[Federal Register Volume 85, Number 161 (Wednesday, August 19, 2020)]
[Notices]
[Pages 51083-51086]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-18151]


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NUCLEAR REGULATORY COMMISSION

[Docket Nos. 72-1031, 50-369, and 50-370; NRC-2020-0044]


Duke Energy Carolinas, LLC; McGuire Nuclear Station, Units 1 and 
2; 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 to Duke Energy Carolinas, LLC (Duke Energy) which would 
permit Duke Energy to maintain MAGNASTOR[supreg] Cask 0FCTKN045 at its 
McGuire Nuclear Station independent spent fuel storage installation 
(ISFSI) in a storage condition where the helium density is above the 
range specified in Certificate of Compliance (CoC) No. 1031, Amendment 
No. 7, Technical Specification (TS) 3.1.1.

DATES: The exemption became effective on August 19, 2020.

ADDRESSES: Please refer to Docket ID NRC-2020-0044 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 Website: Go to https://www.regulations.gov and search for Docket ID NRC-2020-0044. Address 
questions about NRC docket IDs in Regulations.gov to Jennifer Borges-
Roman; telephone: 301-287-9127; 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 https://www.nrc.gov/reading-rm/adams.html. To begin the search, select ``Begin Web-based ADAMS 
Search.'' For problems with ADAMS, please contact the NRC's Public 
Document Room reference staff at 1-800-397-4209, 301-415-4737, or by 
email to [email protected]. For the convenience of the reader, 
instructions about obtaining materials referenced in this document are 
provided in the ``Availability of Documents'' section.

FOR FURTHER INFORMATION CONTACT: Yen-Ju Chen, Office of Nuclear 
Material Safety and Safeguards, U.S. Nuclear Regulatory Commission, 
Washington, DC 20555; telephone: 301-415-1018; email: [email protected].

SUPPLEMENTARY INFORMATION:

I. Background

    Duke Energy is the holder of Renewed Facility Operating Licenses 
No. NPF-9 and NPF-17, which authorize operation of the McGuire Nuclear 
Plant, Units 1 and 2, in Huntersville, North Carolina, pursuant to part 
50 of title 10 of the Code of Federal Regulations (10 CFR), ``Domestic 
Licensing of Production and Utilization Facilities.''
    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. Duke Energy is authorized to operate nuclear 
power reactors under 10 CFR part 50 and holds a 10 CFR part 72 general 
license for storage of spent fuel at the McGuire Nuclear Station ISFSI. 
Under the terms of the general license, Duke Energy stores spent fuel 
at its ISFSI using the NAC MAGNASTOR[supreg] System in accordance with 
CoC No. 1031, Amendment No. 7.

II. Request/Action

    By a letter dated September 12, 2019 (ADAMS Accession No. 
ML19270E395), and supplemented on February 3, 2020 (ADAMS Accession No. 
ML20052D934), and June 15, 2020 (ADAMS Accession No. ML20178A548), Duke 
Energy requested an exemption from the requirements of 10 CFR 
72.212(b)(3), 72.212(b)(5)(i), and 72.212(b)(11) that require Duke 
Energy to comply with the terms, conditions, and specifications of the 
CoC No. 1031, Amendment No. 7 (ADAMS Accession No. ML17013A481). If 
approved, Duke Energy's exemption request would accordingly allow Duke 
Energy to maintain MAGNASTOR[supreg] Cask 0FCTKN045 in a storage 
condition where the helium density is above the range specified in CoC 
No. 1031, Amendment No. 7, TS 3.1.1.
    On June 4, 2018, then-recently loaded MAGNASTOR[supreg] Cask 
0FCTKN045 was transported to the McGuire Nuclear Station ISFSI storage 
pad area. Subsequently, Duke Energy reviewed technical details of the 
completed

[[Page 51084]]

loading procedure and noticed that during the helium backfill process, 
the two helium mass flow meters for MAGNASTOR[supreg] Cask 0FCTKN045 
measured significantly different volumes. Further review revealed the 
cask helium density within MAGNASTOR[supreg] Cask 0FCTKN045 exceeded 
the helium density range specified in CoC No. 1031, Amendment No. 7, TS 
3.1.1, Table A3-1, prior to the transport operations. In addition, the 
TS 3.1.1 corresponding ``Required Actions and Completion Times'' were 
not performed prior to transport operations, as specified.
    Duke Energy conducted an investigation in accordance with the TS 
Required Action B.1 and completed an analysis as part of the corrective 
actions per TS Required Action B.2. Duke Energy concluded, for all 
MAGNASTOR[supreg] modes of operation, that Cask 0FCTKN045 is in a safe 
configuration for continued operation. Duke Energy's analysis concluded 
that the final helium density for MAGNASTOR[supreg] Cask 0FCTKN045 is 
outside the allowed range of 0.694-0.802 grams/liter specified in CoC 
No. 1031, Amendment No. 7, TS LCO 3.1.1, Table A3-1, ``Helium Mass Per 
Unit Volume for MAGNASTOR [transportable storage canister] (TSC),'' and 
it constitutes a nonconformance with the terms, conditions, and 
specifications of MAGNASTOR[supreg] System CoC No. 1031, Amendment No. 
7. The NRC staff has addressed the inspection and enforcement aspects 
of this nonconformance separately from this exemption request.

III. 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 Duke Energy to maintain 
MAGNASTOR[supreg] Cask 0FCTKN045 at its McGuire Nuclear Station ISFSI 
in a storage condition where the helium density is above the range 
specified in CoC No. 1031, Amendment No. 7, TS 3.1.1. The provisions in 
10 CFR part 72 from which Duke Energy is requesting exemption 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. 
Issuance of this exemption is consistent with the Atomic Energy Act of 
1954, as amended, and is not otherwise inconsistent with NRC's 
regulations or other applicable laws. Therefore, the exemption is 
authorized by law.

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

    This exemption would allow Duke Energy to maintain 
MAGNASTOR[supreg] Cask 0FCTKN045 at the McGuire Nuclear Station ISFSI 
in a storage condition where the helium density is above the range 
specified in CoC No. 1031, Amendment No. 7, TS 3.1.1. The requested 
exemption is not related to any aspect of the physical security or 
defense of the McGuire Nuclear Station ISFSI, therefore granting the 
exemption would not result in any potential impacts to common defense 
and security. As detailed in the safety evaluation below, the NRC staff 
has determined that under the requested exemption, the storage system 
will continue to meet the safety requirements of 10 CFR part 72 and the 
offsite dose limits of 10 CFR part 20 and, therefore, will not endanger 
life or property.

Safety Evaluation

    The MAGNASTOR[supreg] System has been approved for storage of spent 
fuel under the conditions of CoC No. 1031. The cask under consideration 
for exemption (0FCTKN045) was loaded under CoC No. 1031, Amendment No. 
7. The requested exemption does not change the fundamental design, 
components, contents, or safety features of the storage system. The NRC 
staff has evaluated the potential safety impacts of granting the 
exemption, as applicable, in the areas of structural integrity, thermal 
performance, and confinement capability. The evaluation and resulting 
conclusions are presented below.
    Structural Review for the Requested Exemption: The TSC contained in 
the NAC MAGNASTOR[supreg] is required by the MAGNASTOR[supreg] TS to be 
within a specific helium density range of 0.694-0.802 grams/liter while 
maintaining internal pressures within evaluated pressure limits for 
normal, off-normal, and accident conditions. The internal pressure 
limits of the TSC with a helium density range of 0.694-0.802 grams/
liter are provided in the MAGNASTOR[supreg] Final Safety Analysis 
Report (FSAR), Revision 6 (ADAMS Accession No. ML20196L776) as 110 
psig, 130 psig, and 250 psig for normal, off-normal, and accident 
conditions, respectively.
    In June 2018, Duke Energy found that the TSC contained in the 
MAGNASTOR[supreg] Cask 0FCTKN045 is filled with a helium density up to 
1.082 grams/liter, which is higher than the helium density specified in 
the TS. As a result, Duke Energy recalculated the internal pressures of 
the TSC due to the helium density of 1.082 grams/liter using the same 
method described in the MAGNASTOR[supreg] FSAR, Revision 6. The new 
internal pressures of the TSC were found to be 142.1 psig, 158 psig, 
and 265 psig for normal, off-normal, and accident conditions, 
respectively. Using these new internal pressures, Duke Energy 
calculated new component stress intensities at the most critical cross 
section (where it has the lowest reported factor of safety) in the TSC 
to demonstrate the adequacy of the TSC's structural design under 
normal, off-normal, and accident conditions.
    Duke Energy used the results of the ANSYS finite element (FE) 
structural analysis and a linear superposition of hand calculations to 
calculate component stresses in the TSC. The ANSYS FE analysis and its 
results were previously reviewed and accepted by the staff, and they 
are provided in the MAGNASTOR[supreg] FSAR, Revision 6. Based on the 
calculated stresses at the critical location of the TSC from the 
previous ANSYS FE analysis, the new stresses at the same critical 
location of the TSC were recalculated by: (i) Adding the induced 
stresses due to the increased pressures from the helium density 
increase, and (ii) subtracting the reduced stresses due to the 
decreased weight of the TSC. For the second factor regarding the stress 
reduction from the weight of the TSC, Duke Energy stated that the 
actual weight of the TSC is 77,000 lbs, while the weight of the TSC in 
the MAGNASTOR[supreg] FSAR, Revision 6 that was used as a bounding 
weight in the previous ANSYS FE analysis was 90,000 lbs. The staff 
reviewed the methodology used to calculate the revised stresses of the 
TSC and finds it acceptable because the superposition method is an 
acceptable approach in engineering practice and the revised 
calculations considered the actual weight and helium density.
    Using the methodology described above, Duke Energy calculated 
component stresses and stress intensities at the critical location of 
the TSC and provided the factor of safety, which is a ratio of the 
allowable stress intensity with respect to the actual stress intensity, 
for normal, off-normal, and accident conditions. The staff reviewed 
Duke Energy's analysis and stress calculation and finds that the 
results of the stress calculation show

[[Page 51085]]

that all calculated factors of safety are greater than 1.0, which meets 
the design criteria for the TSC specified in the MAGNASTOR[supreg] 
FSAR, Revision 6. Revision 6 uses the design criteria required by the 
American Society of Mechanical Engineers (ASME) Boiler and Pressure 
Vessel Code (B&PV) Division I, Section III, Subsection NB. Thus, the 
staff determines that Duke Energy's stress calculation and its results 
are acceptable.
    The staff concludes that, with the helium density higher than that 
specified in the TS, the design of the TSC continues to meet the design 
criteria of the ASME B&PV Code, as specified in the MAGNASTOR[supreg] 
FSAR, Revision 6. The TSC is designed to accommodate the combined loads 
(i.e., dead weight, internal pressure, handling load, and impacts from 
natural phenomena) in normal, off-normal, and accident conditions with 
an adequate margin of safety. The total stresses at the critical 
location of the TSC under the combined loads during normal, off-normal, 
accident conditions are acceptable and are found to be within the 
limits in the ASME B&PV Code, as specified in the MAGNASTOR[supreg] 
FSAR Revision 6. Therefore, the staff finds that the MAGNASTOR[supreg] 
Cask 0FCTKN045 continues to maintain its structural integrity and meet 
the structural requirements of 10 CFR part 72 and the offsite dose 
limits of 10 CFR part 20.
    Confinement Review for the Requested Exemption: According to the 
MAGNASTOR[supreg] System FSAR Revision 5 (ADAMS Accession No. 
ML17132A265), the confinement boundary includes a lid welded consistent 
with Interim Staff Guidance-18, ``The Design and Testing of Lid Welds 
on Austenitic Stainless Steel Canisters as the Confinement Boundary for 
Spent Fuel Storage'' (ADAMS Accession No. ML082750469). The remaining 
confinement boundary is tested to a ``leaktight'' criteria per the 
American National Standard Institute N14.5 standard. Duke Energy stated 
in its exemption request that the increased helium pressure within the 
TSC was used to compute updated factors of safety due to revised stress 
intensities. The calculations were updated for the most critical cross 
sections for the bounding load cases of each of the four service levels 
evaluated in the design basis MAGNASTOR[supreg] TSC structural 
evaluation. The service levels are taken from the ASME B&PV Code, and 
correspond to different conditions of operation. Duke Energy stated 
that the updated factors of safety for Service Level A, Service Level 
B, Service Level C, and Service Level D conditions were greater than 
one. Therefore, Duke Energy determined that MAGNASTOR[supreg] Cask 
0FCTKN045 is safe because it continues to meet the structural criteria 
used to evaluate the MAGNASTOR[supreg] system.
    The NRC staff reviewed the exemption request and concludes that the 
cask confinement performance is not affected by the increased helium 
pressure because, according to Duke Energy's analysis and the staff's 
structural evaluation, the integrity of the TSC is maintained and, 
therefore, there would be no release from the canister.
    The NRC staff finds that the confinement function of 
MAGNASTOR[supreg] Cask 0FCTKN045, loaded under CoC No. 1031, Amendment 
No. 7, addressed in the exemption request remains in compliance with 10 
CFR 72.236(d) and (l) and the offsite dose limits of 10 CFR part 20.
    Thermal Review for the Requested Exemption: According to Duke 
Energy's analysis in the exemption request, the higher helium density 
(1.082 g/L) and pressure of MAGNASTOR[supreg] Cask 0FCTKN045 have a 
positive effect on the thermal performance of the vertical-oriented TSC 
confining the spent fuel. In addition, in the February 2020 submittal 
(ADAMS Accession No. ML20052D934), Duke Energy noted that 
MAGNASTOR[supreg] Cask 0FCTKN045 has a decay heat load of less than 30 
kW which is less than the design basis heat load for the 
MAGNASTOR[supreg] system of 35.5 kW. Duke Energy analyzed a 
MAGNASTOR[supreg] canister with a 30 kW heat load and helium density of 
1.082 g/L. The results were a 575 [deg]F maximum fuel temperature, 
which is less than the design basis temperature (718 [deg]F) found in 
Table 4.4-3 of the MAGNASTOR[supreg] System FSAR, Revision 7 (ADAMS 
Accession No. ML15265A419). The staff concludes that the positive 
effects of the higher pressure and the lower heat load in the canister 
would reduce the actual temperatures and increase the margin between 
the actual temperatures and the design temperatures.
    The NRC staff reviewed the exemption request and concludes that the 
cask thermal performance is not affected by the higher helium density 
because it would not adversely affect thermal performance and, 
according to Duke Energy's analysis and the staff's structural 
evaluation, the integrity of the TSC is maintained. The integrity of 
the primary confinement boundary ensures that the spent fuel is stored 
in an inert environment and with unaffected heat transfer 
characteristics that keep peak cladding temperatures below allowable 
limits.
    The NRC staff finds that the thermal function of MAGNASTOR[supreg] 
Cask 0FCTKN045, loaded under CoC No. 1031, Amendment No. 7, addressed 
in the exemption request remains in compliance with 10 CFR 72.236 (b) 
and (f) and the offsite dose limits of 10 CFR part 20.

Otherwise in the Public Interest

    The proposed exemption is to maintain MAGNASTOR[supreg] Cask 
0FCTKN045 at McGuire Nuclear Station ISFSI in the storage condition 
where the helium density is above the range specified in CoC No. 1031, 
Amendment No. 7, TS 3.1.1. The NRC staff notes that in this condition 
there will be no operations involving the opening of the storage 
canister, which confines the spent nuclear fuel, and there will be no 
operations involving the opening of the MAGNASTOR[supreg] cask.
    In considering whether granting the exemption is in the public 
interest, the NRC staff also considered the alternative of not granting 
the exemption. If the exemption were not granted, in order to comply 
with the CoC, Duke Energy would have to unload MAGNASTOR[supreg] Cask 
0FCTKN045 to restore compliance with helium density in the TS. This 
would subject onsite personnel to additional radiation exposure, 
generate additional contaminated waste, increase the risk of a possible 
fuel handling accident, and increase the risk of a possible heavy load 
handling accident.
    Approving the requested exemption reduces the opportunity for a 
release of radioactive material compared to the alternative to the 
proposed action, while continuing to provide reasonable assurance of 
public health and safety. Therefore, the staff concludes that approving 
the exemption is in the public interest.

Environmental Consideration

    The NRC staff also considered 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. The environmental assessment 
concluded that the proposed action would not significantly impact the 
quality of the human environment. The NRC staff concluded that the 
proposed action would not result in any changes in the types or amounts 
of any radiological or non-radiological effluents that may be released 
offsite, and there is no significant increase in occupational or public 
radiation exposure because of the proposed

[[Page 51086]]

action. The Environmental Assessment and the Finding of No Significant 
Impact was published on July 22, 2020 (85 FR 44329).

IV. Availability of Documents

    The documents identified in the following table are available to 
interested persons through one or more of the following methods, as 
indicated.

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                  Document                       ADAMS accession No.
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Duke Energy Carolinas, LLC (Duke Energy),    ML19270E395.
 McGuire Nuclear Station, Units 1 and 2,
 Independent Spent Fuel Storage
 Installation (ISFSI), Exemption Request
 for NAC MAGNASTOR[supreg] Cask Loaded to
 Incorrect Helium Backfill Density, dated
 September 12, 2019.
Duke Energy Carolinas, LLC (Duke Energy),    ML20052D934.
 McGuire Nuclear Station, Response to NRG
 Request for Additional Information (RAI)
 Regarding NAC MAGNASTOR[supreg] Cask
 Loaded to Incorrect Helium Backfill
 Density, dated February 3, 2020.
Duke Energy Carolinas, LLC (Duke Energy),    ML20178A548.
 McGuire Nuclear Station, Response to NRC
 Request for Additional Information (RAI)
 Regarding NAC MAGNASTOR[supreg] Cask
 Loaded to Incorrect Helium Backfill
 Density, dated June 5, 2020.
NAC International, MAGNASTOR[supreg] Cask    ML17013A481.
 System, Certificate of Compliance No.
 1031, Amendment No. 7.
Final Safety Analysis Report, Revision 6     ML20196L776.
 for MAGNASTOR[supreg] Cask System.
Final Safety Analysis Report, Revision 5     ML17132A265.
 for MAGNASTOR[supreg] Cask System.
Interim Staff Guidance, ISG-18, Revision 1,  ML082750469.
 ``The Design and Testing of Lid Welds on
 Austenitic Stainless Steel Canisters as
 the Confinement Boundary for Spent Fuel
 Storage''.
Final Safety Analysis Report, Revision 7     ML15265A419.
 for MAGNASTOR[supreg] Cask System.
------------------------------------------------------------------------

    The NRC may post materials related to this document, including 
public comments, on the Federal rulemaking website at https://www.regulations.gov under Docket ID NRC-2020-0044. The Federal 
rulemaking website allows you to receive alerts when changes or 
additions occur in a docket folder. To subscribe: (1) Navigate to the 
docket folder (NRC-2020-0044); (2) click the ``Sign up for Email 
Alerts'' link; and (3) enter your email address and select how 
frequently you would like to receive emails (daily, weekly, or 
monthly).

V. Conclusion

    Based on the above considerations, the NRC 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 Duke Energy 
an exemption from the requirements of 10 CFR 72.212(b)(3), 
72.212(b)(5)(i), and 72.212(b)(11) with respect to the ongoing storage 
of MAGNASTOR[supreg] Cask 0FCTKN045.
    This exemption is effective upon issuance.

    Dated: August 14, 2020.

    For the Nuclear Regulatory Commission.
John B. McKirgan,
Chief, Storage and Transportation Branch, Division of Fuel Management, 
Office of Nuclear Material Safety, and Safeguards.
[FR Doc. 2020-18151 Filed 8-18-20; 8:45 am]
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