ML20091J610
| ML20091J610 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 01/07/1992 |
| From: | Gates W OMAHA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-89-10, LIC-91-339R, NUDOCS 9201140175 | |
| Download: ML20091J610 (9) | |
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Onuha, NetnwM GH10N.?17 402/636 2000 January 7, 1992 LIC-91 339R U. S. ':uclear Regulatory Commission Attn: Document Control besk Mail Station Pl 137 Washington, DC 20555
References:
1.
Docket No. 50'285 2.
Letter from NRC (A. D. Beach) to OPPD (W. G. Gates) dated October 2, 1991 Gentlemen:
SUBJEC1:
OPPO Response to Concerns identified in NRC Inspection Report No. 50 285/91-22 As requested by the NRC in Reference 2, the attaciiment to this letter contains Omah.a Public Power District's (OPPD) iesponse to eight (S) concern 3 in NRC insp(ction Report No. 50 285/91 22.
This inspection examined OPPD's program for implementing commitments to Generic Letter Motor Operated Valve Testing and Surveillance."(GL) 89-10, Safety-Related If you should hav". any questions, please contact me.
Sincerely,
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$49 W. G. Gates Division Manag[er Nuclear Opera ions WGG/sel Attachment c:
Leueuf, Lamb, Leiby & MacRae R. D. Martin, NRC Regional Administrator, Reginn IV D. L. Wigginton, NRC Senior Project Manager R. P. Mullikin, NRC Senior Resident inspector l
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4 ATTACHMENT TO Ll.C,91 339R URC ITEM 1 ParagrJDh 3.3.1 i
The scope of the program did not include feedwater regulating isolation valves HCV-Il03 and 1104. Additional information is needed to ensure that these MOVs are capable of performing their intended function, or that emergency operating i
arocedures and training alert the operators to the potential fsilure of these
.iOVs.
The inspectors identified two MOVs in the feedwater system (HCV-1103 and HCV 1104) that were not in the safety dures and received steam goneratorrelated port relied upon in several emergency proce isolation and feedwater isolation signals.
The inspectors were concerned that these MOVs had been assioned a safety-related function without adequate consideration of the capability of the MOVs to perform that function. lhe inspectors indicated that the licensee should ensure that these MOVs are capableofperformingtheirintendedfunction{ialfailureoftheMOVs.or that emergency procedures l
and training alert tfie operators to the poten
@fD RESPRIL: lIRL1 Valves HCV-1103 and HCV 1104 are in Fort Calhoun Station's (FCS)lding, main feedwater system. These vahos are located in the auxiliary bui innediately downstream of the main feedwater-regulating valves.
They are not classified within the TCS design basis as safety do receive a steam generator related. The normal position for these valves is open. Although these valves isolation signal to close, the steam generator isolution functlor is provided by the safety-related check valves motor operated valves (HCV-1385 and(HCV-1386).ftl 161 and FW 162) and the safety rela In accordance with the Generic Letter 89-10 reconntnded actions.
ABB/ Combustion Engineering (ABB/CE) evaluated all motor operated valves at FCS to determine whether they met the criteria for being classified as
" safety related" according to the definitions provided in the Generic Letter, This work was documented in Combustion Engineering Calculation 602512-MPS-SCALC 001 and showed that valves HCV-1103 and HCV-Il04 did not meet the Generic Letter 89-10 safety-related criteria.
Review of these valves' relative importance to-safety shows there is a redundancy requirement for preventing main feedwater pump runout flow during a main steam line break i
accident.
However, upgrading these valves to safety-related is unnecessary, l
as discussed in issue No.1 of NUREG-0138 ' Staff Discussion of 15 Technical i
Issues" dated Hovember 1. 1976.
In order to ensure that HCV-1103 and HCV-1104 are capable of porforming their intended function, OPPD will implement a special testing category for these valves. This category will e:itablish a test frequency consistent with the safety-related MOVs included in the Generic Letter 89-10 Program.
Sinco valves HCV-1103 and HCV 1104.are identical to safety he same.
related valves HCV-1385 and HCV-1386, the valve thrust requirements will be t I
MC IIRL2._ Paraoranh_Lil The licensee committed to the use of design basis parameters in establishing the setpoints for the torque switch settings.
The implementation of this provision on the )ressurizer power operated relief valve (PORV) block valves did not utilize tie design basis value,licensce's position on the issue of use but a lower value. Additional information is required to clt.rify the of design _ basis values.
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LIC-91-339R
' Attachment The inspectors had a concern with the ongoing Splementation of the design basis reviews of the licensee's GL 8910 program, in particular, the licensee's draft Calculation 602512 MPS 5 CALC 004 determined that the worst-case differential pressure for the pressurizer power operated relief valve (PORV)lculation assum(HCV-150 and 151) to be 2485 psid. Nevertheless, blor.k valves the draft ca ed that these MOVs would only need to close under 2285 psid because of an emergency procedure statement to close these valves if pressure fell below 2285 psig.
The inspectors stated that this would constitute a deviation from the licensee's commitment to Generic letter 89 10 if the calculation were complete.
QPPD RESE0NSE l,EM &
In accordance with Generic Letter 89-10 recommended action conditions for valve opening and closing directions are to b(a) determined., design basis e
While it is true that the calculation did identify the maximum differential pressure to ve 2485 psid the calculation also determined the required closing differential pressure con,dition to be 2285 psid and the opening differential pressure to be 2485 psid. The opening condition is not a required valve oper?. tion but merely an operator aid to open the PORV block valves so the PORVs will lift to relieve pressure before the pressurizer code safety valves will lift during an overpressure transient.
However, to further improve the accuracy of the calculations, a design basis re evaluation of the 33 safety related MOVs was initiated.
This includes a detailed system level design basis review of MOV operations during normal, abnormal, surveillance and test, accident response and emergency operation conditions for both valve opening and closing scenarios.
This design basis re evaluation will result in the development and acceptance of in situ design basis test conditions.
The design basis re-evaluation of valves HCV-150 and HCV-151 is complete and documented in ERIN Engineering and Research Calculation 159-90 05.01, " Reactor Coolant System HOVt HCV-150/151." This calculation also identified different o>erating conditions for valve opening and closing operations.
Summaries of tle worst case opening and closing scenarlos for valves HCV-150 and HCV-151 follnw.
VALVE OPENING Since the PORY block valves are otherwise normally open, the maximum upstream pressure at which the PORV block valves would be required to open would occur with the PORVs inoperable valves closed for Reactor Coolant System iso (stuck open) and the block lation in accordance with the station's Technical Specifications.
Automatic pressure relief capability is provided by the safety valves and any manual operator action in response to a pressure transient would likely precede reachino the safaty valve setpoint of 2500 )sia.
However, assuming a loss of all feedwater and initiation of once-tirough-cooling ope ations, the block valves could be required to open with pressure near the safety-valve setpoint of 2500 psia.
VALVECLOJ1HA The PORV block valves are required to close during Emergency Operating Proccoures post-trip actions if a PORV is still open at 2300 psia. To account for instrument inaccuracy, the upstream pressure is con:ervatively assumed tc be at 2369 psia (downstream 'ontainment 2300 + 3%). While the rupture disk setpoint may not be exceeded, atmospheric conditions of 14.7 psia are assumed for consecvat ism.
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.LIC 91 339R Att,achment The approach used in determining the above valve operating scenarios is consistent with the NRC's response to Question 15 of Generic tetter 89-10 Supplement 1:
For MOVs that are relied upon to move to the open position during a
- lesign basis event, the licensee should perform a design-basis review to determine the conditions during which the MOV is called upon to open.
For MOVs that are relied on to move to the closed position, ths licensee should perform a design basis review to determine the conditions under which the MOV is called upon to close.
The licensee should perform a design basis review for NOVs that are relied on,th opening and clos,ing.
at different times to open or close to determine the conditions for bo Since worst case design basis conditions for both valve opening-and closing HCV-150 and(HCV-151, these conditions will be uthlized in2500 psia opening, 2369 psia clo operations determining / verifying the torque switch settings necessary for proper valve This same ap)CS Generic Lo.',er 89-10 MOV Program.. lized for all 33 safety operation.
roach will be within the scope of the r
NRC ITEM 3 - Paraaraoh 3.3.2 The licensee was using a valve factor.of 0.3 for flexwedge gate valves and 0.2 for double disk gate "alues.
These values have been shown to be inadequate for some MOVs during industry and research tests. The licensee needs to address the capability of their te:;ted valves and to assess its methodology to be used in selecting the valve factors.
The licensee was developing its methodology for verification of MOV sizing and switch settings.
The licensee indicated that it intended to use valve factors of 0.3 for fle< wedge gate valves and 0.2 for double disk gate valves. These valve factors have been shown to be inadequate for some McVs durins industry and research tests.
For example, valve factors for closing flexwecge gate valves have been shown to range up to 1.1, with 0.4 to 0.6 range as the average.
For valves manufactured by Crane, the licensee will include additional thrust to account for seating load in accordance with the nianufacturer's instructions. The inspector indicated that the use of low valve factors placed additional emphasis on the petformance of design basis testing.
If such testing demonstrated that the valve factor were inadequate, the licensee would need to address the capability of the tested MOVs and other applicable MOVs, as well as assess its methodology.
QPPD RESPONSE - ITE U Valve factors are dependent not only on the design and manufacturer of the valve but also on the conditions under which it is expected to o>erato.
Recent testing by the Idaho National Engineering Laboratory (3 was) exceeded..
INE. of gate valves indicates that in certain cases the valve factor of 0.
INEL test results yielded factors of 0.4, 0.5, and a few exceeding 0.6.
However, these test results were not conclusive in determining what valve factors are to be assumed for different valve applications, nor did they rule out the use of 0.2 and 0.3.
There are many elements that affect the valve factor and there is no substantial technical basis for changing industry practice at this time.
The use of industry valve factors in actuator sizing / torque switch setting calculations allows engineering personnel to estimate stem thrust requirements.
The proof of an adequate valve factor lies in testing the valve at its " designed for" conditions. This is the philosophy that OPPD has adopted during the development of its Generic Letter 89-10 MOV Program.
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.,N recent'.v u sted steam blowdown testing.f a prototype 4.
This 10 a 2%-inch flexible-wedge gate valve.
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is pr+ 0 bry, analysis shows that valve factors at 2522 os.
a re 0.04
'. pressure isolation and 0.216 at valve disk The au. lysis of this data also showed that this p3rticular valve
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,renotes the use of " low" valve factors in that upstream pressure w
occurs signific ntly, before valve disk wedging, for this particular u
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.gn, ths use of 0.3 tor a valve factor would have been bounding and ee ot a;. 1.
,i committed, OPPD will design basis test all safety design basis testing, the related valves where prat.ticabls. Where it is nol practicable to perform nRC's "two-s' age' approach will be utilized.
Upon completion of the design basis testing, :% results will be examine" to refine ?Se valve stem thrust determination medology where applicable.
To date limited desi testing of g?te valves has been performed at Fort Calhoun Station.gn basis NRC ITF11 - Paraaraohs 3.Llay 3.4.i The l'~
see indicated Aat actuator, motor and valve limitations would be addressed for the ter m switch settings.
This would imply that inertia effects would be addre:. sed.
Information is required to ensure that all applicable limitations, including inertia effects, are considered in establish'ng the torque switch settings and int.orpormed into the final guidanc> document.
For maximum torque switch settings, the licens, indicated that actuator, motor, and valve limitations would be addressco. However, in the draft thrust methodology (August 22, 1991), it was not apparent that motor capability would be considered.
Althouah that document addressed the effects nf inertia of tne motor actuator folfowing torque switch trip in terms c
...ust limits of the actuator, it did not include consideration of the
,cs of inertia with respect to actuator torque or valve thrust limits.
In draft Project Instrection 159-90-03.03 (Revision 0)1 " Switch Setting Determination," the licensee Lddecssed motor capability but did not discuss inertia offects for structural limits. The licensee will need to ensure that all applicable limitations will be censidered in establishing the maximum torque switch settings and incorporated into the final guidr.ce document.
OPPD RESPONSI - ITEM 4 Failure to identify valve structural limits (including inertia effects) in the draft thrust methodology was an oversight by the methodalogy's author.
Currently, a detailed valve weak link analysis for each of the 33 safety-related MOVs is being performed. When completed, these analyses will determina the most limitina conpor nt of the valve / actuator combination and obtain a limiting thru';t value for use in design basis testina.
However, in order to proceed with design basis testing in the interim, OPPD has obtained maximum valve thrust limits from valve manufacturers where pessible.
If it was not possible to obtain vendor data, a review of previous MOV testing data and maintenance records was conducted. The applicable limitations and torque switch settings will be documented in accordance with the MOV Program Plan.
As a result, OPPD has determined conservative maximum allowable valve thrust values to be used initially for testing purposes. ihese maximum allowable thrust limits will be provided to the contractor determining the recommended maximum seitch settings.
To ensure that the absolute maximum stem thrust valuer are not exceeded, the maximum allowable thrust limits incorporate a conservative value for test equipment inaccuracy.
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.LIC-91-339R Attachment in accordance with Task 4.0/ Subtask 4.2 in the Fort Calhoun Station MOV Program Plan appropriate design basis documents are to be developed. These documents will include all applicable valve and motor actuator limitations for ute in establishing maximum torque switch settings. This task / subtask was started in January 1991 and is expected to be completed in December 1993.
NRC ITEM 5 - Paraaranh 3.3.2 The licensee indicated a stem friction coefficient of 0.15 would be used.
This is less than the industry standard of 0.2.
The licensee must provide T
justification for the use of 0.15, the use of its selected lubricant, and the 3
frequency of preventive maintenance to support these positions.
The licensee's calculations indicated the use of a stem friction coefficient of 0.2 which was the typical industry value. However, the licensee stated during the !nspection that it intended to use 0.15 as the stem friction coefficient based on its current lubrication program and the use of Mobilux EP-1 grease. During their walkdown, the inspectors observed several dirty valve stems (See paragraph 3.5)d approximately 17 months ago.
Some of these valves were said to have preventive maintenance performe Considering that the licensee was also attempting to justify c preventive maintenance schedule of approximately 36 months, this frequency for valve stem lubrication was inadequate to support the assumption of a 0.15 stem friction coefficient witi.out additional justification.
Further, the licensee had not justified the use of Mobilux EP-1 in high temperature environments for long time periods.
The licensee will need to provide better justification for the assumed value for FCS.
OPPD RESPONSE - ITEM i 0 PPD has revised its methodology and will utilize a valve stem friction coefficient of 0.2 instead of 0.15.
However, results from future MOV testing may dictr e u, use of a different friction coefficient.
OPPD is i%<.oting a new valve stw lubrication pregram that will utilize Mobilux EP-1 grease and will perform valve stem lubricaticn inspection activities every 18 months.
The results of these inspections will determine if cleaning and re-lubrication of valve stems is warranted. The use of Mobilux EP-1 is recommended by EPRI based upon testing results of EPRI's MOV lubrication study.
Regarding the use of EP-1 in hi0h temperature applications, Mobil Corporation (manufacturer of Mobilux EP-1) recommends a temperature limit of 250 degrees Fahrenheit.
Based on testing, EPRI has increased this temperature limit to 300 degrees Fahrenheit. At FCS, valve nem temerature mearurements taken on safety-related M0V steam valves (HCV-1041C and -lCV-1042C with a surface pyrometer during normal 100% power operation showed e max)imum valve stem temperature of 195 degrees Fahrenheit.
When considering pcit accident high temperature profiles on the Mobilux EP-1 grease, examination of the worst case containment temperature profile curves show that containment temperatures do exceed 300*F. However, this temperature is not reached until 22 seconds after initiation of the event. All auto-sequenced valves inside of containment for this accident would have fully stroked by this tire. Additionally, the time that 300*F is exceeded is only 38 seconds.
After 50 seconds, containment temperature drops sharply to 275 F.
Long term containment temperature is 290*F.
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LIC-91-339R
. Attachaent Insignificant bt eakdown of the Mobilux EP-1 grease will occur because the crease is located inside the motor actuators and 300*F is exceeded only for 38 secads.
Therefore, the use of Mobilux LP-1 grease as a valve stem lubricant for higt temperature applications is justified.
NRC ITEM 6 Paraaraoh 3.3.3 The licensee committed to perform design basis testino, however, the Project Plan listed exceptions to design basis testing.
The licensee needs to provide information addressing any deviations from its commitments to GL 89-10 and incorporate that information into plant documents.
procedures for design basis testing. The NPC The licensee was preparing {o include acceptance criteria for the tests.
expects those procedures The licensee intended to use the two-stage >nproach outlined in GL 89-10 and its supplements for those M0is that cannot b. tested under desicn basis s
conditions.
- he inspectors considered the licensee's statec; plans regarding design bas.s testing to be consistent with the recommei<ations of GL 89-10.
However on page 6-38 of its Project Plan, the licensee listed exceptions to theperformanceofdesignbsistesting.
One of the listed exceptions suggested trat, rather than design basis testing each MOV where practicable, design basis test data from similar valves may be applied, That exception was not consistent with the licensee's commitment to GL 89 10 to test MOVs, where practicable. The licensee indicated that the Project Plan would be revised to be consistent with its commitments to GL 89-10.
OPPD RESPONSE - ITEtL1 The purpose of the FCS MOV Program Plan is to define the tasks necessary for the development and implementation of a successful MOV program. Numerous industry documents from NUMARC, EPRI and Generic Letter 89-10 sup/plements) were used in its development, especially where c rification and or interpretation of the Generic Letter was required.
The FCS M0V Program Plan section to which the response item refers states:
The following exceptions to testing at design basis conditions can be utilized if sufficient technical justification is provided.
elf testing is damaging to the plant or the specific HOV
.*if testing creates a violation of Technical Specifications or other 1icensing conditions eif data on similar valves with appropriate design basis type test data is a'ailable This wording was taken verbatim from a July 30, 1990 letter from NUMARC to Utility Administrative Points of Contact regarding issues identified in Generic Letter 89-10 Sup?lement 1.
The NRC response item appears to be directed at the last exception, regarding use of data on similar valves when appropriate design basis type test data is available. This statement is a paraphresing of the NRC's response to Question 24 in Generic letter 89-10 Supplement 1, which states:
Another alterne ive is the use of te:t data from a protot/pe MOV in the plant, a different plant, or a test facility, provided the application of such data is justified.
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.LIC-91-339R Attachment In keeping with the intent of the Generic Letter recommendations, OPPD has already committed to design basis testing where practicable. Appropriate i
acceptance criteria will be incorporated into the necessary test procedures.
The alternatives to design basis testing mentioned above are applicable and consistent with the NRC's "two-stage" testing approach. OPPD intends to follow this alternative approach where valves cannot be design basis tested in the plant. OPPD successfully used this alternative approach when Fort Calhoun Station's PORV block valve prototype underwent steam blowdown testing in November 1991.
Upon reviewing the FCS MOV Program Plan and ccmparing it to Supplement 1 of Generic letter 89-10, OPPD concludes that the current revision of the Program Plan meets the intent of the Generic Letter regarding M0V testing alternatives. Thetefore, no changes to the FCS M0V Program Plan are necessary.
NRC ITEM 7 - Paraaraoh LM The licensee had not established plans for periodic verification of MOV operability.
The licensee must provide information regarding how it intends to address the commitment for periodic verification of MOV operability.
The licensee stated that it may perform static tests of MOVs in an effort to demonstrate t' air continued capability to perform under design basis conditions. Tne NRC does not accept static tests, at this time, to demonstrate design basis capability because of the uncertainties in the relationship between the performance of MOVs under static and design basis condition:..
Further, the licensee had not established a schedule for these periodic tests. The licensee will need to justify its periodic testing methodology during future NRC inspections, in addition, the licensee will be expected to establish a frequency for periodic test ;ng (verification) consistent with its commitments to GL 89-10.
Observations by the inspectors during the walkdown (see paragraph 3.5) did not support a lubrication frequency beyond the manufacturer's recommendation.
The inspectors did not consider the Heensee's justification for extending the stem lubrication frequency to be adequate.
OPPD RESPONSE - ITEM 7 In accordance with Ge:.eric Letter 89-10, Recommended Action Item d, OPPD has established a task to develop a MOV testing schedule.
Specifically, this is Task 3.0/ Subtask 3.4 - MOV~T9 sting Schedule. The Task / Subtask Performance Item states:
Review and revise as necessary the MOV testing schedule that specifies the frequency of routine testing of the valves.
The valves will be reviewed to determine which MOV may be tested while the plant is on-line i
to reduce the outage workload.
If no schedulin
, establish criteria and the necessary schedule. g c? iteria nists, l
The development of the necessary M0V testing schedule will be based upon several different variables including design basis testing (where practicable) and/or corrective maintenance activities.
Utilization of static testing may be justified where:
1.
A corre!ation between static and design basis testing tar a l
particular MOV exists.
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.LIC-91-339R Att,achment 2.
MOVs experience very low or no differential pressure in performing their safety function (i.e., valve stem packing load dominates).
3.
Valves are stroked at or near design basis conditions in 4
accordance with surveillance tests.
A design basis test (if practicable) ificantly affected the operation of the is justified where corrective maintenance on a valve or motor operator has sign M0V.
This task / subtask began in January 1991 and is expected to be completed by June 1994.
MOVs that will be design basis tested during the 1992 refueling outage will be evaluated for a suitable periodic verification testing schedule within six months of outage completion.
This schedule is consistent with the requirements of Generic Letter 89-10 and with OPPD's commitments.
Concerning the lubrication schedu'ie, see OPPD's reply to NRC ltem 5.
NRC ITEM 8 - Paraaraohs 3.3.4 and 3.4.4 The licensee had not implemented an effective program to evaluate vendor information. The licensee needs to provide its evaluation of how they will evaluate vendors information, including what actions will be taken, if necessary, to address any items of concern.
OPPD RESPONSL ^ 7EM 8 The control of vendor information is implemented by FCS Standing Order 50-G-62, " Control of Vendor Manuals." S0-G-62 defines the vendor manual control measures which ensure that only current revisions of vendor technical manuals are available to support plant activities.
It also addresses the processes for handling vendor manual revisions and updates. The previous revision of 50-G-62 was inadequate regarding updates to procedures as a result of vendor manual changes.
To correct this weakness, 50-G-62 was recently revised. This revision requires technical review of-vendor manual information updates or revisions which could affect maintenance or operating procedures.
OPPD has completed-its technical review of the applicable Limitorque communications mentioned in paragraph 3.4.4 and revised the appropriate procedures.
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