[Federal Register Volume 66, Number 138 (Wednesday, July 18, 2001)]
[Notices]
[Pages 37495-37496]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-17954]


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NUCLEAR REGULATORY COMMISSION

[Docket No. 50-354]


PSEG Nuclear, LLC, Hope Creek Generating Station; Exemption

1.0  Background

    The PSEG Nuclear LLC (PSEG or the licensee) is the holder of 
Facility Operating License No. NPF-57 which authorizes operation of the 
Hope Creek Generating Station (HCGS). The license provides, among other 
things, that the facility is subject to all rules, regulations, and 
orders of the U.S. Nuclear Regulatory Commission (NRC, the Commission) 
now or hereafter in effect.
    The facility consists of a boiling water reactor located in Salem 
County in New Jersey.

2.0  Request/Action

    Title 10 of the Code of Federal Regulations, part 50, appendix G, 
requires that pressure-temperature (P-T) limits be established for 
reactor pressure vessels (RPVs) during normal operating and hydrostatic 
or leak rate testing conditions. Specifically, 10 CFR part 50, appendix 
G, states that ``[t]he appropriate requirements on both the pressure-
temperature limits and the minimum permissible temperature must be met 
for all conditions.'' In addition, Appendix G of 10 CFR part 50 
specifies that the requirements for these limits ``must be at least as 
conservative as limits obtained by following the methods of analysis 
and the margins of safety of Appendix G of Section XI of the ASME Code 
[American Society of Mechanical Engineers Boiler and Pressure Vessel 
Code].''
    By letter dated December 1, 2000, as supplemented by letters dated 
February 12, May 7, and May 14, 2001, PSEG submitted a license 
amendment request to increase the HCGS core thermal power level by 1.4 
percent. The amendment request included proposed P-T limit curves for 
the HCGS RPV. As part of the same submittal, PSEG requested an 
exemption from specific requirements of 10 CFR 50.60(a) and Appendix G. 
The proposed exemption would allow the use of ASME Code Cases N-588, 
``Alternative to Reference Flaw Orientation of Appendix G for 
Circumferential Welds in Reactor Vessels, Section XI, Division 1,'' and 
N-640, ``Alternative Reference Fracture Toughness for Development of P-
T Limit Curves for ASME Section XI, Division 1,'' as alternative 
methods for complying with the fracture toughness requirements in 10 
CFR Part 50, Appendix G. The proposed amendment relies, in part, on the 
requested exemption since the proposed P-T limit curves for the HCGS 
RPV were developed based on the use of Code Cases N-588 and N-640. 
Pursuant to 10 CFR 50.60(b), proposed alternatives to the requirements 
in Appendices G and H of 10 CFR Part 50 may be used by licensees when 
the Commission grants an exemption under 10 CFR 50.12.

3.0  Discussion

    Pursuant to 10 CFR 50.12, the Commission may, upon application by 
any interested person or upon its own initiative, grant exemptions from 
the requirements of 10 CFR part 50, when (1) the exemptions are 
authorized by law, will not present an undue risk to public health or 
safety, and are consistent with the common defense and security; and 
(2) when special circumstances are present. The licensee's application 
states that the proposed exemption meets the special circumstances 
provisions in 10 CFR 50.12(a)(2)(ii), which states that ``[a]pplication 
of the regulation in the particular circumstances would not serve the 
underlying purpose of the rule or is not necessary to achieve the 
underlying purpose of the rule.''
    As previously discussed, the licensee has requested an exemption to 
use ASME Code Cases N-588 and N-640 as alternative methods for 
complying with the fracture toughness requirements in 10 CFR Part 50, 
Appendix G. The underlying purpose of 10 CFR part 50, appendix G, is to 
protect the integrity of the reactor coolant pressure boundary in 
nuclear power plants. This is accomplished through these regulations 
that, in part, specify fracture toughness requirements for ferritic 
materials of the reactor coolant pressure boundary. The staff's review 
related to each of the Code Cases is discussed below.

Code Case N-588

    Code Case N-588 amends the provisions of the 1989 Edition of ASME 
Section XI, Appendix G, by permitting the postulation of a 
circumferentially oriented reference flaw as the limiting flaw in an 
RPV circumferential weld for the purpose of establishing RPV P-T 
limits. The 1989 Edition of ASME Section XI, Appendix G, would require 
that such a reference flaw be postulated as an axially oriented flaw in 
the circumferential weld.
    The licensee addressed the technical justification for this 
exemption by citing industry experience and aspects of RPV fabrication 
which support the postulation of circumferentially oriented flaws for 
these welds. The reference flaw is a postulated flaw that accounts for 
the possibility of a prior existing defect that may have gone 
undetected during the fabrication process. Postulating the ASME Section 
XI, Appendix G reference flaw in a circumferential weld is physically 
unrealistic and overly conservative, because the length of the flaw is 
1.5 times the vessel wall thickness, which is much longer than the 
width of the circumferential weld. Industry experience with the repair 
of weld indications found during preservice inspection, inservice 
nondestructive examinations, and data taken from destructive 
examination of actual vessel welds confirms that any remaining defects 
are small, laminar in nature, and do not cross transverse to the weld 
bead. Therefore, any postulated defects introduced during the 
fabrication process, and not detected during subsequent nondestructive 
examinations, would only be expected to be oriented in the direction of 
weld fabrication. ASME Code Case N-588 also provides appropriate 
procedures for determining the stress intensity factors for use in 
developing RPV P-T limits in accordance with ASME Code, Section XI, 
Appendix G, procedures. The procedures allowed by ASME Code Case

[[Page 37496]]

N-588 are conservative and provide a margin of safety in the 
development of RPV P-T operating and pressure test limits that will 
prevent nonductile fracture of the vessel.
    The staff concurs with the licensee's conclusion that the 
postulation of an axially oriented flaw on a circumferential RPV weld 
is a level of conservatism that is not required to establish P-T limits 
to protect the reactor coolant system pressure boundary from failure 
during hydrostatic testing, heatup, and cooldown. Based on the 
manufacturing processes used to fabricate RPVs for U.S. facilities, it 
is reasonable to conclude that, if a significant defect were to exist 
in a circumferential weld, it would lie in the plane of the welding 
direction. The use of stress magnification factors which account for 
this difference in flaw orientation (i.e., account for a factor of 
approximately two in the difference in the applied pressure stress 
between the axial and circumferential directions) is acceptable.
    The staff also notes that, Code Case N-588, Section 2214.3, 
includes changes to the methodology for determining the thermal stress 
intensity, KIT, which was incorporated into Section XI of the ASME Code 
after the 1989 Edition. The staff has reviewed the basis for these 
changes in the KIT methodology in detail. The staff accepts that the 
modifications made to the KIT methodology in Section 2214.3 of Code 
Case N-588 result in a determination of KIT that is consistent with the 
methodology found in the 1989 Edition of ASME Code Section XI, Appendix 
G, and that the use of equivalent KIT values for axial and 
circumferential flaws is acceptable.
    Application of ASME Code Case N-588 when determining P-T operating 
limit curves per ASME Code, Section XI, appendix G, provides 
appropriate procedures for determining limiting maximum postulated 
defects and considering those defects in developing the P-T limits. 
This application of the code case maintains that margin of safety 
originally contemplated when ASME Code Section XI, appendix G was 
developed.
    Based on the above considerations, the staff concludes that use of 
Code Case N-588 for development of the HCGS RPV P-T limit curves will 
meet the underlying purpose of Appendix G of 10 CFR part 50 with 
respect to protecting the integrity of the reactor coolant pressure 
boundary. In this case, since strict compliance with the requirements 
of 10 CFR 50.60(a) and 10 CFR part 50, appendix G, is not necessary to 
serve the overall intent of the regulations, the staff also concludes 
that application of Code Case N-588 for the HCGS meets the special 
circumstances provisions in 10 CFR 50.12(a)(2)(ii), for granting 
exemptions to the regulations.

Code Case N-640

    Code Case N-640 amends the provisions of ASME Section XI, Appendix 
G, by permitting the use of the Klc equation as found in 
Appendix A in ASME Section XI, in lieu of the Kla equation 
as found in Appendix G in ASME Section XI. Use of the Klc 
equation in determining the lower bound fracture toughness in the 
development of the P-T operating limits curve is more technically 
correct than the use of the Kla equation since the rate of 
loading during a heatup or cooldown is slow and is more representative 
of a static condition than a dynamic condition. The staff has required 
use of the initial conservatism of the Kla equation since 
1974 when the equation was codified. This initial conservatism was 
necessary due to the limited knowledge of RPV materials. Since 1974, 
additional knowledge has been gained about RPV materials, which 
demonstrates that the lower bound on fracture toughness provided by the 
Kla equation is well beyond the margin of safety required to 
protect the public health and safety from potential RPV failure. In 
addition, P-T curves based on the Klc equation will enhance 
overall plant safety by opening the P-T operating window with the 
greatest safety benefit in the region of low temperature operations.
    Based on the above considerations, the staff concludes that use of 
Code Case N-640 for development of the HCGS RPV P-T limit curves will 
meet the underlying purpose of appendix G of 10 CFR part 50 with 
respect to protecting the integrity of the reactor coolant pressure 
boundary. In this case, since strict compliance with the requirements 
of 10 CFR 50.60(a) and 10 CFR part 50, appendix G, is not necessary to 
serve the overall intent of the regulations, the staff also concludes 
that application of Code Case N-640 for the HCGS meets the special 
circumstances provisions in 10 CFR 50.12(a)(2)(ii), for granting 
exemptions to the regulations.

4.0  Conclusion

    Accordingly, the Commission has determined that, pursuant to 10 CFR 
50.12(a), the exemption is authorized by law, will not endanger life or 
property or common defense and security, and is, otherwise, in the 
public interest. Also, special circumstances are present. Therefore, 
the Commission hereby grants PSEG Nuclear LLC an exemption from the 
requirements of 10 CFR 50.60(a) and 10 CFR part 50, appendix G, for 
HCGS.
    Pursuant to 10 CFR 51.32, the Commission has determined that the 
granting of this exemption will not have a significant effect on the 
quality of the human environment (66 FR 33717).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 12th day of July 2001.

    For the Nuclear Regulatory Commission.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 01-17954 Filed 7-17-01; 8:45 am]
BILLING CODE 7590-01-P