to-ductile transition temperatures using the
4 The Commissioners j information submitted in response to the generic letter.
The staff is scheduled to complete detailed reviews of the responses to Generic Letter 92-01 by the end of 1993.
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mes M. T or -
xecutive Director-for Operations
Enclosure:
As Stated 1
DISTRIBUTION:
OPA IP i
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4 ENCLOSURE I i
Plants with reactor vessel upper shelf energies currently below 50 ft-lbs based on the NRC staff generic guidance:
Nine Mile Point I Oyster Creek I Arkansas Nuclear One-1 Crystal River 3 Ginna Oconee 1 i
Oconee 2 Point Beach 1 Point Beach 2 Robinson 2 Three Mile Island 1 Turkey Point 3 Turkey Point 4 Zion 1 Zion 2 1
Plants with reactor vessel upper shelf energies less than 50 ft-lbs before the end of their operating license based on the NRC i
staff generic guidance:
I Oconee 3 Millstone 2 Watts Bar 1 i
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