ML022700358
| ML022700358 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 09/27/2002 |
| From: | FirstEnergy Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| BL-01-001, FOIA/PA-2002-0229 | |
| Download: ML022700358 (26) | |
Text
Agenia Introduction/Background
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Deterministic Model SVProbabilistic Risk Inspection Steve Moffitt Dave Geisen Ar.
Ken Byrd ark McLaughlin
ý Closing Summary*:!
Steve Moffitt BIATIONA4 FENOCE %
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Today's ObGuective Provide Reasonable Assurance that Davis-Besse is safe to operate until February 16, 200 p.,,
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BIckAground:
% NRC Bulletin 2001-01 response provided STelephone call received on September 28
%V Teleconference on October 3
ý Brief drop by visit 0.1v
'otb r
411
,i~ Meeting with NRS Wa ir 2
SNRR Staff a!,"
N-ver
,ý Meeting with NRR.Staff on November 13
'nber Teleconference on November 26 IX v-AT IO V i FENLOC.
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Determilistil Aspects DBNPS's evaluation is based on visual inspections perfqrmed in 10, 11, and 12 RFO (May 1996, April 1998, and April 2000).
The inspection results afford us assurance that all but 4 nozzle penetrations were inspected in 1996, all but 19 inspected in 1998, and all but 24 penetrations inspected in 2000.
The limiting nozzle populaRn isIth*e* nozzles"that could not be inspected inl1998:,or 20.
It is conservatively' p6.pnetrations, an, axial through-weld flaw o'pulrs immec Iiately upon startup from 10 RFO (May 1996).
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lnitialFlaw Size Initial flaw depth of 0.5 mm, 1720 around thed nozzle, is assumed to exist immediately upon achieving a full penetration axial flaw.
BASIS:
is a conservative fl-site size.
It is further consmattivel
- stu.m iple starting flaws could exist arjat th
- ntuY* link togetýhdr.
is conservative it' that by'ass g this starting point, we also are assuming thatw.hve.already had several years of flaw propagation axially through the Alloy 182 weld material.
FENOC 5
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sea of Modified Scott Model The Modified Scott Model is still deemed cred~ble as a mean curve for crack growth rates.
7 Data received to date does not negate the curve.
Numerous-curves have been developed and to a degree, they all rest on eng eringJu,*dement.
certain The data from OTS's foh0 ii.y600 isrelevant for developing the CGR curves I
acti ns:16M eintl.tthesAlloy properties are still y
-working ofit e tubes at the tube support sDet. would in crease the failure rate over non-worked Alloy 60-W ill make,this conservative.
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Risk-IuformedEvaluutionl 7" Davis-Besse risk assessment provides a bounding estimation of risk. Bounding or conservative assumptions were used to resolve uncertainties.
Studies of sensitivity
- parameters.
7ý Results ndind.... incre in the "small" categotynM.
per RG 1.174.
as performed for all significant woud" be boundecl fre''~
o be6 "very small"'
J r Incremental LERF and Public health risk is expected to be negligible.
FENOC TV' t
Risi(-Inform1oIEedEviIuation Nozzle Leah1 FrWOequIecy
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The Davis-Besse plant specific PSA has used the method from the generic Framatome analysis which applies a constant leak initiation
ý The constanat4.Le ov early cycles.
Impact of inspection"on c6nditional leak at a future date is not quantified.
number of leaks Iin probability of a FENOC 8
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Risk-IinformedfEvuluution Nozzle Lea9kFreUquenscY Other approaches have assumed that the onset of leakage can be approximated by a two parameter Weibull:
cumulate probability distribution.
4 rThe Davis-Besse ris sesment was modified to apply a Weibull: djibbutI.
SStudies were;p 1 Q[,te the sensitivityo the Weibull scale a nds;..ape. p aram.eters.
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,..s 7The conditional probability of a leak by a future date given no leak now can be calculated if a nozzle has been inspected and no leakage detected.
RishkIinforimled Evfalfaion Nozzle Leak Frequeicy Predicted Leaks for various Weibull Leak Initiation Iodels Expected Number of Leaking CRoM Nozz.ls Davis-EP'I MRI Besise Davis-Besse Upper M e P.........
Besse Besse EFPY (95%)
da PI**:
S Refueling BeYroection Weibull Paramet.er Outaei EFPY Corrected Projection 1.5ShaeMolofi Outap-e to 600F 1.5 Shape V 1.5 Shape Modeo Parameter Parameter Projec-ton Soe Param r
Paame 10 10.56 12.91 5.0 1.0
\\ 9.5x10-5 0.02 11 12.33 15.07 6.3 1.3 1.7x10 3 0.36 P
12 14.06-17.18 7.6 1.6
/ 1.9xl-2 4.00 13 15.81 19.32 8.9 1
1.9 0.17 28.3 16.37 20.00 9.3
\\ 2.0 0.32 43.7 FENOC 10 1
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Risk-Iuformed Evaluation Pastlispections
- Inspections were assumed to have a failure probability of 1.00 if boron inhibited detection of nozzle leakage.
Ilnspections.'were,ss-.
have a failure probability of G-if n'I bors ':
,r-p...
,resent.
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-,t Sensitivities were p'erfrmed to effect of various leakage detection II investigate the probabilities.
FENOC (I
Risk-IoiformedEfvaluuioi Prohuability of Circumferentfial Crocking
ý Evidence from recent B&W has indicated that not all axial plant i I f nspections cracks have resulted in initiation Qicircumferential cracking.
B&W planl and 6 circuml 27axial cracks
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SzrProbability of the, Intitition of crack is estimated to be 0.22 ba evidence.
12 a circumferential sed on B&W FENOC
Risk'-iuformedlfvuluution Nozzle Failure Proftability
&- Probability of CRDM nozzle failure is determined by performing a Monte Carlo simulation on the Sco:t deterministic crack growth model.
zc Conservati r
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um pons were used when data 4,*a*.-'t,ý`e.
ýV Studies were performed'to investigate the sensitivity to all significant inputs.
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Risk-Informed Evualuation Nozzle Failure ProbabtilitV-Conservative Assum)qtionAs Initial crack size - Applied a uniform distribution from 0-180 degrees.
ýV Stress Profile - U case stresses.
Crack Grc growth rate co'ef
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Risk-InformeEifvalutfioi Nozzle FailureProbmuilify- $ensitiviy$stillies SInitial crack size Initial crack de z Temperature:...
z Stress Profiler r Crack Growth Rate Coefficient FENOC 15
Risk-InlformedfEvlufftio ConditionI Core lhmugel/Release Probabiuity r Davis-Besse conditional core damage probability for a 0.1 ft2 medium LOCA is 2.7 x 10-3.
c Conditional large ear probability for a medium LOCA is about 0
L The conditional *[,,,
b iI It. or th analysis is less than appl.e pnhs A 02beca use medium LOCA range in: te
- tPSA is 0.02 ft2
-0.
dis the ft2.
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Risk-Inlformed Evauatrionu:
Results Constant Initiation Frequency Upper (95%)
Projection 1.5 Shape Par.ameter r
t T
Bounding Best Estimate Bounding Best Estimate Shape Parameter Modit0ed.Scale Bou~ntiug.
Best Estimate CDF 1.8 E-6 9.9 E-8 1.1 E-6 6.3 E-8 3.3 E-7 1.9 E-8 LERF 2.6 E-9 1.5 E-10 1.7 E-9 9.4 E-11 4.9 E-10 2.8 E-11 Person REM 0.16 9.2 E-3
.11 5.9 E-3 3.1 E-2 1.7 E-3 17 FENOC
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Risk-IlnformhfedIEvhluaStionl UIniueO Aspects of lvis-Besse iskAssOssleint SInspection Information - Davis-Besse inspections do not indicate evidence a nozzle leaks.
7 Material Heat Inform,n
-64 of69 Davis-Besse nozzle material heats ha 'or circumferential le*J at ot.
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Rish-InIformedfval8uaftio, Conclusions SOCDF - The plant specific risk assessment conservatively estimates a bounding incremental core damage frequency to be in the range which is categorized as "small" per RG 1.174.
The actual incremental core damage frequency would be categorized as very simai
- riEl Q 1,174.
_LERF
-fThe plappecifu *-S pent conservatively estimates a bound* incre.** !tae arlyelease frequency which is categas.. "-r small" per RG 1.1, 74.
The actual incrementalireiase r~equency is negligible.
SPublic Health Risk - The plant specific risk person rem per year is negligible.
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Insp~ctfionl 13RFO:
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qualified visual
> 100% NDE O Flaw
@ Data characterizat will be 'de S. Vessel Head opportunity Rep plagm-entatfifst available
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Dahvis-Besse Specific Features uAnActiois V,
%rRecord of inspection from last three outages.
rOnly B&W plant with a continuous head vent which provides high confidencqn temperature measurements.
rReduce rea, ture from 605F to 598F.
- Additional training fgQ.
rators-on issues raised in
- Maximize availability of redundant critical safety systems.
e 21 FENOC
Comparison ofhlnspection 1ates December 31 st
- Two Shutdowns Required February 16th
- Single Shutdown for inspection (One Inspection, One Refuel)1 and refueling.
Approximately3 RE dition 30 Nrmal refueling outage dose.
exposure to employe".4,,
-Limited NDE Full NDE and flaw characterization.
No significant difference in risk (incremental CDF).
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-IATION c FENC,~
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Summary Based on Conservative Analysis:
Davis-Besse is S*to Operate until February' 16,ý 2
-.2 02.
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AIONI 23
'I FENOC
Het 69 crack GroWth - ConstfuitLeak1Iiatiuonu FreOuency 13 1.1 4
6.38E-02 1.25E-05 2.70E-03 2.22E-01 NA NA NA 4.78E-10 7.0TE-13 4.44E-05 12 1.1 4
6.38E-02 1.25E-05 2.70E-03 2.22E-01 NA NA i
4.78E-10 7.08E-13 4.44E-05 11 1.1 4
6.38E-02 9.65E-03 2.70E-03 2.22E-01 NA 1
1 3.69E-07 5.46E-10 3.43E-02 10 1.1 4
6.38E-02 4.43E-02 2.70E-03 2.22E-01 1
1 1
1.69E-06 2.51E-09 1.57E-01 2.06E-06 3.05E-09 1.92E-01 13 1.1 15 2.39E-01 1.25E-05 2.70E-03 2.22E-01 NA NA NA 1.79E-09 2.65E-12 1.67E-04 12 1.1 15 2.39E-01 1.25E-05 2.70E-03 2.22E-01 NA NA 1
1.79E-09 2.65E-12 1.67E-04 11 1.1 15 2.39E-01 9.65E-03 2.70E-03 2.22E-01 NA 1
1 1.38E-06 2.05E-09 1.29E-01 10 1.1 15 2.39E-01 4.43E-02 2.70E-03 2.22E-01 0.05 1
1 3.17E-07 4.70E-10 2.95E-02 1.70E-06 2.52E-09 1.58E-01 13 1.1 5
7.97E-02 1.25E-05 2.70E-03 2.22E-01 NA NA NA 5.97E-10 8.85E-13 5.55E-05 12 1.1 5
7.97E-02 1.25E-05 2.70E-03 2.22E-01 NA NA 1
5.97E-10 8.85E-13 5.55E-05 11 1.1 5
7.97E-02 9.65E-03 2.70E-03 2.22E-01 NA 0.05 1
2.31E-08 3.42E-11 2.14E-03 10 1.1 5
7.97E-02 4.43E-02 2.70E-03 2.22E-01 0.05 0.05 1
5.29E-09.7.83E-12 4.91E-04 2.95E-08 4.38E-1 1 2.75E-03 13 1.1 45 7.17E-01 1.25E-05 2.70E-03 2.22E-01 NA NA NA 5.38E-09 7.96E-12 5.OOE-04 12 1.1 45 7.17E-01 1.25E-05 2.70E-03 2.22E-01 NA NA 0.05 2.69E-10 3.98E-13 2.50E-05 11 1.1 45 7.17E-01 9.65E-03 2.70E-03 2.22E-01 NA 0.05 0.05 1.04E-08 1.54E-11 9.64E-04 10 1.1 45 7.17E-01 4.43E-02 2.70E-03 2.22E-01 0.05 0.05 0.05 2.38E-09 3.52E-12 2.21E-04 1.84E-08 2.73E-11 1.71E-03 I
11.75E-06 2.60E-09 1.63E-01 FENOC 24 FENOC Perry
Heat 69 Crack Growth - Low Weiibull Shape Factor 13 4.39E-03 4
8.79E-03 1.25E-05 2.70E-03 2.20E-01 NA NA NA 6.53E-11 9.6"-14 6.07E-06 12 4.1OE-03 4
8.19E-03 1,25E-05 2.70E-03 2.20E-01 NA NA 1
6.08E-11 9.01E-14 5,66E-06 11 3.92E-03 4
7.84E-03 9.65E-03 2.70E-03 2.20E-01 NA 1
1 4.49E-08 6.66E-11 4.18E-03 10 1.51E-02 4
3.03E-02 4.43E-02 2.70E-03 2.20E-01 1
-1 1
7.96E-07 1.18E-09 7.40E-02 1
8.41E-071O.25E-097.82E-02 13 4.50E-03 15 3.37E-02 1.25E-05 2.70E-03 2.20E-01 NA NA 1A 2.51E-10 3.71E-13 2.33E-05 12 4.18E-03 15 3.13E-02 1.25E-05 2.70E-03 2.20E-01 A
N 1
2.33E-10 3.45E-13 2.16E-05 11 3.98E-03 15 2.99E-02 9.65E-03 2.70E-03 2.20E-01 NA 1
1 1.71E-07 2.53E-10 1.59E-02 10 1.51E-02 15 1.14E-01 4.43E-02 2.70E-03 2.20E-01 0.05 1
1 1.49E-07 2.21E-10 1.39E-02 3.21E-07 4.75E-10 2.98E-02 13 4.50E-03 5
1.12E-02 1.25E-05 2.70E-03 2.20E-01 NA NA NA 8.35E-11 1.24E-13 7.76E-06 12 4.18E-03 5
1.04E-02 1.25E-05 2.70E-03 2.20E-01 NA NA 1
7.75E-11 1.15E-13 7.21E-06 11 3.98E-03 5
9.95E-03 9.65E-03 2.70E-03 2.20E-01 NA 0.05 1
2.85E-09 4.22E-12 !2.65E-04 10 1.51E-02 5
3.79E-02 4.43E-02 2.70E-03 2.20E-01 0.05 0.05 1
2.49E-09 3.69E-12 2.31EE-04 15.50E-09 8.15E-12 5.11E-04 13 4.50E-03 45 1.01E-01 1.25E-052.70E-03 2.20E-01 NA NA NA 7.52E-1011.11E-12 6.99E-05 12 4.18E-03 45 9.40E-02 1.25E-05 2.70E-03 2.20E-01 NA NA 0.05 3.49E-11 5.17E-14 3.24E-06 11 3.98E-03 45 8.96E-02 9.65E-03 2.70E-03 2.20E-01 NA 0.05 0.05 1.28E-09 1.90E-12 1.19E-04; 10 1.51E-02 45 3.41E-01 4.43E-02 2.70E-03 2.20E-01 0.05 005 0.05 1.12E-0941.66E-1221.04E-04i
____,_13,19E-09 4.73E-1212.97E-04
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1.3E-06 1.67&-09 1.05E-O 0
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Heat 59 Crack GrowN - High Weibull ShapeI Factor I.
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'Y.73E-1_
21,4.85E-041 12 5.30E-02 4
1.06E-01 1.25E-05 2.70E-031 2.20E-01 NA NA I
7.86E-1011.17E-1217.31E-05 11 4.97E-03 4
9.94E-03 9.65E-03 2.70E-03 2.20E-01 NA I
I 5.70E-08 8.44E-1 1 5.30E-03 10 3.OOE-04 4
6.01E-04 4.43E-02 2.70E-03 2.20E-01 1
1 1
1.58E-08 2.34E-11 1.47E-03 7.88E-08 1..17E-10 7.32E-03 13 3.73E-01 15 2.80E+00 1.25E-05 2.70E-03 2.20E-01 NA NA NA 2.08E-08 3.08E-11 1:93E-03 12 5.32E-02 15 3.99E-01 1.25E-05 2.70E-03 2.20E-01 NA NA 1
2.96E-09 4.39E-12 2.76E-04 11 4.97E-03 15 3.73E-02 9.65E-03 2.70E-03 2.20E-01 NA 1
1 2.14E-07 3.17E-10 1.99E-02 10 3.OOE-04 15 2.25E-03 4.43E-02 2.70E-03 2.20E-01 0.05 1
1 2.96E-09 4.39E-12 2.75E-04 I___
2.40E-07 3.56E-10 2.23E-02 13 3.73E-01 5
9.33E-01 1.25E-05 2.70E-03 2.20E-01 NA NA NA 6.93E-09 1.03E-11 6.44E-04 12 5.32E-02 5
1.33E-01 1.25E-05 2.70E-03 2.20E-01 NA NA I
9.88E-10 1.46Er12 9.19E-05 11 4.97E-03 5
1.24E-02 9.65E-03 2.70E-03 2.20E-01 NA 0.05 1
3.56E-09 5.28E-12 3.31E-04 10 3.OOE-04 5
7.51E-04 4.43E-02 2.70E-03 2.20E-01 0.05 0.05 1
4.93E-11 7.31E-14 4.59E-06 1.15E-08 1.71E-11 1.07E-03 13 3.73E-01 45 8.40E+00 1.25E-05 2.70E-03 2.20E-01 NA NA NA 6.24E-08 9.24E-11 5.80E-03 12 5.32E-02 45 1.20E+00 1.25E-05 2.70E-03 2.20E-01 NA NA 0.05 4.45E-10 6.59E-13 4.13E-05 11 4.97E-03 45 1.12E-01 9.65E-03 2.70E-03 2.20E-01 NA 0.05 0.05 1.60E-09 2.37E-12 1.49E-04 10 3.OOE-04 45 6.76E-03 4.43E-02 2.70E-03 2.20E-01 0.05 0.05 2.22E-11 3.29E-14 2.06E-06 I'_
6.44E-08 9.55E-1 15.99E-03 0
1 3.32E-07 4.92E-10 3.09E-02 FENOC 26
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