ML25353A569
| ML25353A569 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/18/2025 |
| From: | James Holloway Dominion Energy Nuclear Connecticut |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 25-300 | |
| Download: ML25353A569 (0) | |
Text
Dominion Energy Nuclear Connecticut, Inc 5000 Dominion Boulevard, Glen Allen, VA 23060 DominionEnergy.com December, 18, 2025 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 DOMINION ENERGY NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNITS 2 S'); Dominion
- iiiii" Energy Serial No.
NRA/NDM:
Docket No.:
License No.:
25-300 RO 50-336 DPR-65 APPLICATION TO REVISE TECHNICAL SPECIFICATIONS TO ADOPT TSTF-601, "EXTEND SHIELD BUILDING COMPLETION TIME AFTER REFUELING" Pursuant to 10 CFR 50.90, Dominion Energy Nuclear Connecticut, Inc. (DENC) is submitting a request for an amendment to the Technical Specifications (TS) for Millstone Power Station Unit 2 (MPS2).
DENC requests adoption of Technical Specifications Task Force (TSTF) Traveler 601, "Extend Shield Building Completion Time After Refueling," which is an approved change to the Standard Technical Specifications (STS), into the MPS2 TS. TSTF-601 revises the shield building TS to add a new Action that is applicable prior to criticality following a refueling outage. of this letter provides a description and assessment of the proposed change. Attachment 2 provides marked-up MPS2 TS pages showing the proposed changes. Attachment 3 provides marked-up MPS2 TS Bases pages showing the proposed changes.
DENC requests that the amendment be reviewed under the Consolidated Line Item Improvement Process (CLIIP). Approval of the proposed amendment is requested by March 31, 2026, to support the MPS2 Spring 2026 Refueling Outage. Once approved, the amendment shall be implemented within 30 days.
This letter contains no new regulatory commitments.
In accordance with 10 CFR 50.91 (b ), a copy of this amendment request is being provided to the State of Connecticut.
Serial No.: 25-300 Docket No.: 50-336 Page 2 of 3 If you have any questions or require additional information, please contact Nick Maynard at (804) 273-3910.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on December, 18, 2025 Sincerely, James E. Holloway Vice President - Nuclear Engineering and Fleet Support Attachments:
- 1. Evaluation of the Proposed Change
- 2. Marked-up Technical Specification Pages for MPS2
- 3. Marked-up Technical Specification Bases Pages for MPS2 (For Information Only)
cc:
U.S. Nuclear Regulatory Commission Region I 475 Allendale Road, Suite 102 King of Prussia, PA 19406-1415 Theo L. Edwards Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop O-8C04 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station Director, Radiation Division Department of Energy and Environmental Protection 79 Elm Street Hartford, CT 06106-5127 Serial No.: 25-300 Docket No.: 50-336 Page 3 of 3 EVALUATION OF THE PROPOSED CHANGE Dominion Energy Nuclear Connecticut, Inc.
Millstone Power Station Units 2 Serial No.: 25-300 Docket No.: 50-336
1.0 DESCRIPTION
Serial No.: 25-300 Docket No.: 50-336, Page 1 of 4 Dominion Energy Nuclear Connecticut, Inc. (DENC) requests adoption of Technical Specifications Task Force (TSTF) Traveler 601, "Extend Shield Building Completion Time After Refueling," which is an approved change to the Standard Technical Specifications (STS), into the Millstone Power Station Unit 2 (MPS2) Technical Specifications (TS).
TSTF-601 revises the shield building TS to add a new Action that is applicable prior to criticality, following a refueling outage.
2.0 ASSESSMENT
2.1 Applicability of Safety Evaluation DENC has reviewed the safety evaluation for TSTF-601 provided to the Technical Specifications Task Force in a letter dated March 6, 2025. This review included the NRC staff's evaluation, as well as the information provided in TSTF-601. DENC has concluded that the justifications presented in TSTF-601, and the safety evaluation prepared by the NRC staff are applicable to MPS2 and justify this amendment for the incorporation of the changes to the MPS2 TS.
TSTF-601 and the NRC's safety evaluation discuss the application of STS Limiting Condition for Operation (LCO) 3.0.4.b when using the new Action. While not based on the STS, the MPS2 TS contain a similar allowance and the discussion is applicable.
2.2 Variations DENC is proposing the following variations from the TS changes described in TSTF-601 or the applicable parts of the NRC staff's safety evaluation.
MPS2 Variations The MPS2 TS 3.6.5.2, "Enclosure Building," is equivalent to the STS 3.6.8, "Shield Building." The Enclosure Building serves the same purpose as the Shield Building described in the STS.
The MPS2 TS are not based on the STS and the MPS2 TS Actions are not formatted in the "Condition / Required Action / Completion Time" style used in the STS. To accommodate this difference, the TSTF-601 changes to the TS Actions are formatted to be consistent with the MPS2 TS without changing the intent.
The MPS2 TS Actions use Mode labels, provided in MPS2 TS Table 1.1, instead of the Mode numbers used in the STS. However, the Modes and Mode labels correspond to the STS Modes.
Serial No.: 25-300 Docket No.: 50-336, Page 2 of 4 The existing MPS2 TS Action for an inoperable Enclosure Building requires being in Cold Shutdown (Mode 5) within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> if the Enclosure Building is not restored to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Unlike the STS, the existing MPS2 TS does not require being in Hot Standby (Mode 3) within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> in this condition. The requirement to be in Hot Standby (Mode 3) is not added to the MPS2 TS because the proposed Action is only applicable in Hot Standby (Mode 3) and Hot Shutdown (Mode 4 ), so the requirement to be in Hot Standby (Mode 3) would not be applicable to the new Action.
The MPS2 TS do not include the changes in TSTF-422, Rev. 2, "Change in Technical Specifications End States (CE NPSD-1186)," which is incorporated in the STS.
These differences do not affect the applicability of TSTF-601 to the MPS2 TS.
3.0 REGULATORY ANALYSIS
3.1 No Significant Hazards Consideration Dominion Energy Nuclear Connecticut, Inc. (DENC) requests adoption of TSTF-601, "Extend Shield Building Completion Time After Refueling," which is an approved change to the Standard Technical Specifications {STS), into the Millstone Power Station Unit 2 (MPS2) Technical Specifications {TS). TSTF-601 revises the MPS2 enclosure building to add a new Action that is applicable prior to criticality following a refueling outage.
- 1.
Does the proposed amendment involve a significant increase in the probability or consequences of an accident previously evaluated?
Response: No The proposed change provides a longer time for the enclosure building or secondary containment to be inoperable in Hot Standby and Hot Shutdown following the refueling of the reactor and prior to reactor criticality. The enclosure building and secondary containment are not initiators of any accident previously evaluated. As a result, the probability of an accident during the extended time is not significantly increased. The consequences of a previously analyzed accident during the extended time are no different than the consequences of the accident during the existing time. Further, the limitations on the use of the extended time ensure that the consequences are reduced from those that would occur when at power. Hence, the consequences are not significantly increased.
Therefore, the proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.
Serial No.: 25-300 Docket No.: 50-336, Page 3 of 4
- 2.
Does the proposed amendment create the possibility of a new or different kind of accident from any accident previously evaluated?
Response: No The proposed change provides a longer time for the enclosure building or secondary containment to be inoperable in Hot Standby and Hot Shutdown following the refueling of the reactor and prior to reactor criticality. No new or different accidents result from utilizing the proposed change. The change does not involve a physical alteration of the plant (i.e., no new or different type of equipment will be installed). Permitting the enclosure building and secondary containment to be restored in Hot Standby and Hot Shutdown instead of Cold Shutdown does not create a significant change in the methods governing normal plant operation. In addition, the changes only affect a TS Action and therefore do not alter the assumptions made in the safety analysis.
Therefore, the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
- 3.
Does the proposed amendment involve a significant reduction in a margin of safety?
Response: No The proposed change provides a longer time for the enclosure building or secondary containment to be inoperable in Hot Standby and Hot Shutdown following the refueling of the reactor and prior to reactor criticality. The proposed change does not adversely affect existing plant safety margins or significantly affect the reliability of the equipment assumed to operate in the safety analysis.
As such, there are no changes being made to safety analysis assumptions, safety limits or limiting safety system settings that would adversely affect plant safety as a result of the proposed change.
Therefore, the proposed change does not involve a significant reduction in a margin of safety.
Based on the above, DENC concludes that the proposed change presents no significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and, accordingly, a finding of "no significant hazards consideration" is justified.
3.2 Conclusion In conclusion, based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the
Serial No.: 25-300 Docket No.: 50-336, Page 4 of 4 Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
4.0 ENVIRONMENTAL CONSIDERATION
A review has determined that the proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, or would change an inspection or surveillance requirement.
However, the proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or a significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure.
Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.
Serial No.: 25-300 Docket No.: 50-336 MARKED-UP TECHNICAL SPECIFICATIONS PAGES FOR MPS2 Dominion Energy Nuclear Connecticut, Inc.
Millstone Power Station Unit
ENCL s, RE BUILDJNG LIMITfNG CONDI11O fOR.OPERATl N Th Enclosure Building shal1. b1: OPERABLE.,
AP?U. ABJLITY:
MODE I,, 3 anrl 4.
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Serial No.: 25-300 Docket No.: 50-336 Page 1 of 2 Wnh the Enclos:m-e Bu.i1tling inopera'l:ile resw.re tl:re Endus~-m~e:-1.B,..u.+iliTifliFi,* 1""1g'"'t,..,or-fQ""* P-1:Rv. -AAfl_.t:
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- 'll::.tll,I!! v,"tflmr ~"l,-tmw!I ill be iu COLB SHl:JFBO'~"IJ,ji,:&hi.LI,I.he next.16itt1t1n:=
4_6,5.2.1 OP'ERABlLITYof~ Em::Iosu:re Building 1sl1mU be d:emi:m;;trat d at the freqlll]t1i.::;
spocd'i.ed ill the m,rei II:mce Freci11e.r.1cy Conlttll Prog_[am by vet.ifyrng thal each ooi;;e ope1:1111g is lo ed except when lhe a ce ope11ing is-being ll.Sl:'cl for uon:nal tram.it entry and e.xil.
4.u.5.-.2.
At the frequen
>ecil'ied in the urveil:lance Frequ m::y Con.tro1 Program verif.i,*
eacl~ Em:losw-e Bui.ldi:ng Filtration 1:rain produces a negative p.ressure of gre:ater Ilium or e,qual to 0.25 i:nd1e:s W.G. in the Endo uro Building filtration. R_egl-011 withi[l l mim:rt:e after an Em;:losure Buildin!! Pihratio:n Actuation.ignaL MILL TONE -
NIT 3/4 -2
Unit 2 TS Insert With the Enclosure Building inoperable, Serial No.: 25-300 Docket No.: 50-336 Page 2 of 2
- a. If in HOT STANDBY or HOT SHUTDOWN, and STARTUP has not been entered following refueling, restore the Enclosure Building to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in COLD SHUTDOWN within the next 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />; or
- b. Restore the Enclosure Building to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in COLD SHUTDOWN within the next 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
Serial No.: 25-300 Docket No.: 50-336 MARKED-UP TECHNICAL SPECIFICATIONS BASES PAGES FOR MPS2 (FOR INFORMATION ONLY)
Dominion Energy Nuclear Connecticut, Inc.
Millstone Power Station Unit 2
CONTAINMENT SYSTEMS BJ. E.
314.65.2
- CLOSURE B. ILDING Serial No.: 25-300 Docket No.: 50-336 Page 1 of 2 The OP ERABIUTY of th. £ndo. ere But1ding ea ures that the r~Ieases IIf radioactive materials from ihe prim.ary coutai.nm nt atnuisphere will be mstrided to thos leakage pal!hs and, asso
- iated leak rates asswned in ihe a.ident allal.. ses. Thi I trictiol'll, in conjunction with opemtion of 1fl En losure Building Filtration System1 wil] limi:E the SITE BOUNDARY radiation doses lio v ilhin th Litn1 of l I CFR SO. 7 durmg ace idellt conditions, Orie Endosuril! Building F.iltration yst m train is required to slab!" l!J a negative pressure of 0.25 incln~s \\.G. in the Enclosure Buildin Filti-atiol!l Region 'With.in OJW minute after an Enclosure Build:il!lg filtration. c1uatioi1 Signal i! genernied. Th.e 011c minute time requiremerll do.s nol im::lud the: time neces aiy fur th.e m;so *ared em r ency diesel ge1:11.!1*nmrto s1an ood pm\\ret Enclosure Building filtration y:.tem equiprnenl.
To enahle 1he Enclo ure Builr1in~ f' i~trarion ys-tem toe.stablish th.req111.ired aegati presJ..ure in the Enclosu.JJe.Building,_ it is necessary 10 ensm~ 1hat aU Encl.osure Bu11ding access openin ar~ *lo d. for cloulile door ac-
.opeamgs nly one door is requ:ic~cl lo be closoo nud la h d, ~ :pt for J11omul pa sag Fo sing:1.dooir ac. openings. that door * *.requ:it d lo. be closed and 1.a.tch ~ except fo:r normal passage.
[fa required d'oor l!hat is destgnared to automalic:ill.cJ!m'l and la.tch i.s not capabl of automatically dosi.ng,nnd latdJiag, the door s!hall b maintained dQSed aml latch.red or pcrso:mi l hall be. tiorrnd at rh door to~ 1.1re that th dour is I d and latcb.ed after acb transit through th doo.. r. Otherwise. the access ope:oi:ng door) hould be di!.elared in~:ible and appropr.iat~ teilmical specificntiol'II
. ON tarem.ent e-:t1tfil'ed Uml 2 Bases lns t\\.llJL.LSTONE - '
IT 2 B,J/46-5b Amendm nt
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Unit 2 Bases Insert Serial No.: 25-300 Docket No.: 50-336 Page 2 of 2 If the Enclosure Building is inoperable, it must be restored within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. However, if the Enclosure Building is inoperable in HOT STANDBY or HOT SHUTDOWN, and the unit has not entered STARTUP following a refueling, Enclosure Building OPERABILITY must be restored within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The Enclosure Building is allowed to be inoperable for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> instead of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> immediately following a refueling when the reactor has not been critical because of the reduced decay heat generation and radionuclide inventory, the limited leakage design of the containment, the OPERABLE TS systems in the applicable MODES, and the low probability of an event requiring the Enclosure Building.