[Federal Register Volume 65, Number 210 (Monday, October 30, 2000)]
[Notices]
[Pages 64723-64724]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-27807]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-250 and 50-251]
In the Matter of Florida Power and Light Company (Turkey Point
Plant, Units 3 and 4); Exemption
I
Florida Power and Light Company (FPL, the licensee) is the holder
of Facility Operating License Nos. DPR-31 and DPR-41 that authorize
operation of the Turkey Point Plant, Units 3 and 4, respectively. The
licenses provide, among other things, that the facilities are subject
to all rules, regulations, and orders of the U.S. Nuclear Regulatory
Commission (the Commission/NRC) now or hereafter in effect.
The facilities consist of pressurized water reactors located in
Dade County, Florida.
II
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 pressure or leak testing conditions. Specifically, 10
CFR Part 50, Appendix G states that ``The appropriate requirements on
both the pressure-temperature limits and the 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 the provisions of proposed license amendments to the
technical specification (TS) P/T limits, low temperature overpressure
protection (LTOP) system setpoints and LTOP system effective
temperature (Tenable), the licensee requested in its
submittal dated July 7, 2000, as supplemented October 4, 2000, that the
staff exempt Turkey Point Units 3 and 4 from application of specific
requirements of 10 CFR Part 50, Section 50.60(a) and Appendix G, and
substitute use of ASME Code Cases N-588 and N-641. Code Case N-588
permits the use of circumferentially-oriented flaws in circumferential
welds for development of P/T limits. Code Case N-641 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, LTOP setpoints
and Tenable. Since the KIC fracture toughness
curve shown in ASME Section XI, Appendix A, Figure A-2200-1, provides
greater allowable fracture toughness than the corresponding
KIa fracture toughness curve of ASME Section XI, Appendix G,
Figure G-2210-1 (the KIa fracture toughness curve), using
Code Case N-641 for establishing the P/T limits, LTOP setpoints and
Tenable would be less conservative than the methodology
currently endorsed by 10 CFR Part 50, Appendix G and, therefore, an
exemption to apply the Code Case would be required by 10 CFR 50.60. It
should be noted that although the use of the KIC fracture
toughness curve in Code Case N-641 was recently incorporated into the
Appendix G to Section XI of the ASME Code, an exemption is still needed
because the proposed P/T limits, LTOP setpoints and Tenable
(excluding Code Case N-641) are based on the 1996 edition (and 1997
addenda) of the ASME Code. The licensee uses the Westinghouse version
of LTOP which is called Cold Overpressure Mitigation System.
The proposed license amendments will revise both the P/T limits of
TS 3/
[[Page 64724]]
4.4.9.1 related to the heatup and cooldown of the reactor coolant
system (RCS), and the LTOP setpoints and Tenable of TS 3/
4.4.9.3, for operation to 32 effective full power years (EFPY).
Code Case N-588
The licensee has proposed an exemption to allow use of ASME Code
Case N-588 in conjunction with ASME Section XI, 10 CFR 50.60(a) and 10
CFR Part 50, Appendix G, to determine P/T limits for Turkey Point Units
3 and 4.
The proposed license amendments to revise the P/T limits for Turkey
Point Units 3 and 4 rely, in part, on the requested exemption. These
revised P/T limits have been developed using postulated flaws in the
circumferential orientation for the circumferential welds in the Turkey
Point RPVs, in lieu of postulating axial flaws in the circumferential
welds.
The use of circumferential flaws in circumferential welds is more
appropriate than the use of axial flaws in circumferential welds. Since
the flaws postulated in the development of P/T limits have a through-
wall depth of one-quarter of the vessel wall thickness (1.94 inches for
the Turkey Point RPVs), the length of the postulated flaw, six times
the depth, is more than 11 inches. For the circumferential welds in the
Turkey Point RPVs, an axial flaw of this length centered at the weld
would place the tips of the postulated flaw within the adjacent base
metal above and below the weld. Therefore, the only way to maintain a
flaw within the circumferential weld metal is to postulate a
circumferential flaw within the weld, as accomplished using Code Case
N-588. Note that for the base metals adjacent to the circumferential
welds, axial flaws are, and continue to be, postulated for the
development of P/T limits.
Code Case N-641
The licensee has proposed an exemption to allow use of ASME Code
Case N-641 in conjunction with ASME Section XI, 10 CFR 50.60(a) and 10
CFR Part 50, Appendix G, to determine LTOP system effective
temperature, Tenable.
The proposed license amendments to revise Tenable for
Turkey Point Units 3 and 4 rely, in part, on the requested exemption.
The revised Tenable has been developed using the
KIc fracture toughness curve, in lieu of the KIa
fracture toughness curve, as the lower bound for fracture toughness of
the reactor pressure vessel materials.
Use of the KIc curve in determining the lower bound
fracture toughness of RPV steels is more technically correct than use
of 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 conservatism of the
KIa curve since 1974, when the curve was adopted by the ASME
Code. This conservatism was initially necessary due to the limited
knowledge of the fracture toughness of RPV materials at that time.
Since 1974, additional knowledge has been gained about RPV materials
which demonstrates that the lower bound on fracture toughness provided
by the KIa curve greatly exceeds the margin of safety
required to protect the public health and safety from potential RPV
failure. In addition, P/T curves, LTOP setpoints and Tenable
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.
Since an unnecessarily reduced P/T operating window can reduce
operator flexibility without just basis, implementation of the proposed
P/T curves, LTOP setpoints and Tenable as allowed by ASME
Code Cases N-588 and N-641 may result in enhanced safety during
critical plant operational periods, specifically heatup and cooldown
conditions. Thus, pursuant to 10 CFR 50.12(a)(2)(ii), the underlying
purpose of 10 CFR 50.60 and Appendix G to 10 CFR Part 50 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 has determined that this increased knowledge
permits relaxation of the ASME Section XI, Appendix G requirements by
application of ASME Code Cases N-588 and N-641, 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.
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.
The staff has determined that an exemption would be required to
approve the use of Code Cases N-588 and N-641. The staff examined the
licensee's rationale to support the exemption request and concurred
that the use of the Code cases would meet the underlying purpose of
these 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 cases 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. Therefore, the staff concludes that
requesting exemption under the special circumstances of 10 CFR
50.12(a)(2)(ii) is appropriate and that the methodologies of Code Cases
N-588 and N-641 may be used to revise the P/T limits, LTOP setpoints
and Tenable for Turkey Point Units 3 and 4.
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 Florida Power
and Light Company exemption from the requirements of 10 CFR Part 50,
Section 50.60(a) and 10 CFR Part 50, Appendix G, for Turkey Point Units
3 and 4.
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 63265).
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 24th day of October 2000.
For the Nuclear Regulatory Commission.
John A. Zwolinski,
Director, Division of Licensing Project Management, Office of Nuclear
Reactor Regulation.
[FR Doc. 00-27807 Filed 10-27-00; 8:45 am]
BILLING CODE 7590-01-P