IR 05000220/2024002

Integrated Inspection Report 05000220/2024002 and 05000410/2024002

ML24218A057
Person / Time
Site:	Nine Mile Point
Issue date:	08/05/2024
From:	Erin Carfang NRC/RGN-I/DORS
To:	Rhoades D Constellation Energy Generation, Constellation Nuclear
References
IR 2024002
Download: ML24218A057 (1)

Text

August 5, 2024

D av id P. R hoades Senior Vic e President C onstellation Energy G eneration, LLC President and C hief N uc lear O f f ic er (C N O )

Constellation Energy 4300 Winf ield R oad Warrenv ille, IL 60555

SUBJ ECT: NINE M ILE PO INT NUCLEAR STATIO N, UNITS 1 AND 2 - INTEG RATED IN SPEC TIO N R EPO R T 05000220/2024002 AN D 05000410/2024002

D ear D av id R hoades:

On J une 30, 2024, the U.S. N uc lear R egulatory C om m ission (N R C ) c om pleted an inspec tion at N ine M ile Point N uc lear Station, U nits 1 and O n J uly 30, 2024, the N R C inspec tors disc ussed the results of this inspec tion w ith C arl C raw f ord, Plant M anager and other m em bers of y our staff. The results of this inspec tion are doc um ented in the enc losed repor O ne f inding of v ery low saf ety signif ic anc e (G reen) is doc um ented in this report. This f inding did not inv olv e a v iolation of N R C requirem ent If y ou disagree w ith a c r oss-c utting aspec t assignm ent or a f inding not assoc iated w ith a regulatory requirem ent in this report, y ou should prov ide a response w ithin 30 day s of the date of this inspec tion report, w ith the basis f or y our disagreem ent, to the U.S. N uc lear R egulatory C om m ission, ATTN : D oc um ent C ontrol D esk, Washington, D C 20555-0001; w ith c opies to the R egional Adm inistrator, R egion I; and the N R C R esident Inspec tor at N ine M ile Point N uc lear Statio D. R hoades 2

This letter, its enc losure, and y our response (if any ) w ill be m ade av ailable f or public inspec tion and c opy ing at http://w w w.nrc.gov /reading-rm /adam s.htm l and at the N R C Public D oc um ent R oom in ac c ordanc e w ith Title 10 of the C ode of Federal R egulations 2.390, Public Inspec tions, Ex em ptions, R equests f or Withholdin Sinc erely,

Erin E. C arf ang, C hief Projec ts Branc h 1 D iv ision of O perating R eac tor Saf ety

D oc k et N o and 05000410 Lic ense N o DPR-63 and NPF-69

Enc losure:

A s stated

cc w/ encl: D istribution v ia LISTSER V D. R hoades 3

SUBJ ECT: NINE M ILE PO INT NUCLEAR STATIO N, UNITS 1 AND 2 - INTEG RATED IN SPEC TIO N R EPO R T 05000220/2024002 AN D 05000410/2024002 DATED AUGUST 5, 2024

DIST RIBUT ION:

EC arf ang, D O R S EEv e, DORS KSm etana, D O R S EAdam s, D O R S CKline, DORS, SRI BSienel, D O R S, R I ATrudell, DORS, AA MSimmons, RI OEDO R idsN rrPM N ineM ilePoint R esourc e R idsN rrD orlLpl1 R esourc e

DOCUMENT NAME: https://usnrc.sharepoin om /team s/R egion-I-Branc h-1/Shared D oc um ents/Inspec tion R eports/N M P/N M P 2024/N M P IR 2024002.doc x ADAM S ACCESSION NUM BER: M L24218A057 X SU N SI Revi ew X Non-Sensitive X Publicly Available nti N-Publicvailab

OFFIC E RI/D S RI/D S RI/D S

N line ECfang DATE 30/ 31/

OFFICL RECD CY

U.S. NUCLEAR REGULAT ORY COMMISSION

Inspection Report

D oc k et N um bers: 05000220 and 05000410

Lic ense N um bers: DPR-63 and N PF -69

R eport N um bers: 05000220/2024002 and 05000410/2024002

Enterprise Identif ier: I-2024-002-0041

Lic ensee: Constellation Energy G eneration, LLC

Fac ility : N ine M ile Point N uc lear Station, U nits 1 and 2

Loc ation: O sw ego, N Y

Inspec tion D ates: April 1, 2024 to J une 30, 2024

Inspec tors: C. Kline, Senior R esident Inspec tor B. Sienel, R esident Inspec tor E. Ev e, Senior Projec t Engineer

Approv ed By : Erin E. C arf ang, C hief Projec ts Branc h 1 D iv ision of O perating R eac tor Saf ety

Enc losure SUMMARY

The U.S. N uc lear R egulatory C om m ission (N R C ) c ontinued m onitoring the lic ensees perf orm anc e by c onduc ting an integrated inspec tion at N ine M ile Point N uc lear Station, U nits 1 and 2, in ac c ordanc e w ith the R eac tor O v ersight Proc ess. The R eac tor O v ersight Proc ess is the N R C s program f or ov erseeing the saf e operation of c om m erc ial nuc lear pow er reac tors. R ef er to https://w w w.nrc.gov /reac tors/operating/ov ersight.htm l f or m ore inf orm atio List of Findings and Violations

Inc orrec t Applic ation of M aintenanc e Strategy Proc ess Leads to Loss of Feedw ater Flow and Autom atic R eac tor Sc ram C ornerstone Signif ic anc e C r oss-Cutting R eport Aspec t Sec tion Initiating Ev ents G reen [P.3] - 71153 FIN 05000410/2024002-01 R esolution O pen/C losed A self-rev ealed G reen finding w as identif ied f or C onstellations f ailure to adequately ev aluate the im pac t of inc reased f eed w ater lev el c ontrol v alv e c y c ling on balanc e seal longev ity in ac c ordanc e w ith ER-AA-200, "Prev entiv e M aintenanc e Program." Spec if ic ally, f ollow ing installation of the U nit 2 digital f eedw ater lev el c ontrol (D FWLC ) sy stem, C onstellation identif ied that lev el c ontrol v alv e 2FWS -LV10 c y c le f requenc y inc reased approx im ately f iv e-f old. C onstellation rec ognized the inc reased c y c ling c ould ac c elerate w ear of the Tef lon balanc e seal and v alv e pac k ing. The site did not appropriately assess the inc reased w ear and adjust the m aintenanc e interv al f or internal v alv e sof tw are inspec tion and replac em ent. The inc reased c y c le rate led to prem ature balanc e seal f ailure and internal v alv e f low instability,

w hic h resulted in stem /disc c onnec tion f ailur The separation of the disc f rom the v alv e stem resulted in partial loss of f eedw ater f low, and an autom atic reac tor sc ram on Septem ber 2, 202 Additional T racking Items

Ty pe Issue Num ber Title R eport Sec tion Status LER 05000410/2023-001-00 Autom atic R eac tor Sc ram on 71153 C losed Low Lev el D ue to Partial Loss of Feedw ater

LER 05000410/2023-001-01 Supplem ent to LER 2023-71153 C losed 001-00, Autom atic R eac tor Sc ram on Low Lev el D ue to Partial Loss of Feedw ater

PLANT ST AT US

U nit 1 began the inspec tion period at rated therm al pow er. O n April 12, 2024, the unit reduc ed pow er to 65 perc ent f or rod sequenc e ex c hange, sc ram tim e testing, reheater steam leak repairs, and turbine v alv e testing. The unit returned to rated therm al pow er on April 13, 2024.

O n April 14, 2024, the unit reduc ed pow er to 90 perc ent f or rod line adjustm ent and returned to rated therm al pow er the sam e day. O n M ay 23, 2024, the unit reduc ed pow er to 95 perc ent to rem ov e reac tor rec irc ulating pum p (R R P) 12 f rom serv ic e f or c orrec tiv e m aintenanc e and returned to rated therm al pow er the sam e day. O n M ay 23, 2024, the unit reduc ed pow er to 85 perc ent to return R R P 12 to serv ic e and returned to rated therm al pow er the sam e day. O n M ay 25, 2024, the unit reduc ed pow er to 95 perc ent to rem ov e R R P f rom serv ic e due to high v ibrations and returned to rated therm al pow er the sam e day. O n M ay 26, 2024, the unit reduc ed pow er to 85 perc ent to return R R P 12 to serv ic e and returned to rated therm al pow er the sam e day.

U nit 2 began the inspec tion period at rated therm al pow er. O n April 4, 2024, the unit reduc ed pow er to 94 perc ent in response to a f eedw ater heater transien The unit returned to rated therm al pow er April 5, 202 O n M ay 17, 2024, the unit reduc ed pow er to 74 perc ent f or rod pattern adjustm ent and sequenc e ex c hange. O n M ay 18, 2024, the unit returned to rated therm al pow e INSPECT ION SCOPES

Inspec tions w ere c onduc ted using the appropriate portions of the inspec tion proc edures (IPs) in ef f ec t at the beginning of the inspec tion unless otherw ise note C urrently approv ed IPs w ith their attac hed rev ision histories are loc ated on the public w ebsite at http://w w w.nrc.gov /reading-rm /doc-c ollec tions/insp-m anual/inspec tion-proc edure/index.htm l. Sam ples w ere dec lared c om plete w hen the IP requirem ents m ost appropriate to the inspec tion ac tiv ity w ere m et c onsistent w ith Inspec tion M anual C hapter (IM C ) 2515, Light-Water R eac tor Inspec tion Program - O perations Phas The inspec tors perf orm ed ac tiv ities desc ribed in IM C 2515, Appendix D, Plant Status, observ ed risk signif ic ant ac tiv ities, and c om pleted on-site portions of IPs. The inspec tors rev iew ed selec ted proc edures and rec ords, observ ed ac tiv ities, and interv iew ed personnel to assess lic ensee perf orm anc e and c om plianc e w ith C om m ission rules and regulations, lic ense c onditions, site proc edures, and standard REACT OR SAFET Y

71111.01 - Adv erse Weather Protec tion

Seasonal Ex trem e Weather Sam ple (IP Sec tion 03.01) (1 Sam ple)

The inspec tors ev aluated readiness f or seasonal ex trem e w eather c onditions prior to the onset of seasonal hot tem peratures f or the f ollow ing sy stem s:

(1) U nit 1 em ergenc y diesel generators 102 and 103 and U nit 2 high pressure c ore spray on M ay 22, 2024

71111.04 - Equipm ent Alignm ent

Partial Walk dow n Sam ple (IP Sec tion 03.01) (4 Sam ples)

The inspec tors ev aluated sy stem c onf igurations during partial w alk dow ns of the f ollow ing sy stem s/tr ains:

(1) U nit 2 reac tor c ore isolation c ooling sy stem on April 19, 2024 (2) U nit 2 high pressure c ore spray sy stem on April 25, 2024 (3) U nit 2 standby liquid c ontrol sy stem on M ay 13, 2024 (4) U nit 1 c ontainm ent spray sy stem on J une 12, 2024

C om plete Walk dow n Sam ple (IP Sec tion 03.02) (1 Sam ple)

(1) The inspec tors ev aluated sy stem c onf igurations during a c om plete w alk dow n of the U nit 1 c ore spray sy stem on J une 24, 202.05 - Fire Protec tion

Fire Area Walk dow n and Inspec tion Sam ple (IP Sec tion 03.01) (7 Sam ples)

The inspec tors ev aluated the im plem entation of the f ire protec tion program by c onduc ting a w alk dow n and perf orm ing a rev iew to v erif y program c om plianc e, equipm ent f unc tionality,

m aterial c ondition, and operational readiness of the f ollow ing f ire areas:

(1) U nit 2 turbine building 277', w est sw itc hgear room, f ire area 84, on April 11, 2024 (2) U nit 2 turbine building 250' w est, f ire area 50, on April 11, 2024 (3) U nit 1 turbine building 369' storage tank area, f ire area 5, on M ay 22, 2024 (4) U nit 1 turbine building 289' aux iliary ex tension, f ire area 5, on M ay 22, 2024 (5) U nit 1 reac tor building east 198' to 237' c ore spray 12 areas, f ire area 1, on J une 24, 2024 (6) U nit 1 reac tor building w est 198' to 237' c ore spray 11 areas, f ire area 2, on J une 24, 2024 (7) U nit 2 c ontrol building 261' D iv ision I diesel room, f ire area 28, on J une 25, 2024

Fire Brigade D rill Perf orm anc e Sam ple (IP Sec tion 03.02) (1 Sam ple)

(1) The inspec tors ev aluated the onsite f ire brigade training and perf orm anc e during an unannounc ed f ire drill on M ay 31, 202.11Q - Lic ensed O perator R equalif ic ation Program and Lic ensed O perator Perf orm anc e

Lic ensed O perator Perf orm anc e in the Ac tual Plant/M ain C ontrol R oom (IP Sec tion 03.01)

(2 Sam ples)

(1) The inspec tors observ ed and ev aluated U nit 2 lic ensed operator perf orm anc e in the c ontrol room during a pow er reduc tion to 74 perc ent and rod pattern adjustm ent on M ay 17, 202 (2) The inspec tors observ ed and ev aluated U nit 1 lic ensed operator perf orm anc e in the c ontrol room during reac tor protec tion sy stem and f ire pum p surv eillanc es on J une 17, 202 Lic ensed O perator R equalif ic ation Training/Ex am inations (IP Sec tion 03.02) (3 Sam ples)

(1) The inspec tors observ ed a U nit 2 sim ulator ev aluation that inc luded rapidly low ering intak e bay lev els, loss of a low pressure reheater string, ' B' f eed pum p trip and rec irc ulating pum p runbac k, and unisolable leak f rom the reac tor c ore isolation c ooling sy stem on M ay 7, 202 (2) The inspec tors observ ed a U nit 1 sim ulator ev aluation that inc luded a seism ic ev ent, rec irc ulation pum p seal f ailure, and large break loss of c oolant ac c ident on M ay 14, 202 (3) The inspec tors observ ed a U nit 2 sim ulator ev aluation that inc luded an instrum ent air c om pressor trip, c ontrol rod driv e pum p trip, stuc k open prim ary relief v alv e, reac tor sc r am, and loss of c oolant c asualty on J une 18, 202.12 - M aintenanc e Ef f ec tiv eness

M aintenanc e Ef f ec tiv eness (IP Sec tion 03.01) (1 Sam ple)

The inspec tors ev aluated the ef f ec tiv eness of m aintenanc e to ensure the f ollow ing struc tures, sy stem s, and c om ponents (SSC s) rem ain c apable of perf orm ing their intended f unc tions:

(1) R ev iew of periodic ev aluation in ac c ordanc e w ith Title 10 of the C ode of Federal R egulations (10 C FR ) 50.65(a)(3) on April 9, 2024

71111.13 - M aintenanc e R isk Assessm ents and Em ergent Work C ontrol

R isk Assessm ent and M anagem ent Sam ple (IP Sec tion 03.01) (5 Sam ples)

The inspec tors ev aluated the ac c urac y and c om pleteness of risk assessm ents f or the f ollow ing planned and em ergent w ork ac tiv ities to ensure c onf iguration c hanges and appropriate w ork c ontrols w ere addressed:

(1) U nit 2 elev ated risk during D iv ision II em ergenc y diesel generator sy stem outage w indow on April 29, 2024 (2) U nit 1 elev ated risk during 122 c ore spray sy stem and 121 c ontainm ent spray sy stem planned m aintenanc e on M ay 7, 2024 (3) U nit 1 elev ated risk due to f ailure of the U nit 1 diesel f ire pum p m onthly surv eillanc e on M ay 14, 2024 (4) U nit 2 elev ated risk due to high pressure c ore spray unit c ooler c leaning and c apac ity test on M ay 21, 2024 (5) U nit 1 elev ated risk due to battery c harger 161B out of serv ic e on M ay 29, 2024

71111.15 - O perability D eterm inations and Func tionality Assessm ents

O perability D eterm ination or Func tionality Assessm ent (IP Sec tion 03.01) (6 Sam ples)

The inspec tors ev aluated the lic ensee' s justif ic ations and ac tions assoc iated w ith the f ollow ing operability determ inations and f unc tionality assessm ents:

(1) U nit 2 reac tor c ore isolation c ooling turbine bearing oil pressure greater than alert range on April 18, 2024

(2) U nit 2 autom atic depressurization sy stem saf ety relief v alv e 127 stem nut unable to be adjusted on M ay 13, 2024 (3) U nit 2 nitrogen leak on supply line to autom atic depressurization sy stem ac c um ulator on J une 3, 2024 (4) U nit 2 serv ic e w ater spring c an bloc k ed on J une 3, 2024 (5) U nit 2 starting air sy stem m alf unc tion alarm f or D iv ision I diesel on J une 17, 2024 (6) U nit 2 serv ic e w ater pum p 1F strainer bac k f lush v alv e bloc k age on J une 26, 2024

71111.24 - Testing and M aintenanc e of Equipm ent Im portant to R isk

The inspec tors ev aluated the f ollow ing testing and m aintenanc e ac tiv ities to v erif y sy stem operability and/or f unc tionality :

P ost-M aintenanc e Testing (PM T) (IP Sec tion 03.01) (9 Sam ples)

(1) N2-OSP-EGS-R 001, D iesel G enerator EC C S Start and Load R ejec t D iv ision I and II, f ollow ing diesel generator slow start m odif ic ation, on April 10, 2024 (2) N2-M FT-327B, D igital Feedw ater Lev el C ontrol Sy stem Pow er Asc ension Test, f ollow ing ac tuator m odif ic ation during ref ueling outage N 2R 19, on April 11, 2024 (3) N2-OSP-RPV-R @003, R eac tor Pressure Vessel and C lass I Sy stem s Leak age Test, w ith the reac tor pressure v essel solid, f ollow ing ref ueling outage N 2R 19, on April 11, 2024 (4) N2-OSP-EGS-M @001 D iesel G enerator and D iesel Air Start Valv e O perability Test-D iv ision I and II, f ollow ing D iv ision II em ergenc y diesel generator sy stem outage w indow, on April 30, 2024 (5) N1-ST-Q 8B Liquid Poison Pum p 12 and C hec k Valv e O perability Test, f ollow ing test sw itc h replac em ent and break er testing, on April 30, 2024 (6) N2-OSP-SLS-Q 001 Standby Liquid C ontrol Pum p C hec k Valv e R elief Valv e O perability Test and ASM E XI Pressure Test, f ollow ing pum p v alv e seat inspec tion, on M ay 2, 2024 (7) N1-ST-Q 1D, C ore Spray 122 Pum p and Valv e O perability Test, f ollow ing c ore spray topping pum p 122 seal replac em ent, on M ay 10, 2024 (8) N1-ST-Q 1C, C ore Spray 112 Pum p and Valv e O perability Test, f ollow ing v alv e prev entiv e m aintenanc e, on J une 11, 2024 (9) N1-PM-C 3, D iesel Fire Pum p, C om bined Auto Start O rif ic e Flow and Low Air Pressure O perability Test, f ollow ing diesel f ire pum p replac em ent, on J une 13, 2024

Surv eillanc e Testing (IP Sec tion 03.01) (3 Sam ples)

(1) N2-OSP-EGS-R 007, O perating C y c le D iesel G enerator Sim ulated Loss of O f f site Pow er D iv ision III, on April 23, 2024 (2) N1-ST-M 4B, Em ergenc y D iesel G enerator 103 and PB 103 O perability Test, on M ay 6, 2024 (3) N2-OSP-EGS-R 008, O perating C y c le D iesel G enerator Sim ulated Loss of O f f site Pow er w ith an Em ergenc y C ore C ooling Sy stem D iv ision III Initiation, on M ay 23, 2024

71114.06 - D rill Ev aluation

R equired Em ergenc y Preparedness D rill (1 Sam ple)

(1) O n J une 11, 2024, the inspec tors ev aluated a U nit 2 em ergenc y preparedness drill w hic h inc luded Alert, Site Area Em ergenc y, and G eneral Em ergenc y ev ent dec laration Additional D rill and/or Training Ev olution (1 Sam ple)

(1) The inspec tors ev aluated a U nit 2 sim ulator sc enario that inc luded a stuc k open prim ary relief v alv e, reac tor sc ram, and loss of c oolant c asualty that required an Alert dec laration on J une 18, 202 OT HER ACT IVIT IES - BASELINE

71151 - Perf orm anc e Indic ator Verif ic ation

The inspec tors v erif ied lic ensee perf orm anc e indic ators subm ittals listed below :

BI01: R eac tor C oolant Sy stem (R C S) Spec if ic Ac tiv ity Sam ple (IP Sec tion 02.10) (2 Sam ples)

(1) U nit 1 (f or the period of April 1, 2023 through M arc h 31, 2024)

(2) U nit 2 (f or the period of April 1, 2023 through M arc h 31, 2024)

BI02: R C S Leak R ate Sam ple (IP Sec tion 02.11) (2 Sam ples)

(1) U nit 1 (f or the period of April 1, 2023 through M arc h 31, 2024)

(2) U nit 2 (f or the period of April 1, 2023 through M arc h 31, 2024)

71152S - Sem iannual Trend Problem Identif ic ation and R esolution

Sem iannual Trend R ev iew (Sec tion 03.02) (1 Sam ple)

(1) The inspec tors rev iew ed C onstellations c orrec tiv e ac tion program to identif y potential trends that m ight be indic ativ e of a m ore signif ic ant saf ety issu Follow U p of Ev ents and N otic es of Enf orc em ent D isc retion

Ev ent R eport (IP Sec tion 03.02) (1 Sam ple)

The inspec tors ev aluated the f ollow ing lic ensee ev ent reporting determ ination to ensure it c om plied w ith reporting requirem ent (1) LER s 05000410/2023-001-00 and 05000410/2023-001-01, Autom atic R eac tor Sc ram on Low Lev el D ue to Partial Loss of Feedw ater, and Supplem ent to the Autom atic R eac tor Sc ram on Low Lev el D ue to Partial Loss of Feedw ater (AD AM S Ac c ession N os. M L23306A048 and M L24060A053, respec tiv ely ). The inspec tors rev iew ed the original and updated LER subm ittal The inspec tion c onc lusions assoc iated w ith these LER s are doc um ented in this report under Inspec tion R esult These LER s are c lose INSPECT ION RESULT S

O bserv ation: Sem iannual Trend 71152S The inspec tors ev aluated a sam ple of issues and ev ents that oc c urred f rom J anuary 2024 through J une 2024 to determ ine w hether issues w ere appropriately c onsidered as em erging or adv erse trends. The inspec tors v erif ied issues w ere appropriately ev aluated by C onstellation staf f f or potential trends and addressed w ithin the sc ope of the c orrec tiv e ac tion program or through departm ent rev iew.

The inspec tors did not identif y any new trends that c ould indic ate a m ore signif ic ant saf ety issu The inspec tors determ ined that C onstellation personnel identif ied trend issues at a low threshold and entered them into the c orrec tiv e ac tion program f or resolution. The inspec tors noted that issues w ere identif ied w ith the U nit 1 diesel f ire pum p engine reliability ev en af ter it w as replac ed in late 2023. The engine w as again replac ed this quarter. The inspec tors w ill c ontinue to m onitor the reliability of this equipm ent through routine inspec tio Inc orrec t Applic ation of M aintenanc e Strategy Proc ess Leads to Loss of Feedw ater Flow and Autom atic R eac tor Sc ram C ornerstone Signif ic anc e C r oss-Cutting R eport Aspec t Sec tion Initiating Ev ents G reen [P.3] - 71153 FIN 05000410/2024002-01 R esolution O pen/C losed A self-rev ealed G reen Finding w as identif ied f or C onstellations f ailure to adequately ev aluate the im pac t of inc reased f eedw ater lev el c ontrol v alv e c y c ling on balanc e seal longev ity in ac c ordanc e w ith ER -AA-200, "Prev entiv e M aintenanc e Program." Spec if ically, f ollow ing installation of the U nit 2 digital f eedw ater lev el c ontrol (D FWLC ) sy stem, C onstellation identif ied that lev el c ontrol v alv e 2FWS -LV10 c y c le f requenc y inc reased approx im ately f iv e-f old. C onstellation rec ognized the inc reased c y c ling c ould ac c elerate w ear of the Tef lon balanc e seal and v alv e pac k ing. The site did not appropriately assess the inc reased w ear and adjust the m aintenanc e interv al f or internal v alv e sof tw are inspec tion and replac em ent. The inc reased c y c le rate led to prem ature balanc e seal f ailure and internal v alv e f low instability,

w hic h resulted in stem /disc c onnec tion f ailur The separation of the disc f rom the v alv e stem resulted in partial loss of f eedw ater f low, and an autom atic reac tor sc ram on Septem ber 2, 202 D esc ription: O n Septem ber 2, 2023, at approx im ately 0632, U nit 2 ex perienc ed an autom atic reac tor sc ram on low reac tor w ater lev el due to a sudden loss of f eedw ater f low, dow nstream of the B f eedw ater pum p 2FWS -P1B. O perations personnel rec eiv ed m ultiple alarm s and identif ied that reac tor w ater lev el w as rapidly low erin Shortly af ter rec eiv ing initial alarm indic ations, the reac tor sc ram m ed on low reac tor w ater lev el and operators entered N2 -EO P-R PV, "R eac tor Pressure Valv e C ontrol f or M odes 1-3."

The D FWLC sy stem c ontrols reac tor w ater lev el during norm al pow er operations using tw o of three elec tric ally -driv en, c onstant speed f eed pum ps w hic h disc harge to pneum atic ally c ontrolled lev el c ontrol v alv es 2FWS -LV10 A, B, or C (LV10s). The f low rate is c ontrolled by a f eedw ater c ontroller w hic h c ontrols lev el c ontrol v alv e position based on inputs f rom reac tor v essel w ater lev el, steam f low rate, and f eedw ater f low rate transm itter In M arc h 2020, N ine M ile Point im plem ented a U nit 2 D FWLC sy stem, per approv ed engineering c hange ECP-17-00688. The new sy stem m odif ied v alv e ac tuators but retained the f eed f low throttle v alv es f rom the legac y desig The legac y design f eed f low throttle v alv es regulate f low by

positioning a c y lindric al plug w ithin a perf orated disc stac k. The plug is positioned v ertic ally w ithin the disc stac k by the v alv e stem, c ov ering or unc ov ering f low ports as nec essary to raise or low er f low. The disc stac k is ported to prom ote unif orm c ir c um f erential f low distribution that is required f or high pressure, high f low applic ation A balanc e seal k eeps the plug c entered w ithin the disc stac k and ensures leak tightnes The legac y design required the replac em ent of the stem and plug assem bly and sof t goods at 6-y ear interv al The inspec tors noted that at the tim e of m odif ic ation, the 6-y ear ov erhaul prev entiv e m aintenanc e f or LV-10B w as due in 2024 and no internal v alv e inspec tion or repairs w ere c onduc te P ost-m odif ic ation testing in 2020 identif ied sev eral issues w ith v alv e response, inc luding that the v alv es c y c led roughly f iv e tim es m ore f requently than the legac y c ontrol sy stem. A w ork group ev aluation w as c onduc ted to address D FWLC design def ic ienc ies and perf orm anc e issues, and a digital f eedw ater team w as established to ev aluate and c orrec t the unex pec ted v alv e respons In M ay 2020, the digital f eedw ater team rec ognized and doc um ented that the inc reased c y c ling of the LV10s w ould ac c elerate w ear of the Tef lon balanc e seal and v alv e pac k ing.

The inspec tors noted that, in J uly 2020, C onstellation initiated m aintenanc e ac tion to adv anc e v alv e pac k ing replac em ent by tw o y ears. H ow ev er, c ontrary to ER-AA-200, "Prev entiv e M aintenanc e Program," Sec tion 4.6, "M aintenanc e Strategy Analy sis and O ptim ization,"

Step 4 w hic h states, If trend or predic tiv e m aintenanc e predic ts signif ic ant equipm ent degradation or equipm ent f ailure bef ore the nex t sc heduled PM then Engineering or M aintenanc e should initiate an issue report (IR) per the C orrec tiv e Ac tions Proc ess and ensure a w ork request is c reated f or c orrec tiv e m aintenanc e, C onstellation f ailed to c reate w ork orders to v erif y the c ondition of the balanc e seals bef ore the ex piration of the legac y 6-y ear m aintenanc e interv a Follow ing the scram on Septem ber 2, 2023, 2FWS-LV10B w as disassem bled f or inspec tion.

Inspec tions rev ealed that the plug w as disc onnec ted f rom the stem. Inspec tions also noted that an anti-rotation pin w as absent f rom a tab w asher that w as w elded to the v alv e stem.

R em nants of the Tef lon balanc e seal assem bly w ere loc ated on the top surf ac e of the plu Subsequent f ailure analy sis determ ined that the f ailed balanc e seal allow ed high pressure f luid to pass betw een the plug and plug c age to the region abov e the plug c ausing hy draulic instability, side loading, and v ibration on the stem /plug assem bly. O v er tim e the anti-rotation pin w elded c onnec tion ex perienc ed f atigue f ailure and separate C om bined w ith the v ibration, this resulted in loss of preload betw een the stem and plug, w hic h allow ed the stem to unthread, f all into the f low stream, and stop f eed f low through the ' B' f eed header, c ausing an autom atic reac tor sc ram on low reac tor w ater lev e C orrec tiv e Ac tions: Follow ing the reac tor sc ram, C onstellation replac ed the stem and disc assem bly and installed an engineering c hange to im prov e the stem to plug anti-rotation c onnec tion on 2FWS-LV10B (additional w elds betw een loc k w asher and plug). Additionally,

C onstellation inc reased m aintenanc e f requenc y to replac e internal v alv e sof tw ar C orrec tiv e Ac tion R ef erenc es : IR s 04700148, 04334474, and 04332838

Perf orm anc e Assessm ent:

Perf orm anc e D ef ic ienc y : C onstellation' s f ailure to initiate an IR and c reate a w ork order request f or m aintenanc e on the lev el c ontrol v alv e balanc e seals per ER-AA-200, Prev entiv e M aintenanc e Program, w hen perf orm anc e m onitoring indic ated ac c elerated w ear that represented a signif ic ant risk to c om ponent reliability, w as a perf orm anc e def ic ienc y.

Sc reening: The inspec tors determ ined the perf orm anc e def ic ienc y w as m ore than m inor bec ause it w as assoc iated w ith the Equipm ent Perf orm anc e attribute of the Initiating Ev ents c ornerstone and adv ersely af f ec ted the c ornerstone objec tiv e to lim it the lik elihood of ev ents that upset plant stability and c hallenge c ritic al saf ety f unc tions during shutdow n as w ell as pow er operation Spec if ic ally, the f ailure to m odif y m aintenanc e periodic ity f or replac ing the balanc e seal, giv en the signif ic antly inc reased v alve cycle rate, resulted in ring f ailure w hic h c aused a f eedw ater transient resulting in an unplanned autom atic reac tor sc ram.

Signif ic anc e: The inspec tors assessed the signif ic anc e of the f inding using IM C 0609, Appendix A, The Signif ic anc e D eterm ination Proc ess (SD P) f or Findings At-Pow e The inspec tors assessed signif ic anc e using Q uestion B, Transient Initiators, of Ex hibit 1, Initiating Ev ents Sc reening Q uestions, and determ ined the f inding did not c ause a reac tor trip and the loss of m itigation equipm ent relied upon to transition the plant f rom the onset of the trip to a stable shutdow n c onditio Theref ore, the inspec tors determ ined the f inding to be of v ery low saf ety signif ic anc e (G reen).

C r oss-C utting Aspec t: R esolution: The organization tak es ef f ec tiv e c orrec tiv e ac tions to address issues in a tim ely m anner c om m ensurate w ith their saf ety signif ic anc e. Spec if ic ally,

c orrec tiv e ac tions did not resolv e and c orrec t the im pac t of inc reased lev el c ontrol v alv e c y c ling on the balanc e sea Enf orc em ent: Inspec tors did not identif y a v iolation of regulatory requirem ents assoc iated w ith this f indin EXIT M EET INGS AND DEBRIEFS

The inspec tors c onf irm ed that proprietary inf orm ation w as c ontrolled to protec t f rom public disc losur * O n J uly 30, 2024, the inspec tors presented the integrated inspec tion results to C arl C raw f ord, Plant M anager and other m em bers of the lic ensee staf f.

DOCUM ENT S REVIEWED

Inspec tion Ty pe D esignation D esc ription or Title R ev ision or Proc edure D ate 71111.01 Proc edures N1-OP-64 M eteorologic al M onitoring 02100 N2-OP-102 M eteorologic al M onitoring 02800 WC-AA-107 Seasonal R eadiness 29 Work O rders C 93920534 C 93938972 C 93976602 71111.04 C orrec tiv e Ac tion 04703406 D oc um ents 04777820 D raw ings C-18007-C R eac tor C ore Spray Piping and Instrum entation D iagram 064 C-18012-C R eac tor C ontainm ent Spray Sy stem 047 Proc edures N1-OP-14 C ontainm ent Spray Sy stem 048 N1-OP-2 C ore Spray Sy stem 03900 N2-OP-33-H igh Pressure C ore Spray Sy stem - Lineups 002 Lineups N2-OP-36A-Standby Liquid C ontrol Sy stem - Lineups 000 Lineups 71111.05 Fire Plans N1-PFP-0101 U nit 1 Pre-Fire Plans 00700 N2-FPI-PFP-0201 U nit 2 Pre-Fire Plans 007 M isc ellaneous DCD-805 N ine M ile Point U nit 1 N FPA 805 D esign C riteria 4 Proc edures N1-FPM-FPE-Annual Inspec tion of Portable Fire Ex tinguishers 22 A001 OP-AA-201-003 Fire D rill Perf orm anc e 22 OP-AA-201-009 C ontrol of Transient C om bustible M aterial 31 71111.07A Work O rders C 93852040 71111.13 C orrec tiv e Ac tion 04774076 D oc um ents C orrec tiv e Ac tion 04772681 D oc um ents R esulting f rom Inspec tion Proc edures N1-PM-M9 O peration of Fire Pum ps 019

Inspec tion Ty pe D esignation D esc ription or Title R ev ision or Proc edure D ate Work O rders C 93953647 71111.15 C orrec tiv e Ac tion 04760604 D oc um ents 04773482 Proc edures N2-OSP-ADS-Autom atic D epressurization Sy stem Ac c um ulator and 001T2 R 106 Pneum atic Supply Leak R ate Test N2-OSP-ICS-R C IC Pum p and Valv e O perability Test and Sy stem Integrity 018 Q @002 Test and ASM E XI Func tional Test and Analy sis Work O rders C 93849925 C 93976604 71111.24 Proc edures N1-NMP-081-113 O v erhaul of C ore Spray Topping Pum p and Ac c essories 00600 Inspec tion N1-PM-C 3 N1-PM-C 3 D iesel Fire Pum p, C om bined Auto Start O rif ic e 019 Flow and Low Air Pressure O perability Test N1-ST-M 4B Em ergenc y D iesel G enerator 103 and PB 103 O perability 028 Test N1-ST-Q 1C C ore Spray 112 Pum p and Valv e O perability Test 023 N1-ST-Q 1D C ore Spray 122 Pum p and Valv e O perability Test 026 N1-ST-Q 8B Liquid Poison Pum p 12 and C hec k Valv e O perability Test 016 N2-OSP-EGS-D iesel G enerator and D iesel Air Start Valv e O perability Test-026 M @001 D iv isions I and II N2-OSP-EGS-O perating C y c le D iesel G enerator Sim ulated Loss of O f f site 010 R 007 Pow er D iv ision III N2-OSP-EGS-O perating C y c le D iesel G enerator Sim ulated Loss of O f f site 013 R 008 Pow er w ith an EC C S D iv ision III Initiation N2-OSP-SLS-Standby Liquid C ontrol Pum p C hec k Valv e R elief Valv e 024 Q 001 O perability Test and ASM E XI Pressure Test Work O rders C 93766938 C 93793759 C 93958210 C 93975470 71151 M isc ellaneous N EI 99-02 R egulatory Assessm ent Perf orm anc e Indic ator G uideline 7 71152S C orrec tiv e Ac tion 04758100 D oc um ents 04774076

Inspec tion Ty pe D esignation D esc ription or Title R ev ision or Proc edure D ate 04774366

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