ML17321A900: Difference between revisions

From kanterella
Jump to navigation Jump to search
(Created page by program invented by StriderTol)
(Created page by program invented by StriderTol)
 
(3 intermediate revisions by the same user not shown)
Line 3: Line 3:
| issue date = 09/30/1985
| issue date = 09/30/1985
| title = Notifies of Error in 10CFR50.46 LOCA Analyses Performed for Facilities.Input Error in TOODEE2 Code Used to Calculate Fuel Rod Heatup Resulted in Rod Decay Heat Power Too Low & Subsequent Underpredicted Cladding Temp.Part 21 Related
| title = Notifies of Error in 10CFR50.46 LOCA Analyses Performed for Facilities.Input Error in TOODEE2 Code Used to Calculate Fuel Rod Heatup Resulted in Rod Decay Heat Power Too Low & Subsequent Underpredicted Cladding Temp.Part 21 Related
| author name = MALODY C
| author name = Malody C
| author affiliation = SIEMENS POWER CORP. (FORMERLY SIEMENS NUCLEAR POWER
| author affiliation = SIEMENS POWER CORP. (FORMERLY SIEMENS NUCLEAR POWER
| addressee name = MARTIN J B
| addressee name = Martin J
| addressee affiliation = NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
| addressee affiliation = NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
| docket = 05000000, 05000261, 05000315
| docket = 05000000, 05000261, 05000315
Line 18: Line 18:


=Text=
=Text=
{{#Wiki_filter:EQONNUCLEARCOMPANY,INC.2101HORNRAPIDSROAD.POBOX130.RICHLANDWA88352I50gi375-8100TEL%,-15.2878September 30,1985Mr.JohnB.MartinRegionalAdministrator, RegionVUnitedStatesNuclearRegulatory Commission 1450MariaLane,Suite210WalnutCreek,CA94596
{{#Wiki_filter:EQON            NUCLEAR COMPANY, INC.
2101 HORN RAPIDS ROAD. PO BOX 130. RICHLAND WA 88352 I50gi 375-8100 TEL%,-15.2878 September 30, 1985 Mr. John B. Martin Regional Administrator, Region                  V United States Nuclear Regulatory Commission 1450 Maria Lane, Suite 210 Walnut Creek, CA 94596


==SUBJECT:==
==SUBJECT:==
Notification ofErrorinLOCAAnalysesOearMr.Martin:Asreportedinatelephone conversation onSeptember 30,1985betweenMr.YuhasofRegionVandme,anerrorwasdiscovered inthe10CFR50.46lossofcoolantaccident(LOCA)analysesperformed byExxonNuclearfortheH.B.RobinsonUnit2andD.C.CookUnit1reactors.
Notification of Error in          LOCA Analyses Oear Mr. Martin:
TheerrorwasaninputerrorintheTOODEE2codewhichisusedtocalculate fuelrodheatup.Theerrorresultedintheroddecayheatpowerbeingtoolowwhichcausedthecalculated peakcladdingtemperature tobeunderpredicted.
As reported in a telephone conversation on September 30, 1985 between Mr.
Attachedisadetaileddescription oftheeffectoferrorforeachunitandtheresulting under-prediction inthepeakcladdingtemperatures.
Yuhas    of Region V and me, an error was discovered in the 10 CFR 50.46 loss of coolant accident (LOCA) analyses performed by Exxon Nuclear for the H.B.
Allofthepressurized waterreactorsforwhichExxonNuclearprovidesLOCAanalyseshavebeenreviewed.
Robinson Unit 2 and D.C. Cook Unit 1 reactors. The error was an input error in the TOODEE2 code which is used to calculate fuel rod heatup. The error resulted in the rod decay heat power being too low which caused the calculated peak cladding temperature to be underpredicted.                     Attached is a detailed description of the effect of error for each unit and the resulting under-prediction in the peak cladding temperatures.
Theerrorwasverifiedtohaveoccurredintheanalysesforonlythesetwoplants.ForD.C.CookUnit1,thecalculation wasrerunwiththeerrorcorrected andusingmorerealistic valuesofthepelletdensityandinternalpressure.Thisanalysiswasincompliance withtherequirements of10CFR50.46.ForH.B.RobinsonUnit2,thecalculated PCTswiththeerrorcorrected wereabove2200F.Areduction inFqwhichcorresponds totheunderestimate oftherodpowerwasnecessary tomaintaincompliance withthe10CFR50.46requirements.
All of the pressurized water reactors for which Exxon Nuclear provides LOCA    analyses have been reviewed. The error was verified to have occurred in the analyses for only these two plants. For D.C. Cook Unit 1, the calculation was rerun with the error corrected and using more realistic values of the pellet density and internal pressure . This analysis was in compliance with the requirements of 10 CFR 50.46.
AsrequiredbytheExxonNuclearprocedures, aHazardsReviewBoardwasconvenedonSeptember 28,1985whentheeffectoftheerrorshadbeendetermined.
For H.B. Robinson Unit 2, the calculated PCTs with the error corrected were above 2200 F. A reduction in Fq which corresponds to the underestimate of the rod power was necessary to maintain compliance with the 10 CFR 50.46 requirements.
TheBoardconcluded thattheaffectedutilitiesshouldbenotified, thattheyshouldinturnnotifytheNRC,andthatH;B.RobinsonUnit2shouldimmediately reducetheallowedFqasindicated intheattachment.
As required by the Exxon Nuclear procedures,           a Hazards Review Board was convened      on            September 28, 1985 when the effect of the errors had been determined.                   The Board concluded that the affected uti lities should be notified, that they should in turn notify the NRC, and that H;B. Robinson Unit 2 should immediately reduce the allowed Fq as indicated in the attachment.
Basedonsubsequent conversations withtheaffectedutilities, theserecom-mendations havebeenfollowed.
Based on subsequent conversations with the affected utilities, these recom-mendations have been followed.
851008030i 8Si002'.pDR'"AoaCXOS00>>iS"p,-.-"-PDR.
" 851008030i p,-
Mr.J.Hartin(USNRC)September 30,1985Thisletterprovidesthewrittennotification usingtheprocedures givenin10CFR21.21(b).
pDR'" AoaCX        .
Iftherearequestions, oriffurtherinformation isneeded,pleasecontactme.Sincerely, C.Malody,ManagerCorporate Licensinnaacc:Mr.R.DeYoung(3copies)(D/OIEUSNRC)Mr.J.Bell(AEPSC)Mr.T.Dresser(CPKL)
OS00>>iS 8Si002'.
Attachment ErrorinLOCA-ECCS AnalysisforH.B.RobinsonUnit2andD.C.CookUnit1Ref.:(1)XN-NF-84-72, "H.B.RobinsonUnit2LargeBreakLOCA-ECCS AnalysiswithIncreased EnthalpyRiseFactor,"ExxonNuclearCompany,July1984(2)XN-NF-84-72, Supp.1,"H.B.RobinsonUnit2LargeBreakLOCA-ECCSAnalysiswithIncreased EnthalpyRiseFactor:BreakSpectrumAnalysis,"
                                  -"-PDR.
ExxonNuclearCompany,August1984.(3)XN-NF-84-72, Supp.2,"H.B.RobinsonUnit2LargeBreakLOCA-ECCSAnalysiswithIncreased EnthalpyRiseFactor:K(Z)Curve,"ExxonNuclearCompany,August1984(4)XN-NF-83-61, "D.C.CookUnit1LOCA-ECCS AnalysisforExtendedExposure,"
ExxonNuclearCompany,August1983(5)Letter,G.F.Owsley,Manager,ReloadLicensing Liaison(ENC)toRichardDeYoung,DirectorofInspection andEnforcement (USNRC),datedMarch22,1985(GFO:85:010)
TheLOCA-ECCS analysesforthereactorsH.B.RobinsonUni,t2andD.C.CookUnit1reportedintheabovereferences havebeenfoundtocontainanerror.TheerrorwasintheinputtothecodeTOODEE2.ThecodeTOODEE2calculates thethermalresponse(heatup)ofthehotfuelrodfollowing theendoftheblowdowntransient untilthecoretemperature transient isterminated.
Thefuelrodsintheanalysesweremodeledwitheightradialringsinthefuelpellet.Theerrorconsisted oftheassignment ofarelativedecayheatpowerdensityof0.0intheouterringofthefuelpelletandresultedincalculated peakcladtemperatures whichweretoolow.H.B.RobinsonUnit2Asummaryofthepeakcladtemperatures fortheH.B.RobinsonUnit2analysis, reportedinReferences 1,2and3,andofthecalculated peakcladtemperatures'ith theerrorcorrected ispresented intheattachedTable1.ThefirstthreecasesinTable1wereoriginally performed aspartofanexposuresensitivity study,andthefinaltwocaseswereperformed todefinetheaxialpowerpeakingfactordependence (K(2)curve).Ascanbeseenfromthetable,threeofthesecasesresultinpeakcladtemperatures greaterthan2200oFandthusexceedthe10CFR50.46criteria.
Ananalysiswasperformed todetermine anFqwhichwouldresultinpeakcladtemperatures lessthan2200oF.Thisrequiredareduction inFqof8Xwhichwasachievedbyareduction ofthehotrodpowerintheTOODEE2codeof8X.Thisisaconservative calculation becausetheFqintheblowdownportionofthetransient hasnotbeenreduced.Theinitialtemperatures atthestartoftheTOODEE2(heatup)calculation aretherefore conservative withrespecttotheFqintheTOODEE2calculation.
Areduction oftheFqintheblowdownportionofthetransient wouldresultinthecalculation ofevenlowertemperatures.
Theresultsofthesecalculations aresummarized inTable2.
TheFqlimitsforH.S.RobinsonUnit2whichwillresultinLOCA-ECCS calculational resultsinconformance withthe10CFR50.46criteriaareshowninTable3.Thelimitsaredividedintotwoexposurerangesconsistent withtheanalysis, 0to9MWD/kgand9MWD/kgto49MWD/kg.D.C.CookUnit1TheerrorintheD.C.CookUnit1analysis(References 4and5)occurredonlyinthecalculation forthecaseat48MWD/kg.Thecasesatlowerexposures donotcontaintheerror.Thecalculation inerrorwasrerunwiththeerrorcorrected andmorerealistic valuesforthepelletdensityandinternalrodpressure.
Thereanalysis resultedinapeakcladtemperature changefrom1827Fto2189oF,whichisstillincompliance with10CFR50.46.Thisrevisedcalculation isveryconservative inthatthestoredenergyusedinthecalculation isthepeakstoredenergyovertherange0to48MWD/kgratherthanalowervalueofstoredenergythatwouldbeappropriate forthe48MWD/kgexposureforthiscase.Additionally, itisourunderstanding thattheENC-designed fuelinD.C.CookUnit1isnotintheexposurerangeforwhichthiscalculation isapplicable.
Table1H.B.RobinsonUnit2ErrorinTOODEE2Input;RodRadialPowerDistribution CaseDescription (Exposure/Power Shape)PreviousPeakCladTemperature (oF)Corrected PeakCladTemperature (oF)BOL/Cosine 9MWD/kg/Cosine EOL/Cosine BOL/TopPeaked9MWD/kg/Top Peaked20421815178521972183>220019231888>2200>2200 Table2H.B.RobinsonUnit2Reanalysis withFq*.92inTOODEE2Calculation CaseDescription (Exposure/Power Shape)PeakCladTemperature
(<<)BOL/Cosine BOL/TopPeaked9MWD/kg/Top Peaked206421952187 Table3H.B.RobinsonUnit2LOCA-ECCS Limits0to9MWD/kgHotRodAveraeExposure9to49MWD/kgHotRodAveraeExposureX/L0.0000.5000.9161.000~F(Z)2.1302.1301.6900.8351.0001.0000.7930.392X/L0.0000.5000,9161.000~F(Z)2.3202.3201.7260.8351.0001.0000.7440.360 Attachment 2toAEP:NRC:0940B OCTOfm85Hj(ONUCLEARCOMPANY,INC.210tHORNRD8ROAO.POBOXI30,RCHLANO,WA 8835210O81318.81TLEX:tb2878Mr.JPropreIndiac/oOneRColuSUBJERef.:September 30,1985JSH:044:85 IIIltIsephL.8elltManager,D.C.CookUnit1a5NichiganElectricCompanyericanElectricPowerServiceCorp.',versidePlazaus,OH43216-6631 T:ErrorinLOCA/ECCS AnalysisforD.C.CookUnit1(1)XN-NF-83-61, "D.C.CookUnit1LOCA-KCCS AnalysisforExtendedExposure,"
ExxonNuclearCompany,August1983(2)Letter,G,F.Owsley,Manager,ReloadLicensing Liaison(ENC)toRichardOeYoung,DirectorofInspection andEnforcement (USNRC),datedMarch22,1985(GFO:85:010)


==Dearr.8ell:==
Mr. J. Hartin (USNRC)                                        September 30, 1985 This letter provides the written notification using the procedures given in  10 CFR  21.21(b). If there are questions, or if further information is needed, please contact me.
ECCSerror)calcu)ofthhThefhpelletdensicalcuinthvalue~tempesunnathes0to;.4appropsdiscussed withMr.GeorgeJohn(AEP)onSeptember 28,1985,theLOCA-nalysisforD.C.CookUnit1reportedtin References 1and2containsanTheerrorwasintheinputtothecodeTOOOEE2.ThecodeTOODEE2atesthethermalresponse(heatup)ofithehotfuelrodfollowing theendblowdowntransientuntilthecoretemperature transient isterminated.
Sincerely, C. Malody, Manager Corporate Licensin naa cc:  Mr. R. DeYoung (3 copies) (D/OIE  USNRC)
elrodintheanalysiswasmodeledwitheightradialringsinthefuelTheerrorconsisted oftheassignment ofarelativedecayheatpoweryof0.0intheouterringofthefuelpellet.Thisresultedinaatedpeakcladtemperature whichwas'oolow.Theerroroccurredonlycalculation forthecaseat48MWD/kg.thecalculation inerrorwasrerunwiththeerrorcorrected andwiththeodpelletdensityincreased andtheinternalrodpressuredecreased toappropriate for48MWD/kg.Thiscalculation resultedinapeakcladatureof2189oFincompliance with10'CFR50.46.Thesecalculations areizedinTable1.Thiscalculation isstillveryconservative inthatoredenergyintheca'Iculation isth)peakstoredenergyovertherange8MWD/kgratherthanalowervalueofstoredenergythatwouldberiateforthe48MWD/kgexposureforthiscase.Additionally, itisourANASS<ATCOSEXXONCOIISaORATON I
Mr. J. Bell (AEPSC)
I~'SaIIS&&laI~IalMr.J.Bell(AEP)JSH:044:85 September 30,1985gfAttactIaa cc:4.J.M.Cleveland (AEP)Nr.M.P.Alexich(AEP)Hr.G.John(AEP)Mr.H.G.Shaw(ENC)Mr.R.A.Copeland(KNC)r.R.L.Heiks(ENC)understanding thattheENCfuelinO.C.CookUnit1isnotintheexposurerangeforwhichthiscalculation isapplicable.
Mr. T. Dresser (CPKL)
Sincerely, J.S.Holm,ManagerPNSafetyAnalysisRAPID<go..<<~7PAGE~,Oag Table1O.C.CookUnit1ErrorinTOOOEE2Input;RodRadialPowerDistribution seOescritioneviousResult*PeakCladTemperature OF1827CrrectedResultwithincreased pelletdensityandreducedfuelrhdpressurel2189III*Thepreviousresultwasforacosinepowerdistribution at48,0NMD/kgexposure, Fq*l.82,reportedinReferences 1and2.}}
 
Attachment Error in  LOCA-ECCS  Analysis for H.B. Robinson Unit    2 and D.C. Cook  Unit  1 Ref.:      (1)    XN-NF-84-72,      "H.B. Robinson Unit 2 Large Break LOCA-ECCS Analysis with Increased Enthalpy Rise Factor," Exxon Nuclear Company,    July 1984 (2)    XN-NF-84-72, Supp. 1, "H.B. Robinson Unit      2 Large Break LOCA-ECCS  Analysis with Increased      Enthalpy  Rise  Factor: Break Spectrum Analysis," Exxon Nuclear Company, August 1984 .
(3)    XN-NF-84-72, Supp. 2, "H.B. Robinson Unit      2  Large Break LOCA-ECCS    Analysis with Increased Enthalpy Rise Factor:            K(Z)
Curve," Exxon Nuclear Company, August 1984 (4)  XN-NF-83-61, "D.C. Cook Unit      1 LOCA-ECCS Analysis for Extended Exposure," Exxon Nuclear Company, August 1983 (5)  Letter, G.F. Owsley,      Manager, Reload Licensing Liaison (ENC) to Richard      DeYoung, Director of Inspection and Enforcement (USNRC), dated March 22, 1985 (GFO:85:010)
The LOCA-ECCS analyses      for the reactors H.B. Robinson Uni,t 2 and D.C.
Cook  Unit 1  reported in the above references have been found to contain an error. The error was in the input to the code TOODEE2. The code TOODEE2 calculates the thermal response (heatup) of the hot fuel rod following the end of the blowdown transient until the core temperature transient is terminated.
The fuel rods in the analyses were modeled with eight radial rings in the fuel pellet. The error consisted of the assignment of a relative decay heat power density of 0.0 in the outer ring of the fuel pellet and resulted in calculated peak clad temperatures which were too low.
H. B. Robinson    Unit  2 A summary of the peak clad temperatures          for the H.B. Robinson Unit 2 analysis, reported in References 1, 2 and 3, and of the calculated peak clad temperatures'ith the error corrected is presented in the attached Table 1.
The first three cases in Table 1 were originally performed as part of an exposure sensitivity study, and the final two cases were performed to define the axial power peaking factor dependence (K(2) curve). As can be seen from the table, three of these cases result in peak clad temperatures greater than 2200oF and    thus exceed the 10      CFR 50.46  criteria.
An analysis  was  performed to determine an Fq which would result in peak clad temperatures    less than 2200oF. This required a reduction in Fq of 8X which was achieved by a reduction of the hot rod power in the TOODEE2 code of 8X. This is a conservative calculation because the Fq in the blowdown portion of the transient has not been reduced. The initial temperatures at the start of the TOODEE2 (heatup) calculation are therefore conservative with respect to the Fq in the TOODEE2 calculation. A reduction of the Fq in the blowdown portion of the transient would result in the calculation of even lower temperatures. The results of these calculations are summarized in Table 2.
 
The Fq  limits for H.S. Robinson Unit 2 which will result in LOCA-ECCS calculational results in conformance with the 10 CFR 50.46 criteria are shown in Table 3. The limits are divided into two exposure ranges consistent with the analysis, 0 to 9 MWD/kg and 9 MWD/kg to 49 MWD/kg.
D. C. Cook Uni  t 1 The error in the D.C. Cook Unit 1 analysis (References 4 and 5) occurred only in the calculation for the case at 48 MWD/kg. The cases at lower exposures do not contain the error. The calculation in error was rerun with the error corrected and more realistic values for the pellet density and internal rod pressure. The reanalysis resulted in a peak clad temperature change from 1827 F to 2189oF, which is still in compliance with 10 CFR 50.46.
This revised calculation is very conservative in that the stored energy used in the calculation is the peak stored energy over the range 0 to 48 MWD/kg rather than a lower value of stored energy that would be appropriate for the 48 MWD/kg exposure for this case. Additionally, it is our understanding that the ENC-designed fuel in D.C. Cook Unit 1 is not in the exposure range for which this calculation is applicable.
 
Table  1  H.B. Robinson Unit 2 Error in TOODEE2 Input; Rod Radial Power Distribution Previous Peak Clad    Corrected Peak Clad Case  Description                  Temperature            Temperature (Exposure/Power  Shape)                  (oF)                    (oF)
BOL/Cosine                                2042                  >  2200 9 MWD/kg/Cosine                            1815                      1923 EOL/Cosine                                1785                      1888 BOL/Top Peaked                            2197                  >  2200 9 MWD/kg/Top  Peaked                      2183                  >  2200
 
Table  2    H.B. Robinson Unit 2 Reanalysis with Fq*.92 in TOODEE2 Calculation Case Description                                    Peak Clad Temperature (Exposure/Power  Shape)                                    (<<)
BOL/Cosine                                                  2064 BOL/Top Peaked                                              2195 9 MWD/kg/Top Peaked                                          2187
 
Table 3    H.B. Robinson Unit 2 LOCA-ECCS  Limits 0 to  9 MWD/kg                                  9 to  49 MWD/kg Hot Rod Avera e Exposure                        Hot Rod Avera e Exposure X/L        ~F(Z)                                X/L      ~F(Z) 0.000      2.130      1.000                    0.000      2.320    1.000 0.500      2. 130    1.000                    0.500      2.320    1.000 0.916      1.690      0.793                    0,916      1. 726    0.744 1.000      0.835      0.392                    1.000      0.835    0.360 to AEP:NRC:0940B OCTO      f m85 Hj(O          NUCLEAR COMPANY, INC.
210t HORN R  D8 ROAO. PO BOX I30, RCHLANO,WA88352 10O81 318.81  TLEX: tb2878 September 30, 1985 JSH:044:85 I
I I
lt I
Mr. J seph L. 8ell Propre  t  Manager, D.C. Cook Unit 1 Indi a a 5 Nichigan Electric Company c/o    erican Electric Power Service Corp.                        ',
One R  verside Plaza Colu    us,  OH      43216-6631 SUBJE  T:    Error in        LOCA/ECCS    Analysis for D.C.                Cook Unit 1 Ref.:          (1)    XN-NF-83-61, "D.C. Cook Unit 1 LOCA-KCCS Analysis for Extended Exposure," Exxon Nuclear Company, August 1983 (2)    Letter, G,F.      Owsley, Manager, Reload Licensing Liaison (ENC) to Richard      OeYoung, Director of Inspection                  and Enforcement (USNRC),      dated    March 22, 1985 (GFO:85:010)
 
==Dear    r. 8ell:==
 
s discussed with Mr . George John (AEP) on September 28, 1985, the LOCA-ECCS    nalysis for D.C. Cook Unit 1 reportedtin References 1 and 2 contains an error) The error was in the input to the code TOOOEE2. The code TOODEE2 calcu) ates the thermal response (heatup) ofithe hot fuel rod following the end of thh blowdown tr ansient until the core temperature transient is terminated.
The fh el rod in the analysis was modeled with eight radial rings in the fuel pellet The error consisted of the assignment of a relative decay heat power densi y of 0.0 in the outer ring of the fuel pellet. This resulted in a calcu ated peak clad temperature which was'oo low. The error occurred only in th calculation for the case at 48 MWD/kg.
t he  calculation in error was rerun with the error corrected and with the od  pellet density increased and the internal rod pressure decreased to value~ appropriate for 48 MWD/kg. This calculation resulted in a peak clad tempe ature of 2189oF in compliance with 10'CFR 50.46. These calculations are sunna ized in Table 1. This calculation is still very conservative in that the s ored energy in the ca'Iculation is th) peak stored energy over the range 0 to;.4 8 MWD/kg rather than a lower value of stored energy that would be approp riate for the 48 MWD/kg exposure for this case. Additionally, it is our AN ASS <ATC OS EXXON COIISaORATON I
 
I ~ 'Sa  I  IS& & la  I ~         I al JSH:044:85 Mr. J. Bell (AEP)                                           September 30, 1985 understanding that the ENC fuel in O.C. Cook Unit  1 is not in the      exposure range for which this calculation is applicable.
Sincerely, J. S. Holm, Manager PN Safety Analysis gf AttactIaa cc:   4 . J. M. Cleveland (AEP)
Nr. M. P. Alexich (AEP)
Hr. G. John (AEP)
Mr. H. G. Shaw (ENC)
Mr. R. A. Copeland (KNC)
: r. R. L. Heiks (ENC)
RAPID<         go.. <<~7 PAGE      ~ ,Oag
 
Table  1  O.C. Cook Unit 1  Error in  TOOOEE2  Input; Rod  Radial Power  Distribution Peak Clad Temperature se Oescri  tion                                            OF evious Result*                                           1827 C  rrected Result with increased                            2189 pellet density and reduced fuel rhd pressure l
I I
I
*The previous    result  was for  a cosine power  distribution at 48,0  NMD/kg exposure,   Fq*l.82, reported in References    1  and 2.}}

Latest revision as of 06:13, 29 October 2019

Notifies of Error in 10CFR50.46 LOCA Analyses Performed for Facilities.Input Error in TOODEE2 Code Used to Calculate Fuel Rod Heatup Resulted in Rod Decay Heat Power Too Low & Subsequent Underpredicted Cladding Temp.Part 21 Related
ML17321A900
Person / Time
Site: Robinson, Cook, 05000000
Issue date: 09/30/1985
From: Malody C
SIEMENS POWER CORP. (FORMERLY SIEMENS NUCLEAR POWER
To: Martin J
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML17321A899 List:
References
REF-PT21-85-431-000 PT21-85-431, PT21-85-431-000, NUDOCS 8510080301
Download: ML17321A900 (11)


Text

EQON NUCLEAR COMPANY, INC.

2101 HORN RAPIDS ROAD. PO BOX 130. RICHLAND WA 88352 I50gi 375-8100 TEL%,-15.2878 September 30, 1985 Mr. John B. Martin Regional Administrator, Region V United States Nuclear Regulatory Commission 1450 Maria Lane, Suite 210 Walnut Creek, CA 94596

SUBJECT:

Notification of Error in LOCA Analyses Oear Mr. Martin:

As reported in a telephone conversation on September 30, 1985 between Mr.

Yuhas of Region V and me, an error was discovered in the 10 CFR 50.46 loss of coolant accident (LOCA) analyses performed by Exxon Nuclear for the H.B.

Robinson Unit 2 and D.C. Cook Unit 1 reactors. The error was an input error in the TOODEE2 code which is used to calculate fuel rod heatup. The error resulted in the rod decay heat power being too low which caused the calculated peak cladding temperature to be underpredicted. Attached is a detailed description of the effect of error for each unit and the resulting under-prediction in the peak cladding temperatures.

All of the pressurized water reactors for which Exxon Nuclear provides LOCA analyses have been reviewed. The error was verified to have occurred in the analyses for only these two plants. For D.C. Cook Unit 1, the calculation was rerun with the error corrected and using more realistic values of the pellet density and internal pressure . This analysis was in compliance with the requirements of 10 CFR 50.46.

For H.B. Robinson Unit 2, the calculated PCTs with the error corrected were above 2200 F. A reduction in Fq which corresponds to the underestimate of the rod power was necessary to maintain compliance with the 10 CFR 50.46 requirements.

As required by the Exxon Nuclear procedures, a Hazards Review Board was convened on September 28, 1985 when the effect of the errors had been determined. The Board concluded that the affected uti lities should be notified, that they should in turn notify the NRC, and that H;B. Robinson Unit 2 should immediately reduce the allowed Fq as indicated in the attachment.

Based on subsequent conversations with the affected utilities, these recom-mendations have been followed.

" 851008030i p,-

pDR'" AoaCX .

OS00>>iS 8Si002'.

-"-PDR.

Mr. J. Hartin (USNRC) September 30, 1985 This letter provides the written notification using the procedures given in 10 CFR 21.21(b). If there are questions, or if further information is needed, please contact me.

Sincerely, C. Malody, Manager Corporate Licensin naa cc: Mr. R. DeYoung (3 copies) (D/OIE USNRC)

Mr. J. Bell (AEPSC)

Mr. T. Dresser (CPKL)

Attachment Error in LOCA-ECCS Analysis for H.B. Robinson Unit 2 and D.C. Cook Unit 1 Ref.: (1) XN-NF-84-72, "H.B. Robinson Unit 2 Large Break LOCA-ECCS Analysis with Increased Enthalpy Rise Factor," Exxon Nuclear Company, July 1984 (2) XN-NF-84-72, Supp. 1, "H.B. Robinson Unit 2 Large Break LOCA-ECCS Analysis with Increased Enthalpy Rise Factor: Break Spectrum Analysis," Exxon Nuclear Company, August 1984 .

(3) XN-NF-84-72, Supp. 2, "H.B. Robinson Unit 2 Large Break LOCA-ECCS Analysis with Increased Enthalpy Rise Factor: K(Z)

Curve," Exxon Nuclear Company, August 1984 (4) XN-NF-83-61, "D.C. Cook Unit 1 LOCA-ECCS Analysis for Extended Exposure," Exxon Nuclear Company, August 1983 (5) Letter, G.F. Owsley, Manager, Reload Licensing Liaison (ENC) to Richard DeYoung, Director of Inspection and Enforcement (USNRC), dated March 22, 1985 (GFO:85:010)

The LOCA-ECCS analyses for the reactors H.B. Robinson Uni,t 2 and D.C.

Cook Unit 1 reported in the above references have been found to contain an error. The error was in the input to the code TOODEE2. The code TOODEE2 calculates the thermal response (heatup) of the hot fuel rod following the end of the blowdown transient until the core temperature transient is terminated.

The fuel rods in the analyses were modeled with eight radial rings in the fuel pellet. The error consisted of the assignment of a relative decay heat power density of 0.0 in the outer ring of the fuel pellet and resulted in calculated peak clad temperatures which were too low.

H. B. Robinson Unit 2 A summary of the peak clad temperatures for the H.B. Robinson Unit 2 analysis, reported in References 1, 2 and 3, and of the calculated peak clad temperatures'ith the error corrected is presented in the attached Table 1.

The first three cases in Table 1 were originally performed as part of an exposure sensitivity study, and the final two cases were performed to define the axial power peaking factor dependence (K(2) curve). As can be seen from the table, three of these cases result in peak clad temperatures greater than 2200oF and thus exceed the 10 CFR 50.46 criteria.

An analysis was performed to determine an Fq which would result in peak clad temperatures less than 2200oF. This required a reduction in Fq of 8X which was achieved by a reduction of the hot rod power in the TOODEE2 code of 8X. This is a conservative calculation because the Fq in the blowdown portion of the transient has not been reduced. The initial temperatures at the start of the TOODEE2 (heatup) calculation are therefore conservative with respect to the Fq in the TOODEE2 calculation. A reduction of the Fq in the blowdown portion of the transient would result in the calculation of even lower temperatures. The results of these calculations are summarized in Table 2.

The Fq limits for H.S. Robinson Unit 2 which will result in LOCA-ECCS calculational results in conformance with the 10 CFR 50.46 criteria are shown in Table 3. The limits are divided into two exposure ranges consistent with the analysis, 0 to 9 MWD/kg and 9 MWD/kg to 49 MWD/kg.

D. C. Cook Uni t 1 The error in the D.C. Cook Unit 1 analysis (References 4 and 5) occurred only in the calculation for the case at 48 MWD/kg. The cases at lower exposures do not contain the error. The calculation in error was rerun with the error corrected and more realistic values for the pellet density and internal rod pressure. The reanalysis resulted in a peak clad temperature change from 1827 F to 2189oF, which is still in compliance with 10 CFR 50.46.

This revised calculation is very conservative in that the stored energy used in the calculation is the peak stored energy over the range 0 to 48 MWD/kg rather than a lower value of stored energy that would be appropriate for the 48 MWD/kg exposure for this case. Additionally, it is our understanding that the ENC-designed fuel in D.C. Cook Unit 1 is not in the exposure range for which this calculation is applicable.

Table 1 H.B. Robinson Unit 2 Error in TOODEE2 Input; Rod Radial Power Distribution Previous Peak Clad Corrected Peak Clad Case Description Temperature Temperature (Exposure/Power Shape) (oF) (oF)

BOL/Cosine 2042 > 2200 9 MWD/kg/Cosine 1815 1923 EOL/Cosine 1785 1888 BOL/Top Peaked 2197 > 2200 9 MWD/kg/Top Peaked 2183 > 2200

Table 2 H.B. Robinson Unit 2 Reanalysis with Fq*.92 in TOODEE2 Calculation Case Description Peak Clad Temperature (Exposure/Power Shape) (<<)

BOL/Cosine 2064 BOL/Top Peaked 2195 9 MWD/kg/Top Peaked 2187

Table 3 H.B. Robinson Unit 2 LOCA-ECCS Limits 0 to 9 MWD/kg 9 to 49 MWD/kg Hot Rod Avera e Exposure Hot Rod Avera e Exposure X/L ~F(Z) X/L ~F(Z) 0.000 2.130 1.000 0.000 2.320 1.000 0.500 2. 130 1.000 0.500 2.320 1.000 0.916 1.690 0.793 0,916 1. 726 0.744 1.000 0.835 0.392 1.000 0.835 0.360 to AEP:NRC:0940B OCTO f m85 Hj(O NUCLEAR COMPANY, INC.

210t HORN R D8 ROAO. PO BOX I30, RCHLANO,WA88352 10O81 318.81 TLEX: tb2878 September 30, 1985 JSH:044:85 I

I I

lt I

Mr. J seph L. 8ell Propre t Manager, D.C. Cook Unit 1 Indi a a 5 Nichigan Electric Company c/o erican Electric Power Service Corp. ',

One R verside Plaza Colu us, OH 43216-6631 SUBJE T: Error in LOCA/ECCS Analysis for D.C. Cook Unit 1 Ref.: (1) XN-NF-83-61, "D.C. Cook Unit 1 LOCA-KCCS Analysis for Extended Exposure," Exxon Nuclear Company, August 1983 (2) Letter, G,F. Owsley, Manager, Reload Licensing Liaison (ENC) to Richard OeYoung, Director of Inspection and Enforcement (USNRC), dated March 22, 1985 (GFO:85:010)

Dear r. 8ell:

s discussed with Mr . George John (AEP) on September 28, 1985, the LOCA-ECCS nalysis for D.C. Cook Unit 1 reportedtin References 1 and 2 contains an error) The error was in the input to the code TOOOEE2. The code TOODEE2 calcu) ates the thermal response (heatup) ofithe hot fuel rod following the end of thh blowdown tr ansient until the core temperature transient is terminated.

The fh el rod in the analysis was modeled with eight radial rings in the fuel pellet The error consisted of the assignment of a relative decay heat power densi y of 0.0 in the outer ring of the fuel pellet. This resulted in a calcu ated peak clad temperature which was'oo low. The error occurred only in th calculation for the case at 48 MWD/kg.

t he calculation in error was rerun with the error corrected and with the od pellet density increased and the internal rod pressure decreased to value~ appropriate for 48 MWD/kg. This calculation resulted in a peak clad tempe ature of 2189oF in compliance with 10'CFR 50.46. These calculations are sunna ized in Table 1. This calculation is still very conservative in that the s ored energy in the ca'Iculation is th) peak stored energy over the range 0 to;.4 8 MWD/kg rather than a lower value of stored energy that would be approp riate for the 48 MWD/kg exposure for this case. Additionally, it is our AN ASS <ATC OS EXXON COIISaORATON I

I ~ 'Sa I IS& & la I ~ I al JSH:044:85 Mr. J. Bell (AEP) September 30, 1985 understanding that the ENC fuel in O.C. Cook Unit 1 is not in the exposure range for which this calculation is applicable.

Sincerely, J. S. Holm, Manager PN Safety Analysis gf AttactIaa cc: 4 . J. M. Cleveland (AEP)

Nr. M. P. Alexich (AEP)

Hr. G. John (AEP)

Mr. H. G. Shaw (ENC)

Mr. R. A. Copeland (KNC)

r. R. L. Heiks (ENC)

RAPID< go.. <<~7 PAGE ~ ,Oag

Table 1 O.C. Cook Unit 1 Error in TOOOEE2 Input; Rod Radial Power Distribution Peak Clad Temperature se Oescri tion OF evious Result* 1827 C rrected Result with increased 2189 pellet density and reduced fuel rhd pressure l

I I

I

  • The previous result was for a cosine power distribution at 48,0 NMD/kg exposure, Fq*l.82, reported in References 1 and 2.