ML24110A057
| ML24110A057 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 05/21/2024 |
| From: | Pelton J NRC/NRR/DORL/LPL1 |
| To: | Carr E Dominion Energy Nuclear Connecticut |
| References | |
| EPID L-2023-LLE-0013 | |
| Download: ML24110A057 (1) | |
Text
NUCLEAR REGULATORY COMMISSION
Docket No. 50-423
Dominion Energy Nuclear Connecticut, Inc.,
Millstone Power Station, Unit No. 3
Exemption
I. Background.
Dominion Energy Nuclear Connecticut, Inc. (DENC, the licensee) is the holder of
Renewed Facility Operating License No. NPF-49, which authorizes operation of M illstone Power
Station, Unit No. 3 (Millstone 3), a pressurized-water reactor (PWR). The license provides, among
other things, that the facility is subject to all rules, regulations, and orders of the U.S. Nuclear
Regulatory Commission (NRC) now or hereafter in effect.
Millstone 3 shares the site with Millstone Power Station, Unit 1, a permanently defueled
boiling water reactor nuclear unit, and Millstone Power Station, Unit 2, a PWR. The facility is
located in Waterford, Connecticut, approximately 3.2 miles west southwest of New London,
Connecticut. This exemption applies to Millstone 3 only. The other units, Units 1 and 2, are not
covered by this exemption.
II. Request/Action.
By letter dated May 2, 2023 (Agencywide Documents Access and Management System
(ADAMS) Accession No. ML23123A279), as supplemented by letter dated April 1, 2024
(ML24093A216), DENC, requested an exemption to title 10 of the Code of Federal Regulations
(10 CFR), part 50, section 50.46, Acceptance criteria for emergency core cooling systems for
light-water nuclear power reactors, and part 50, Appendix K, ECCS [Emergency Core Cooling
Systems] Evaluation Models, for Millstone 3.
This exemption request relates solely to the specific types of cladding materials for
which 10 CFR 50.46 and 10 CFR part 50, Appendix K, are expressly applicable, namely zircaloy
and ZIRLO'. Since these regulations specific ally apply only to zircaloy and ZIRLO', an
exemption would be required to apply them to fuel clad with other materials, in this case
Framatome M5TM. Therefore, the licensee has requested such an exemption to support the
introduction of Framatome GAIA fuel with the M5 TM cladding. The proposed request would not
exempt Millstone 3 from other requirements of 10 CFR 50.46 or 10 CFR part 50, appendix K,
such as acceptance criteria, evaluation model features and documentation, and reporting of
changes or errors.
This exemption request is specific to the M5 TM cladding material exemption request only.
The technical analysis necessary to support the use of M5 TM cladding in the Millstone 3 GAIA
Small Break and Large Break Loss-of-Coolant Accident (SBLOCA and RLBLOCA) evaluations
under Framatome methods is documented in a separate safety evaluation for the related license
amendment request (ML24109A003).
III. Discussion.
Pursuant to 10 CFR 50.12, the licensee requested an exemption from the requirements
of 10 CFR 50.46, and appendix K to 10 CFR part 50. The proposed exemption request would
permit application of the requirements of 10 CFR 50.46 and appendix K to 10 CFR part 50 to
fuel assemblies containing fuel rods fabricated with M5 TM cladding material at Millstone 3.
The technical basis for the use of fuel clad with M5 TM in PWRs is documented in Topical
Report (TR) BAW-10227P-A, Revision 1, Evaluation of Advanced Cladding and Structural
Material (M5) in PWR Reactor Fuel, dated June 2003 (ADAMS Package No. ML15162B043).
This TR describes Framatomes evaluation for the use of the M5 TM alloy in PWR fuel
assemblies as a replacement for Zircaloy-4. This TR discusses material properties of M5 TM, as
well as its behavior under normal operation, anticipated transients, and postulated accident
conditions.
The regulation in 10 CFR 50.46(a)(1)(i) requires, in part, that each boiling or pressurized
light-water nuclear power reactor fueled with uranium oxide pellets within cylindrical zircaloy or
ZIRLOTM cladding must be provided with an ECCS that must be designed so that its calculated
cooling performance following postulated loss-of-coolant accidents conforms to the criteria set
forth in 10 CFR 50.46(b). Since 10 CFR 50.46 specifically refers to fuel with zircaloy or ZIRLO'
cladding, the use of fuel with M5' cladding requires an exemption from this section of the
regulations.
Paragraph I.A.5, Metal - Water Reaction Rate, of appendix K to 10 CFR part 50
requires the Baker-Just equation be used in the ECCS evaluation model to determine the rate of
energy release, hydrogen generation, and cladding oxidation. The requirement for using the
Baker-Just equation in appendix K conformant loss-of-coolant accident (LOCA) evaluation
models presume use of zircaloy-or ZIRLO'-clad fuel rods. Therefore, application of 10 CFR
part 50, appendix K to cladding materials other than zircaloy or ZIRLO' also requires an
exemption. Pursuant to 10 CFR 50.12, the NRC 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 the public
health or safety, and are consistent with the common defense and security; and (2) when
special circumstances are present. Under 10 CFR 50.12(a)(2)(ii), special circumstances include,
among other things, when application of the specific regulation in the particular circumstances
would not serve, or is not necessary to achieve, the underlying purpose of the rule.
A. The Exemption is Authorized by Law.
In accordance with 10 CFR 50.12, the NRC may grant an exemption from the
requirements of 10 CFR part 50 if the exemption is authorized by law. The exemption requested
in this instance is authorized by law, because no other prohibition of law exists to preclude the
activities which would be authorized by the exemption.
This exemption would allow the use of M5 TM cladding at Millstone 3 for GAIA SBLOCA
and RLBLOCA analyses performed using Framatome (FRM) methods, instead of zircaloy or
ZIRLOTM cladding. Selection of a specific cladding material in 10 CFR 50, appendix K was at the
discretion of the Commission consistent with its statutory authority. No statute required the NRC
to adopt this specification. As stated above, 10 CFR 50.12 allows the Commission to grant
exemptions from the requirements of 10 CFR part 50. The NRC staff has determined that
granting of an exemption from 10 CFR part 50, appendix K related to M5 TM cladding, which is
neither Zircaloy nor ZIRLO, will not result in a violation of the Atomic Energy Act of 1954, as
amended, or the Commission's regulations. Therefor e, the exemption is authorized by law.
B. The Exemption Presents no Undue Risk to Public Health and Safety.
The 10 CFR 50.46 requirements establish acceptance criteria for ECCS performance for
reactors fueled with zircaloy or ZIRLO cladding during a LOCA. The technical basis for the use
of fuel clad with M5TM in PWRs is documented in NRC-approved TR BAW-10227P-A, Revision
1, Evaluation of Advanced Cladding and Structural Material (M5) in PWR Reactor Fuel, dated
June 2003 (ADAMS Package No. ML15162B043). In this TR, Framatome demonstrated that the
effectiveness of the ECCS will not be affected by a change from zircaloy or ZIRLO fuel rod
cladding to M5TM fuel rod cladding. The analysis described in the TR demonstrated that the
ECCS acceptance criteria applied to reactors fueled with zircaloy or ZIRLO clad fuel are also
applicable to reactors fueled with M5 TM fuel rod cladding.
Paragraph I.A.5 of appendix K to 10 CFR 50 requires that the Baker-Just equation be
used in the ECCS evaluation models to determine the rate of energy release, cladding
oxidation, and hydrogen generation. In the NRC-approved TR BAW-10227-P-A, Revision 1,
Framatome demonstrated that the Baker-Just model is conservative in the postulated LOCA
scenarios with respect to the use of the M5 TM alloy as a fuel rod cladding material. The Baker-
Just equation is used to calculate cladding oxidation for the SBLOCA methodologies in the
NRC-approved TR EMF-2328-P-A, Revision 0 (ML011410383) for fuel with M5 TM cladding. The
SBLOCA analysis (Attachments 3 and 4 in the licensees May 2, 2023, letter) using the
methodologies in TR EMF-2328-P-A, Revision 0 for Millstone 3 demonstrated that the amount
of hydrogen generated in an M5-clad core meets the 10 CFR 50.46 criteria.
The NRC staff has reviewed the SBLOCA and RLBLOCA analyses in Attachments 3
through 6 in the licensees May 2, 2023, letter, and concluded in a safety evaluation
(ML24109A003) that the LOCA analyses meet the applicable acceptance criteria, confirming
that the use of M5TM fuel cladding at Millstone 3 would not result in an increase in the
consequences of postulated LOCAs beyond the required limits. Based on these reviews, the
NRC staff concludes that the exemption pres ents no undue risk to public health and safety.
C. The Exemption is Consistent with the Common Defense and Security.
The proposed exemption will allow the licensee to use M5 TM fuel rod cladding material,
an improved fuel rod cladding material relative to the zircaloy material for which the
requirements of 10 CFR 50.46 and 10 CFR Part 50, appendix K were originally established. In
its letter dated May 2, 2023, the licensee stated that the M5 TM fuel rod cladding material is
similar in design to the current cladding material used in Millstone 3. The change in cladding
material will not result in any changes to the security aspects associated with control of special
nuclear material and is unrelated to other security issues. In addition to its review of the
exemption request, the NRC staffs technical an alysis necessary to support the use of M5 TM
cladding in the Millstone 3 GAIA SBLOCA and RLBLOCA evaluations under Framatome
methods is documented in a separate safety evaluation for the related license amendment
request (ML24109A003). Based on these reviews, the NRC staff concludes that the use of
M5TM fuel rod cladding at Millstone 3 will not significantly affect plant operations and is
therefore consistent with the common defense and security.
D. Special Circumstances
Special circumstances, in accordance with 10 CFR 50.12(a)(2)(ii), are present whenever
application of the regulation in the circumstances would not serve the purpose of the rule or is
not necessary to achieve the 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 to provide reasonable assurance of safety
in the event of a LOCA. Although the regulations in 10 CFR 50.46 and appendix K to 10 CFR
part 50 are not expressly applicable to M5 TM fuel rod cladding, the evaluations described in the
above section show that the purpose of the regulations are met by this exemption; specifically,
the NRC-approved topical report (TR) BAW-10227-A, Revision 1 demonstrated that the
effectiveness of the ECCS will not be affected by a change from zircaloy or ZIRLO fuel rod
cladding to M5TM fuel rod cladding and that that the ECCS acceptance criteria applied to
reactors fueled with zircaloy or ZIRLO clad fuel are also applicable to reactors fueled with M5 TM
fuel rod cladding.
Paragraph I.A.5 of appendix K to 10 CFR 50 requires that the Baker-Just equation be
used in the ECCS EMs to determine the rate of energy release, cladding oxidation, and
hydrogen generation. The NRC-approved TR BAW-10227-P-A, Revision 1 demonstrated that
the Baker-Just model is conservative in the postulated LOCA scenarios with respect to the use
of the M5TM alloy as a fuel rod cladding material.
Neither 10 CFR 50.46 acceptance criteria nor the 10 CFR 50 appendix K requirements
for use of the Baker-Just equation in the ECCS EMs allows the use of M5 TM fuel rod cladding
material, even though the analysis demonstrated that applying the zircaloy or ZIRLO criteria to
M5TM fuel produces acceptable results. Application of the regulatory requirements of 10 CFR
50.46 and 10 CFR 50 appendix K in this circumstance is not necessary to achieve the purpose
of the rule. The purpose of these regulations is achieved through the application of the
requirements to the use M5TM fuel rod cladding material. Therefore, the NRC staff determines
that special circumstances for granting of an exemption, defined in 10 CFR 50.12(a)(2)(ii), exist.
E. Environmental Considerations
With respect to its impact on the quality of the human environment, the NRC has
determined that the issuance of the exemption discussed herein meets the eligibility criteria for
categorical exclusion set forth in 10 CFR 51.22(c)(9) because it is related to a requirement
concerning the installation or use of a facility component located within the restricted area, as
defined in 10 CFR Part 20, and issuance of this exemption involves: (i) no significant hazards
consideration; (ii) no significant change in the types or a significant increase in the amounts of
any effluents that may be released offsite; and (iii) no significant increase in individual or
cumulative occupational radiation exposure. Therefore, in accordance with 10 CFR 51.22(b), no
environmental impact statement or environmental assessment need be prepared in connection
with the NRCs consideration of this ex emption request. The basis for the NRC staffs
determination is discussed as follows with an evaluation against each of the requirements in 10
CFR 51.22(c)(9)(i) - (iii).
Requirements in 10 CFR 51.22(c)(9)(i)
The NRC evaluated whether the exemption involv es no significant hazards consideration
using the standards described in 10 CFR 50.92(c), as presented below:
- 1. Does the proposed exemption involve a significant increase in the probability or
consequences of an accident previously evaluated?
Response: No.
The proposed exemption would allow the use of M5 TM cladding at Millstone 3 for GAIA
SBLOCA and RLBLOCA analyses performed using FRM methods. The NRC approved topical
reports cited above demonstrate that M5 TM cladding has similar properties as the currently
licensed Zircaloy. The fuel cladding itself is not a postulated initiator of previously evaluated
accidents; thus, fuel cladding material does not affect the probability of occurrence of any
accident. The consequences of none of the previously evaluated accidents were affected by fuel
cladding material, and M5 TM fuel cladding, likewise, is not expected to have any effect on the
consequences of any previously evaluated accidents.
Therefore, the proposed exemption does not involve a significant increase in the
probability or consequences of an accident previously evaluated.
- 2. Does the proposed exemption create the possibility of a new or different kind of
accident from any accident previously evaluated?
Response: No.
The use of M5TM fuel rod cladding material will not result in changes in the operation or
configuration of the facility. The above cited topical reports demonstrated that the material
properties of M5TM cladding are similar to those of standard Zircaloy. Therefore, M5 TM fuel
cladding material will perform similarly to those fabricated from standard Zircaloy. The fuel
cladding itself is not a postulated initiator of previously evaluated accidents and does not create
the possibility of a new or different kind of accident.
Therefore, the proposed exemption does not create the possibility of a new or different
kind of accident from any previously evaluated.
- 3. Does the proposed exemption involve a significant reduction in a margin of safety.
Response: No.
The proposed exemption will not involve a significant reduction in the margin of safety
because it has been demonstrated that the material properties of the M5 TM cladding is not
significantly different from those of the standard Zircaloy. M5 TM fuel cladding material is
expected to perform similarly to standard Zircaloy for all normal operating and accident
scenarios. Use of M5TM cladding does not require changing any of the current regulatory
acceptance criteria, or relaxation of the methods of analysis.
Therefore, the proposed exemption does not in volve a significant reduction in a margin
of safety.
Based on the above evaluation of the standards set forth in 10 CFR 50.92(c), the NRC
staff concludes that the proposed exemption involves no significant hazards consideration.
Accordingly, the requirements of 10 CFR 51.22(c)(9)(i) are met.
Requirements in 10 CFR 51.22(c)(9)(ii)
The proposed exemption would allow the use of M5 TM cladding at Millstone 3 for GAIA
SBLOCA and RLBLOCA analyses performed using FRM methods. M5 TM cladding has similar
properties and performance characteristics as th e currently licensed Zircaloy cladding. Thus, the
use of M5TM fuel cladding material will not significantly increase the amount of effluents that may
be released offsite. Therefore, the requirements of 10 CFR 51.22(c)(9)(ii) are met.
Requirements in 10 CFR 51.22(c)(9)(iii)
The proposed exemption would allow the use of M5 TM cladding at Millstone 3 for GAIA
SBLOCA and RLBLOCA analyses performed using FRM methods. M5 TM cladding has similar
properties and performance characteristics as th e currently licensed Zircaloy cladding. Thus, the
use of M5TM fuel cladding material will not significantly increase individual occupational radiation
exposure, or significantly increase cumulative occupational radiation exposure. Therefore, the
requirements of 10 CFR 51.22(c)(9)(iii) are met.
Based on the above, the NRC staff concludes that the proposed exemption meets the
eligibility criteria for the categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, in
accordance with 10 CFR 51.22(b), no environmental impact statement or environmental
assessment need be prepared in connection with the NRCs issuance of this exemption.
IV. Conclusions.
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 DENC an exemption from the requirements
of 10 CFR 50.46 and 10 CFR part 50, appendix K. The proposed exemption request would
permit application of the requirements of 10 CFR 50.46 and appendix K to fuel rod cladding with
M5TM at Millstone 3. As stated above, this exemption relates solely to the cladding material
specified in these regulations.
Dated at Rockville, Maryland, this 21 st day of May, 2024
For the Nuclear Regulatory Commission.
Jamie Pelton, Deputy Director, Division of Operating Reactor Licensing, Office of Nuclear Reactor Regulation.