[Federal Register Volume 65, Number 148 (Tuesday, August 1, 2000)]
[Notices]
[Pages 46995-46996]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-19391]


=======================================================================
-----------------------------------------------------------------------

NUCLEAR REGULATORY COMMISSION

[Docket No. 50-400]


Carolina Power & Light Company; (Shearon Harris Nuclear Power 
Plant, Unit 1); Exemption

    I. Carolina Power & Light Company (CP&L or the licensee) is the 
holder of Facility Operating License No. NPF-63, which authorizes 
operation of the Shearon Harris Nuclear Power Plant, Unit 1 (HNP). The 
facility consists of one pressurized-water reactor located at the 
licensee's site in Wake and Chatham Counties, North Carolina. The 
license provides, among other things, that the licensee is subject to 
all rules, regulations, and orders of the Nuclear Regulatory Commission 
(NRC, the Commission) now or hereafter in effect.
    II. Title 10 of the Code of Federal Regulations (10 CFR) Part 50, 
Appendix G requires that pressure-temperature (P-T) limits be 
established for reactor pressure vessels (RPVs) during normal 
operation, and hydrostatic pressure or leak testing conditions. 
Specifically, 10 CFR Part 50, Appendix G states that ``[t]he 
appropriate requirements on * * * the pressure-temperature limits and 
minimum permissible temperature must be met for all conditions.'' 
Appendix G of 10 CFR Part 50 specifies that the requirements for these 
limits are the American Society of Mechanical Engineers (ASME) Code, 
Section XI, Appendix G Limits. Both 10 CFR Part 50, Appendix G and the 
ASME Code require that the effects of neutron

[[Page 46996]]

irradiation on the material properties of the RPV be considered. 
Regulatory Guide (RG) 1.99, Revision 2, ``Radiation Embrittlement of 
Reactor Vessel Materials,'' dated May 1988, provides an acceptable 
method to account for these effects.
    To address provisions of amendments to the technical specifications 
(TS) P-T limits and low temperature overpressure protection (LTOP) 
system setpoints, the licensee requested in its submittal dated April 
12, 2000, as amended by letter dated June 2, 2000, that the staff 
exempt HNP from application of specific requirements of 10 CFR Part 50, 
Section 50.60(a) and Appendix G, and substitute use of ASME Code Case 
N-640. Code Case N-640 permits the use of an alternate reference 
fracture toughness (KIC fracture toughness curve instead of 
Kla fracture toughness curve) for reactor vessel materials 
in determining the P-T limits and LTOP setpoints. Since the 
KIC fracture toughness curve shown in ASME Section XI, 
Appendix A, Figure A-2200-1 (the KIC fracture toughness 
curve) provides greater allowable fracture toughness than the 
corresponding KIa fracture toughness curve of ASME Section 
XI, Appendix G, Figure G-2210-1 (the KIa fracture toughness 
curve), using Code Case N-640 for establishing the P-T limits and LTOP 
setpoints would be less conservative than the methodology currently 
endorsed by 10 CFR Part 50, Appendix G and, therefore, an exemption to 
apply the Code Case would be required by 10 CFR 50.60. It should be 
noted that although Code Case N-640 was incorporated into the ASME Code 
recently, an exemption is still needed because the proposed P-T limits 
and LTOP setpoints (excluding Code Case N-640) are based on the 1989 
edition of the ASME Code.
    The proposed amendment will revise both the P-T limits of TS 3/
4.4.9.2 related to the heatup and cooldown of the reactor coolant 
system (RCS), and the LTOP setpoints of TS 3/4.4.9.4, for operation to 
36 effective full-power years (EFPYs).
    The licensee has proposed an exemption to allow use of ASME Code 
Case N-640 in conjunction with ASME Section XI, 10 CFR 50.60(a) and 10 
CFR Part 50, Appendix G, to determine P-T limits and LTOP setpoints.
    The proposed amendment to revise the P-T limits and LTOP setpoints 
for HNP relies in part on the requested exemption. These revised P-T 
limits and LTOP setpoints have been developed using the KIC 
fracture toughness curve, in lieu of the Kla fracture 
toughness curve, as the lower bound for fracture toughness of the RPV 
materials.
    Use of the KIC curve in determining the lower bound 
fracture toughness in the development of P-T operating limit curves and 
LTOP setpoints is more technically correct than use of the 
KIa curve 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 KIC curve appropriately implements 
the use of static initiation fracture toughness behavior to evaluate 
the controlled heatup and cooldown process of a reactor vessel. The 
staff has required use of the conservatism of the KIa curve 
since 1974, when the curve was adopted by the ASME Code. This 
conservatism was initially necessary due to the limited knowledge of 
the fracture toughness of RPV materials at that time. Since 1974, 
additional knowledge has been gained about RPV materials, which 
demonstrates that the lower bound on fracture toughness provided by the 
KIa curve greatly exceeds the margin of safety required to 
protect the public health and safety from potential RPV failure. In 
addition, P-T curves and LTOP setpoints based on the KIC 
curve will enhance overall plant safety by opening the P-T operating 
window, with the greatest safety benefit in the region of low 
temperature operations.
    Since an unnecessarily reduced P-T operating window can reduce 
operator flexibility without just basis, implementation of the proposed 
P-T curves and LTOP setpoints as allowed by ASME Code Case N-640 may 
result in enhanced safety during critical plant operational periods, 
specifically heatup and cooldown conditions. Thus, pursuant to 10 CFR 
50.12(a)(2)(ii), the underlying purpose of 10 CFR 50.60 and Appendix G 
to 10 CFR Part 50 will continue to be served.
    In summary, the ASME Section XI, Appendix G, procedure was 
conservatively developed based on the level of knowledge existing in 
1974 concerning RPV materials and the estimated effects of operation. 
Since 1974, the level of knowledge about these topics has been greatly 
expanded. The NRC staff concurs that this increased knowledge permits 
relaxation of the ASME Section XI, Appendix G requirements by 
application of ASME Code Case N-640, while maintaining, pursuant to 10 
CFR 50.12(a)(2)(ii), the underlying purpose of the NRC regulations to 
ensure an acceptable margin of safety.
    III. 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 staff accepts the 
licensee's determination that exemption would be required to approve 
the use of Code Case N-640. The staff examined the licensee's rationale 
to support the exemption requests and concurred that the use of the 
Code case would meet the underlying intent of these regulations. Based 
upon a consideration of the conservatism that is explicitly 
incorporated into the methodologies of 10 CFR Part 50, Appendix G; 
Appendix G of the Code; and Regulatory Guide 1.99, Revision 2, the 
staff concludes that application of the Code case as described would 
provide an adequate margin of safety against brittle failure of the 
RPV. This conclusion is also consistent with the determinations that 
the staff has reached for other licensees under similar conditions 
based on the same considerations. Therefore, the staff concludes that 
requesting an exemption under the special circumstances of 10 CFR 
50.12(a)(2)(ii) is appropriate and that the methodology of Code Case N-
640 may be used to revise the P-T limits and LTOP setpoints for HNP.
    IV. 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. Therefore, the Commission hereby grants Carolina 
Power & Light Company an exemption from the requirements of 10 CFR Part 
50, Section 50.60(a) and 10 CFR Part 50, Appendix G, for HNP.
    Pursuant to 10 CFR 51.32, the Commission has determined that the 
granting of the exemption will not result in any significant effect on 
the quality of the environment (65 FR 45628).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 26 day of July 2000.

    For the Nuclear Regulatory Commission.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 00-19391 Filed 7-31-00; 8:45 am]
BILLING CODE 7590-01-P