ML102980465
| ML102980465 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 04/23/2010 |
| From: | Dolan B - No Known Affiliation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| FOIA/PA-2010-0334 SA-SURV-2010-001, Rev. 1 | |
| Download: ML102980465 (4) | |
Text
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,RM~: DOUMNATO NO. SASRV:10\~ REV 1+:GEN.
UNIT(S) 'AFFECTED: j2 TITLE: Risk Assessment of Missed Surveillance - Auxiliary Feedwater discharge line underground piping pressure testing
SUMMARY
(include UREs incorporated): On 04/2112010 itwas discovered that requiredi ASME 'Setion Xl surveillance tests (pressure testing), had~ not been perform~edfor buried Auxiliary Feedwater piping as required by ER-AA-330-001 and:
OU-AA-335-015. This condition is documented in Notification 20459689.
A risk assessment of the condition was performed in accordance with procedure ER-AA-600-1 045, "Risk Assessments of Missed or Deficient Surveillances." A surveillance deferral time of up to the end of the current operating cycle was evaluated and found to.
be acceptable,.
'Re~visioni 1of this calculation was prepared to incorporate a refined assessment approach, thereby increasing the deferral time.
fJReviw reu~ired~after periodic Update Internal RM."ocumentation External
- X] RM Docuentoation Electronic ýCalculation Data Files:
(Q:\System Eng ineering\Salem\PRA\Applications\Missed Surveillance\SA-SURV-0OQI)
~Salemn PNA,ýRlevision 4.3; Equipment Out of Service (EQOS), version 3.3a from EPRI Risk and
- Reliability Workstation.
Methiod of Review: x ]i Detailed [IAlternate IReview of External Document This RM documentation supersedes:. Rev 0 in its entirety.
Preparedc by: ~Brad Dolan I ______________/04/23/2010 Print Sign Date Reviewed by: Victoria Warren [~.fper telecom] 04/23/2010 Print Sign Date Approved by: N/A_____________ ______
Print Sign Date ii:!ii*~
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On 04/21/2010 at 11:32 a~m. it was§ý discovered that buried segments of the AFW discharge lines supplying #22 and #24 Steam generators had not been subjected to surveillance testing as required. Testing will be performed every, period in the 10 year interval.
When.: a required *surveillance test is discoveredl not to have been performed as required, Salem's technic'alspecifica~tions ~permit the test to be performed within/
associated risk is performed within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and the risk is acceptable for the
~deferral period. This evaluation is provided to support that requirementt.
This evaluation was prepared in accordance with Risk Manageme~nt procedureý ER-AA-600-1 045, R1, "Risk Assessments~of issed. or Deficient Surveillances."
That procedure indicates that if results :afeaeptable, a5risk1ssessment may n be:
performed, which assumes that affected components and syste!ms are unavailable for the period of time from discovery until the su.k~pdjpip a , s. ttest.
rveiilance :,ais.' ý performed. Alternately a refined approach which increases the assumred.
,likelihood offailure of the untested components:may be employed. That.
approach was employed here.
The function of the AFW discharge lines is to. direct auxiliay feedwater to the secondary sideJopfthe steam generators. Paiping integrity also acts to prevent loss of necessary inventory of auxiliary feedwater supply. There are approximately 170 feet of piping in the subject piping section leading to~the 22AF23 valve and approximately 170 feet of piping in the subject section leading.
to the 24AF23 valve.
There are two potential failure modes postulated which could occur inthe buried AFW discharge piping to the #22 and #24 steam generators. The piping could collapse or otherwise obstruct, preventing flow from being delivered to the affected steam generators. It is also possible that the piping could leak or rupture, res'ulting in a diversion of inventory from the stored supplies maintained for ~the~ AFWV system.
This condition was modeled using the Salem internal events model of record (v.
4.3).
The potential for loss of inventory was conservatively bounded in this way.
A pipe failure frequency from NUREG/CR-6928, (ref. I) of 2.2E-7/ft-yr was, believed to be appropriate and was adopted,.
The next scheduled refueling outage for Unit 2 is scheduled to begin on April '5, T 2011. The absence of a failure in the subject piping was last de~monstrated duringoperatonof th AFIsAaua/ 2010. Therefore the a likelihood of failure of the AFW discharge piping during the subsequent1.L25: P'
- xremaining
'years*:.::i to the next refueling
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Qutage may be calculated::
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2.2E-7ift-y
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340 ftof subject AFW piping *1.25 y= 9.E-5. T'h'e~average likelihood of failure:
of the subject AFW system piping during that interval is 9A'E-5 /2 or 4.7E-5.
A postulated failure of AFW system piping inv~olving substantial leakage was assuJmed to result in inability of the AFW system to perform its, mission for any initiating events. In reality, or most events such as uncomplicated reactor trips,~
there would be ~ample indication oithe..proIbIermand operato6rs cau~ai~~t~a-fada~d-inhe and additional makeup to the AFW system from any of a fr~i-or numb~er of unlimjifte ources~including service water or fire water. The potential folr filure o ~--entire AF- system was mo~deled by increassing the_"common-cause failure of all AF-W pumps" term AFS-MDP-FS-DFO4, 'fro~n4.2-5E-4 to.
(4.25E-4 + 4.7E-5) =4,72E-4/y),
Similarly the potential for obstruction of the AFW supply lines, thetreby. preventing supply to the #22 or #24 steam generators was~ evaluated.
The potenitial impact to the paths to the #22 and #24 SGs~wvere evaluated by increasing the failure likelihood for events AFS-CKV7CC-2AF23, ("SCV 22AF23.
FAILS TO OPEN") and AFS-CKV-CC-4AF23. These events represent the potential that check valves in the subject lines could close, thereby preventing
-flow [n the. lines. The base failure probability for these events is 1.3E-5/y. The, absence, ofafailure ini Lh-es-e -o-mp-o-n-e-n-twaslast demois'trated: during operation of the AFW system on January 21, 2010. The likelihood of a failure in the subject, ines was calculated above (4.7E-5/y). Thi's failure likelihood was apotoe qal to the two lines (4.7E-5 / 2 = 2.3E-5 abd that value was added to the base value for each of the lines (1.3E-5 + 2.3E-5 3i6E-51y).
The model was then quantified and a negligible increase in risk resulted (CDF increased from 2 .25E-5/y to 2.28E-51y).
&Anaý was then evaluated involving a doubling of the likelihood of a fail-ureindtbe-itj..ect piping, from 2.3E-5/year per line to 4.61H-51y-aff-p-er Me, or a combined failure frequency per year of 9.2E-5Iy total. In this instance, the values:
of AFS-CKV-CC-2AF23 and AFS-CKV-CC-4AF23 representing individual line obstru~ctions were increased from 1.3E-5/y to (1,,3E-5 + 4.6EH-5) = 5.9E-5/y and the likelihood of CCF of the entire AFW system (to address potential inventory loss due toy rupture) was increased from 4.25E-4 to( 4.'25E-4 + 9.2E-5 )=5,17E-4.
CDF in'creas~ed, from 2i.25E-5Iy base to 2~.30E-5Iy. This indicates that an ICCDP of less than 1E-6 would be expected diuring the remaining 50 weeks to the next reuln ouCtage, even given this bounding, sensitivity case. This measure of conservatism can be considered to address the potential for external event contributions which were not directly evaluated.
A similar set of modifications were made to the average test a'nd maintenance CAFTA model of record and LERF was quantified, to confirm th~at ICCDP was the limiting parameter. Even in the sensitivity 'case, LERF increased from a baseline value of 1.1 8E-6 to 1.22E-6, thus confirming that the CDF calculation is limiting.
Conclusion Detprral of the missed surveillance for a period of ýup to the and of the current
~operating -cycle is acceptablearidresults in a riegligiblq increase inrisk.k7Pervthe gu~idance ofER-AA-6QO-1O45, online risk assessments may be performed as usual without modification:
References:
1.) NU'REGiCR-6928,lIndusty-Average Performance for Components and Initiating Events at U.S. Commercial Nuclear Power Plants (NURE.GICR-69.28),,:
2007.