[Federal Register Volume 66, Number 188 (Thursday, September 27, 2001)]
[Notices]
[Pages 49424-49425]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-24175]


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NUCLEAR REGULATORY COMMISSION

[Docket No. 50-458]


Entergy Operations, Inc. River Bend Station, Unit 1; Exemption

1.0  Background

    Entergy Operations, Inc. (the licensee) is the holder of Facility 
Operating License No. NPF-47 which authorizes operation of the River 
Bend Station, Unit 1 (RBS). 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 or the Commission) now or 
hereafter in effect.
    The facility consists of a boiling water reactor located in West 
Felciana Parish in Louisiana.

2.0  Request/Action

    Title 10 of the Code of Federal Regulations (10 CFR) part 50, 
appendix G requires that pressure-temperature (P-T or 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, section IV.2.a states that ``* * *[t]he 
appropriate requirements on both the pressure-temperature limits and 
the minimum permissible temperature must be met for all conditions.'' 
Pursuant to 10 CFR part 50, appendix G, section IV.2.b, the 
requirements for these limits are the American Society of Mechanical 
Engineers (ASME) Boiler and Pressure Vessel Code (Code), section XI, 
appendix G Limits.
    To address provisions of amendments to Technical Specification (TS) 
3.4.11, ``RCS [Reactor Coolant System] Pressure and Temperature (P/T) 
Limits,'' and the RCS P/T limits in TS Figure 3.4-11, ``Minimum 
Temperature Required Vs. RCS Pressure,'' in the submittal dated January 
24, 2001, as supplemented by

[[Page 49425]]

letters dated July 2, and August 6 and 20, 2001, the licensee requested 
that the staff exempt RBS 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 KIa fracture toughness curve) for reactor vessel 
materials in determining the P-T limits. Since the KIc 
fracture toughness curve shown in ASME Code Section XI, appendix A, 
Figure A-2200-1 provides greater allowable fracture toughness than the 
corresponding KIa fracture toughness curve of ASME Code 
Section XI, appendix G, Figure G-2210-1, using the KIc 
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 has proposed to revise the P-T limits for RBS using 
the KIc fracture toughness curve, in lieu of the 
KIa fracture toughness curve, as the lower bound for 
fracture toughness.
    Use of the KIc curve in determining the lower bound 
fracture toughness in the development of P-T operating limits curve is 
more technically correct than 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 initial conservatism of the KIa 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 KIa 
curve is well beyond the margin of safety required to protect the 
public health and safety from potential RPV failure.
    In summary, the ASME Code 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 concludes that this increased knowledge permits 
relaxation of the ASME Code Section XI, appendix G requirements by 
applying the KIc 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 accepts the 
licensee's determination that an exemption would be required to approve 
the use of Code Case N-640.
    The staff examined the licensee's rationale to support the 
exemption request and concluded that the use of the Code Case would 
meet the underlying purpose of 10 CFR part 50. 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 concluded that 
application of Code Case N-640 as described would provide an adequate 
margin of safety against brittle failure of the RPV. This is also 
consistent with the determination that the staff has reached for other 
licensees under similar conditions based on the same considerations.
    The safety evaluation may be examined, and/or copied for a fee, at 
the NRC's Public Document Room, located at One White Flint North, 11555 
Rockville Pike (first floor), Rockville, Maryland. Publicly available 
records will be accessible electronically from the ADAMS Public Library 
component on the NRC website, http://www.nrc.gov (the Electronic 
Reading Room).
    Therefore, the staff concludes that requesting 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 
for RBS, subject to the limitation of 16 EFPYs.

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 Entergy Operations, Inc., an exemption 
from the requirements of 10 CFR part 50, Section 50.60(a) and 10 CFR 
part 50, appendix G, for River Bend Station, Unit 1.
    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 48069, published on September 
17, 2001).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 20th day of September, 2001.

    For the Nuclear Regulatory Commission.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 01-24175 Filed 9-26-01; 8:45 am]
BILLING CODE 7590-01-P