ML17258B153
| ML17258B153 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 06/30/1981 |
| From: | Maier J ROCHESTER GAS & ELECTRIC CORP. |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-15-07, TASK-15-7, TASK-RR NUDOCS 8107080182 | |
| Download: ML17258B153 (40) | |
Text
REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR: 810708018 DOC. DATE: 81/06/30 NOl IZED:
NO FACIL:50-244 Robert Emmet Qinna Nuclear Plant>
Unit 1> Rochester Q
AUTH. NAME AUTHOR AFFILIATION MAIER a J. E.
Roc h ester Qas Zc El ec tric Corp.
" RECIP. NAME RECIPIENT AFFILIATION CRUTCH=I ELDER D.
Operating Reactors Branch 5
For ward s resp onse to NRC quest 1 ons re SEP Top i c XV-7 concerning locked rotor transient. Effeet of.
pump coastdoton on locked rotor transient 0 comparison of-loss oF floe u~
loc ked rotor transientsi calculated bg vendorsi provided.
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i, IOAC zz ailzzrtrl ROCHESTER GAS AND ELECTRIC CORPORATION o
89 EAST AVENUE, ROCHESTER, N.Y. 74649 JOHN E.
MAILER VICE PRESIDENT TCCCPHONC AREA COOC 7IC 546.2700 June 30, 1981 Director of Nuclear Reactor Regulation Attention:
Mr. Dennis M. Crutchfield, Chief Operating Reactors Branch No.
5 U. S. Nuclear Regulatory Commission Washington DC 20555 Subj ect:
I SEP Topic XV-7; Locked Rotor Transient R.
E. Ginna Nuclear Power Plant
~'I Docket No. 50-244
Dear Mr. Crutchfield:
The two attachments to this letter are being sent to you for information in response to questions asked by members of the SEP Branch reviewing Design Basis Events.
The SEP reviewers requested information regarding the effect of a pump coastdown on a locked rotor transient.
Attachment B illustrates this effect using the Retran computer code.
Attachment A provides comparison of the loss of flow and locked rotor transients calculated by vendors for Ginna to the results calculated by RG&E with Retran.
As can be seen, the Retran calculations are bracketed by the vendor calculations.
From these results, we have reasonable confidence in the accuracy of the Retran
- Code, although it is not our intent to use the Retran results for licensing calculations.
The Retran cal-culations are used to check vendor calculations and produce relative sensitivity type calculations.
Very truly yours, Jo n E. Maier Attachments
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ATTACHMENT A The loss of flow transients consisting of pump coastdowns and locked rotor events have been compared.
The transient presented in Reference 1 by Exxon Nuclear (ENC) was compared to the same transient presented in Reference 2 by Westinghouse (W).
The flow coastdowns were also compared to startup test data from Ginna.
Figures 1 through 6 illustrated the difference in parameters calculated by the two vendors.
System parameters calculated by Retran are also illustrated.
Figure 1 illustrates total core flow during a two pump coastdown.
The Ginna startup test data is represented by The flow coastdown calculated by Westinghouse is con-servative with respect to the Ginna data.
Westinghouse claims to have taken pressure drops at. their maximum value.
The flow coastdown calculated by ENC is initially unconservative with respect to Ginna data but then becomes conservative toward the end of the transient.
Retran underpredicts the coastdown for the first 5 seconds based on Ginna data.
Figure 2 compares the flow coastdown calculated by Retran to that, from Ginna startup test data for a one pump coastdown.
The comparison is good.
Figure 3 illustrates reactor power during the transient.
The reactor is tripped 0.6 seconds after flow in either loop decreases below 878.
Since Westinghouse calculates a faster flow coastdown, trip occurs sooner in the Westinghouse transient than that for Retran or ENC.
The Retran transient is bounded by the two vendor calculations.
Figure 4 illustrates the DNBR calculated by the two vendors and Retran for this transient.
The following state points are presented for interest at the minimum DNBR point:
t total flow power pressurizer pressure-psia oF DNBR Westinghouse 78.5 72 1.495 Retran 82 ~
93.5 2243 580.9 1.613 ENC 83 83 2242 584.3 1.61 The faster flow coastdown calculated by Westinghouse causes a lower DNBR even though power is less.
The DNBR for Retran and ENC are similar even though power and tempera-ture differ slightly.
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Figure 5 illustrates the change in pressurizer pressure during the transient.
As shown in other comparisons, Exxon pressure response is slow compared to that of Retran.
Nesting-house did not present pressure in Reference 2.
Figure 6 illustrates the change in Tave and the change in hot leg and cold leg temperatures (TH'.and 'TG respectively).
Exxon and Retran compare favorably until approximately 5
sec.
The difference after 5 sec,. is most likely due to the earlier trip and associated power reduction in Retran.
The Retran two pump coastdown model appears to give reasonable results when compared to the transients calculated by the two vendors'n addition, the Retran flow coastdown is in good agreement with plant data.
The locked rotor transient results calculated by the two vendors and Retran are presented on Figures 7 though 9
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Figure 7 illustrates total and loop flow for the locked rotor transient.
The initial portion of the flow coastdown is slowest for Exxon and fastest for Nestinghouse.
Again the Retran model is bracketed by the two vendors.
A slight flow perturbation occurs in the Retran results when the dead loop flow reverses.
The Ginna startup data indicates a similar effect for the one.pump coastdown but the effect is not as noticeable.
The dead loop flow, calculated by Retran is larger than that calculated by Nestinghouse.
A similar effect was noticed in the pump coastdown transient.
Increasing the loop pressure drops in the Retran model may result in closer agreement.
However, the asymptotic total flow calculated by the vendors and Retran is in good agreement.
Figure 8 illustrates pressurizer pressure during the transient.
As illustrated in other transient comparisons, the Exxon model pressure change is slower than that of Retran or Nestinghouse.
The Nestinghouse analysis presented in Reference 2 states that the transient was started from 2250+30 psia.
The curve plotted in Reference 2 starts at 2330 psia.
The reason for the discrepancy is not known.
The Exxon and Retran transient are both started at 2250-30 psia to minimize initial DHBR.
The following figures compare only Exxon and Retran parameters because compatible Nestinghouse results are not available.
Figure 9 illustrates reactor power calculated by Exxon and Retran.
Since loop flow decreases to 874 in both models at approximately the same time, the reactor power change is very similar.
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Comparing the figures for the loss of flow and the locked rotor transients indicates that the Retran results fall between those calculated by Exxon and Westinghouse.
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References XN-NF-77-40, "Plant Transient Analysis for the R.
E. Ginna Unit 1 Nuclear Power Plant,"
November 1977 "Rochester Gas and El'ectric Corporation R. E. Ginna Nuclear Power Plant Unit No.
1 Technical Supplement Accompanying Application to Increase Power" February 1971
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46 1242 FIGURE 1 TWO PUMP COASTDOWN TOTAL FLOW ENC r
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46 1242 FIGURE 2
Retran Total Flow ONE PUMP COASTDOWN FLOW.
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Ginna Data Retran Loop B Flow Tiine (seconds)
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TWO PUMP COASTDOWN POWER Retran ENC Westinghouse E(
F Time (seconds)
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46 1242 Retran ENC Westinghouse
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TWO PUMP COASTDOWN DNBR Time (seconds)
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46 1242 FIGURE 5, TWO PUMP COASTDOWN PRESSURE CHANGE ENC Retran S
Time (seconds)
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FIGURE= 6 TWO PUMP COASTDOWN CHANGE IN PRIMARY TEMPERATURE ENC H
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LOCKED ROTOR FLOW Total Flow Westinghouse Total Flow f@QVr Westinghouse Dead Loop Retran otal Flo~;
Retran Dead LooP Time (seconds)
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46 1242 Westinghouse Retran ENC FIGURE 8
LOCKED,ROTOR PRESSURIZER PRESSURE Time (seconds)
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46 1242 FIGURE 9
LOCKED ROTOR POWER
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ATTACHMENT B The purpose of this attachment is to illustrate the effect of a pump coastdown and locked rotor,event.
Previous analyses have assumed that the operable pump was not. tripped but remained running.
Figure 1 illustrates the difference in total core flow with and without the good loop coasting down.
As expected total flow is less for the case with the good loop coasting down.
According to the Exxon Nuclear Analysis, minimum DNBR occurs at approxi-mately 2.2 seconds as illustrated on Figure 6.
Figure 6
was taken from Reference
- 1. 't this time there is approximately a 4 percent reduction in flow due to pump coastdown.
This should decrease DNBR.
Figure 2 illustrates the differences in good "loop flow and locked rotor loop flow.
As expected, there is a difference in good loop flow.
The locked rotor loop flow is approxi-mately the same until flow reversal occurs; then the difference in the good loop pump head causes different reverse flows through the locked rotor.
Figure 3 illustrates core power for both cases.
Since the initial flow response is similar for both cases in the locked rotor loop, trip occurs at approximately the same time resulting in no change in the power response.
Figure 4 illustrates pressurizer pressure for both cases.
Since total flow is less for the case with the good loop coasting down heat transfered to the steam generators should be less.
This would cause a greater heatup of the primary system resulting in a greater pressure.
The minimum DNBR occurs around 2 seconds.
At this time the pressure in both cases is approximately the same.
Therefore, there is no increase in DNBR due to pressure difference.
Figure 5 illustrates core inlet temperature and average core temperature.
For the first 5 seconds core inlet temperature for the two cases is similar.
After 5 seconds the inlet temperature for the good loop operating case is greater because of the greater flow.
The converse is true for core average temperature.
The lower core flow associated with the coasting down of the good loop results in greater heatup of the water which results in higher core average temperatures.
Since core inlet temperature is the same around the time of minimum DNBR there is no DNBR decrease due to inlet temperature.
The effect on DNBR of the good loop coasting down can be estimated by comparing the change in the major DNB parameters at, the point of interest.
Since minimum DNBR occurs around 2 seconds, the parameters for the two cases are presented below.
Locked Rotor Locked Rotor
& Coastdown time seconds total flow core power 2 ~ 0 55
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2 '
2.4 54.2 53.1
'9.5 48.7 2 '
2 ~ 2 2 '
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- 48. 5 70-0,
'59.2 48.6 pressure psia 2298 2315 2335 2301 2319 2338 core inlet temp.
oF 548.0 548.1 548.2 548.0 548.1 548.2 DNBR flow
-0.11
-0.12
-0.12 DNBR 1.235 1.230 1.240 1.125 1.11 1.120 The above DNBRs were obtained by reducing the flow to the hot channel in a 100$ power steady state run.
Since core power, pressure, and core inlet temperature are approximately the same for the locked rotor transient with and without loop coastdown, the DNBR associated with these parameters is negligible.
The calculated DNBRs should be used to indicate the sensitivity of minimum DNBR to pump coastdown.
They should not. be used as precise values.
The analysis demonstrates a slight minimum DNBR reduction for a locked rotor transient with a pump coastdown compared with the case with the intact pump remaining in operation.
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References XN-NF-77-40, "Plant Transient Analysis for the R.
E. Ginna Unit 1 Nuclear Power Plant,'"
November 1977 "Rochester Gas and Electric Corporation R.
E. Ginna Nuclear Power Plant Unit No.. 1.Technical Supplement Accompanying Application to Increase Power" February 1971
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46 1242 LOCKED ROTOR + COASTDOWN FIGURE 1
TOTAL FLOW Locked. Rotor Locked Rotor + Coastdozn 6'ime (seconds)
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46 1242 Locked Rotor Good Loop Locked Rotor + Coastdown Good Loop LOCKED ROTOR + COASTDOWN FIGURE 2
LOOP FLOW Locked Rotor + Coastdown eaa l.oop
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POWER Locked Rotor Locked Rotor + Coastdown Time (seconds)
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PRESSURIZER PRESSURE Locked Rotor + Coastdown-Locked Rotor Time (seconds)
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46 1242 LOCKED ROTOR + COASTDONN FIGURE 5
TEMPERATURE AVE Locked Rotor + Coastdown Locked Rotor AVE IN Locked Rotor Locked Rotor + Coastdown IN Tame (seconds)
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