80 FR 58509 - Duke Energy Carolinas, LLC; Oconee Nuclear Station Units 1, 2, and 3; Independent Spent Fuel Storage Installation

NUCLEAR REGULATORY COMMISSION

Federal Register Volume 80, Issue 188 (September 29, 2015)

The U.S. Nuclear Regulatory Commission (NRC) is issuing an exemption in response to a request submitted by Duke Energy Carolinas, LLC., on August 28, 2014, from meeting Technical Specification (TS) 1.2.4a of Attachment A of CoC No. 1004, which limits the leak rate of the inner seal weld to 1.0 X 10-7 reference cubic centimeters per second (ref cc/s) at the highest DSC limiting pressure, for five (5) dry shielded canisters (DSCs) at the Oconee Nuclear Station, Independent Spent Fuel Storage Installation (ISFSI).

[Federal Register Volume 80, Number 188 (Tuesday, September 29, 2015)]
[Notices]
[Pages 58509-58512]
From the Federal Register Online  [www.thefederalregister.org]
[FR Doc No: 2015-24655]


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NUCLEAR REGULATORY COMMISSION

[Docket Nos.: 72-1004, 72-40, 50-269, 50-270, 50-287; and NRC-2015-
0191]


Duke Energy Carolinas, LLC; Oconee Nuclear Station Units 1, 2, 
and 3; Independent Spent Fuel Storage Installation

AGENCY: Nuclear Regulatory Commission.

ACTION: Exemption; issuance.

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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is issuing an 
exemption in response to a request submitted by Duke Energy Carolinas, 
LLC., on August 28, 2014, from meeting Technical Specification (TS) 
1.2.4a of Attachment A of CoC No. 1004, which limits the leak rate of 
the inner seal weld to 1.0 X 10-7 reference cubic centimeters per 
second (ref cc/s) at the highest DSC limiting pressure, for five (5) 
dry shielded canisters (DSCs) at the Oconee Nuclear Station, 
Independent Spent Fuel Storage Installation (ISFSI).

ADDRESSES: Please refer to Docket ID NRC-2015-0191 when contacting the 
NRC about the availability of information regarding this document. You 
may obtain publicly-available information related to this document 
using any of the following methods:
     Federal Rulemaking Web site: Go to http://www.regulations.gov and search for Docket ID NRC-2015-0191. Address 
questions about NRC dockets to Carol Gallagher; telephone: 301-415-
3463; email: [email protected]. For technical questions, contact 
the individual listed in the FOR FURTHER INFORMATION CONTACT section of 
this document.
     NRC's Agencywide Documents Access and Management System 
(ADAMS): You may obtain publicly-available documents online in the 
ADAMS Public Documents collection at http://www.nrc.gov/reading-rm/adams.html. To begin the search, select ``ADAMS Public Documents'' and 
then select ``Begin Web-based ADAMS Search.'' For problems with ADAMS, 
please contact the NRC's Public Document Room (PDR) reference staff at 
1-800-397-4209, 301-415-4737, or by email to [email protected]. The 
ADAMS accession number for each document referenced (if it available in 
ADAMS) is provided the first time that a document is referenced.
     NRC's PDR: You may examine and purchase copies of public 
documents at the NRC's PDR, Room O1-F21, One White Flint North, 11555 
Rockville Pike, Rockville, Maryland 20852.

FOR FURTHER INFORMATION CONTACT: John Vera, Office of Nuclear Material 
Safety and Safeguards, U.S. Nuclear Regulatory Commission, Washington, 
DC 20555-0001; telephone: 301-415-5790; email: [email protected].

SUPPLEMENTARY INFORMATION:

1.0 Background

    Duke Energy Carolinas, LLC (the applicant) is the holder of 
Facility Operating License Nos. DPR-38, DPR-47, and DPR-55, which 
authorize operation of the Oconee Nuclear Station, Units 1, 2, and 3 in 
Oconee County, South Carolina, pursuant to part 50 of Title 10 of the 
Code of Federal Regulations (10 CFR), ``Domestic Licensing of 
Production and Utilization Facilities.'' The licenses provide, among 
other things, that the facility is subject to all rules, regulations, 
and orders of the NRC now or hereafter in effect.
    Consistent with 10 CFR part 72, subpart K, ``General License for 
Storage of Spent Fuel at Power Reactor Sites,'' a general license is 
issued for the storage of spent fuel in an ISFSI at power reactor sites 
to persons authorized to possess or operate nuclear power reactors 
under 10 CFR part 50. The applicant is authorized to operate a nuclear 
power reactor under 10 CFR part 50, and holds a 10 CFR part 72 general 
license for storage of spent fuel at the Oconee Nuclear Station ISFSI. 
Under the terms of the general license, the applicant stores spent fuel 
at its ISFSI using the Transnuclear, Inc. (TN) Standardized 
NUHOMS[supreg] dry cask storage system Certificate of Compliance (CoC) 
No. 1004, Amendment No. 9.

2.0 Request/Action

    The applicant has requested an exemption from the requirements of 
10 CFR 72.212(b)(3), 10 CFR 72.212(b)(5)(i), and the portion of 10 CFR 
72.212(b)(11) that requires compliance with the terms, conditions, and 
specifications of CoC No. 1004, Amendment No. 9, for the Standardized 
NUHOMS[supreg] Horizontal Modular Storage System, to the extent 
necessary for the applicant to maintain 5 DSCs in their current 
position at the ISFSI associated with the operation of Oconee, Units 1, 
2, and 3. These regulations specifically require storage of spent 
nuclear fuel under a general license in dry storage casks approved 
under the provisions of 10 CFR part 72, and compliance with the terms 
and conditions set forth in the CoC for each dry storage spent fuel 
cask used by an ISFSI general licensee. Specifically, the exemption 
would relieve the applicant from meeting TS 1.2.4a of Attachment A of 
CoC No. 1004, which limits the leak rate of the inner seal weld to 1.0 
x

[[Page 58510]]

10\-7\ reference cubic centimeters per second (ref cc/s) at the highest 
DSC limiting pressure. As a result, granting this exemption will allow 
for continued storage of DSCs numbers 93, 94, 100, 105, and 106 at the 
Oconee Nuclear Station ISFSI.
    In January 2014, the applicant identified a discrepancy on a test 
report processed from the helium leak rate instrument vendor. The 
discrepancy was that the temperature coefficient was stated as four (4) 
percent per degree Celsius (%/[deg]C), when previously this value was 
three (3) %/[deg]C. The applicant stated that the instrument vendor 
confirmed that the three (3) %/[deg]C coefficient was incorrect for 
this instrument, and that canisters loaded at ambient temperatures 
greater than (>) 23[deg]C would have had a non-conservative temperature 
coefficient applied to the helium leak rate measurement. The applicant 
stated that the incorrect value had been used to calculate the leak 
rates of forty-seven (47) DSCs.
    According to the applicant, forty-two (42) of the forty-seven (47) 
DSCs affected were verified to meet the TS. The applicant's re-
evaluation involved verifying the ambient temperature when the DSCs 
were loaded and applying the appropriate temperature coefficient. 
However, the applicant stated that the actual temperature correction 
value datasheets could not be found for DSCs 93, 94, 100, 105, and 106, 
and that these canisters were loaded in the summer months when ambient 
conditions during helium leak testing would likely have exceeded 
23[deg]C, so the revised temperature correction factor would have been 
applicable. The applicant stated that for these DSCs, without evidence 
of the actual ambient temperature or test value, confirmation that the 
TS was met with the revised temperature coefficient was not possible.
    In a letter dated August 28, 2014, (ADAMS Accession No. 
ML14255A005), as supplemented December 8, 2014 (ADAMS Accession No. 
ML14346A008), and June 12, 2015 (ADAMS Accession No. ML15169B103), the 
applicant requested an exemption from certain parts of the following 
requirements to allow storage of the 5 DSCs at the Oconee Nuclear 
Station ISFSI:
     10 CFR 72.212(b)(3), which states that ``[t]he general 
licensee must [e]nsure that each cask used by the general licensee 
conforms to the terms, conditions, and specifications of a CoC or an 
amended CoC listed in Sec.  72.214.''
     10 CFR 72.212(b)(5)(i), which requires that, ``The general 
licensee perform written evaluations, before use and before applying 
the changes authorized by an amended CoC to a cask loaded under the 
initial CoC or an earlier amended CoC, which establish that [t]he cask, 
once loaded with spent fuel or once the changes authorized by an 
amended CoC have been applied, will conform to the terms, conditions, 
and specifications of a CoC or an amended CoC listed in Sec.  72.214.''
     10 CFR 72.212(b)(11), which states in part that ``[t]he 
licensee shall comply with the terms, conditions, and specifications of 
the CoC and, for those casks to which the licensee has applied the 
changes of an amended CoC, the terms, conditions, and specifications of 
the amended CoC. . . .''
    Upon review, in addition to the requirements from which the 
applicant requested exemption, the NRC staff determined exemptions from 
the following requirements are also necessary in order to authorize the 
applicant's request and added the following requirements to the 
exemption for the proposed action pursuant to its authority under 10 
CFR 72.7, ``Specific exemptions'':
     10 CFR 72.212(a)(2), which states that ``[t]his general 
license is limited to storage of spent fuel in casks approved under the 
provisions of this part.''
     10 CFR 72.214, which lists the approved spent fuel storage 
casks.

3.0 Discussion

    Pursuant to 10 CFR 72.7, the Commission may, upon application by 
any interested person or upon its own initiative, grant such exemptions 
from the requirements of the regulations of 10 CFR part 72 as it 
determines are authorized by law and will not endanger life or property 
or the common defense and security and are otherwise in the public 
interest.

Authorized by Law

    This exemption would allow the applicant to continue storage of 
DSCs numbers 93, 94, 100, 105, and 106 in their as-loaded 
configurations at the Oconee ISFSI by relieving the applicant of the 
requirement to meet the inner seal weld leak rate limit as required by 
TS 1.2.4a of Attachment A of CoC No. 1004. The provisions in 10 CFR 
part 72 from which the applicant is requesting exemption, as well as 
provisions determined to be applicable by the NRC staff, require the 
licensee to comply with the terms, conditions, and specifications of 
the CoC for the approved cask model it uses. Section 72.7 allows the 
NRC to grant exemptions from the requirements of 10 CFR part 72. 
Granting the licensee's proposed exemption is not otherwise 
inconsistent with NRC regulations or other applicable laws. As 
explained below, the proposed exemption will not endanger life or 
property, or the common defense and security, and is otherwise in the 
public interest. Therefore, the exemption is authorized by law.

Will Not Endanger Life or Property or the Common Defense and Security

    This exemption would relieve the applicant from meeting TS 1.2.4a 
of Attachment A of CoC No. 1004, which limits the leak rate of the 
inner seal weld to less than or equal to 1.0 X 10-7 ref cc/s 
at the highest DSC limiting pressure, allowing for continued storage of 
DSCs numbers 93, 94, 100, 105, and 106 in their as loaded conditions at 
the Oconee Nuclear Station ISFSI. This exemption only addresses the 5 
DSCs for which the ambient temperature at time of loading could not be 
confirmed by the applicant. Because the temperature at the time of 
loading cannot be confirmed, the applicant cannot demonstrate that the 
leak rate of the inner seal weld would be less than or equal to 1.0 x 
10-7 ref cc/s at the highest DSC limiting pressure. As 
detailed below, NRC staff reviewed the exemption request to determine 
whether granting of the exemption would cause potential for danger to 
life, property, or common defense and security.

Review of the Requested Exemption

    Background: The NUHOMS[supreg] system provides for the horizontal 
dry storage of canisterized spent fuel assemblies in a concrete 
horizontal storage module (HSM). The cask storage system components for 
NUHOMS[supreg] consist of a reinforced concrete HSM and a DSC vessel 
with an internal basket assembly that holds the spent fuel assemblies. 
The HSM is a low-profile, reinforced concrete structure designed to 
withstand all normal condition loads, as well as abnormal condition 
loads created by natural phenomena such as earthquakes and tornados. It 
is also designed to withstand design basis accident conditions. The 
Standardized NUHOMS[supreg] Horizontal Modular Storage System has been 
approved for storage of spent fuel under the conditions of Certificate 
of Compliance No. 1004. The DSCs under consideration for exemption were 
loaded under Certificate of Compliance No. 1004, Amendment No. 9.
    The NRC has previously approved the Standardized NUHOMS[supreg] 
Horizontal Modular Storage System storage system. The requested 
exemption does not change the fundamental design, components, contents, 
or safety features

[[Page 58511]]

of the storage system. The NRC staff evaluated the applicable potential 
safety impacts of granting the exemption to assess the potential for 
danger to life or property or the common defense and security. The 
potential impacts identified for this exemption request were in the 
areas of structural integrity and confinement capability.
    Structural Review for the Requested Exemption: The two objectives 
of TS 1.2.4a are to (1) demonstrate that the top cover is ``leak 
tight'' as defined in ANSI N14.5--1997, ``American National Standard 
for Leakage Tests on Packages for Shipment of Radioactive Materials,'' 
and (2) to retain helium cover gases within the DSC to provide heat 
dissipation and minimize oxidation of the fuel cladding. There are two 
tests used to verify the ``leak tight'' condition of the inner top 
cover seal weld. The first is a dye penetrant test (PT) and the second 
is a helium leak test (LT).
    The applicant stated that the dye penetrant tests conducted met the 
limits of TS 1.2.5 for the population of forty-seven (47) canisters for 
which the helium leak rates were calculated with the incorrect 
temperature coefficient.
    The structural acceptance criteria for both the inner top cover 
weld and the outer top cover weld is predicated on the successful 
results of the dye penetrant test in accordance with Interim Staff 
Guidance (ISG)--15 ``Materials Evaluation'' (ADAMS Accession No. 
ML010100170). The NRC staff finds that because the dye penetrant tests 
were acceptable, the staff finds that welds are structurally 
acceptable. There are no structural implications with the inner top 
cover seal weld as a result of the helium leak test having been 
conducted with an incorrect temperature correction coefficient. The NRC 
staff finds that the structural properties of the five (5) CoC No. 
1004, Amendment No. 9 DSCs addressed in the exemption request remain in 
compliance with 10 CFR part 72 and the applicable design and acceptance 
criteria have been satisfied.
    Confinement Review for the Requested Exemption: For canisters 
affected by use of an incorrect temperature coefficient for leakage 
rate, the licensee was unable to verify compliance with the technical 
specifications and thus performed a bounding leak rate calculation 
based on the maximum bounding temperature (40.6[deg]C) expected during 
the loading of the DSCs. The NRC staff finds that this temperature is 
bounding based on publicly published values for the maximum temperature 
for the area surrounding Oconee (ADAMS Accession No. ML15218A297). This 
calculation resulted in a calculated leak rate limit of 1.02 x 
10-7 ref cc/s (air), or a 2% increase. This does not mean 
that an actual leakage rate of 1.02 x 10-7 ref cc/s (air) is 
expected but that the licensee asserts it is a reasonable estimate of 
the worst case leakage rate that can be derived in the absence of an 
actual recorded temperature data at the time of leak testing.
    The NRC staff finds that the assumption of a maximum bounding 
temperature, as described above, is appropriate, because the actual 
ambient temperature is unknown. Use of this assumption demonstrated 
that the calculated revised leakage rate limit cannot be greater than 
reported (1.02 x 10-7 ref cc/s (air)). The ambient 
temperature in part determines the maximum size of the equivalent hole 
for leak rate calculations, and since the maximum likely temperature 
value was used, the NRC staff determined that it is reasonable for the 
license to conclude that a bounding leak rate would be achieved with a 
maximum equivalent hole size.
    The NRC staff reviewed the applicant's calculation method for 
determining the equivalent leak rate hole size and the estimated 
leakage rate corrected for assumed gas mixtures (i.e., air: helium). 
The NRC staff determined that, based on this calculation, even if 
significant uncertainty in the physical parameters used in the 
calculation were considered, the maximum equivalent hole size was the 
main driver that would account for any large change in a calculated 
leak rate criteria. Accordingly, the NRC staff determined that the 
revised calculated leakage rate with a bounding maximum temperature 
could not also result in large changes in the calculated leakage rate 
depending on the geometric or other physical parameters, such as 
pressure, which are used in the calculation. Therefore, the NRC staff 
concludes that consideration of the maximum expected temperature 
provides a reasonable best estimate of the maximum leakage rate that 
could be expected for the subject DSCs. Inspection of the revised 
bounding leak rate calculation demonstrates that even if the package 
was leaking at the revised leakage rate, there would still be no 
significant release of radioactive material to the environment nor 
would this leakage rate result in a depletion of the inert helium 
environment necessary to ensure spent fuel cladding integrity.
    The NRC staff finds that the confinement functions of the five (5) 
CoC No. 1004, Amendment No. 9 DSCs addressed in the exemption request 
remain in compliance with 10 CFR part 72.
    The NRC staff considered the potential impacts of granting the 
exemption on the common defense and security. The requested exemption 
is not related to any security or common defense aspect of the Oconee 
Nuclear Station ISFSI, therefore granting the exemption would not 
result in any potential impacts to common defense and security.
    Based on its review, the NRC staff has reasonable assurance that in 
granting the exemption, the storage system will continue meet the 
thermal, structural, criticality, retrievability and radiation 
protection requirements of 10 CFR part 72 and the offsite dose limits 
of 10 CFR part 20 and, therefore, will not endanger life or property. 
The NRC staff also finds that there is no threat to the common defense 
and security.
    Therefore, the NRC staff concludes that the exemption to relieve 
the applicant from meeting TS 1.2.4a of Attachment A of CoC No. 1004, 
which limits the leak rate of the inner seal weld to less than or equal 
to 1.0 x 10-7 ref cc/s at the highest DSC limiting pressure, 
allowing for continued storage of DSCs numbers 93, 94, 100, 105, and 
106 at the Oconee Nuclear Station ISFSI, will not endanger life or 
property or the common defense and security.

Otherwise in the Public Interest

    In considering whether granting the exemption is in the public 
interest, the NRC staff considered the alternative of not granting the 
exemption. If the exemption were not granted, in order to comply with 
the CoC, the five DSCs which are subject to the exemption request would 
have to be unloaded from the storage module, transported back to the 
cask handling area, opened, rewelded, retested, transported back to the 
HSM, and reloaded. This would entail a higher risk of a cask handling 
accident and additional personnel exposure. This alternative would also 
generate additional radioactive contaminated material and waste from 
operations.
    The proposed exemption to permit the continued storage of DSCs 
numbers 93, 94, 100, 105, and 106 at the Oconee Nuclear Station ISFSI 
is consistent with NRC's mission to protect public health and safety. 
Approving the requested exemption produces less of an opportunity for a 
release of radioactive material than the alternative to the proposed 
action because there will be no operations involving opening the DSCs 
which confine the spent nuclear fuel. Therefore, the exemption is in 
the public interest.

[[Page 58512]]

Environmental Consideration

    The NRC staff also considered in the review of this exemption 
request whether there would be any significant environmental impacts 
associated with the exemption. For this proposed action, the NRC staff 
performed an environmental assessment pursuant to 10 CFR 51.30, 
``Environmental assessment.'' The proposed action is the approval of an 
exemption from the requirements of 10 CFR 72.212(a)(2), 72.212(b)(3), 
72.212(b)(5)(i), 72.214, and the portion of 72.212(b)(11) that states 
the licensee shall comply with the terms, conditions, and 
specifications of the CoC. This exemption would relieve the applicant 
from meeting Technical Specification (TS) 1.2.4a of Attachment A of CoC 
No. 1004, allowing for continued storage of DSCs numbers 93, 94, 100, 
105, and 106 at the Oconee Nuclear Station ISFSI.
    The environmental assessment concluded that the proposed action 
would not significantly impact the quality of the human environment. 
The NRC staff concludes that the proposed action will not result in any 
changes in the types or amounts of any radiological effluents that may 
be released offsite, and there is no significant increase in 
occupational or public radiation exposure because of the proposed 
action. The proposed action only affects the requirements associated 
with Technical Specification (TS) 1.2.4a of Attachment A of CoC No. 
1004, which limits the leak rate of the inner seal weld to 1.0 x 
10-7 ref cc/s at the highest DSC limiting pressure, and does 
not affect plant effluents, or any other aspects of the environment, 
for DSCs numbers 93, 94, 100, 105, and 106 at the Oconee Nuclear 
Station ISFSI.
    The Environmental Assessment and the Finding of No Significant 
Impact was published on September 3, 2015; 80 FR 53350.

4.0 Conclusion

    Based on the foregoing considerations, the NRC staff has determined 
that, pursuant to 10 CFR 72.7, the exemption is authorized by law, will 
not endanger life or property or the common defense and security, and 
is otherwise in the public interest. Therefore, the NRC grants the 
applicant an exemption from the requirements of 10 CFR 72.212(a)(2), 
72.212(b)(3), 72.212(b)(5)(i), 72.214, and the portion of 72.212(b)(11) 
that states the licensee shall comply with the terms, conditions, and 
specifications of the CoC, only with regard to meeting Technical 
Specification (TS) 1.2.4a of Attachment A of CoC No. 1004. This 
exemption approval is limited to authorizing continued storage of DSCs 
numbers 93, 94, 100, 105, and 106 in the TN Standardized NUHOMS[supreg] 
dry cask storage system at the Oconee Nuclear Station ISFSI.
    This exemption is effective upon issuance.

    Dated at Rockville, Maryland, this 17 day September, 2015.

For the Nuclear Regulatory Commission.
Michele Sampson,
Branch Chief, Spent Fuel Licensing Branch, Division of Spent Fuel 
Management, Office of Nuclear Material Safety and Safeguards.
[FR Doc. 2015-24655 Filed 9-28-15; 8:45 am]
 BILLING CODE 7590-01-P