ML20214J952
| ML20214J952 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 02/28/1984 |
| From: | Dudek D, Kemper R WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML20214J938 | List: |
| References | |
| NUDOCS 8608150245 | |
| Download: ML20214J952 (44) | |
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.o-s CENTRIFUGAL CHAR 6ING PUMPS AND SAFETY INJECTION PUMPS SYSTEMS PERFORMANCE EVALUATION
(
TENNESSEE VALLEY AUTHORITY SEQUOYAH UNITS 1 & 2 l
- 0. F. DUDEK l FLUID SYSTEMS DESIGN R. M. KEMPER NUCLEAR SAFETY I
FEBRUARY, 1984 8608150245 860008 PDR ADOCK 05000327 P PDR 0615Y/J8/2/84 j ,
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- TABLE OF CONTENTS Page Centrifugal Charging Pump Introduction 1 Discussion 4 System Performance 5 Conclusion 8 Nuclear Safety Evaluation 8 Safety Injection Pump 10 Introduction 10 Discussion of Pump Test Data 10 System Performance 12 Conclusion ,
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This report will discuss the Westinghouse Emergency Core Cooling System (ECCS) evaluation of the Tennessee Valley Authority (TVA) Sequoyah Unit 2 Test Data for:
o Centrifugal Charging Pump (CCP) o Safety Injection Pump (SIP)
CENTRIFUGAL CHARGING PUMP Introduction Last year, the Sequoyah Unit 2 CCP's rotating elements were removed and the Watts Bar Unit 1 CCP rotating elements wre installed. These elements w re field tested, and determined to be unacceptable since the branch line measurements did not meet the Technical Specification Sec. tion 4.5.2 requirements. The Watts 8ar Unit 2 elements wre subsequently installed and field tested. The results indicated a large difference betwen pump '
developed heads at runout causing system balancing problems.
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.- The safety injection branch lines and charging line (simulated seal injection) measurements were used to detensine the total pump flow at various throttled positions. All the field test data, when compared with the Pacific Pump shop test data, indicated a reduced pump performance.
Field testing of the four Watts Bar CCP's using calibrated test
- instrumentation were unable to duplicate the vendor shop test results. It would be expected that the field test data may exhibit a difference but j not the large variance as seen at Unit 2.
The header flow element measurement readings demonstrated higher flow than l the branch line instrumentation but TVA preferred not to use these header reaoings since the Technical Specification alluded to branch line measured flow.
Westinghouse's Recommendation The CCP's are tested at the Pacific Pump test facility using sophisticated measurement techniques to develop the shop test data. Pacific Pump has I assured Westinghouse that the element performance characteristics will not noticeably change when operating % the field. Also. Westinghouse believes that the combined offer.t of errors in flow measurement on measured pump performance will exhibit a reduced developed runout head relative to the shop test. (A discussion of the combined error offact is given in Attachment 1.)
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e g Therefore, based on the Westinghouse study of the effects of errors in flow measurement and the Pacific Pump sophisticated shop testing of the rotating element, it is Westinghouse's recommendation:
o that the Sequoyah Unit 2 header flow element be used to establish total pump flow rate; o the branch line orifice Ap's are to be used as an indication of the relative flowrate between each branch line; o that the header flow measurement and the branch line relative flow indications be used to demonstrate compliance with the Technical Specifications.
Attachment 2 provides a procedure for balancing the branch lines.
Per TVA's request, Westinghouse used the Unit 2 branch line field test data in an ECCS reanalysis to deter:nine the safety performance of the
( plant.
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. . Discussion of Pumo Test Data Per TVA request, Westinghouse performed the Safeguard Data evaluation Emergency Core Cooling System Analysis assuming the following.
o Use the branch line plus charging line flowrates to equal total flow o Remove the "S" signal from the CCP siniflow path and evaluate the system flowrates with the mini-flow path open.
The following test data were transmitted by TVA to Westinghouse:
Table 1 Pump A PUMP HEAD.FT BRANCH LINE. GPM CHARGING. GPM T.0TAL. GPM l r N 5769 0 152.9 152.9 5855 0 77.5 77.5 5843 0 100.7 100.7 5574 0 197.1 197.1 5771 0 130.6 130.6 l
5524 193.2 27.8 221.0 5169 248.1 26.9 275.0 ,
4810 288.9 26.0 314.9 4319 338.0 24.6 362.6 3693 31 5.9 78.1 394.0 3065 361.4 79.5 440.9
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2326 409.8 76.9 486.7 1775 436.1 79.3 515.4 971 470.6 77.8 548.4 964 467.0 80.0 547.0
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.. e Table 2 Pump 8 Pumo Head. FT Branch line. GPM Charoina. GPM Total. GPM 5738 0 77.96 77.96 5704 26.03 77.80 104.10 5683 71.00 77.55 148.55 5472 121.70 80.03 201.63 5162 169.10 79.23 248.33 4667 221.70 78.01 299.70 i
4128 268.70 77.64 346.30 3454 318.50 78.80 395.30 2688 359.20 78.02 447.20 1
2204 399.20 77.09 476.30 1662 427.80 79.14 506.90 791- 448.90 78.00 526.90 Test data is plotted on Figure 1.
As can be seen Pump B is the weaker of the two pumps and will be used in determining the minimum safeguards Data for use in the Nuclear Safety ECCS Analysis.
System Performance The Sequoyah Unit 2 Centrifugal Charging Pump Safety Injection System was
., modeled to represent the TVA test data as follows:
The minimum safety injection system performance was evaluated on the following assu:aptions:
o Flowrates consider single failure, therefore only one pump is operating.
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o One injection lina spills to containment pressures; r
o Pre-operation test data and the as built piping layout were
- utilized to determine the system header and branch line P resistances;
{ o The pump performance characteristic is based upon the test data minus 5% of 5800 feet, see Table 3 ;
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This information was used in the development of the computer model resulting in the flowrates in Table 4 to be used in the Nuclear Safety ECCS Analysis.
Table 3 Pump Performance
}L,_F_T 5% REDUCED. HD. O. .GPM
=
5750 5460 0 5740 5450 50 5700 5410 100 5625 5335 150 I 5490 5200 200 5175 4885 250 4650 4360 300 4050 3760 350 3375 3080 400
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2575 2285 450
. 1700 1410 500 L
791 501 576
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, ^i i TABLE 4 INJECTION FLOWRATES
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PRESSURE- TOTAL FLOW INTO CORE PSI 6 LBS/SEC GPM
<. 0.00 43.60 315.64 100.00 40.79 295.26 200.00 38.06 275.50 300.00 35.38 256.15 400.00 32.74 237.04 500.00 30.12 218.05 600.00 27.49 199.02 l- 700.00 24.64 179.86 800.00 '
22.15 160.37 900.00 19.38 140.33 1000.00 16.49 118.28 1100.00 13.44 -
97.33 1200.00 11.06 90.23 1300.00 8.56 61.99 1400.00 8.82 42.10 1500.00 2.71 19.61 1600.00 0.00 0.00 i
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t The Sequoyah Unit 2 CCP branch line pump test data was used as a basis in developing the system model in determining the minimum safeguards data.
(Table 4). The results of the Nuclear Safety Evaluation is discussed in Attachment 3. The evalestion concluded that the reduction in pumped safety injection will not affect the safety performance of the plant.
The Sequoyah Technical Specifications have been revised and are in Attachment 4. Also the minimum CCP ECCS curve in shown on Figure 2.
The Sequoyah Unit 2 charging pump field test results are consistent with trends noted by Westinghouse at other utility field tests. These results i
are also consistent with published comparisons between calibration data and flowrates pedicted by means of A!ME Fluid Meters for two arrJ four-inch high diameter ratio orifices. (See Attachment I) Based on thGse facts, the following recommendations are made:
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o The Pacific Pump performant.e curves are determined in conjunction with
' careful 7y calibrated flow meters and should provide a reliable representation of actual pump performance. Since field pump performance bassJ on header flow measurements acre closely agrees with the vendor perforiaance curves than does the perforinance indicated by l branch line flowrates, Westinghouse recommends that:
)
the header indicated flow rate be used in setting total pump )
flowrate 1
the branch line orifices AP's be used only as a measure of relative branch lir.e flow balance Consistency with the plant Technical Specification can be ascertained through knowledge of total header flowrates and relative branch line flow balance.
o At some point in the future consistent with plant schedules, the orifice element installed in FE-917 could be replaced by a lower diameter ratio (e.g., = 0.65). This should provide a reductie in the measurement uncertainty associated wth that channel.
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Safety Iniection Puen Introduction Tennessee Valley Authority requested Westinghouse to evaluate the Sequoyah Unit 2 Intermediate Safety Injection Pump test data.
The pump test data did not meet the safety injection pump minimum FSAR curve.
Discussion of Pumo Test Data TVA transmitted the following test data to Westinghouse:
TABLE 5 "
PUMP 2A HEAD. (FT) FLOW. (GPM) 3111.6 285.6 2864.0 371.0 2686.0 410.0 2575.0 438.6 2471.0 467.0 1511.0 648.0
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l TABLE 6 PUMP 2B HEAD. (FT) FLOW. (GPM) 3112.6 304.0 3106.0 306.6 2765.6 415.9 2615.0 449.0 2303.0 517.0 1575.5 666.5 :
This test data is plotted on Figure 3.
To complete the pump curve near the pump shutoff head it was assumed the Pacific Pump performance curve was applicable since the test data closely followed the performance curve at higher pump heads. Based on the test data the weak pu.g is Pump 2A.
The pump test data was reduced by five percent (120 feet) and was used in the computer model to determine the Safeguarrds Data for use in the ECCS
- Analysis. The minimum FSAR Safety Injection Pump Curve is shown on Figure 4.
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' l System Performance The following assumptions were used as input to develop the Safeguards Data system computer model:
)
o Pump test data was reduced five percent o System model reflects the test data at 650 gpm at 1500 feet j o Mini flow is 45 spm at pump runout i o The spilling line delivers against 0 psig containment backpressure o The spilling line is the least resistive line of the
- injection paths.
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( Nuclear Safety in their ECCS Evaluation.
TABLE 7 PRESSURE TOTAL FLOW INTO CORE (PSIG) L85/SEC GPM 0.00 61 .29 443.70 100.00 58.44 423.09 i 200.00 55.25 399.99 300.00 51.91 375.81 400.00 48.45 350.75 500.00 44.85 324.66 600.00 41.07 297.33 700.00 37.09 268.50 800.00 32.84 231.75 900.00 28.24 204.47 1000.00 23.16 167.65 1100.00 17.32 125.38 1200.0d 10.10 73.15 1300.00 0.00 0.00 1400.00 0.00 0.00 l 1500.00 0.00 0.00 l
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. Conclusion
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Westinghouse has evaluated the 'as measured" safety injection pump performance data The ECCS evaluation demonstrated the reduced safety injection pump flow rates does not result in unacceptable ECCS performance. See the attached Nuclear Safety Evaluation Check List (Attachment 3) for further information.
The attached Technical Specification Section and FSAR figure are in Attachment 4 which reflect the latest evaluation. !
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ATTACHMENT 1 THE EFFECT OF ERRORS IN FLOW MEASUREMENT ON MEASURED PUMP PERFORMANCE FIELD EXPERIENCE Field test data for the charging and safety injection pumps at several plants exhibits a consistent trend with respect to shop test data. This trend is characterized by a depressed total developed head (TOH) at runout for the field curve relative to the shop curve, and by relatively equivalent performance for the two curves near the shutoff point.
Westinghouse has verified this relationship by performing our own reduction of the raw test data, making appropriate allowances for the following factors:
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Velocity head Difference in elevation between the static pressure gages used to measure pump head ,
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, Line losses between the static pressure gages Pump speed None of these factors has been found sufficient to explain the phenomenon. This has prompted additional investigations into possible causes for reduction in developed head common to all the pumps. The following have been considered.
Installation Differences. It may be postulated that some peculiarity of installation, common to all pumps, is to blame.
This is considered unlikely, however, as site visits by the vendor have confirmed the typical plant layout closely resemble their test loop.
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4 Orifice Cavitation. This has been effectively ruled out, based on the fact that the plant layout provides adequate back pressure to
, prevent cavitation. Also, slight cavitation has been shown negligible effects on orifice coefficient.
Nesurement Error. The most likely theory seems to be that some systematic error exists in the measuring system at the sites.
Systematic errors are characterized by consistency regarding both sign and magnitude and becuase of their consistency may sometimes be corrected by calibration. (Random errors, on the other hand, are distinguished by their lack of consistency. Given the consistent nature of the problem, they may therfore be eliminated from consideration). We suspsect the error exists in the field, rather than at the vendor's shop, because the vendor's tests are performed with laboratory quality equipment specifically designed and calibrated for that purpose. Furthermore, the vendor has been able to reproduce at their facility the results of tests originally performed in 1977, lending credence to our belief that the actual pumps' performance'is greater than the performance measured in the field.
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REFERENCES
- 1. Fluid Meters. Their Theory and Application, American Society of Mechanical Engineers, NY, NY 5th ed, 1959, 6 th ed. 1970.
- 2. ' History of Orifice Meters and the Calibration, Construction, and Operation of Orifices for Metering," American Society of Mechanical Engineers NY, NY 1935.
- 3. R. B. Dowell and YL Chen "A Statistical Approach to the Prediction of Discharge Coefficients for Concentric Orifice Plates. Transactions of the ASNE - December,1970.
- 4. R. W. Miller and O. Kneisel, "A Comparison Between Orifice and Flow
, Nozzle Laboratory Data and Published Coefficients." Transations of the
. ASNE - March,1969.
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. ATTACHMENT 2 CHG/SI FLOW BALANCING / RUNOUT A0JUSTMENT PROCEDURES The following procedure provides a method for adjusting the four CHG/SI branch line throttling valves such that the specified flow balance is established for the branch line and the specified flow distribution through the charging /SI header with simulated seal injection is obtained.
The flow indicator, across the CMG/SI header flow element FE-917 will be used to establish the actual CHG/S! header flow rate. The flow indicator, across the normal CHG header flow element FE-121, will be used to establish an initial simulated seal injection flowrates. The four branch line indictors will be used to balance each of the four CHG/SI branch lines flow resistances.
The operational procedure should be performed only af ter the pump with the lower TDH at runout has been identified as the weaker pump. This pump will be operated during the adjustment of the cold leg branch line throttling valves (FE-917 flow path). Note that subsequent operation of '**
the stronger pump must not produce a runout concern. If necessary an orifice plate must be installed at the strong pump discharge to limit flow to its runout.
During the following operations, the four CHG/SI cold leg branch line throttling valves will be adjusted independently such that the branch line I flows are balanced and the total CHG/SI flow delivered through the four l branch lines is 462 gpm. Asimulatedsealflowrateof70;0 gp, 1 , will be established through the normal charging line coincident with the adjustment operations of the branch line throttling valves.
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The following procedures can be used to balance the branch lines:
o Maintainsimulatedsealinjectionflowat70jgpe. The RC pump seal injection flow at normal operations is to be limited to 6.8 gpm*
per pump (Reference S.S.O.C. 1.6A).
o Each of the throttling valves are to be simultaneoulsy opened, using the AP indicators to balance lines. The difforene between between the highest and lowest branch line should not exceed a AP equal to 2 spe.
o Continue the procedure until FE-gl7 indicates 462 gpe.
o The weak pump head / flow performance would be 536 gpm at 1610 feet. If these values are not obtained, please call Westinghouse.
To determine the Technical Specification, the following equation can be used to determine the sum of th injection line flow rates, excluding the highest flow rate. Say, for example, that branch lines 1, 2, and 3 have the lowest flowrates as indicated by the orifice AP's. Then the sum of the three lowest branch line flows is:
, Ah l + ah 2
+ Ah 3
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F5D /ss-TVA- 2149 W5fEMGME 1
WERAE SAFETT EUAtm4 Tim OECE UST -
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l (3) G E R LI57 Appu CAR K 19:. Reduced charging pump flow /HHS! flow (a nsest of meeges s ..
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(3) The urfteen se suelecties of the revised spessesre, doofen change er mostffeatten
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If a safety escluetten is not required er is tesemplete for any reases, empleta en
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perte A and B of this Safety tweluetten Chest Lfst are to to' completed only a to teefs of the safety evaluetten performed.
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.. O B E LIST . PRET A (3.1) Tee 1 as _ A shenge to the plant as described in tRd 75 ART ;
j (3.3) Its _ h 1 A shenge to precederne as deserthed fa tre FSAAf i l
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$3.3) Tee _ Re d A test er auserfeert est deserfted la the PEART l (3.4) ?se _ As 1 A abange to the plant teshafael seestffeations (Appensis A to the Werettag Lleense)t (4) ONE LIST . fAsf 8 (Justiftestfee ese part I ameners emot to insiemed en page 3.)
(4.1) fue _ as ,,,,X,,,, W11 the probettif ty of as asefdont proviene1y esclusted to the F344 to toereeneef (4.3) fte _ Re X Wil the ennessmenses of an assident prettauely :
... . evaluated to the PSAR to increasset (4.3) vte _ lhe X lity the pestin111ty of an aesfeent unten is effferent than any already evaluated le the 75AR to treateer i L
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ORM 2 W 3 (4.4) hs _ es 1 W11 me presettitty of a selftmetim of eestment tesertent to safety presteesly sueleeted to tee fB M he tsaressest (4J) IIIe h 1 W11 me ennesennese of a anlinesesten of aestament i
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- If the asemers to any of the atese geanteens are witness. testate ender (5) EMAES
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WCItAA SAPETY EVAlUATICM CHECK t.!sf
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i The following sunnarizes the ,fustification, based upon the written safety evaluation $l),
for answer $ given in Part I of the Safety Evaluation Check tfsts i i In actual measured performance, the, centrifugal charging pumps have met but HHSI pumps at Sequoyah Unit Two have failed to meet design flowrates. The mpact of redu'c ed flow on the large break and small break LOCA analyses which upport plant ' operation during Cycle 2 must be evaluated and shown to be acceptable. The large break ECCS performance analysis was redone for Cycle 2, while the smal'l break analysis of record remains that pres *ented in,the Sequoyah FSAR.
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Pumps safety ilnjection is modeled in bulli tlie UHISATAN and Ull!',mE codes in the large break LOCA analysis. The effect of the reduced safety injei. Lion ficW on large brcok performance is accommodated within the recent LOCA analysis.I Overly conservative input for SI flow was utilized in the analysis Since that ana1 sis demonstrates ,
along with 10% steam generator tube plugging.tnat tne Tech.' Spec. peakisig rec serv'atism in oth SGTP and SI flow input. Sequoyah 2 may be gperated safely with puw.p pei formance cs dccumented in the reference.
l In the Sequoyah small break LOCA.FSAR analysis, the six-inch and eight-inch break sizes gave calculated PCT values 10'F apart; both values were more than 40p'F higher in calculated PCT than the fo,ur-inch break. Since the core is uncqvered
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Tur+far-longer-peMod-of-t4mc4n-the-54 Mach bre@ em thAn in the eitht-inch case, the impact of lower pumped cafety injection shoyld be greater for the six-inch break, sc it will be the case evaluated herein. Core uncovery first occurs at 253.2 secords in the FSAR six-inch break case. At this time, the RCS pressure isabout800 dst. Water delivered by the UHI accumulator has enabled the core
- to remain covered! the impact of reduced SI flow to the cold legs is therefore small. Since.the UHI accumulator at this time has delivered basically all the
, watergtisggingtoandisabouttobeisolatedfrcmthevessel,thecorequickly}
I Amference to dooment(s) centaining written safety evaluations (Conti_nued
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l becomes uncovered and remains so until the cold leg accumulators provide the water necessary for recovery. Once the cold leg accumulator activates at 400 psi, the pumped SI flow will be a small contributor to the total water flow being delivered to the RCS. Clearly, the period of interest in assessing the effect reduced SI flow has on the Sequoyah six-inch break ECCS performance cal-culation is the period when system pressure is falling from 800 psi to 400 psi.
At 600 psig, the shortfall in pump flow is such that the total pumped SI flow-rate is reduced by ten percent from the FSAR value. Therefore, a reduction in pumped SI flow of ten percent needs to be evaluated for Sequoyah.
This evaluation supersedes a checklist on the same topic previously done for Sequoyah Unit 1. Since the reduction in pumped safety injection considered herein is greater than that previously evaluated for Unit 1, this evaluation bounds the impact of reduced SI flow for both units.
Since the core uncovery period in the six-inch break case is similar to a non-UH) plant uncovery transient (i.e., UNI effects are minimal), the non-UNI plant smal'.
- break sensitivity to changes in pumped injection flow may be applied. This sen-sitivity has been established as a 20*F increase in calculated PCT for each per-
! cent reduction in pumped SI flowrate. The impact of the Sequoyah shortfall is therefore estimated as (20).10 or a 200*F increase in PCT. Since the current l calculated PCT is less than 1500*F for all Sequoyah small breaks, adequate margir.
remains to assure compliance with thg 2200*F regulatory limit.
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.', Pmburgh Pennsylvania 15230 TVA-86-510 January 16, 1986 Mr. C. C. Mason
Reference:
Division of Nuclear Power RD #987400 Tennessee Valley Authority G0 #CO-41594 1750 Chestnut Street Tower Chattanooga, TN 37401 Tennessee Valley Authority Sequoyah Units 1 & 2 Safety Injection System Pumo Performance
Dear Mr. Maso.1:
As part of our analysis concerning Sequoyah Safety Injection System pump performance, Westinghouse is pleased to provide responses to the following items for TVA's information and use:
Item 1:
Provide the appropriate documentation to support TVA performing the ECCS Safety Injection testing portion of the Technical Specification using the flow measurement branch lines. element in the header to determine the flows in the
Response
The Sequoyah Units have been performing the Safety Injection Pump system testing to demonstrate corrpliance with Technical Specification 4.5.2.
TVA test results showed a significant difference between the flow measurement elements in the header and branch lines flow results. At that time TVA requested that Westinghouse recommend to TVA what flow measurement element should be used to demonstrate Technical Specification compilante. Westinghouse had performed a similar evaluation for TVA on the Centrifugal Charging Pump system and that work is documented in letter. TVA-83-624.
The Safety Injection Pumps are tested at the Pacific Pump test facility using sophisticated measurement techniques to develop the shop test data. Pacific Pump has assured Westinghouse that the element performance characteristics will not noticeably change when operating in the field. ~
4339e:12 4Mb
. TVA-86-510 C. C. Mason January 16, 1986 Also, Westinghouse has performed an evaluation of the effect of errors in flow measurement on measured pump performance (Attachment 1). Therefore, based on the Westinghouse study of the effects of errors in the flow measurement and the Pacific Pump sophisticated shop testing of the rotating element, it is Westinghouse's recommendation:
0 the Sequoyah Safety Injection System header be used to establish the total pump flow rate:
0 the branch line orifice differential pressures are to be used to determine the flow rate in each branch line:
0 the header flow measurement and the branch line differential pressures be used to demonstrate compliance with the Sequoyah Ttchnical Spectfications.
Attachment II provides a procedure for balancing the branch lines.
Item 2:
Provide the ' supporting documentation addressing the telecon between M. Harding (TVA) and R. Jansen/S. Swantner/D. Dudek in which Westinghouse recommended that when performing the ECCS Safety Injection Pump Test the .
gauge reading need not be corrected for instrument accuracy or elevation differences.
Response
The elevation variances between the RHST and the RCS are small (+25 ft.)
and it is Westinghouse's opinion that this would have an insignificant effect on injection flow during Safety Injection Pump testing. The effect is a +/- 2gpm variation in flow, which is relatively small.
Attached is a figure showing the +/-25 feet elevation difference and its effect on flow. The differential pressure instruments used in the ECCS testing are recommended to be within an accuracy of +/-17. of. Instrument span and are to be calibrated within its specification prior to the test.
During the conversation between TVA and Westinghouse it was stated that the instrument reading did not have to be corrected for any flow measurement inaccuracies. The following is information taken from the Technical Specifications and the ASME Section XI on flow measurement readings during pump testing:
Paragraph 4.5.2.f of the Sequoyah Technical Specifications provides acceptance criteria or reference values to be met when performing surveillance in accordance with paragraph 4.0.5. Paragraph 4.0.5 requires inspection of ASME Code Class 1, 2 and 3 components be in accordance with Section XI of the ASME Boller and Pressure Vessel Code. ,
The portion of Section XI applicable to pumps is Article IHP.
Paragraph IHP-3100 states: '
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TVA-86-510
, C. C. Mason - 4- January 16, 1986 Pacific Pump will not authorize operation of the Safety Injection Pump at 685 gpm. However, TVA may assume the responsibility for running at this point if in-plant testing shows that no cavitation occurs. The in-plant testing would require complete instrumentation of the pump to insure that pump operation at 685 gpm will have no detrimental effect on impellers are mounted in two opposed groups, back to back, which provides a balanced thrust for the rotating element. Cavitation in this type of pump can result in severe axial imbalance. -
If TVA has any questions or comments concerning the above, please contact me.
Very truly yours, HESTINGHOUSE ELECTRIC CORPORATION L. . Hilliams, Manager -
ESSO Projects Mid South Area cc: H. L. Abercrombie, IL IA M. R. Harding, IL 1A J. H. Sullivan, IL 1A R. U. Mathieson, IL 1A I. R. Williamson, IL 1A
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ATTACHMENT I .
I THE EFFECT OF ERRORS IN FLOW MEASUREMENT ON MEASURED PUMP PERFORMANCE FIELD EXPERIENCE Field test data for the charging and safety injection pumps at several I plants exhibits a consistent trend with respect to shop test data. This trend is characterized by a depressed total developed head (TDH) at runout for the field curve relative to the shop curve, and by relatively i equivalent performance for the two curves near the shutoff point. l Westinghouse has verified this relationship by performing our own reduction of the raw test data, making apprspriate allowances for the following factors: l l
1 Velocity head
- Differences in elevation between the static pressure gages used to i measure pump head
- Line losses between the static pressure gages Pump speed None of these factors has been found sufficient to explain the phenomenon. This has prompted additional investigations into possible causes for reduction in developed head common to all the pumps. The following have been considered:
Installation Differences. It may be postulated that some
- peculiarity of installation, common to all pumps, is to blame.
This is considered unlikely, however, as site visits by the vendor have confirmed the typical plant layout closely resembles their test loop. l
- Orifice Cavitation. This has been effectively ruled out, based on the fact that the plant layout provides adequate back pressure to prevent negligible effects on orifice coefficient.
- Measurement Error. The most likely theory seems to be that some i systematic error exists in the measuring system at the sites. ,
Systematic errors are characterized by consistency regarding both l sign and magnitude and because of their consistency may sometimes i be corrected by calibration. (Random errors, on the other hand, l are distinguished by their lack of consistency. Given the consistent nature of the problem, they may therefore be eliminated fromconsideration). We suspect the error exists in the field, rather than at the vendor's shop, because the vendor's tests are 1 of 3 05025.0073PW.S .
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t performed with laboratory quality equipment specifically designed and calibrated for that purpose. Furthermore, the vendor has been able to reproduce at their facility the results of tests originally performed in 1977, lending credence to our belief that the actual pumps' performance is greater than the performance measured in the field.
THE ASME FLOW COEFFICIENTS -
The ASME equations given in Reference 1 are industry standards for calculating orifice flow coefficients. These equat. ions are based on a series of tests pcrformed in 1932/33 at the Ohio State University under the supervision of Professor S. R. Beitler. The analysis of the data was originally performed at the National Bureau of Standards by Dr. E. Buckingham and H. S. Bean between 1933 and 1935 (Reference 2).
In 1970, the ASME commissioned a computerized reanalysis (Reference 3) of the Ohio State data as well as data from six other sources representing calibrations in recognized hydraulic laboratories in the United States. This analysis. indicates that at relatively high bore
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Reynolds numbers (R2 -s> /xAnd ) and orifice diameter ratios (870.7) a systematic bias exists such that calculated flow coefficients (and hence predicted flow) using the ASME equation would be consistently low relative to actual values. This is confirmed in a separate paper .
(Reference 4) based on orifice calibrations performed at the Foxboro hydraulic laboratories. Specifically, the laboratory calibration data indicates that for certain pipe diameters (e.g. 2 and 4 inch) and orifice diameter ratios weigh tank and it(me measurements) are consistently higher than thoseB>0.7) the predicted by the ASME formula. In particular it was noted that:
a) the magnitude of the bias is greater for 2-inch orifices than for 4-inch orifices b) the magnitude of the bias increases with increasing orifice diameterration(S) i l
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REFERENCES
- 1. Fluid Meters, Their Theory and A3 plication , American Society of Mechanical Engineers, NY, NY, 5t1 ed., 1959, 6th ed., 1970.
- 2. " History of Orifice Meters and the Calibration, Construction, and Operation of Orifices for Metering," American Society of Mechanical Engineers, NY, NY 1935.
- 3. R. B. Dowell and YL Chen, "A Statistical Approach to the Prediction of Discharge Coefficients for Concentric Orifice Plates."
Transactions of the ASME - December, 1970.
1 R. W. Miller and O. Kneisel, "A Comparison Between Grifice and Flow 4.
Nozzle Laboratory Data and Published Coefficients." Transactions of the ASME - March, 1969.
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ATTACHMENT II HIGH HEAD SAFETY INJECTION FLOW B'ALANCING/RUN0VT ADJUSTMENT PROCEDURES The following procedures provides a method for adjusting the four High Head Safety Injection System (HHSI) branch line throttling valves such that the specified flow balance is established for the branch line and the specified flow distribution through the SI header with mini-flow is obtained.
The flow indicator, across the HHSI System header flow element FE-918/922 will be used to establish the actual HHSI header flow rate.
The flow indicator, across the comon mini-flow path flow element FE-973, will be used to establish the mini-flowrate. The four branch line indicators will be used to balance each of the four HHSI System branch lines flow resistances.
This operational procedure should be performed only after the pump with the lower TDH at runout has been identified as the weaker pump. This pump will be operated during the adjustment of the cold leg branch line throttling valves. Note that subsequent operation of the stronger pump must not produce a runout concern. If necessary an orifice plate must be installed at the strong pump discharge to limit flow to its runout.
During the following operations, the four HHSI system cold leg branch line throttling valves will be adjusted independently such that the branch line flows are balanced and the total HHSI flow delivered through the four branch lines is the Tech Spec value in 4.5.2.
The following procedures can be used to balance the branch line:
o Each of the throttling valves are to be simultaneously opened, using the AP indicators to balance lines. The difference between the highest and lowest branch line should not exceed a Ah of 30 in.
o Continue the procedure until FE-918/922 indicates a flowrate tech spec o The HHSI Pump Flowrate should not exceed Pump Runout.
To determine the Technical Specification, the following equation can be used to determine the sum of the injection line flow rates, excluding 1
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the highest flowrate. Say, for ext.mple, that branch lines 1, 2, and 3 have the lowest flowrates as indicated by the orifice AP's. Then the sum of the three lowest branch line flows is:
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Electric Corporation DMslons scim i PifflOJ$n pOnf@fW8Sf81NSJ TVA-86-671 FSD/CWBS-239 June 27, 1986 Ref.: 1. TVA Memo, 2/10/86 from H.L. Abercrombie
?. W Prniect Letter. ~
Mr. J. A. Raulston TVA-83-632 ! Chief Nuclear Engineer 3. W Project Letter. l TENNESSEE VALLEY AUTHORITY TVA-84-057 1 400 West. Summit Hill Drive, 4. CO-41594; WAF-A10112 W10C126 Knoxville,TN 37902 Attn: H. L. Abercrombie TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT UNIT NUMBERS 1 AND 2 Seal Injection Flowrates Maximized
Dear Mr. Raulston:
Reference 1 t'ransmitted a request from the Tennessee Valley Authority (TVA) for Westinghouse to re-evaluate the ECCS Appendix K analysis for the Sequoyah Units 1 and 2 to reflect a Reactor Coolant Pump (RCP)sealinjectionflowrateof10.0~spmperpump. A brief description of each evaluation which has been perfomed prior to this request is listed belo'w: e Initially, the ECCS Appendix K analysis for the Sequoyah Units was performed with the assumptions of an 8.0 gpm seal injection flow per RCP with a pressure drop of 100 psig and a total RCP seal flowrate of 78 gpm at pump runout conditions. e Per Reference 2, the RCP seal injection flow at normal operations was then limited to 6.8 gpm per pump with a pressure drop of 138 psig and a total RCP seal flowrate of 70 gpm at pump runout conditions. This reduced seal flow allowed the Sequoyah Units to meet their technical specifications for the Centrifugal charging Pump injection flow, e A third evaluation was performed which determined that in order to _ obtain the desired total RCP seal flowrate of 72 gpm at pump runout conditions, a RCP seal flowrate of 9.75 gpm per pump was required, with a pressure drop of 100 psig. rn . . ::1.. w e-dai l
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y*, sa TVA-86-671 J. A. Raulston June 27., 1986 i{ In response to Reference 1, the seal water injection line resistance and flow l values have been evaluated for a seal flow of 10.0 gpm per RCP with a pressure drop of 100 psig and a total RCP seal flowrote of 74 gpm at pump runout conditions. In comparison, these results do not differ significantly from those obtained in tie third evaluation with a seal flow of 9.75 gpm per RCP at j normal operations. Therefore, the ECCS Appendix K analysis and the proposed ' revised Technical Specifications for the Sequoyah Units 1 and 2 (Reference 3) do not require ra-evaluation. In addition, Nuclear Safety was consulted ) regarding any necessary modifications to the Safety Evaluation Check List. It has been determined that the Check List transmitted to TVA per Reference 3 remains applicables no revisions are required. Should you have any questions or coments, please contact the undersigned. Yery truly yours,
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WEST NGHOUSE E ECTRIC CORPORATION W
. L. Williams, Manager Operating Plant Projects
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/CA Manno /plw/05025.0261.D Mid-South Region l cc: J. A. Raulston H. L. Abercrombie R. U. Mathieson I. R. Williamson M. A. Cooper i D. W. Wilson l
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Technicai s,-ification EMERGENCY CORE COOLING SYSTEMS . g SURVEILLANCE REQUIREMENT 5
- h. By performing a flow balance test during shutdown following completion .
of modifications to the ECCS subsystem that alter the subsystem flow characteristics and verifying the following flow rates:
- 1. For safety injection pump lines with a single pump running:
a.- The sum of the injection line flow rates, excluding the highest flow rate is greater than or equal to 444 gps, and
- b. The total pump flow rate is less than or equal to 660 gpm.
O 2. ,or .entrifu.ai charging , ump iines with . . ingle pum, running:
- s. The sum of the injection line flow rates, excludirig the highest flow rate is greater than or equal to 3,16 spm, and
- b. The total pump flow rate is less than or equal to 555 gpm.
- 3. For all four cold leg injection lines with a single RHR pump running a flow rate greater than or equal to 3976 gpm.
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, SIGNIFICANT HAZARDS CONSIDERATIONS
- 1. Is the probability of an occurrence or the consequences of an accident previously evaluated in the safety analysis report significantly increased?
No. The emergency core cooling system (ECCS) is designed to deliver adequate coolant flow to the reactor to meet the acceptance criteria of 10CFR50.46. Westinghouse has performed an analysis per 10CFR50 Appendix K to evaluate the effects of operating the ECCS within the limits specified by this amendment. This analysis concluded that although an increase in peak clad temperature (PCT) may occur, the PCT remains well below its limit of 22000F.
- 2. Is the possibility for an accident of a new or different type than evaluated previously in the safety analysis report created?
No. No new accident scenario is created by changing the flowrate requirements for the CCP and SIP portions of the ECCS at runout conditions. Runout conditions are experienced only during system operation post-LOCA and analysis has shown that PCTs resulting from the reduced performance are well within the 10CFR50.46 22000F limit. Evaluation has also shown that cavitation will not occur for SIPS operated at the increased maximum allowable flowrate; therefore, system availability is not affected.
- 3. Is the margin of safety significantly reduced?
No. The margin of safety provided by the ECCS is defined by the acceptance criteria for ECCS as present in 10CFR50.46. The analysis performed by Westinghouse (see reference 1) in their nuclear safety I checklist evaluates that this margin of safety is not approached. l l l l 0012h l l \ .
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r ENCLOSURE 3 Proposed Technical Specification Change Sequoyah Nuclear Plant Docket Nos. 50-327. -328 (TVA SQN TS 73) l Determination of No Significant Hazards Considerations for Proposed Changes to Flow Rate Requirements for ECCS Pumps w .i r.. . 7w . qqQ,
,/ SIGNIFICANT HAZARDS CONSIDERATIONS
- 1. Is the probability of an occurrence or the consequences of an accident previously evaluated in the safety analysis report significantly increased?
No .- The emergency core cooling system (ECCS) is designed to deliver adequate coolant flow to the reactor to meet the acceptance criteria of 10CFR50.46. Westinghouse has performed an analysis per 10CFR50 Appendix K to evaluate the effects of operating the ECCS within the limits specified by this amendment. This analysis concluded that although an increase in peak clad temperature (PCT) may occur, the PCT l remains well below its limit of 22000F. l 1 l
- 2. Is the possibility for an accident of a new or different type than evaluated previously in the safety analysis report created?
I No. No new accident scenario is created by changing the flowrate 1 requirements for the CCP and SIP portions of the ECCS at runout j conditions. Runout conditions are experienced only during system operation post-LOCA and analysis has shown that PCTs resulting from the ; reduced performance are well within the 10CFR50.46 2200 0F limit. Eraluation has also shown that cavitation will not occur for SIPS operated at the increased maximum allowable flowrate; therefore, system availability is not affected.
- 3. Is the margin of safety significantly reduced?
No. The margin of safety provided by the ECCS is defined by the acceptance criteria for ECCS as present in 10CFR50.46. The analysis performed by Westinghouse (see reference 1) in their nuclear safety checklist evaluates that this margin of safety is not approached. I l l
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