[Federal Register Volume 65, Number 178 (Wednesday, September 13, 2000)]
[Notices]
[Pages 55306-55307]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-23526]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-412]
Firstenergy Nuclear Operating Company, (Beaver Valley Power
Station, Unit 2); Exemption
I
The FirstEnergy Nuclear Operating Company (FENOC/the licensee) is
the holder of Facility Operating License No. NPF-73 that authorizes
operation of the Beaver Valley Power Station, Unit 2. The license
provides, among other things, that the licensee 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 pressurized water reactor located in
Shippingport, Beaver County, Pennsylvania.
II
Title 10 of the Code of Federal Regulations (10 CFR) Part 50,
Sec. 50.60(a), requires that ``all light-water nuclear power reactors *
* * must meet the fracture toughness and material surveillance program
requirements for the reactor coolant pressure boundary set forth in
appendices G and H to this part.'' Appendix G to 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, this regulation states
that ``[t]he appropriate requirements on * * * the pressure-temperature
limits and the minimum permissible temperature must be met for all
conditions.'' Additionally, it specifies that the requirements for
these limits are the American Society of Mechanical Engineers (ASME)
Code, Section XI, Appendix G, Limits. This section of the ASME Code in
turn specifies that RPV P/T limits be developed using the
KIa fracture toughness curve of ASME Section XI, Appendix G,
Figure G-2210-1, as the lower bound for fracture toughness.
Pressurized water reactor licensees have installed low temperature
overpressure protection (LTOP) systems in order to protect the reactor
coolant pressure boundary (RCPB) from being operated outside of the
boundaries established by the P/T limit curves and to provide pressure
relief of the RCPB during low temperature overpressurization events.
The licensee is required by the Beaver Valley Unit 2 Technical
Specifications (TSs) to update and submit the changes to its LTOP
setpoints whenever the licensee is requesting approval for amendments
to the P/T limit curves in the Beaver Valley Unit 2 TSs.
In order to address provisions of amendments to the TS P/T limits
and LTOP curves, the licensee requested in its submittal dated June 17,
1999, that the staff exempt Beaver Valley Unit 2 from application of
specific requirements of 10 CFR Part 50, Sec. 50.60(a), and 10 CFR Part
50, appendix G, and substitute the use of ASME Code Case N-640. It
should be noted that, as a result of ASME Code committee action, the
original designation for this Code Case (N-626) was changed to N-640.
Therefore, Code Case N-640 will be discussed below rather than Code
Case N-626, which is the designation referenced in Attachments C and D
of the submittal. Code Case N-640 is an alternate reference for
fracture toughness for reactor vessel materials for use in determining
the P/T limits.
The proposed action is in accordance with the licensee's
application for exemption contained in a submittal dated June 17, 1999,
and is needed to support the TS amendment that is contained in the same
submittal. The proposed amendment will revise the P/T limits of TS 3/
4.4.9 for Beaver Valley Unit 2 related to the heatup, cooldown, and
inservice test limitations for the reactor coolant system (RCS) to 15
Effective Full Power Years (EFPYs). It will also revise the section of
the TSs that relates to the overpressure protection system (OPPS) to
reflect the revised P/T limits of the reactor vessels.
Code Case N-640 (formerly Code Case N-626)
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.
The proposed amendment to revise the P/T limits for Beaver Valley
Unit 2, relies, in part, on the requested exemption. In accordance with
Code Case N-640, these revised P/T limits have been developed using the
KKIc fracture toughness curve shown in ASME Section XI,
Appendix A, Figure A-2200-1, in lieu of the KKIa fracture
toughness curve of ASME Section XI, Appendix G, Figure G-2210-1, as the
lower bound for fracture toughness. The other margins involved with the
ASME Section XI, Appendix G, process of determining P/T limit curves
remain unchanged.
Use of the KIC curve in determining the lower bound
fracture toughness in the development of the P/T operating limits curve
is more technically correct than the KIa curve. 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 use of the initial
conservatism of the KIa curve when the curve was codified in
1974 was justified. This initial conservatism was necessary due to the
limited knowledge of RPV materials. Since 1974, however, 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 addition, P/T
curves 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. Current OPPS
setpoints produce operational constraints by limiting the P/T range
available to the operator for heatup or cooldown of the plant. The
operating window through which the operator heats up and cools down the
RCS is established by the difference between the maximum allowable
pressure determined by Appendix G of ASME Section XI and the minimum
required pressure for the reactor coolant pump (RCP) seals adjusted for
OPPS overshoot and instrument uncertainties. The operating window
becomes more restrictive with continued reactor vessel service.
Since the RCS P/T operating window is defined by the P/T operating
and test limit curves developed in accordance with the ASME Section XI,
Appendix G, procedure, continued operation of Beaver Valley Unit 2 with
these P/T curves without the relief provided by ASME Code Case N-640
would unnecessarily restrict the P/T operating window, especially at
low temperature conditions. Reducing this operating window could
potentially have an adverse safety impact by increasing the possibility
of inadvertent OPPS actuation due to pressure surges
[[Page 55307]]
associated with normal plant evolutions such as RCP start and swapping
operating charging pumps with the RCS in a water-solid condition.
Additionally, the impact on the P/T limits and OPPS setpoints has
been evaluated for an increased service period to 15 EFPYs based on
ASME Section XI, Appendix G, requirements. The results indicate that
OPPS would significantly restrict the ability to perform plant heatup
and cooldown, create an unnecessary burden to plant operations, and
challenge control of plant evolutions required with OPPS enabled.
Implementation of the proposed P-T curves, as allowed by ASME Code Case
N-640, does not significantly reduce the margin of safety. Thus,
pursuant to 10 CFR 50.12(a)(2)(ii), the underlying purpose of the
regulation 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
CFR50.12(a)(2)(ii), the underlying purpose of the ASME Code and 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. Special circumstances are
present whenever, according to 10 CFR 50.12(a)(2)(ii), ``Application 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 * * *.''
The underlying purpose of 10 CFR part 50, section 50.60(a), and 10
CFR part 50, appendix G, is to protect the integrity of the reactor
coolant pressure boundary in nuclear power plants. This is accomplished
through these regulations that, in part, specify fracture toughness
requirements for ferritic materials of the reactor coolant pressure
boundary. The NRC staff accepts the licensee's determination that an
exemption would be required to approve the use of Code Case N-640.
The NRC staff examined the licensee's rationale to support the
exemption request. Based upon a consideration of the conservatism that
is explicitly incorporated into the methodologies of 10 CFR part 50,
Appendix G; ASME Section XI, appendix G; and Regulatory Guide 1.99,
Revision 2, the NRC staff finds that the application of Code Case N-640
will provide results which are sufficiently conservative to ensure the
integrity of the reactor coolant pressure boundary and, thus, meet the
underlying intent of 10 CFR part 50, section 50.60(a), and 10 CFR part
50, appendix G. This is also consistent with determinations that the
NRC staff has reached for other licensees under similar conditions, and
based on the same considerations. Therefore, the NRC staff finds that
special circumstances set forth in 10 CFR 50.12(a)(2)(ii) are present
and that the methodology of Code Case N-640 may be used to revise the
P/T limits and the LTOP setpoints for the Beaver Valley Unit 2 RCS.
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 FENOC an
exemption from the requirements of 10 CFR part 50, section 50.60(a),
and 10 CFR part 50, appendix G, for the Beaver Valley Unit 2 reactor
coolant system.
Pursuant to 10 CFR 51.32, the Commission has determined that the
granting of this exemption will not result in any significant effect on
the quality of the human environment. (65 FR 50722).
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 6 day of September 2000.
For the Nuclear Regulatory Commission.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear
Reactor Regulation.
[FR Doc. 00-23526 Filed 9-12-00; 8:45 am]
BILLING CODE 7590-01-U