ML20116L145
| ML20116L145 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 11/13/1992 |
| From: | William Cahill, John Marshall TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.D.1, TASK-TM TXX-92548, NUDOCS 9211180184 | |
| Download: ML20116L145 (9) | |
Text
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Log # TXX-92548
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File # 10010 1
j 922.2 r
r TUELECTRIC November 13, 1992 Withm J. Cahllt. Jr.
Gump Vwe hrsident U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION.CPSES) - UNIT 2 DOCKET NO. 50-446 ADDITIONAL INFORMATION CONCERNING N!! REG-0737 ITEM II.D..t - PERFORMANCE TESTING 0F RELIEF AND SAFETY VALVES REF:
TV Electric letter logged TXX-92246 f rom Mr. William J, Cahill, Jr. to USNRC-dated %v 18.1C92 Gy 'lemen:
The aDove referenced letter provides the Comanche Peak Steam Electric Station,_ Unit 2 pressurizer safety and relief line thermal hyo aulic analysis (NUREG WT37, Item II.D.1).
The NRC staff reviewed this analysis and requested that additional information be provided.
Attached is the uested additional information, there are any questions, please contact Mr. Manu C. Patel at (214) 812-8298.
Sincerely, Willia J. Cahill, Jr.
By:
6_. S. Marshall Generic-Licensing Manager
-MCP/ds Attachment c - Mr. J.
t.
Milhoan, Region IV Resident inspectors. CPSES (2)
Mr. B. E. Holian,-NRR 17-104 92111g0184 921113 PDR ADOCK 05000446 32 eon a
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- o Attachment to TXX-92548 Page 1 of 8-L
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(1)
Backoressure The-submittal in Reference-2 did not provide the maximum 1 backpressure calculated for Comanche Peak, Unit 2.
Review of the.
Comanche Peak, Unit 2, Final Safety Analysis Report -(FSAR),- Table 5.4416, Amendment 14, 1981, provided a backpressure ofL500 psig for a safety valve discharge.
Because this information is-over 10 years old, clarify if this value accurately represents the currently-calculated,- maximum backpressure, if not, provide the new value.
If the maximum plant backpressure _for the safety valves,
exceeds the tested backpressure, justify the applicability of the EFRI tests to the Comanche' Peak, Unit 2 valve configuration, CPSES Resoonse 500 psig-backpressure it conservative for Unit 1 and Unit 2.
Stone
& Webster documented the backpressure calculation in MECB 380 and 2-ME-0068:for Unit 1 and Unit 2, respectively, The calculated backpressure was less than_500 osig.
(2)
Apolicability of Valve Inlet Conditions Reference 4 the Westinghouse valve inlet conditions report, is'now' more than 10 years old, and some of the information in the-report' is based on even older analyses. - For. example, the feedwater line break valve inlet conditions given in Reference 4 s'or. Comanche Peak, Unit 2, were based-on a 1976 FSAR analysis. Clarify if the valve inlet conditions in Reference 4 'are still applicable to Comanche -Peak, Unit '2, for FSAR steam discharge, FSAR liquid discharge. extended high pressure injection,:and cold overp.' essure protection transients.
If not, provide updatedivalve inlet conditions for Comanche-Peak,- Unit 2,! and identify the applicable EPRI tes'.s for-the newovalve. inlet 1 conditions.
If none of-the1EPRI' tests are applicable to the new' inlet, conditions or the EPRI tests-applicable'to the new inlet conditions indidate potential valve operability problems (chatter, test' valve 'did-not close..etc. ) _for:
the safety valves-or PORVs, provide information and test data to justify valve operability for the-new valve inlet conditions, a
.CPSES Response The valve inlet condition for FSAR steam discharge, FSAR liquid'
-discharge, extended high pressure injection.-and_ cold. overpressure protection transients-described in'EPRI-NP-2296 (December'1982) are applicable to CPSES Unit 2.
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AttachmentLto TXX 92548 Page 2 of 8 (3)
Safety Valve Inlet Fluid Temoerature The submittal indicated the safety valve loop seal was insulated to provide a loop seal water temperature of 300 F at the valve inlet.
Has Texas Utilities Electric Company (TVEC) verified by field measurement the actual loop seal tempereture?
If yes, provide the measured temperature to verify the actual temperature is consistent with the assumed temperature, if not, verify the loop seal temperature and compare it to the assumed.value.
If the measured temperatures is lowered than the assumed temperature, discuss the.
effect of the lower temperature on valve operability and reanalyze the safety value discharge case with the lower temperature.
CPSES Response TV Electric has verified by field measurement the loop seal temperature in CPSES Unit 1 as 314 degrees F.
The insulation design for the Unit 2 loop seal is the same as 'or Unit 1.
(4)
Bendina Moments The information in Reference 2 provided the maximum bending moment calculated to occur on'the valve inlet f'anges of.the safety valves and PORVs at Comanche Peak, Ut 2.
According to the EPRI-test reports, however the test bending moment for the safety' valves was measured at the valve discharge.
it is'not. clear from the EPRI-test reports where the test bending moment was measured-for the PORVs.
Therefore, to ensure bounding-the EPRI test results, provide the maximum expected bending moment at the valve. discharge
.for the Comanche Peak, Unit 2, safety-valves and-PORVs.
The calculated worst -case should include the effects of. deadweight,.
thermal: expansion. -earthquake -(SSE), and. valve actuation' loads; If the new values exceed those applied to the test valves, justify that the plant valves vill operate' satisfactorily with the higher.
bending moment.
CPSES Rescense The Comanche Peak Unit 2 safety valve inlet moment of 172.428 in-kips.is an enveloping nozzle load ~value considering both the j
inlet and outlet nozzles of all three safety valves.
The Comanche
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Peak Unit-2,PORV valve inlet moment of.21.625 in-kips is-an 1
enveloping load value~considering both the inlet and outlet nozzles
.of both PORVs.
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Attachment-to TXX-92548 Dage 3aof;81 (5)
BJs5k Valve' Motor Operator Toroue j
According to the information ~available to-the NRCL the PORV-block -
valves at Comanche Peak, Unit 2, are Westinghou'se.3GH88.vhlves with-Limitorque SB-00 15 operators.
Verify if this -is true. lin:the EPRI tests. the Westinghouse 3GM88 opened 'and closed completely with a motor operator torque output of_182 ft-lbs.
Westinghouse recommended the block valve operators be modified from torque -
control closure to limit control closure to ensure complete closure.
To ensure that the plant block valve 1 operators provide sufficient torque to open and'close the valves at Comanche Peak, Unit 2, clarify whether TUEC made this-modification' to' the plant-block valves.
Also. clarify whether the torque supplied by the-plant mo'.:or operators is greater than or equal-to 182 f t lbs:when using the limit control method.
If the plant operator torque output is less -than 182 f t-lbs, justifyL that they provide sufficient torque to close_the valves under all expected' inlet fluid conditions.
This justificatior should be supported by test; data.
CPSES Responsg The PORV block valves are H 3GH88 with.Limitorque SB-00 15 operators.
These valve operators were modified to. limit control closure for Unit ~2.
Maximum required closing torque was determined to be 152 ft-lbs equivalent to a maximum _ required closing thrust of-13158 pounds._ The operability of the valve in closing is based on
-80% voltage-stall-thrust being greater than 13158Lpounds.
Stall-thrust for t' + valves at-80%' voltage'is 18045 lbs. -[80% voltage -
stall closing torque exceeds 182-ft-lbs.].
(6)
Extended Safety Valee-Blowdown.
The safety valve. blowdown in the applicable EPRI tests; ranged Jf rom 4.8% to 12.7%..This-indicates operation of the plantJsafety valves.
may result in-blowdowns that exceeduthe_ design safety 1valver blowdown of 5%.
Provide sufficient information to showi -(a) the extended safety' valve blowdown _ will ~ not:cause voiding of: the' primary system'or degrade decay heat? removal if. voiding occurs, (b) the safety valves ~will operate-acceptably if the extended safety valve blowdown results in filling the pressurizer' and, (c) the extended-safety valve _ blowdown wil1~. noti challenge. plant safety systems.
~j CPSES Response.
-l CPSES.is currently. reviewing the extended: safety valve blowdown ar.d-its impact on plant safety systems.
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Attachment to TXY 92548 Page 4 of 8 (7)
EQRV Control Circuitry As noted in the introduction. NUREG-0737 Item 11.0.1. requires qualification of -the PORV control circuitry.
i A)
An environmental qualification, the NRC staff agreed that meeting the licensing requirements of 10 CFR 50.49 for this circuitry is satisfactory and specific testing per NUREG-0737 is not required.
From the:information provided in Reference 2, it would appear the-Comanche Peak, Unit 2. PORV-control circuitry is included in TUEC's-10 CFR 50.49 program; however, TUEC never stated.this, Therefore, clarify if the.
PORV control circuitry was reviewed and accepted in the" 10 CFR 50.49 program for Comanche Peak. Unit 2.
If the.PORV-j circuitry was not qualified to the requirements of
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10 CFR 50.49, provide information to demonstrate that'the-control circuitry is qualified per the guidance provided in Reg.-Guide 1.89, Revision 1,' Appendix'E.-
B)
Clarify how the PORV control _circuitryf s qualified for i
normal operatica.
That is clarify what tests'TUEC performs to ensure the-PORV control circuits will respond properly: to-operator actions in normal operation or emergency situationsi or automatic signals in emergency situations.
How the operability of-the PORV's is assured?
[Elfl_RgsDonse
-A)
The PORV. control circuitry, including pressure sensors was reviewed and accepted in. the-10 CFR.50.49 program for CPSES; Unit-2.
B)
These. issues were addressedLby? Generic-Letter 90706.
TV1 Electric has: responded to Generic. Letter 90-06'in TXX 901053, dated-December 21, 1990,-- as supplemented by TXX-92255, dated May-27, 1992. This generic 11ettertwas closed by the NRC in SSER 25.
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The followina information i's needed to' complete the re' view of the.
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Comanche Peak. Unit 2. thermal-hydraulic analysis:
A)
-Identify the valve-opening / closing times'used'in the thermal ~
hydraulic-analysis. -Compare.the. time.used to the open/ closing. times measured in the EPRI tests, ifJthe timesJ used in;the thermal-hydraulic analysis are greater than'the measured valve open/ closing times.. justify that piping; forces were.not underestimated.
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Attachment to TXX-92548 Page 5 of 8 B)
Justify that_tne valve discharge cases analyzed result in forces that bound the forces fr om all transient conditions expected at Comanche Peak, Unit 2.
-While it is clear the safety valve and PORY_ loop seal discharge cases would' bound most situations, it is not clear-this includes steam *to-water transition with hot water-(such as the feedwater line b r e a k.1, steam to-water transition tith cold water (such as a -
cold overpressure transient). and bot and cold water discharge only transients.
C)
The peak pressure in the PORV discharge case was 2350' psia; This is lower than the peak pressure calculated by-Westinghouse, 2532-psia. for PORV discharge at Coranche Peak, Unit 2.
Justify that the thermal hydraulic analysis did not underestimate piping forces during a PORV discharge due to-the lower pressure used or provide the.results of_a new analysis usin_g the higher pressure.
CPSES Resognig
.j A)
The valve opening times used'in the Safety and Relief valve-thermal hydraulic blowdown analyses are-0.040 and 1.000 seconds, respectively.
Westir.chouse' computer. codes and methods used to perform these blowdown analyses'were-established basedLon analytical ~ benchmarking of the EPRI_ test configuration.
This test configuration was analyzed:using the above opening times :and the results.were 'found to be equal to or-greater than.the-actual' EPRI test results.
B)
Interviews with the current and' previous Westinghouse personnel who perform these analyses' indicates.that there has.
been. plant specific investigatior into the severity;of_'
Pressurizer Saf tiyf and Relief Vaive (PSARV)1 discharge cases-other than the." loop seal slug" discharge case.
The_ result-of_ the other discharge cases hav?lbeen found-to be less-severe than the " loop seal stag" discharge.
C)
'The. thermal-hydraulic blowdown event 1 takes placeLwhen-theE PORVs open at 2350 psi.
Under certain condition's such as::
" loss of load", the pressurizer-pressure will1 continue to rise, in this exampic to"2532 psi,;at a maximum rate'of 130' psi /sec.. Since the " slug" clears the Tin ~e in.
approximately 1.7 seconds there will be some-increase in the-g pressurizer driving pressure during the transient event.
l Since the maximum pressure is less'than 10%'above the1 val've:
opening pressured and since_ the' critical _ loadings on1the Valves and-pressurizer. nozzle peak within 0.5 -seconds, tne.
transient increase ~in the system pressure:is not considered' significant and Lis not. included in the Westinghouse fanalysjt.
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-Attachment to TXY 92548-Page 6 of 8 t
(9)
Additional information on the structural,ar 'vsis is needed.
Please n,rovide the followina information:
A)
Ida,,t.fy the time step, the mass point spacing, damping factors, and the cuto'f frequency used in the analysis model-for various pipe sizes.
Give the rationale for the values chosen for the above parameters,- Justify they provide bounding analyses for the Comanche Peak, Unit.2, pressurizer-piping system.
The values chosen for the above parameters should adequately analyze the piping rystem response to:
frequencies of at least 100 Hz, For example, the time steps chosen should be approximately 0.001 s to allow a minimum of eight points per; cycle to define the forces applied to the-piping.
If the values of the_ parameters chosen do not adequately address frequencies of at least 100 Hz, provide suf icient information to justify that the structura' analysis accounts for-the dominant piping frequencies c Comanche Peak, Unit 2, B)
Compare the stresses and loads calculated for the pressurizer nozzles -for the safety valves and PORVs to the-allowable stresses and loads, if the calcuinted strestas and loads-exceed the allowable values, discuss the modifications TUEC will make to bring the system into compliance; CPSES Response A)
The time step, mass point spacing, damping ' actors, Land tutoff frequency used for the Unit 2.P$ARV mnalyses are the same as the Unit 1 analyses-previously reviewed by the NRC, The time step 13 0.001 sec, the damping-used is 2%,-and the cutoff frequency.used.is 1000 Hz, B)
Qualification of all components.of the PSARV! system is a-requirement of the' Class 1 piping, additionally-qualification.
of nozzle loads for. valves and equipment is a check 1.iot item in the stress report, The Comanche'Feak Unit 2 stress report-format also provides a reference for.the? additional' efforts.
required to. qualify nozzle loads if the Comanche' Peak: Hoit 2 loads exceed the published allowable' values.
The stress
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report for the PSARV system is available fo, review.
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Attachment to TXX-92548 Page 7 of 8 (10)
Reference 2. TUEC stated. "The hydraulic forcinq function inout used for Unit I was also used for Unit 2 in Reference 2. TUEC stated. *1he hydraulic forcing function input used for 'Jnit 1 was also used for Unit 2.
The piping system layouts, geometrics, and components are nearly identical in Units 1 and 2 with only small differences in the support system configuration."
Clarify this statement by identifying all the differences between the Unit 1 and 2 piping and support systems.
Given the identified differences in the Unit 1 and 2 piping end support systems, provide sufficient information to justify that applying the Unit I hydraulic forcing functions to Unit 2 will not result in underestimating the piping forces for i t 2.
CPSES Resoonse The only practical way to ' identify all the differences between the Unit 1 and Unit 2 piping and support systems" is to obtain the piping isometrics and the support location drawings for both Units 1 and 2 and make the comparison according to the relevant criteria.
Westinghous2 has made this comparison and found that the Unit 2 piping geometry is a ' mirror image
- of the Unit i geometry, within acceptable NCIG 05 tolerances and therefore the Unit 2 hydraulic forcing functions were created by reflecting the Unit I hydraulic forcing functions.
This forcing function was then-applied to the Unit 2 specific structural model (Unit 2 geometry, support locations and stiffness).
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Attachment to TXX 92548.
Page 8 of'8
'l REFERENCES 1.
Letter from H. C. Schmidt, Texas: Utilities Services, Inc.,'to S. B.
Burwell, NRC,
Subject:
' Comanche Peak Steam Electric Station,-Draft-
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Response to Generic letter No. 81-36, ' Log.No. TXX-3503, File No.- 10035, March 31. 1982.
2.
Letter from W. J. Cahill, TUEC, to USNRC Document Control Desk,
Subject:
' Comanche Peak Steam Electric Station (CPSES) - Unit 2. Docket 1No.
50-446 NUREG-0737, item 11.D.1 Performance -resting of Relief and Safety Valves." Log No'. TXX-92246. File No. 10010, May-18 1992.
3.
HPR Associates, Inc., EPRI PWR Safety j 4 Relief Valve Test Procramu Guide for Aonlication of Valve fest
.rocrbm Results to Plant Soecific Evaluations, Revision 2, Interim Report, July 1982.
4.
Westinghouse Electric-Company, Valve Inlet Fluid Conditions ~fqr Pressurizer Safety and' Relief Valves in Westinchouse-Desianed Plants',
EPRI-NP 2296, December 1982.
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