NUREG-0744 Rev, 1; Pressure Vessel Material Fracture Toughness (Generic Letter No. 82-26)
UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON. D.C. 20555
November 12, 1982
TO ALL POWER REACTOR LICENSEES (EXCEPT FT. ST. VRAIN)
Gentlemen:
SUBJECT: NUREG-0744 REV, 1; (GENERIC LETTER NO. 82-26 ) -
PRESSURE VESSEL MATERIAL FRACTURE TOUGHNESS
Appendix G to 10 CFR 50 specifies fracture toughness requirements for
pressure retaining components, fabricated from ferritic materials, in the
reactor coolant pressure boundary of water cooled reactors. In the event a
pressure retaining component fails to meet the material toughness
requirements during its service life due to neutron radiation embrittlement,
continued operation of the component is permissible provided certain
requirements, specified in Section V.C of Appendix G, are satisfied.
One of the requirements of Section V.C is that a fracture analysis of the
component is to be performed to demonstrate the existence of adequate margin
for continued operation. The proposed program for satisfying this
requirement is to be submitted to the USNRC for review and approval at least
3 years prior to the date fracture toughness levels are predicted to no
longer satisfy requirements.
Appendix H to 10 CFR 50 specifies the surveillance program which all power
reactor licensees must maintain to monitor irradiation-induced fracture
toughness changes. Impact data from this program are used to adjust the
reference toughness curve for irradiation effects through the application of
the adjusted reference temperature. The Charpy V-notch 50 ft-lb level is
used to determine the temperature shift; therefore, when the upper shelf
energy falls below 50 ft-lb, the requirements of 10 CFR 50 Appendix G are no
longer met.
To provide guidance to licensees who may be required to submit a fracture
analysis to justify continued operation of a pressure vessel, the USNRC has
developed an elastic-plastic fracture mechanics analytical procedure. This
analytical methodology is presented in NUREG-0744, Revision 1 (Office of
Management and Budget Clearance Number 3150-0011), a copy of which is
enclosed with this letter.
8211160047
.
ALL POWER REACTOR LICENSEES -2-
This document presents one methodology which is acceptable to the USNRC
staff for meeting the requirement for a fracture analysis with sufficient
accuracy and reliability to demonstrate adequate margins for continued
operation in accordance with Section V.C.3 of Appendix G to 10 CFR 50.
Licensees, however, need not employ this specific fracture analysis
methodology and may submit an analysis based on other techniques for NRC
review and approval.
Available evidence reveals that the upper shelf energy of a number of power
reactor pressure vessels may fall below the 50 ft-lb level before the end of
their design life unless measures such as revised fuel management schemes
are instituted. It is likely that several licensees may elect to submit
fracture analysis to support continued operation. All licensees are
encouraged to review NUREG-0744, Revision 1 and consider its application in
those cases where it may be necessary to submit a fracture analysis to the
NRC for review and approval.
Sincerely,
Darrell G. Eisenhut, Director
Division of Licensing
Office of Nuclear Reactor Regulation
Enclosure:
NUREG-0744, Rev. 1
Page Last Reviewed/Updated Tuesday, March 09, 2021