[Federal Register Volume 69, Number 233 (Monday, December 6, 2004)]
[Notices]
[Pages 70473-70475]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 04-26692]


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NUCLEAR REGULATORY COMMISSION

[Docket No. 50-346]


Firstenergy Nuclear Operating Company; Davis-Besse Nuclear Power 
Station; Amended Exemption

1.0 Background

    The FirstEnergy Nuclear Operating Company (the licensee) is the 
holder of Facility Operating License No. NPF-3, which authorizes 
operation of the Davis-Besse Nuclear Power Station (DBNPS). 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 
Ottawa County, Ohio.

2.0 Request

    Title 10 of the Code of Federal Regulations (10 CFR), Part 50, 
Section 50.46 provides acceptance criteria for the emergency core 
cooling systems (ECCS), including an option to develop the ECCS 
evaluation model in conformance with Appendix K requirements (10 CFR 
50.46(a)(1)(ii)). 10 CFR Part 50, Appendix K, Section 1.D.1, in turn, 
requires that accident evaluations use the combination of ECCS 
subsystems assumed to be operative ``after the most damaging single 
failure of ECCS equipment has taken place.''
    An exemption issued on May 5, 2000, exempted the licensee from the 
single-failure requirement for the two systems (paths) for preventing 
boric acid precipitation (boric acid precipitation control or BPC) 
during the long-term cooling phase following a loss-of-coolant accident 
(LOCA). Additionally, the licensee was exempted from the calculation 
requirements of 50.46(b)(5) and Appendix K, Section I.A.4 for the 
second or backup path for BPC. The proposed action would amend the 
existing exemption by approving a new path for BPC. This new path would 
become the primary path and the original primary path would become the 
backup path. The original backup path would no longer be credited as 
part of

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the licensing basis, although it would remain as a third option 
procedurally. As such, the parts of the exemption related to the 
calculation requirements of 50.46(b)(5) and Appendix K, Section I.A.4 
are removed from the exemption as they only applied to the original 
backup path and are no longer needed.
    Specifically, DBNPS requested the following amended exemption: 
FirstEnergy Nuclear Operating Company, with respect to the Davis-Besse 
Nuclear Power Station, is exempt from the single-failure criterion 
requirement of 10 CFR 50, Appendix K, Section I.D.1, with respect to 
failure of either Motor Control Center E11B or Motor Control Center 
F11A and the resulting inability to initiate an active means of 
controlling core boron concentration.
    In summary, the licensee has modified the plant to install a better 
method of post-LOCA BPC and wants to credit the new method for use.

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. 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 requirements of 10 CFR Part 50 apply to the DBNPS request to 
amend the existing exemption. The underlying purpose of the single-
failure criterion requirement is to assure long-term cooling 
performance of the ECCS in the event of the most damaging single-
failure of ECCS equipment.
    As a licensing review tool, the single-failure criterion helps 
assure reliable systems as an element of defense in depth. As a design 
and analysis tool, it promotes reliability through enforced redundancy. 
Since historically only those systems or components that were judged to 
have a credible chance of failure were assumed to fail, the criterion 
has been applied to such responses as valve movement on demand, 
emergency diesel generator start, short circuit in an electrical bus, 
and fluid leakage caused by gross failure of a pump or valve seal 
during long-term cooling. Certain types of structural elements, when 
combined with other unlikely events, were not assumed to fail because 
the probabilities of the resulting scenarios were deemed sufficiently 
small that they did not need to be considered.
    The single-failure criterion was developed without the benefit of 
numerical failure assessments. Regulatory requirements and guidance 
consequently were based upon categories of equipment and examples that 
must be covered or that are exempt, and do not allow a probabilistic 
consideration during routine implementation. Hence, a single failure 
that was not judged to be exempt would need to be addressed, whether or 
not there is a substantial impact upon overall system reliability. A 
result that does not improve safety is inconsistent with the objective 
of the single-failure criterion, which was not intended to force 
changes if essentially no benefit would accrue. This is the case with 
potential failure of the active means of BPC.
    No U.S. plants have encountered LOCA conditions where BPC was of 
concern. BPC measures are not needed for hot-leg breaks because water 
will flow through the core, thus preventing significant boric acid 
buildup. Additionally, BPC measures are not needed if excore 
thermocouples indicate an adequate subcooling margin because there is 
no boiling to cause concentration of boric acid. Neither are they 
needed for many of the remaining pipe breaks until decay heat is low, 
because water will flow from the core to the upper downcomer via the 
reactor vessel vent valves, thus providing a mechanism to control 
accumulation of boric acid in the core. Active means for BPC are needed 
in case one of the above conditions is not satisfied.
    In reviewing the proposed BPC ECCS alignments, the NRC staff used 
substantial improvement in reliability as its criterion for acceptance, 
since the existing BPC ECCS alignments were found acceptable on a 
probabilistic basis.
    The licensee submitted information that compared the previously 
approved BPC alignments with the proposed alignments to show that the 
proposed BPC ECCS alignments are more reliable than the previously 
approved alignments.
    The new proposed primary path takes suction from the ECCS sump 
through decay heat pump 1-1 to a newly installed crossover line to the 
decay heat removal system hot leg drop line and through decay heat 
system valves DH-11 and DH-12 to the reactor coolant system (RCS) hot 
leg, and finally to the reactor vessel to back-flush precipitated boron 
from the core. The NRC staff determined that this is an improvement 
over the previous primary alignment in that it provides a faster, 
higher, flushing/diluting flow to the reactor vessel from the RCS hot 
leg side. For RCS cold leg pipe breaks, this alignment would provide 
the optimal flow direction for flushing of the core.
    The new proposed backup path is the previous primary path through 
the pressurizer spray line. This continues to be an acceptable path as 
was determined by the staff's review for the exemption issued on May 5, 
2000. Additionally, the new proposed backup path through the 
pressurizer spray line does not need additional exemptions regarding 
the calculation requirements of 50.46(b)(5) and Appendix K, Section 
I.A.4 that the original backup path needed.
    The proposed new BPC primary path is significantly more reliable in 
terms of capacity and timeliness than the previous primary path. As 
stated above, the proposed new backup path is the previous primary path 
and does not need two additional exemptions regarding calculation 
requirements that the original backup path needed. Therefore, the staff 
concludes that the proposed backup path is significantly better than 
the original backup path.
    Based on its review, the NRC staff has determined that the proposed 
BPC alignment paths are significantly more reliable than the previously 
approved paths and, therefore, the staff concludes that they are 
acceptable.
    For the foregoing reasons, the NRC staff has concluded that 
amending the existing exemption to the requirements of Appendix K, 
Section I.D.1, and 10 CFR 50.46(a)(1)(ii) with respect to the revised 
alignment paths for active means of BPC at DBNPS is acceptable. The NRC 
staff has determined that there are special circumstances present, as 
specified in 10 CFR 50.12(a)(2)(ii), in that application of the 
specific regulations is not necessary in order to achieve the 
underlying purpose of these regulations to assure long term cooling 
performance of the ECCS.
    Additionally, the NRC staff has concluded that the parts of the 
exemption related to the calculation requirements of 10 CFR 50.46(b)(5) 
and Appendix K, Section I.A.4 are now withdrawn as they are no longer 
needed.

4.0 Conclusion

    Accordingly, the Commission has determined that, pursuant to 10 CFR 
50.12(a), the amendment to the exemption is authorized by law, will not

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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 
FirstEnergy Nuclear Operating Company an amendment to the exemption 
from the requirements of 10 CFR 50.46(a)(1)(ii) and 10 CFR Part 50, 
Appendix K, Section 1.D.1 for Davis-Besse Nuclear Power Station.
    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 (69 FR 47469).
    This exemption is effective upon issuance and shall be implemented 
within 120 days.

    Dated at Rockville, Maryland, this 29th day of November 2004.

    For the Nuclear Regulatory Commission.
Ledyard B. Marsh,
Director, Division of Licensing Project Management, Office of Nuclear 
Reactor Regulation.
[FR Doc. 04-26692 Filed 12-3-04; 8:45 am]
BILLING CODE 7590-01-P