[Federal Register Volume 68, Number 235 (Monday, December 8, 2003)]
[Notices]
[Pages 68428-68430]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-30360]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-286]
Entergy Nuclear Operations, Inc., Indian Point Nuclear Generating
Unit No. 3; Exemption
1.0 Background
Entergy Nuclear Operations, Inc. (Entergy, the licensee) is the
holder of Facility Operating License No. DPR-64 which authorizes
operation of the Indian Point Nuclear Generating Unit No. 3 (IP3). The
license provides, among other things, that the facility is subject to
all rules, regulations, and orders of the Nuclear Regulatory Commission
(NRC, the Commission) now or hereafter in effect.
The facility consists of a pressurized-water reactor located in
Westchester County in the State of New York.
2.0 Request/Action
Title 10 of the Code of Federal Regulations (10 CFR), part 50,
requires that reactor coolant system (RCS)
[[Page 68429]]
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 both the pressure-temperature
limits and the minimum permissible temperature must be met for all
conditions.'' Furthermore, Appendix G to 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 Boiler and Pressure Vessel Code (ASME
Code). Appendix G to 10 CFR part 50 also specifies that the Editions
and Addenda of the ASME Code which are incorporated by reference in 10
CFR 50.55a apply to the requirements in Appendix G to 10 CFR part 50.
In the 2003 Edition of 10 CFR, the NRC endorsed Editions and Addenda of
the ASME Code through the 1998 Edition and 2000 Addenda. However,
Entergy has currently incorporated the 1989 Edition of the ASME Code
into the IP3 licensing basis for defining the ASME Code requirements
which apply to the facility's ASME Code, Section XI program. Hence,
with respect to the statements from Appendix G to 10 CFR part 50
referenced above, it is the 1989 Edition of Appendix G to Section XI of
the ASME Code which continues to apply to IP3. Finally, 10 CFR 50.60(b)
states that, ``[p]roposed alternatives to the described requirements in
[Appendix G] of this part or portions thereof may be used when an
exemption is granted by the Commission under [10 CFR 50.12].''
Entergy has requested, in a separate submittal dated May 28, 2003,
an amendment to the IP3 Technical Specification (TS) P-T limit curves.
In order to address the provisions of this amendment, Entergy has also
requested that the staff exempt IP3 from the application of specific
requirements of Appendix G to 10 CFR part 50, and substitute the 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 when
determining P-T limits. The proposed exemption request is consistent
with, and is needed to support, the proposed IP3 TS amendment that was
provided in the separate submittal. The proposed IP3 TS amendment will
revise the P-T limits for heatup, cooldown, and inservice test
limitations for the reactor coolant system (RCS) through 20 effective
full-power years of operation.
Code Case N-640
The requested exemption would allow use of ASME Code Case N-640 in
conjunction with Appendix G to Section XI of the ASME Code, 10 CFR
50.60(a), and Appendix G to 10 CFR part 50 to establish P-T limits for
the IP3 RPV.
The licensee's proposed TS amendment to revise the P-T limits for
IP3 relies, in part, on the requested exemption. These revised P-T
limits have been developed using the lower bound KIC
fracture toughness curve given in Appendix A to Section XI of the ASME
Code, Figure A-2200-1, in lieu of the lower bound KIA
fracture toughness curve given in Appendix G to Section XI of the ASME
Code, Figure G-2210-1, as the basis fracture toughness curve for
defining the IP3 P-T limits. All other margins involved with the ASME
Code, Section XI, Appendix G process of determining P-T limit curves
remain unchanged.
Use of the KIC curve as the basis fracture toughness
curve for the development of P-T operating limits is technically
correct. 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, as given in Appendix G to
Section XI of the ASME Code, was developed from 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. Since that time, however, additional
knowledge about RPV materials has been gained, 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, P-T limit curves based on the KIC fracture
toughness 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. The operating window through which the operator
heats up and cools down the RCS is determined by the difference between
the maximum allowable pressure, determined by Appendix G to Section XI
of the ASME Code, and the minimum required pressure for the reactor
coolant pump (RCP) seals adjusted for instrument uncertainties. A
narrow operating window could potentially have an adverse safety impact
by increasing the possibility of inadvertent overpressure protection
system (OPPS) actuation due to pressure surges associated with normal
plant evolutions such as RCS pump starts and swapping operating
charging pumps with the RCS in a water-solid condition.
Since application of ASME Code Case N-640 provides appropriate
procedures to establish maximum postulated defects and to evaluate
those defects in the context of establishing RPV P-T limits, this
application of the Code Case maintains an adequate margin of safety for
protecting RPV materials from brittle failure. Therefore, the licensee
concluded that these considerations were special circumstances pursuant
to 10 CFR 50.12(a)(2)(ii), ``[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.''
In summary, the ASME Code, Section XI, Appendix G procedure was
conservatively developed based on the level of knowledge existing in
1974 concerning reactor coolant pressure boundary materials and the
estimated effects of operation. Since 1974, the level of knowledge
about the fracture mechanics behavior of RCS materials has been greatly
expanded, especially in regard to the effects of radiation
embrittlement and the understanding of fracture toughness properties
under static and dynamic loading conditions.
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 the public health
and safety, and are consistent with the common defense and security;
and (2) when special circumstances are present.
Special circumstances, pursuant to 10 CFR 50.12(a)(2)(ii), are
present because the continued operation of IP3 with the P-T curves
developed in accordance with Appendix G to Section XI of the ASME Code,
without the relief provided by ASME Code Case N-640, is not necessary
to achieve the underlying purpose of Appendix G to 10 CFR part 50.
Application of ASME Code Case N-640 in lieu of the requirements of
Appendix G to Section XI of the ASME Code provides an acceptable
alternative evaluation procedure, which will
[[Page 68430]]
continue to meet the underlying purpose of Appendix G to 10 CFR part
50. The underlying purpose of the regulations in Appendix G to 10 CFR
part 50 is to provide an acceptable margin of safety against brittle
failure of the RCS during any condition of normal operation to which
the pressure boundary may be subjected over its service lifetime.
The NRC staff examined the licensee's rationale to support the
exemption request, and accepts the licensee's determination that an
exemption would be required to approve the use of ASME Code Case N-640.
The staff has also concluded that the use of ASME Code Case N-640 would
meet the underlying intent of Appendix G to 10 CFR part 50. The NRC
staff concluded that the application of the technical provisions of
ASME Code Case N-640 provided sufficient margin in the development of
RPV P-T limit curves such that the underlying purpose of the
regulations contained in Appendix G to 10 CFR part 50 continued to be
met. Therefore, the specific conditions required by the regulations;
i.e., the use of all provisions in Appendix G to Section XI of the ASME
Code, were not necessary. The NRC staff has, therefore, concluded that
the exemption requested by Entergy is justified based on the special
circumstances of 10 CFR 50.12(a)(2)(ii), ``[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.''
Based upon a consideration of the conservatism that is explicitly
incorporated into the methodologies of Appendix G to 10 CFR part 50 and
Appendix G to Section XI of the ASME Code, the staff concluded that the
application of ASME Code Case N-640 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 staff
concludes that the exemption requested by Entergy is appropriate under
the special circumstances of 10 CFR 50.12(a)(2)(ii), and the
methodology of ASME Code Case N-640 may be used to revise the P-T
limits for the IP3 RPV. Pursuant to 10 CFR 50.12(a)(1), the granting of
this exemption is authorized by law, will not present undue risk to the
public health and safety, and is consistent with the common defense and
security. Therefore, the staff considers granting an exemption to 10
CFR 50.60(a) and Appendix G to 10 CFR part 50 to allow use of ASME Code
Case N-640 as part of the basis for generating the P-T limit curves for
IP3 is appropriate.
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 Entergy an exemption from the
requirements of 10 CFR 50.60 and Appendix G to 10 CFR part 50, to allow
for the application of ASME Code Case N-640 in establishing TS
requirements for the RPV P-T limits for IP3.
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 (68 FR 67490).
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 2nd day of December, 2003.
For the Nuclear Regulatory Commission.
Ledyard B. Marsh, Director,
Division of Licensing Project Management, Office of Nuclear Reactor
Regulation.
[FR Doc. 03-30360 Filed 12-5-03; 8:45 am]
BILLING CODE 7590-01-P