[Federal Register Volume 67, Number 62 (Monday, April 1, 2002)]
[Notices]
[Pages 15420-15421]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-7797]


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NUCLEAR REGULATORY COMMISSION

[Docket Nos. 50-260 and 50-296]


Tennessee Valley Authority; Browns Ferry Plant, Units 2 and 3; 
Exemption  

1.0  Background

    The Tennessee Valley Authority (TVA, the licensee) is the holder of 
Facility Operating License Nos. DPR-52 and DPR-68 which authorize 
operation of the Browns Ferry Plant, Units 2 and 3 (BFN 2 and 3), 
respectively. The licenses provide, 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 three boiling-water reactors located in 
Limestone County in the State of Alabama.

2.0  Request/Action

    Title 10 of the Code of Federal Regulations (10 CFR), part 50, 
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, appendix G to 10 CFR 
part 50 states that ``[t]he appropriate requirements on . . . the 
pressure-temperature limits and minimum permissible temperature must be 
met for all conditions.'' Further, appendix G of 10 CFR part 50 
specifies that the requirements for these limits are based on the 
application of evaluation procedures given in Appendix G to Section XI 
of the American Society of Mechanical Engineers (ASME) Code. In this 
exemption, consistent with the current provisions of 10 CFR 50.55(a), 
all references are to the ASME Code denote the 1995 Edition of the ASME 
Code, including the 1996 Addenda.
    In order to address the provisions of amendments to the BFN 2 and 3 
Technical Specifications (TS) P-T limit curves, TVA requested in its 
submittal dated August 17, 2001, as supplemented December 14, 2001, and 
February 6, 2002, that the staff exempt the BFN 2 and 3 from the 
application of the specific requirements of appendix G to 10 CFR part 
50, and substitute use of ASME Code Case N-640. ASME Code Case N-640 
permits the use of an alternate reference fracture toughness curve for 
RPV materials for use in determining the P-T limits. The proposed 
exemption request is consistent with, and is needed to support, the BFN 
2 and 3 TS amendments that were contained in the same submittals. The 
proposed BFN 2 and 3 TS amendments will establish revised P-T limits 
for heatup, cooldown, and inservice test limitations for the reactor 
coolant system (RCS) through 17.2 effective full-power years (EFPY) of 
operation for BFN 2 and through 13.1 EFPY of operation for BFN 3.

ASME Code Case N-640

    The licensee has proposed an exemption to allow the 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 establish P-T limits for the BFN 2 
and 3 RPVs.
    The proposed TS amendments to revise the P-T limits for BFN 2 and 3 
rely in part on the requested exemption and the application of ASME 
Code Case N-640. These revised P-T limits have been developed using the 
lower bound KIC fracture toughness curve shown in ASME 
Section XI, Appendix A, Figure

[[Page 15421]]

A-2200-1, in lieu of the lower bound KIA fracture toughness 
curve of ASME Section XI, Appendix G, Figure G-2210-1, as the basis 
fracture toughness curve for defining the BFN 2 and 3 P-T limits.
    Use of the KIC curve as the basis fracture toughness 
curve for the development of P-T operating limits is more technically 
correct than the use of the KIA curve. The KIC 
curve appropriately implements the use of a relationship based on 
static initiation fracture toughness behavior to evaluate the 
controlled heatup and cooldown process of an RPV, whereas the 
KIA fracture toughness curve codified into Appendix G to 
Section XI of the ASME Code was developed from the more conservative 
crack arrest and dynamic fracture toughness test data. The application 
of the KIA fracture toughness curve was initially codified 
in Appendix G to Section XI of the ASME Code in 1974 to provide a 
conservative representation of RPV material fracture toughness. This 
initial conservatism was necessary due to the limited knowledge of RPV 
material behavior in 1974. However, additional knowledge has been 
gained about RPV materials which demonstrates that the lower bound on 
fracture toughness provided by the KIA fracture toughness 
curve is well beyond the margin of safety required to protect the 
public health and safety from potential RPV failure. In addition, the 
P-T limit curves based on the KIC fracture toughness curve 
will enhance overall plant safety by minimizing challenges to operators 
since requirements for maintaining a high vessel temperature during 
pressure testing would be lessened. Personnel safety would also be 
enhanced because of the corresponding lower temperatures which would 
exist inside containment as leakage walkdown inspections are conducted.
    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 has determined 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.
    The NRC staff has reviewed the exemption request submitted by TVA 
and has concluded that the application of the technical provisions of 
the ASME Code Case N-640 provides sufficient margin in the development 
of RPV P-T limit curves for BFN 2 and 3 such that the underlying 
purpose of the NRC regulations continues to be met 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 has determined 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 concurred that the use 
of the Code Case would meet the underlying purpose of the 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.
    The staff has examined the licensee's rationale to support the 
exemption request and concludes that the 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 
the BFN 2 and 3 RPVs such that the underlying purpose of 10 CFR part 
50, appendix G, continues to be met to ensure an acceptable margin of 
safety.

4.0  Conclusion

    Accordingly, the Commission has determined that, pursuant to 10 CFR 
50.12(a), the exemption is authorized by law, will not present an undue 
risk to the public health and safety, and is consistent with the common 
defense and security. Also, special circumstances are present. 
Therefore, the Commission hereby grants the Tennessee Valley Authority 
an exemption from the requirements of 10 CFR 50, appendix G, for Browns 
Ferry Plant, Units 2 and 3.
    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 (67 FR 11721).
    This exemption is effective upon issuance.

    For the Nuclear Regulatory Commission.

    Dated at Rockville, Maryland, this 21st day of March, 2002.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 02-7797 Filed 3-29-02; 8:45 am]
BILLING CODE 7590-01-P