[Federal Register Volume 77, Number 169 (Thursday, August 30, 2012)]
[Notices]
[Pages 52765-52766]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-21485]


=======================================================================
-----------------------------------------------------------------------

NUCLEAR REGULATORY COMMISSION

[Docket No. 50-423; NRC-2012-0197]


Dominion Nuclear Connecticut, Inc. Millstone Power Station, Unit 
3; Exemption

1.0 Background

    Dominion Nuclear Connecticut, Inc., (the licensee, Dominion) is the 
holder of Renewed Facility Operating License No. NPF-49, which 
authorizes operation of the Millstone Power Station, Unit 3 (MPS3). 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.
    MPS3 shares the site with Millstone Power Station Unit 1, a 
permanently defueled boiling water reactor nuclear unit, and Millstone 
Power Station Unit 2, a pressurized water reactor. The facility is 
located in Waterford, Connecticut, approximately 3.2 miles west 
southwest of New London, CT. This exemption applies to MPS3 only. The 
other units, Units 1 and 2, are not part of this exemption.

2.0 Request/Action

    Section 50.46 of Title 10 of the Code of Federal Regulations (10 
CFR), ``Acceptance criteria for emergency core cooling systems [ECCS] 
for light-water nuclear power reactors,'' requires that each power 
reactor meet the acceptance criteria for ECCS provided therein for 
zircaloy or ZIRLO\TM\ cladding. Appendix K of 10 CFR part 50, ``ECCS 
Evaluation Models,'' requires the rate of energy release, hydrogen 
generation, and cladding oxidation from the metal/water reaction to be 
calculated using the Baker-Just equation (Baker, L., Just, L.C., 
``Studies of Metal Water Reactions at High Temperatures, III. 
Experimental and Theoretical Studies of the Zirconium-Water Reaction,'' 
ANL-6548, page 7, May 1962).
    Both of the above requirements require the use of zircaloy or 
ZIRLO\TM\ cladding. The licensee proposes to use Optimized ZIRLO\TM\ as 
the cladding material and therefore is requesting an exemption from the 
requirements.
    In summary, by letter dated November 17, 2011, (Agencywide 
Documents Access and Management System (ADAMS), Accession No. 
ML11329A003), the licensee requested an exemption from the requirements 
of 10 CFR 50.46 and Appendix K to 10 CFR part 50. The reason for the 
exemption is to allow the use of Optimized ZIRLO\TM\ as a cladding 
material.

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. These circumstances include 
the special circumstances that application of the regulation is not 
necessary to achieve the underlying purpose of the rule.

Authorized by Law

    This exemption would allow the licensee to use Optimized ZIRLO \TM\ 
fuel rod cladding material at MPS3. As stated above, 10 CFR 50.12 
allows the NRC to grant exemptions from the requirements of 10 CFR part 
50. The NRC staff has determined that granting of the licensee's 
proposed exemption will not result in a violation of the Atomic Energy 
Act of 1954, as amended, or the Commission's regulations. Therefore, 
the exemption is authorized by law.

No Undue Risk to Public Health and Safety

    The underlying purpose of 10 CFR 50.46 is to establish acceptance 
criteria for adequate ECCS performance. By letter dated June 10, 2005 
(ADAMS Accession No. ML051670408), the NRC staff issued a safety 
evaluation (SE) approving Addendum 1 to Westinghouse Topical Report 
WCAP-12610-P-A and CENPD-404-P-A, ``Optimized ZIRLOTM'' 
(ADAMS Accession No. ML062080576), wherein the NRC staff approved the 
use of Optimized ZIRLOTM as a fuel cladding material. The 
NRC staff approved the use of Optimized ZIRLOTM as a fuel 
cladding material based on: (1) Similarities with ZIRLOTM, 
(2) demonstrated material performance, and (3) a commitment to provide 
irradiated data and validate fuel performance models ahead of burnups 
achieved in batch application. The NRC staff's SE for Optimized 
ZIRLOTM includes 10 conditions and limitations for its use. 
As previously documented in the NRC staff's review of topical reports 
submitted by Westinghouse Electric Company, LLC (Westinghouse), and 
subject to compliance with the specific conditions of approval 
established therein, the NRC staff finds that the applicability of 
these ECCS acceptance criteria to Optimized ZIRLOTM has been 
demonstrated by Westinghouse. Ring compression tests performed by 
Westinghouse on Optimized ZIRLOTM (NRC reviewed, approved, 
and documented in Appendix B of WCAP-12610-P-A and CENPD-404-P-A, 
Addendum 1-A, ``Optimized ZIRLOTM'') (ADAMS Accession No. 
ML062080576) demonstrate an acceptable retention of post-quench 
ductility up to 10 CFR 50.46 limits of 2200[emsp14][deg]F and 17 
percent equivalent clad reacted. Furthermore, the NRC staff has 
concluded that oxidation measurements provided by the licensee 
illustrate that oxide thickness (and associated hydrogen pickup) for 
Optimized ZIRLOTM at any given burnup would be less than 
both zircaloy-4 and ZIRLOTM. Hence, the NRC staff concludes 
that Optimized ZIRLOTM would be expected to maintain better 
post-quench ductility than ZIRLOTM. This finding is further 
supported by an ongoing loss-of-coolant accident (LOCA) research 
program at Argonne National Laboratory, which has identified a strong 
correlation between cladding hydrogen content (due to in-service 
corrosion) and post-quench ductility.
    The underlying purpose of 10 CFR Part 50, Appendix K, Section 
I.A.5, ``Metal-Water Reaction Rate,'' is to ensure that cladding 
oxidation and hydrogen generation are appropriately limited during a 
LOCA and conservatively accounted for in the ECCS evaluation model. 
Appendix K states that the rates of energy release, hydrogen 
concentration, and cladding oxidation from the metal-water reaction 
shall be calculated using the Baker-Just equation. Since the Baker-Just 
equation presumes the use of zircaloy clad fuel, strict application of 
the rule would not permit use of the equation for Optimized ZIRLO \TM\ 
cladding for determining acceptable fuel performance. However, the NRC 
staff has found that metal-water reaction tests performed by 
Westinghouse on Optimized ZIRLO \TM\ demonstrate conservative reaction 
rates relative to the Baker-Just equation and are bounded

[[Page 52766]]

by those approved for ZIRLO \TM\ under anticipated operational 
occurrences and postulated accidents.
    Based on the above, no new accident precursors are created by using 
Optimized ZIRLO \TM\, thus, the probability of postulated accidents is 
not increased. Also, based on the above, the consequences of postulated 
accidents are not increased. Therefore, there is no undue risk to 
public health and safety.

Consistent With Common Defense and Security

    The proposed exemption would allow the use of Optimized ZIRLO\TM\ 
fuel rod cladding material at MPS3. This change to the plant 
configuration has no relation to security issues. Therefore, the common 
defense and security is not impacted by this exemption.

Special Circumstances

    Special circumstances, in accordance with 10 CFR 50.12(a)(2)(ii), 
are present whenever application of the regulation in the particular 
circumstances is not necessary to achieve the underlying purpose of the 
rule. The underlying purpose of 10 CFR 50.46 and Appendix K to 10 CFR 
part 50 is to establish acceptance criteria for ECCS performance and to 
ensure that cladding oxidation and hydrogen generation are 
appropriately limited during a LOCA and conservatively accounted for in 
the ECCS evaluation model. The wording of the regulations in 10 CFR 
50.46 and Appendix K is not directly applicable to Optimized ZIRLO 
\TM\, even though the evaluations above show that the intent of the 
regulation is met. Therefore, since the underlying purposes of 10 CFR 
50.46 and Appendix K are achieved through the use of Optimized ZIRLO 
\TM\ fuel rod cladding material, the special circumstances required by 
10 CFR 50.12(a)(2)(ii) for the granting of an exemption from certain 
requirements of 10 CFR 50.46 and Appendix K exist.

4.0 Conclusion

    Accordingly, the Commission has determined that, pursuant to 10 CFR 
50.12, 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 Dominion an exemption from 
certain requirements of 10 CFR 50.46 and Appendix K to 10 CFR part 50, 
to allow the use of Optimized ZIRLO \TM\ fuel rod cladding material, 
for MPS3.
    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 (77 FR 50533).
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 23rd day of August 2012.

    For the Nuclear Regulatory Commission.

Michele G. Evans,
Director, Division of Operating Reactor Licensing, Office of Nuclear 
Reactor Regulation.
[FR Doc. 2012-21485 Filed 8-29-12; 8:45 am]
BILLING CODE 7590-01-P