ML20096F453
| ML20096F453 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 08/23/1984 |
| From: | Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | Bishop T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| ANPP-30304-TDS, DER-84-39, NUDOCS 8409100025 | |
| Download: ML20096F453 (13) | |
Text
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Arizona Public Service Company August 23, 1984 ANPP-30304-TDS/TRB
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-U. S. Nuclear Regulatory Commission Region V Creekside Oaks' Office Path 1450 Maria. Lane - Suite 210 Walnut Creek, CA 94596-5368-Attention: Mr. T. W.-Bishop, Director Division of Resident-Reactor Projects and Engineering Programs
Subject:
Final Report - DER 84-39 A 50.55(e) Reportable Condition Rela' ting To LPSI And Containment Spray Pumps Have Experienced Abnormal Rumbling i
Noisas.
File: 84-019-026; D.4.33.2
Reference:
A) Telephone Conversation between J. Ball and T. Bradish on June 5, 1984 B) ANPP-29866, dated June 29, 1984 (Interim Report)
Dear Sir:
Attached is our final written report of the deficiency referenced above, which has been determined to be Not Reportable under the requirements of 10CFR50.55(e).
Very truly yours, Om E. E. Van Brunt, Jr.
APS Vice President Nuclear Production ANPP Project Director EEVB/TRB/nj At tachment cc:
See Page Two Pl!/>I 0193h 8409100025 8 23
$DRADOCM05 528 PDR f.y 03A!3JJtt
'Mr. T. W. Bishop DER 84-39
'Page Two ec:.
~ Richard DeYoung,' Director Office of Inspection and. Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555 T. G. Woods, Jr.
D. B. Karner W. E. Ide D. B. Fasnacht A. C. Rogers L. A. Souza D. E. Fowler T. D. Shriver C. N. Russo J. Vorees J. R. Bynum J. M.~ Allen J. A. Brand A. C. Gehr W. J. Stubblefield W. G. Bingham R. L. Patterson R. W. Welcher H. D. Foster D. R. Hawkinson L. E. Vorderbrueggen R. P. Zimmerman S. R. Frost J. Self M. Woods T. J. Bloom D. N. Stover D. Canady Records Center Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, GA 30339
FINAL REPORT - DER'84-39 DEFICIENCY. EVALUATION 50.55(e)
ARIZONA PUBLIC SERVICE ~ COMPANY. (APS) o PVNGS UNITS 1, 2, 3
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Description of Deficiency During performance verification tests on modified-Low Pressure Safety Injection' (LPSI) Pumps and modified Containment Spray-
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(CS) Pumps on Unit i during May 1984 (reference DER 83-61.for details of modifications), an~aperiodie " rumble".was evidenced.
in LPSI pumps 1MSIA-P01 and 1MSIB-P01_ and CS pumps 1MSIA-P03 and 1MSIB-P03 and their adjacent suction piping. In the case of the LPSI pumps the " rumble" was noted in the capacity range of.2800 to 3400 gym. In the case 'of - the _ CS pumps ' the " rumble" was of lower magnitude and was noted in the' capacity range of -
1800~to 2800 spa.
The " rumble condition" had not-been reported prior to the DER 83-61 modifications as previous-operation of these pumps did l
not include sufficient time in their: respective " rumble" ranges for this phenomenon to be identified, i.e.:
The LPSI pumps would normally be started at 100.gpm fixed (continuous) minimum flow against a closed discharge control valve, and the discharge valve then opened to permit design flow of 4300 gpa (or in the case of the 100 start test - reference DER 83 maintained at a 2000 to 2100 gpm valve setting).
In the case of the CS pumps, startup would normally be at 150 gpa fixed minimum flow against a closed discharge control valve which is then opened to permit the 3900 gpm design flow.
The minor modifications to the pumps (reference DER 83-61) concerned the impeller running fits and have no influence on whether or not the pumps do or do not operate with a " rumble" in the flow range (off peak efficiency) between minimum flow and design capacity.
This " rumble" phenomenon is the result of interaction between intermittent (aperiodic) ' inlet flow disturbances caused by the suction piping configuration and prerotation of the inlet stream caused by the pump impeller while operating off peak efficiency. The noise source is due to cavitation from
. collapsing of bubbles in the flow stream about one foot below the pump casing.
The' root cause of the " rumble" phenomonon is explained in Reference 1 with respect.to the.LPSI pumps.
Based on the similarity of pump designs and suction piping configurations,
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the same root cause is.also applicable to the CS numps.
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ANPP-30304-TDS/TRB Page Two Should prolonged operation in the " rumble" range ever become an operating: requirement, this condition can be corrected by
-incorporating either a splitter at the pump inlet to negate the prerotation, or straightening vanes in the. suction pipe below'the pump to reduce the inlet flow turbulence-to the pump.
The LPSI Pumps and the CS Pumps are supplied by Combustion Engineering (C-E) and are manufactured by Ingersoll-Rand (IR). They are identified b'y tag numbers as
-follows:
Unit 1-Unit'2
-2MSIA-P01 3MSIA-P01 1MSIB-P01' 2MSIB-P01 3MSIB-P01 CS IMSIA-P03 2MSIA-P03 3SMIA-P03 i
1MSIB-P03 2MSIB-P03 3SMIB-P03 i
II.
Analysis of Safety Implications During shutdown cooling, the LPSI pumps are used to reduce the temperature of the Reactor Coolant System (RCS) in post-shutdown periods from an RCS temperature of 350*F to the refueling temperature of 125'F. Additionally, the LPSI pumps are used to provide emergency core cooling flow following a large break Loss of Coolant Accident (LOCA) up to initiation of a Recirculation Actuation Signal (RAS).
The shutdown cooling mode flow rate is 4500 gpa and is
. controlled by the operator. Operation through the 2800 to 3400 gpa " rumble" range'will be of a transient nature and of short duration. No impact resulting from the " rumble" phenomenon is anticipated as a result of operating in the shutdown cooling mode.
In the emergency core cooling mode of operation, the LPSI system could operate in the " rumble" flow range. 'A Probabilistic Risk Assesment (PRA) was employed to evaluate the operation of LPSI pumps in the range of flow where the
" rumble" occurs. The probability of operating in this flow range is very low, calculated to be a mean occurrence of 4.65 x 10-4 per operating year. Operation in.the rumble range will depend on the combination of pumps running, LOCA break
- size and configuration, decay heat rate, andd operation of the steam generators as an alternate energy removal path, (reference 2)..
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Mr. T. W. Bishop.
ANPP-30304-TDS/TRB-Page Three i
The upper limit of time for which the rumble could occur, assuming no corrective operator action, would be four hours.
-This is based on a~ maximum Refueling Water Tank (RWI) volume of approximately 700,000 gallons with only one.LPSI pump operating until automatic shut-off by the RAS.
The RWT is the safety injection. system suction reservoir, prior to RAS..C-E has stated '(reference 3) that if a-LPSI pump operates for at least one minute, there are no break sizes where an LPSI failure would result in significant core damage. Also, IR has confirmed (reference 3, enclosure 2, item 4), that operation.in the rumble range for up to four hours would not cause pump damage.
The pumps.were field tested with the same system conditions as would be encountered during a LOCA. LPSI pump 1B was run in its " rumble" range during tests for a duration of about two hours. Post-test inspection revealed no pump degradation.
The CS pumps are designed to remove heat from the containment atmosphere in the event of a LOCA while pumping at a rate of.
3750 gpe. They:are also used (below 200*F) to circulate reactor coolant, at a rate of 4500 gpa, to remove decay heat during the latter stages of shutdown cooling.-
The CS pumps will not have occasion to operate in the range where rumbles occur.
Based upon the above, the " rumble" condition for both the LPSI and CS pump systems are evaluated as not reportable under the requirements of 10 CFR part 50.55(e) since, if left uncorrected, it would not reprenent a significant safety condition.
Also, this condition is evaluated as not reportable under the requirements of 10 CFR Part 21 since it does not constitute a.
substantial safety hazard and, if left uncorrected, would not
- adversely affect the capability to safely shut down the t
I reactor.
III.
Corrective Action l
NCis SM-4201 and SM-4229'have been dispositioned to use the l
pumps as is.
No corrective action is required as a result of
(
thic condition, (reference 3). The LPSI pump operating l
procedures are being revised to incorporate a warning not to operate in the 2500 to 3500 flow range during the shut-down cooling mode of-operation.
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Mr.'T. W. Bishop-ANPP-30304-TDS/TRB
'Page Four IV.
R_e fere nces.
(1)' Root Causes of " Rumble" in LPSI Pumps, Palo Verde Project.
(2) Probability Calculations.
(3) V-CE-30530 dated July 10, 1984 with two enclosures.
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' DER 84-39' r
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Reference (1)-
.,._l Root.Causes of " Rumble" in LPSI Pumps-Palo Verde Project The.LPSIupumps develop noise.and vibration when operating in'a flow range of 2800 to 3400 gpm.. Based on aural observations and on accelerometer and
. pressure data obtained by the startup personnel, the cause of;this " rumble" l(noise and associated vibration) has been determined to be as follows:
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The fact'that the problem only occurs'in the 2800 to 3400 gpm range which is at approximately 75% of rated flow, strongly suggests that pre-rotation induced by back flow from the impeller is part of the cause.
The intermittency of the events suggests that some other source of-flow
' kjy disturbance is combining with the prerotation to produce the noise and
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vibration. The aural observation indicated that the noise was due to
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. ;3 cavitation which occurs in the intake pipe about I foot below the pump
- Mf casing. The cavities collapse within the water column.
In such cases,-
the cavitation produces vibration and sound but no metal damage.
Aural observation of the intake piping at.several locations disclosed that strong turbulence develops in the flow aperiodically. The bends, tees and reducers in the system are sufficient to generate random, large scale turbulence.
It'is concluded, therefore, that cavitation conditions develop intermittently when the swirl, associated with a burst of turbulence, interacts with the prerotation induced in the intake pipe by opera-tion of the pump at partial discharge. Justification for this con-clusion is as follows:
Tests conducted at the California Institute of Technology, for' pumps of about the.same specific speed as those at Palo Verde, demonstrated that backflow from the impeller induced'prerotation in certain partial flow ranges depending on the impeller design.
The source of*the noise was determined from. aural observations and was corroborated by the vibration data. The accelerometer data showed a definite time lag betweer. the beginning of an event for an accelerometer mounted on the intake pipe and units mounted upstream.
Calculation of the apparent acoustic wave speed gave values of approximately 3750 feet per second, a value to be expected. It is apparent, therefore, that the noise and vibration starts in the intake pipe.
During early startup a strainer was installed in the spoolpiece upstream from the intake. This strainer was concentric but was placed in an eccentric reducer.
It, therefore, presented an eccentric configuration to the flow. While it was in place the
" rumbles" occurred at.from 2800 to 3200 gpm. After removal of the strainer, the " rumbles" moved to the 3200 - 3400 gpm range.
This substantiates the conclusion that the piping configuration
'is contributing to the event and that minor changes can cause appreciable changes in results.
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DER 84-39 Reference (2)
Page 1 of 2 ll PROBABILITY' CALCULATIONS The. probability of a LPSI pump running at 2500 to 3500 gpm during safety injection is determined by the_ probability that a leak would occur which would require the LPSI pump to deliver 2500-3500 gpm, and the probability that the number and configuration of running pumps requires-the LPSI pump (s) to deliver 2500-3500 gpm. The " rumble" was determined by tests to occur in the 2800 to 3400 gpm flowrange. For conservatism, this range was expanded to-2500 to 3500 gpm for these calculations.
P Rumble = P Leak X P Matching Configuration Number Running Gallons / Minute Case LPSI HPSI LPSI HPSI Total 1
2 2
5000 2400 7400 7000 2400 9400 l
2 2
l' 5000 1200 6200 7000 1200 8200 1
3 2
0 5000 0
5000 7000 0
7000 4
1 1
2500 1200 3700 3500 1200 4700 5
1 0
2500 0
2500 3500 0
3500 A range of leaks between 2500 gpm and 9400 gpm could thus cause the rumble.
. The LPSI pumps shutoff at 475 feet of head (204 psi) and run out at 5100 gpm at 285' (124 psi). They will run at 2500-3500 gpm in the SI mode at about 145-165 psi.
Flows of 2500-9400 gpm at 145-165 psi would come from reactor coolant system leaks with equivalent hole diameters of 2-1/2" to 5".
Such leaks are clagsed as medium LOCA's. The mean probability of a medium LOCA is 4.65 X 10 per year, Reference A.
The sum of-the probabilities of a leak giving the required flow for each specific case is equal to this number. We are conservative if we use the medium LOCA frequency for all cases.
The LPSI pumps run for about 40 minutes in the injection mode before the recirculation actuation signal (RAS), triggered by. low RWT level, will shut them off. This shortest run time applies when both HPSI pumps, both LPSI pumps, and both CS pumps are running. If only one LPSI pump were running at 2,500 gpm, it would take.3.2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to regch RAS cutoff. The probability of only one LPSI pump running-is 3.32 X 10 lower than having all~ pumps running.
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- 7 DER 84,'
Reference (2) e.
Page 2 of 2 PROBABILITY CALCULATIONS (continued) i-.h
'The probability of having a given combination of pumps running is determined as follows:
P Running + P Failure = 1 or P Running = l-P Failure Case Comb.
Probability 1
2L 2H (1-PL)
X.(1-PH)
El 2
2L lH PH-(1-PH) X (1-PL)
EPH 3
2L OH (PH)
X ' (1-PL)
E(PH) 4 lL 1H (PH) X (PL) X (1-PH) X (1-PL) EPHPL 5
lL OH (PH) (PL) X (1-PL) EPH PL Where PH = Probability of failure to start or run (HPSI)
PL = Probability of failure.to start or run'(LPSI)
HPSI -
LPSI Failure to start 3.29 X 10 3 3.29 X 10 3 Reference A Failure to run for one hour
.03 X 10 3
.03 X 10 3 Reference A W
PH 3.32 X 10-PL 3.32 X 10-Evaluating the cases:
P1 = (1-3.32 X 10 3) 2 (1-3.32 X 10 3)2 E1.0 X
P2 = PH = 3.32 X 10-P3 = (PH)
= 1 X 10-P4 = PH X PL = 1 X 10-PS = (PH) (PL) = - 3. 32 X 10-As Case 1 dominates the configurations with probability of 1, and the probability of leak is conservatively equal to the probability of'a medium i
IOCA, the;mean probability of LPSI pumps ope ating in the SI mode in the flow
)
range where rurbles will occur is 4.65 x 10 g/yr or less than once in 2150 l
years of plant operation.
. Reference A - Pickard, Lowe and Garrick, Inc., Generic Database for PWR's.
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C E P:w:r Sy:t:ms T6l. 203/6881911 Combustion Engineenng. Inc.
Tslax: 99297 1000 Prospect Hill Road ygM l.
. Post Office Box Soo Windsor. Connecticut o6095.o500 c f 7 * *-
M POWER SYSTEMS July 10,1984 3,16 M V-CE-30530 MI Is "
.x Mr. W. G. Bingham ij =1 Bechtel Power Corporation
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12400 East Imperial Highway 1
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Norwalk, CA 90650
Subject:
Low Pressure Safety Injection (LPSI)
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Reference:
(A) B/CE-E-48279 dated May 30, 1984
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(B) B/CE-E-48429 dated June 20, 1984 y
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Enclosure:
(1) LPSI Pump Probability Risk Assessment (PRA)
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e' (2) LPSI System Noise Anomaly
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Dear Mr. Bingham:
This letter addresses the LSPI system disturbance / noise / rumble found to occur when a LPSI pump is operated in the 2800 to 3400 gpm range. An evaluation has
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been made to determine if the safety functions of the system would be impacted by this rumble phenomenon. The LPSI pump / system ~is used to provide safe cooldown to cold shutdown in a shutdown cooling mode of operation and also may provide emergency core cooling flow in the short term (up to RAS actuation) if there is a LOCA.
The shutdown cooling flow rate is 4500 gpm and is contro11'ed by the operator.
Operation through the 2500 - 3500 gpm will be of a transient nature and ~ very short duration. No impact resulting from the runble phenomenon is anticipated as a result of operating in the shutdown cooling mode.
In emergency core coolirig mode of operation, one can expect the system to operate at the " rumble" flow rates.
It is felt that the upper bound of the time period for which rumble could occur assuming no corrective action would be four hours. This is based on a maximum RWT volume of approximately 700,000 gallons with one LPSI pump operating.
- Enclosure (1) provides a more detailed analysis of required run times for various break sizes.
Operation in the rumble m@ will depend on the combination of pumps running, break size and configuration, decay heat rate, and operation of the steam generators as an alternate energy removal path. The approximate break size range where one would anticipate flows in the rumble regi7n fog different pump combinagionswouldbebreaksof3to8inchdiameters(0.05ft to 0.35 ft ).
The pumps have been field tested in the same configuration and the same system conditions as would be encountered during a LOCA. One pump was run during testing in the rumble mode for a duration of about 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. No pump degradation was observed as a result.
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a Further, IR has advised that operation in this mode for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> was not expected to be detrimental to pump performance or its expected life.
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An analysis was also performed from a survey of LOCA analyses.
Specifics of the survey are shown in Enclosure (1). The reference to "significant fuel damage" pertains to fuel clad temperatures in excess of 2200 F.
The results of the survey show that if the LPSI pump operates for at least one minute or more, there are no break sizes where a LSPI failure would result in significant core damage, consequently, from a PRA standpoint, no increase in risk would be predicted.
Of the two assessments, the latter is considered the more realistic situation; one LPSI pump operating requirement between 1 minute and I hour.
Reference (B) asked for Ingersoll Rand input to three questions. Their replies plus their reply to a fourth C-E question are included in Enclosure (2).
Reference (A) requested that C-E have Ingersoll Rand-(IR) design and fabricate a flow straightening device for the LPSI pump suction.
C-E und,erstands that this effort has been put on hold. Please be advised that IR has completed the design portion of this effort.
If you should have any questions, please contact me.
Very truly ours, C. Fergu Proje nager CF/JDI/CDB: sic F73181 cc: Messrs:
E. E. Van Brunt, Jr. w/e J. Vorees w/e W. H. Wilson R. H. Holm J. W. Dilk G. A. Butterworth S. N. Mager
'D. B. Amerine w/e W. L. MacDonald J. R. Bynum 1
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-Enclosure.(1) to V-CE-30530 Page 1 of 2 AfiPP/PALO VERDE LPSI SiSTEM tiOISE A!CMALY PROBASILITY RISK ASSES 5 MENT (FRA)
OlSCUSSION A noise, in itself, of course will not contribute to risk.
The extent to E.ich f
the "rochle" is indicative of over-stressing of pump or ;iping cc Gonents is l
currently unknown.
The discussion below is based on consideration of two l
alterr.ative cases:
Case 1: A rumble that persists for more than one minute is assumed to lead to a co plete loss of punp ficw.
Case 2: A ra ble that persists f or more than one hour is assumed to lead to
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co.plete loss of punp flow.
C-E herf ccmed a survey of LOCA a.alyses in crder to deter.-ine hich apprcti: ate y
break sizes could lead to LPSI purp flow in the range of 3003 + 500 gpm for
.i' suf ficient tir.e to cause pump dar. age (See Cases 1 & 2 atc.e).
The results of the survey incicate that:
For Case 1 (i.e., one minute runble tolerance) LPSI puep f ailure would not be 2 For breaks in the predicted for break sizeg greater than about 0.2 ft range of 0.005 to 0.2 ft, LPSI pump f ailure could occur but the LPSI pumpsFor would not be needed for either in4ection or pcst-LOCA shutdoan cooling.
I breaks sr. aller than about.005 f t, the LPS! pump would not produce flows in the 3000 gpm range prior to post-LOCA shutdcwn cooling.
In post-LOCA shutdown cooling the LPSI pump flow can be controlled to avoid the 3000 gpm range.
f-For Case 2 (i.e., one hour rumble tolerance) no break sizes would be expected l-to lead to LPSI punp f ailure.
Operation in the injection mode is not required l
for longer than one hour.
In post-LOCA shutdown cooling the LPSI pump flow can I
be contrclied to avoid the 3000 gpm range.
RISK IMPACT The recent Calvert Clif f s IREP assuned LOCA frequencies of approximately:
j 2 (<.02ft3 3 x 10-2 per year Snall, Small LOCA, 5
Snall LOCA, 53 (.02 - 0.1) 3 x 10-4 ger year Large LOCA, A (>0.1) 1 x 10-4 per year l-I Using these f requencies as a basis, we can draw the following preliminary conclusions:
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' i, Enclosure (1) to l
Y-CE-30530 l
1 Page 2 of 2 i
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- l CASE 1 8 2.
Given a cre r.inute, or one hour rur.ble tolerance, there are 'no break sizes that
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Therefore, was1d result in LPSI f ailure lending to significant. core da.Tage.
b? sed on' traditional FRA ccasideration, no increase in risk would be H: ever, there :ust be asssrence that the f.; ps.can really tcierate precicted.
the rurtle at the ti.,e that they are der.anded.
To be st,re of.this would' rquire'. aking sure that the rc:ble is not a sjepto of continual ct.t.31ati e o
. degradation of the. pump or ;,iping such that flow delisery reliability is decreasing-nith age. The tests cor. ducted at PVNGS and t'.e subsequent inspection previde this assurance.
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.y" Enclosure (2) to V-CE-30530 ANPP/PALO VERDE LPSI SYSTEP. NOISE (RUMBLl%) A%".ALY I'.
In IR's opinion, what is causing the disturbance (ncise) in the subject system?
1R: It.was the conclusion of hydraulic experts at site, including IR, that noise was emnatirg f r.:r. the piping upstream of the pump.
There prcbably is some interaction of pump with the system in tnat changes to the p.,p alone or system above could affect the rurbling.
This is not kncsn for certain.
It is kncwn that identical pumps with different piping do r.ot -
exhibit the ru.dling.
2.
What would be IR's recosendation to alleviate the prcblem?
(As you are a are, a cresspiece type si.raightener in.the suction spool piece did not reduce the r..ble.)
1R: Sirce i.dividual eierents such as elbows, reducers, and tees interact, it is cif ficult to recc. end piping changes withoat a flo,t visuali ation nodel There are various ccmbinations of flow straighteners or baffles that test.
mi S51 werk.
Several'have been examined.
The two under consideration (are at the strainer and the other just upstream of ir;eller) were rect nanded i
due to ease of installation and expected hydraulic benefit.
3.
Does IR recon.end the installation of straightener sanes in the pump case suction? Why? Will the vanes solve the problem?
IR has previously advised that straightening vanes upstream of 'the impeller 1R: may suf ficiently c'orrect non-uniform flow to the. pump to reduce or eliminate the rumbling. While these vanes are expected to help.
IR cannot say for sure that rumbling will decrease.
4 Is the problem detrinental to the pump performance or its expected life?
1R: The rumbling does not appear to be related to a loss in punp perforr.ance.
It has been noted that when the rumbling occurs there is a ninor fluctuation of the discharge gage.
Normally pump head-capacity is affected
..by pre-whirl (rotating flow) into the impeller but in this case the disturbance is cyclical and apparently the full head-capacity is still being produced.
The life of the pump may be affected by continuous operation in the rumbling node.
IR has previously advised in response to f-C-E cuestions that operation in this mode for a few hours was not expected I
to harm the pumps.
(per Teleton, C-E/lR this' includes 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />).
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