ML20082P669
| ML20082P669 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 04/20/1995 |
| From: | George Thomas DUQUESNE LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9504270111 | |
| Download: ML20082P669 (16) | |
Text
.
D rmine L.ijlt COfT4XM1y S*fifl*v" **' S
ggA --
(412) 643-8069 FAX GEORGES. THOMAS ll%," R,'f,',""*"' '
April 20,1995 Nuclear Power Division U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001
Subject:
Beaver Valley Power Station, Unit No. 2 Docket No. 50-412, License No. NPF-73 Proposed Operating License Change Request No. 93 Submitted on April 10,1995 The purpose of this letter is to forward the results of our engineering evaluation of the revised pump 2RSS*P21A performance values for developed differential pressure and flow. Upon completion of repairs, pump 2RSS*P21A was retested on April 17, 1995. The pump performance value for developed differential pressure, when corrected to the 3500 gpm flow point, is approximately 110.5 psid. As agreed upon in a telecon conducted between members of the Beaver Valley Power Station staff and members of the Nuclear Regulatory Commission staff on April 12, 1995, the attached contains the revised engineering evaluation of pump 2RSS*P21 A performance values.
The analysis, which supports the revision of pump 2RSS*P21 A performance acceptance criteria, is contained in Attachment A. A summary of the analysis results and action plan is contained in Attachment B.
If you have any questions regarding the attached information, please contact Mr. Nelson R. Tonet, Manager, Nuclear Safety, at (412) 393-5210.
Sincerely, v$
"3 George S. Thomas Attachment c:
Mr. L. W. Rossbach Sr. Resident Inspector Mr. T. T. Martin, NRC Region I Administrator Mr. D. S. Brinkman, Sr. Project Manager I
Mr. W. P. Dornsife, Director BRP/ DER Mr. R. Maiers (BRP/ DER) 9504270111 950420 1 i PDR ADOCK 0500o412 i
P PDR g
ATTACHMENT A Analysis To Support the Revision of Pump 2RSS*P21A Performance Acceptance Criteria
Duquesn Light C:mpany At i SIS NO.
10080 24-0 PAGE A'
COMPil.ED BY cDeM DATE % S'*/
OF
'd Analysis Sh::t CHECKED BY.(( h [
DATE #er".r PAGE I2 v =
is PURPOSE The purpose of this analysis is to determine the minimum RSS pump performance requiremuts as a function of the number of tubes plugged in the associated RSS heat exchanger. This analysis will apply only to 2RSS-P21A and 2RSS-P21B. Additional evaluations would be required for 2RSS-P21C and 2RSS-P21D due to the additional functions of these pumps during the SI recirculation mode of operation.
I
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BACKGROUND The Recirculation Spray System at Beaver Valley Unit 2 consists of four subsystems which consist of a pump, a heat exchanger, and associated piping from the containment I
sump to the spray header. The function of the individual subsystems is not identical. The 2RSS-P21 A and B pumps provide spray water from the sump, through the associated heat exchanger, to the spray ring following a CIB. The 2RSS-P21C and D pumps also start on CIB and supply flow to the spray header through the associated heat exchanger until a transfer to SI recirculation mode occurs. At this point, the C and D pumps re-align to supply the low head SI header and HHSI pump suction.
The containment analysis n vides the basis for the minimum system requirements.
The system performance is input into the containment analysis program as system flow to the spray header, and a UA value which defines the performance of the heat exchanger.
Also, Service Water flow and temperature impact the heat exchanger performance and therefore, the spray temperature or the SI recirculation flow temperature during recirculation mode. Spray effectiveness is also input and is dependent to some degree on spray flow. The system performance is important in consideration of limiting cases for depressurization tima and sub-atmospheric peak pressure. Peak containment pressure is not affected since the peak prrssure occurs prior to startup of the spray systems and is j
therefore not considered as part of this evaluation. The current design basis analysis includes allowance for degradation in both the pump and the heat exchanger. The current system flow to the spray header is based on pump performance at approximately 4%
below the design value. This performance is consistent with the current Tech Spec limit of 112 psid at 3500 gpm. The allowable tube plugging level in the RSS heat exchangers is cuirently analyzed for 100 @es. The margins on spray system flow and tube plugging level are interchangeable, i.e., reducing the margin in tube plugging will allow an increase in the pump margin and vice versa. However, since the current pump performance limit is a Technical Specification, the flexibility to change this limit easily is not available.
Therefore, it has been proposed that a Tech Spec amendment be submitted to allow the performance limits on the pumps to be controlled by the IST program which is based on the analysis limits anu can be changed under 10CFR50.59. This analysis will define the relationship between the minimum pump performance for the A and B pumps and the heat exchanger tube plugging levels.
Duquesne Light C:mpany ANALYSIS NO.
10080-N-724-0 PAGE 8
^7*
COMPILED BY _ OO J?
DATE~* W OF An lysis Sh00t CHECKED BY
. /2 DATEvhe/r5 PAGE N2-METIIOD OF ANALYSIS The following steps were followed to generate the results:
- 1. Choose a spray system flow. This flow is defined by the intersection of the system curve and a corresponding degraded pump curve as shown on Figure 1.
The corresponding Minimum Operating Point (MOP) for this " analysis" flow is determined by the TDH associated with the pump curve at a flow of 3500 gpm. The MOP could theoretically be anywhere on the pump curve but will be defined at the 3500 gpm value in order to be consistent with the current MOP for the C and D pumps.
- 2. Perform a STER analysis of RSS heat exchanger in order to determine the UA (heat transfer coeflicient x surface area) value at the selected flow and various plugging levels.
These values are used as input for the LOCTIC containment analysis. STER is a heat exchanger analysis program that is capable of calculating performance at off-design conditions.
- 3. Run the LOCTIC contrNment analysis program to determine the maximum tube plugging level which results in acceptable results for a given spray system flow. Initially, runs are performed for the limiting sub-atmospheric peak pressure. Additional cases are then performed to confirm acceptable results for depressurization time and non-limiting subatmospheric peak pressure cases defined by the Maximum Allowable Primary Containment Air Pressure (MAO) curve (Figure 3.6-1, Reference 1). Also, an evaluation of the impact on the Main Steam Line Break analysis and the spray system efTectiveness will be performed.
- 4. The results of the acceptable combinations of flow and tube plugging level will be presented in terms of minimum pump performance (MOP) vs. tube plugging level.
D ' SIGN INPUTS
- 1. LOCTIC inputs are derived from the standard input base deck (B ASE2R) which has t
been updated to the current code version and verified in Reference 9.
- 2. Specific change card file inputs for each case listed are attached. The initial conditions for containment pressure and temperature are based on the MAO curve from Reference 1 for various Service Water Temperatures.
- 3. Design conditions for input to the STER program are based on Reference 8 results page 14, liTRI Shell and tube Heat Exchanger Program ST-5 Mod 0.10-1.05 1
QUqu;5n3 Light Campany ANALYSIS NO.
10080-N-724-0 PAGE r^r*
COMPILED BY Ch')
DATE #77 O OF l
- Di An: lysis Shect CHECKED BY
[M, DATE v/'J/ff PAGE N2 REFERENCES
- 1. Beaver Valley Unit 2 Technical Specifications
- 2. STER User's hianual; Holtec Report HI-88228
- 3. LOCTIC User's Manual; Reissue January 1993; Stone & Webster Engr. Corp.
- 6. Csiculation 10080-DMC-0080-0; Heat Exchanger Performance at Increased River Water Temperature (89 F)
- 7. Calculation 10080-PH(B)-174-0; Recirculation Spray Heat Exchanger UA Study for Tube Plugging Margin Analysis
- 8. Calculation 10080-DMC-0081-0; Recirculation Spray Heat Exchanger UA Study
- 9. Calculation 17800-US(B)-223-1, Addendum 1; Confirmation of 89 *F Tech Spec Curve with Reduced Service Water Flow
- 10. Calculation 10080-N-716-0; Containment Response for Degraded Condition of 2RSS-P21A
- 11. Calculation 12241-US(B)-193-0; Maximum Head Degradation of Quench and Recirculation Spray Systems l
ACCEPTANCE CRITERIA Acceptable results from LOCTIC containment analysis are demonstrated by depressurization times ofless than I hour, and maintenance of subatmospheric conditions thereafter. Of particular interest for this analysis is the pressure peak which occurs following depletion of the RWST (sub-atmospheric peak pressure). The sub-atmospheric peak pressure is sensitive to performance of the recirculation spray system since this remains as the only containment atmosphere heat removal system following RWST depletion.
l 1
.~.
I Duquesne Light Campany ANALYSIS NO.
10080-N-7210 PAGE E COMPILED BY.
C 'v 2
- * @r N *An: lysis'Sh:st CHECKED BY
.2de ___
DATE
- W OF i
DATE */< t'r5 PAGE M ASSUMPTIONS
- 1. A standard assumption for the containment analysis has been to use the minimum UA value calculated for the spray temperature at the RWST depletion time.
This is conservative since at higher spray temperatures earlier in the transient, the UA value is higher. This is required due to the fact that LOCTIC will only accept a single value for this parameter, i.e., it can not be time dependent.
- 2. The degraded pump curves generated are asstmed to follow a constant percentage degradation from the reference curve or the manufacturer's curve. This is standard practice for pumps in the IST program with minimum performance defined by a single point.
t
- 3. Spray system flows are determined by the intersection of the system curve and the pump performance curves. The system curve is based on static head with minimum sump level and is therefore conservative since spray system flow will increase as sump level increases throughout the transient.
BODY OF ANALYSIS The STER program, when run in the design point mode, requires a set of design conditions and various physical parameters. The following values taken from Reference 8 were used:
Service Water Flow 5500 GPM Service Water Inlet Temperature 89 F Spray Flow 3440 GPM
^
Spray Inlet Temperature 111.4 F Design Fouling
.0003 HR-sq. ft-F/B'IU Number ofTubes 1148 Overall Heat Transfer Coeflicient 523.65 BTU /HR-sq. fi-F Tube O.D.
0.625 in Tube Material 304 SS Tube Thickness
.035 in Effective Tube Length 36.75 ft These values establish the base conditions from which the STER program calculates performance at other off-design conditions. Runs were made for various spray flow, tube plugging levels and service water temperatures. The results are shown on Table 1. ' Note that a constant U value was used for the range of tube plugging levels for each spray flow condition. Initial runs were performed for each plugging level, however, the U value did not change significantly based only on changes in the tube plugging level. Therefore, the
Duqtcsne Light Campany ANALYSIS NO.
10080-N-724-o PAGE 6
^:
- COMPILED BY OCM DATE T Wrr OF cC Analysis Shret CHECKED BY dhm Ax '
DATE 4/d/rs-PAGE kJ.-
//
constant value is used along with the area associated with the tube plugging level to calculate the overall UA value.
LOCTIC runs were performed at various RSS spray flow rates to determine the minimum UA value which would yield acceptable results in terms of sub-atmospheric peak pressure for the limiting case. The limiting case was established by review of the results of Reference 9. For sub-atmospheric peak pressure, the most limiting case occurs with a minimum containment temperature of 100 F and a service water temperature of 89 F.
An additional run was performed at 87 *F and a minimum containment temperature of 85
'F to confirm that this remains as a non-limiting case for sub-atmospheric peak pressure.
Additional cases were run to confirm that depressurization times were acceptable for the revised conditions of spray flow and tube plugging. These were run over the range of spray flow and tube plugging levels established by the sub-atmospheric peak pressure results. The depressurization time limiting case has been shown in previous analyses to occur at lower Service Water temperatures.
A case was run at 53 F and the corresponding containment initial pressure and temperature conditions to evaluate the efTect of reduced flow / tube plugging.
Degraded pump curves were generated corresponding to the operating spray flow points analyzed as shown on Figure 1. The TDH associated with the degraded curves at 3500 gpm defines the new MOP for the given flow condition. These values are listed in Table 4.
A review of the Main Steam Line Break analysis results indicates that the limiting cases for peak containment pressure result from large breaks at 30% power.
The time associated with the peak pressure is approximately 260 seconds. This indicates that the peak pressure occurs prior to startup of the recirculation spray pumps and will therefore not be affected by changes in system performance.
Recirculation Spray system effectiveness is calculated based on test results which provide droplet size distribution and dispersion data. The tests were conducted and the calculation was based on a pressure drop of 10 psi across the nozzle. Based on the system head loss calculation, this minimum pressure drop corresponds to a system flow of 2200 gpm. Since none of the system flows based on pump degradation drop below this value, spray system effectiveness is not impacted.
i
QUQUCSn3 Light C:mpany ANALYSIS NO.
10080-N-724-0 PAGE 7 COMPILED BY OCd DATE j Mh r OF PAGEk2 Analysis Sh;et CHECKED BY
// d ____
DATE j i/f5 RESULTS The results of the final containment runs at various flow conditions are shown in Table 2.
Table 3 shows the results of runs done for confirmation of depressurization time acceptability at various flow and tube plugging conditions.
The results of this analysis are presented in Figure 2 as a curve of MOP as a function of tubes plugged in the associated heat exchanger.
e F
6
TABLE 1: RECIRCULATION SPRAY HEAT EXCHANGER PERFORMANCE (UA) 87 F SW SPRAY FLOW (GPm 3275 3300 3320 3335 3350 3380 3390 3400 3440
" "^
^
517.97 518.57 519.11 519.41 519.76 520.46 520.69 520.92 521.84 s FT.F
UA(BTU /HR F)
UA(BTU /HR F)
UA(BTU /HR F)
UA(BTUN F)
UA(BTUN F)
O 3575599 3579741 3583468 3585539 3587955 3592787 3594375 3595963 3602314 20 3513306 3517376 3521038 3523073 3525447 3530195 3531755 3533315 3539556 28 3488389 3492430 3496067 3498087 3500444 3505158 3506707 3508256 3514452 40 3451013 3455011 3458609 3460607 3462939 3467603 3469136 3470668 3476798 60 3388721 3392646 3396179 3398142 3400431 3405011 3406516 3408021 3414039 80 3326428 3330281 3333749 3335676 3337924 3342419 3343896 3345373 3351281 100 3264135 3267916 3271319 3273210 3275416 3279827 3281276 3282726 3288523 120 3201843 3205552 3208890 3210744 3212908 3217235 3218656 3220078 3225765 140 3139550 3143187 3146460 3148278 3150400 3154643 3156037 3157431 3163007 160 3077257 3080822 3084030 3085812 3087892 3092051 3093417 3094783 3100249 180 3014965 3018457 3021600 3023347 3025384 3029458 3030797 3032136 3037491 200 2952672 2956092 2959171 2960881 2962876 2966866 2968177 2969488 2974733 89 F SW smAY FLOW (GPM) 3275 3300 3320 3335 3350 3380 3390 3400 3440 Fr.' F 519.73 520.37 521.2 521.46 521.64 522.39 522.74 522.89 523.87 s
8 TUBES PLUGGED UA(BTU /HR F)
UA(BTU /HR F)
UA(BTUN F)
UA(BTU /HR F)
UA(BTU /HR F)
UA(BTU /HR F)
UA(BTUN F)
O 3587748 3592166 3597896 3599691 3600933 3606110 3608526 3609562 3616327 20 3525244 3529585 3535215 3536978 3538199 3543286 3545660 3546678 3553325 28 3500242 3504552 3510142 3511893 3513105 3518156 3520514 3521524 3528124
{'
40 3462740 3467004 3472533 3474266 3475465 3480462 3482794 3483793 3490323 60 340023G 3404422 3409852 3411553 3412731 3417638 3419928 3420909 3427320 80 3337731 3341841 3347171 3348841 3349997 3354814 3357061 3358025 3364318 g;
100 3275227 3279260 3284490 3286129 3287263 3291989 3294195 3295140 3301316 yl 120 3212722 3216678 3221809 3223416 3224529 3229165 3231329 3232256 3238314 e-140 3150218 3154097 3159128 3160704 3161795 3166341 3168462 3169371 3175312 160 3087714 3091516 3096447 3097991 3099061 3103517 3105596 3106487 3112309 g
180 3025209 3028935 3033766 3035279 3036327 3040692 3042730 3043603 3049307 J
^'
200 2962705 2966353 2971085 2972567 2973593 2977868 2979863 2980718 2986305 L
h
RESULTS OF CONTQiNMENT ANQLVSES T art E 2 CONT AINMFNT SUB ATMOSPHERIC PEAK C' AESSURE RFSULTS
' '^
RSS HX INITIAL SUB ATMOS RSS PUMP BSS HX UA SW TEMP CONT CASE CONT PEAK FEESSURE FOW (GPM)
(BTU /te F)
(F)
PRESS TWPO M)
(PStA) 1 3440 100 3301316 89 10.20 100 4.04 2
3400 80 3350025 89 10.20 100
-0.02 3
3350 40 3475465 89 10.20 100 4.01 4
3335 28 3511893 89 10.20 100 4.01 5
3320 0
3597896 89 10.20 100 4.01 6
3320 0
3583468 87 9.85 85 4.05 T art E 3 CONTAINMENT Of PRESSimt?ATtON TIME RESULTS RSS PUMP RSS HX UA SW TEMP CO T DEFHESS TIME g
O FOW (GPM)
PLUGGED TEMP (F)
(PSIA) 7 3440 100 3208523 87 9.85 85 3490
=
8 3440 100 3053910 53 11.10 85 3570 9
3400 80 3345373 87 9.85 85 3480 10 3350 40 3462939 87 9.85 85 3480 11 3320 0
3583468 87 9.85 85 3480 b
TART E 4 MINIMUM TDH @ 3500 GPM
^
ANALYSIS
- TUBES FLOW (GPM)
PLUGGED T
(FEET)
CURVE (%)
3440 100 260 4.06 %
[
3400 80 250 5.54 %
3350 40 251 7.38 %
3335 28 250 7.75 %
3320 0
248 849%
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i 3200 3250 3300 3350 3400 3450 3500 3550 3600 3650 3700 3750 RSS PUMP FLOW [GPM]
FIGURE 1
dt.
2RSS-P21 A,B MOP VARIANCE BASFsD ON RSS HX TUBE PLUGGING 260 i
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0 10 20 30 40 50 60 70 80 90 100 TUBES PLUGGED IN ASSOCIATED RSS HX (# TUBES)
FIGURE 2
ATTACHMENT B Summary of Analysis Results and Plan of Action l
A
Summary of Analysis Results and Proposcd Plan of Action Acceptable pump performance at various heat exchanger plugging levels has been plotted on a graph (Attachment A, Figure 2). The data which supports this graph is 1
contained in Tables 2 and 3 of Attachment A.
As shown in Tables 2 and 3, the subatmospheric peak pressure reaches a maximum of.01 psig while the containment depressurization time reaches a maximum of 3570 seconds for the various cases of j
recirculation spray pump flow and heat exchanger plugging levels.
Therefore, by selecting a pump developed head value at a given heat exchanger plugging level in the
)
area of the curve designated as " Acceptable Operation," the design basis requirement for the containment depressurization system will continue to be met.
Also shown on Figure 2 is the current pump performance level at the curren: heat exchanger pluggmg l
level. This point is clearly in the acceptable operation area.
It has been demonstrated that the acceptance criteria for pump 2RSS*P21A can be revised to correspond to the 250 ft. developed head point at the current plugging level of 28 tubes. The containment depressurization time which corresponds to the revised acceptance criteria stated above is bounded by the limiting case for depressurization time of 3570 seconds. The subatmospheric peak pressure which corresponds to the revised acceptance criteria stated above is bounded by the limiting case for subatmospheric peak pressure of.01 psig. The curve titled " Recirculation Spray Pump [2RSS*P21A] Head Curve," contained in this attachment, shows a graphical representation of actual pump performance versus the revised acceptable pump performance, which is defined as the analysis minimum operating point (MOP) curve.
The MOP curve, which is to be incorporated in the Insenice Testing Program, is also contained in this attachment.
It should be noted that there are additional margins that ensure the transient analysis results for this recirculation spray subsystem will be conservative.
These margins include the following conservative assumptions:
- 1. A standard assumption for the containment analysis has been to use the minimum UA value calculated for the spray temperature at the RWST depletion time. This is required due to the fact that LOCTIC will only accept a single value for this parameter, i.e., it cannot be time dependent. This approach is conservative since at higher spray temperatures earlier in the transient, the UA value is higher.
- 2. Spray system flows are detennined by the intersection of the system curve and the pump perfonnance cunes. The system curve is based on static head with minimum sump level and is therefore conservative since spray system flow will increase as sump level increases throughout the transient.
In addition, the analysis assumes a maximum service water temperature of 89 F. The site maximum temperature was 86 F as recorded in 1988. Therefore, the maximum site river water temperature of 86 F provides additional conservatism.
i RECIRCULATION SPRAY PUMP [2RSS*P21 A] HEAD CURVE 260 NEW PUMP CURVE (4/17/95) 15 g A' %
250 MOP CURVE w
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,g 210 3500 3550 3600 3650 3700 3750 3800 3850 3900 3950 FLOW (GPM)
DATA FOR BASELINE PUMP CURVE WAS OBTAINED BY MOP POINTIS AT 250 FT AT 3500 GPM ANDIS BASED 2BVT 1.13.5 USING TEST PRES GAUGES ON 4/17/95.
ON THE NUMBER OF TUBES PLUGGED IN [2RSS*E21 A1 MOP CURVE DERIVED AS 97.88% OF PUMP CURVE.
PER EM -
(CURRENT # TUBES PLUGGED = 28)
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DAT A POINTS:
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(FT.)
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2000 2250 2500 2750 3000 3250 3500 3750 4000 C
3 FLOW (GPM) 2 THE MOP CURVE IS BASED ON THE SHAPE OF THE MOP POINT IS AT 250 FT AT 3500 GPM AND IS BASED h
CURRENT PUMP PERFORMANCE CURVE AS A CONSTANT ON THE NUMBER OF TUBES PLUGGED IN f 2RSS*E21 AI
{
2 PERCENTAGE (97.88%) TO THE MOP POINT. (4/17/95)
PER EM
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