[Federal Register Volume 66, Number 161 (Monday, August 20, 2001)]
[Notices]
[Page 43594]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-20886]


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NUCLEAR REGULATORY COMMISSION

[Docket No. 50-423]


Dominion Nuclear Connecticut, Inc., Millstone Nuclear Power 
Station, Unit No. 3; Exemption

1.0  Background

    The Dominion Nuclear Connecticut, Inc., (the licensee) is the 
holder of Facility Operating License No. NPF-49 which authorizes 
operation of the Millstone Nuclear Power Station, Unit No.3 (MP3). The 
license provides, among other things, that the facility is subject to 
all rules, regulations, and orders of the U.S. Nuclear Regulatory 
Commission (the Commission) now or hereafter in effect.
    The facility consists of a pressurized water reactor located in New 
London County, Connecticut.

2.0  Request/Action

    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 operating 
and hydrostatic or leak rate 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.
    To address provisions of amendments to the technical specifications 
(TSs) P-T limits in the submittal dated April 23, 2001, the licensee 
requested that the staff exempt MP3 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 (Klc fracture 
toughness curve instead of Kla. fracture toughness curve) 
for reactor vessel materials in determining the P-T limits. Since the 
Klc fracture toughness curve shown in ASME Section XI, 
Appendix A, Figure A-2200-1 provides greater allowable fracture 
toughness than the corresponding Kla fracture toughness 
curve of ASME Section XI, Appendix G, Figure G-2210-1, using the 
Klc fracture toughness, as permitted by Code Case N-640, in 
establishing the P-T limits would be less conservative than the 
methodology currently endorsed by 10 CFR Part 50, Appendix G. 
Considering this, an exemption to apply the Code Case would be required 
by 10 CFR 50.60.
    The licensee proposed to revise the P-T limits in the TSs for MP3 
using the Klc fracture toughness curve, in lieu of the 
Kla fracture toughness curve, as the lower bound for 
fracture toughness.
    Use of the Klc curve in determining the lower bound 
fracture toughness in the development of P-T operating limits curve is 
more technically correct than the Kla 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 
Klc 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 initial conservatism of the Kla curve since 1974 
when the curve 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 
curve 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 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.
    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 Commission concurs that this increased knowledge permits 
relaxation of the ASME Section XI, Appendix G requirements by applying 
the Klc fracture toughness, as permitted by Code Case N-640, 
while maintaining, pursuant to 10 CFR 50.12(a)(2)(ii), the underlying 
purpose of the ASME Code and the NRC regulations to ensure an 
acceptable margin of safety.

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 staff considers that 
pursuant to 10 CFR 50.12(a)(2)(ii) special circumstances are present 
and that an exemption may be granted to allow use of the methodology of 
Code Case N-640 to revise the P-T limits for MP3 because it would 
provide an adequate margin of safety against brittle fracture. See the 
safety evaluation supporting these findings dated August 14, 2001.

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 Dominion Nuclear Connecticut, Inc., an 
exemption from the requirements of 10 CFR 50.60(a) and 10 CFR Part 50, 
Appendix G, for MP3. 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 
42567).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 14th day of August.

    For the Nuclear Regulatory Commission.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 01-20886 Filed 8-17-01; 8:45 am]
BILLING CODE 7590-01-P