ML19317G944
| ML19317G944 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 02/01/1978 |
| From: | SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | |
| Shared Package | |
| ML19317G941 | List: |
| References | |
| NUDOCS 8004020601 | |
| Download: ML19317G944 (13) | |
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llh SECTION I - OVERVIEW Following the first refueling of Rancho Seco Unit #1, the startup test program was begun with initial criticality established at 2107 hours0.0244 days <br />0.585 hours <br />0.00348 weeks <br />8.017135e-4 months <br /> on November 2, 1977 Zero power physics testing commenced at that time and was successfully completed on November 5,1977 As planned, the Zero power physics testing program was conducted at the iso-thermal Reactor Coo' ant 0
temperature 532 F and below the power level commensurate with nuclear heat.
Power escalation and testing was begun on November 5 and completed on November 21 with the successful conclusion of the power imbalance detector correlation test.
The power escalation testing was done at the three major power plateaus of 40%, 75% and 100% of full power.
The following descriptions of test data and results refer to the Dis trict's Augus t 29, 1977 response to the Commission's August 17, 1977 request for detailed descriptions of test methods and procedures.
Re ference is made to that information rather than repeating it here.
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SECTION 11 - PRE-CRITICAL TEST The control rod trip time testing was done prior to establishing initial criticality and while maintaining refueling boron concentration.
The conditions were, all four Reactor Coolant pumps running with the Reactor Coolant system established at 532oF and a pressure of 2155 PSIG.
All of the droppable control rods, which are assigned to Groups 1 through 7, were fully withdrawn, with Group 8 (APSR's) established at an intermediate position.
Using the manual Reactor trip button to initiate the drop, all 61 control rods assigned to Groups 1 through 7 were dropped into the core from the full out position.
Drop time was determined by using the plant computer and measuring the time from " trip" to three-fourths insertion. The fastest rod dropped in 1.166 seconds, and the slowest rod was at 1.212 seconds.
For acceptance, the drop is to be less than 1.66 seconds. The measurement technique includes the control circuit and logic times in addition to the time for drop. All drop times were well below the acceptance criteria and met the Technical Specifications requirements for full-flow drop time.
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SECTION 111 - ZERO POWER PHYSICS TESTING
.I All Rods Out Boron Concentration This test was accomplished as described in the August 29 letter to the co'mmission. With control rod Group 8 at 37.5% withdrawn, the results were as follows:
Meas ured Vendor Prediction SMUD Prediction 1354 ppmB 1381 +100 ppmB 1337.7 ppmB The vendor prediction has been adjusted from the original value of 1401 ppmB to account' for the Cycle 1 extension of 10 EFPD beyond the value assume,d when the beginning of Cycle 2 ARO concentration was determined. All acceptance criteria was met and no other adjustments were necessary.
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.2 Boron Concentration at Maximum Controlling Rod Group Insertion Limit l
1 Meas ured Vendor Prediction SMUD Prediction i
1049 ppmB 1071 +100 ppmB 1035 7 ppmB
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This measurement was added to provide a second just critical Boron concentration measurement which corresponds to a predicted value.
At the time of this measurement, control rod Groups 5, 6 and 7 were (3)
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fully inserted and control rod Group 8 positioned at 37.5% withdrawn.
The measured data was consistant with predictions and met all acceptance criteria.
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3 Temperature Coefficient of Reactivity at All Rods Out Boron Measured Vendor Prediction
-0.13x10-4 ak/k/F"
-0.14x10-4 Ak/k/F" This value was determined as specified in the August 29 letter and i
met the acceptance criteria that specified the value shall not be more positive than +0.5x10-" ak/k/F* and should be within
+ 0.4x10-4 ak/k/F* of the predicted value.
.4 Temperature Coef ficient of Reactivity Corresponding to the Maximum insertion Boron Concentration Measure Measured Vendor Prediction
-1.34xio 4 ak/k/F*
-1.20x10-4 Ak/k/F*
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The acceptance criteria for this value is the same as above. Again, this measurement met all criteria and is acceptable for operation, (4)
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.5 CRA Group Reactivity Worth Vendor SMUD Measured Worth Predicted Predicted Tole rance
%Ak/k Worth, %Ak/k Worth, %Ak/k Allowed Group 5 0.622 0.59 0.65
+15%
Group 6 1.455 1.37 1.34 115%
Group 7 1.106 1.01 0.99 115%
Total 3.183.
2.97 2.98 110%
As described in the August 29 letter, if the total measured group worths were within +10% of the predicted value, a further cailbration of control rod Group.4 pnd subsequent second drop for worth of Groups 1 through 3 would not be required.
This condition was met by these measurements, hence the second drop was not required.
A rod drop was done as planned of control rod Groups I through 4 to determine the shutdown margin avaliable at the point of maximum insertion as allowed by Technical Speci fications. While no direct acceptance criteria applies to this rod drop, the resulting shutdown margin must be greater than or equal to 1.0% Ak/k to be able to meet minimum Technict.1 Specification requi remen ts. The shutdown margin which existed at the rod drop configuration was determined to be 3.64% ak/k and, therefore, verifies that the Technical Specification requirement is satisfied.
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.6 Ejected Rod Worth Measurement Error Adjusted Ejected Rod Worth P redicted Tole rance Ejected Rod from Group 5 Swap, Wo rth,
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Worth, %Ak/k
%Ak/k
%Ak/k-0.421 0 360 0.36
+20%
As described in the August 29 letter, the ejected rod worth is determined at the point corresponding to the maximum insertion condition allowed by Technical Specifications, namely, Groups 5, 6 and 7 fully inserted at zero power, with Group 8 at 37.5% WD.
From this configuration, the maximum worth " Ejected Rod," whi.ch is a rod in Group 6, was borated to full out and then swapped against Group 5 to return it to the full insertion position as a second determination of. Its worth. Those two values were then adjusted for uncertainties, averaged, and are reported as the Error Adjusted value. These results are consistent with the prediction and meet the absolute acceptance criteria of Technical Specifications by being less than 1.0 %Ak/k at zero power.
As a matter of interes t, it was determined to estimate the worth of four Group 6 rods symmetric with the measured ejected rod. This was done simply by_
swapping them against Group 5 and using the calibrated worth of Group 5 over its interval to estimate the ejected rod worth. The non-error adjusted Group 5 rod swap determined the highest worth of these rods to be 0.409 %ak/k and the minimum measured at 0.324 %Ak/k. These results are certainly within the margin of tolerance and provide confirmatica of the symmetry of ejected rod worth for cycle 2.
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SECTION IV - POWER ESCALATION
.1 Core Power Distribution Core power distribtulons were taken and analyzed at the requisite Reactor power test plateaus of 40%, 75%, and 100% FP during cycle 2 power escalation.
The purpose of these measurements was to verify that the minimum DNBR, maximum linear heat rate, quadrant power tilt, power imbalance, and related power peaking factors would not exceed allowable Ilmits.
In each case the measured variables were extrapo-lated to the over power trip setpoint for the next test plateau so as to assess the margin of conservatism prior to escalation.
A summary of the test results follows:
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POWER DISTRIBUTION TEST RESULTS Meas ured/ Des i red Date of Data 11/7/77 11/11/77 11/14/77 Power level, %FP 39.7/40 75.1/75 100.2/100 Group 1-5, %WD 100/100 100/100 100/100 Group 6, %VD' 100/100 100/100 100/100 Group 7, %WD 87.7/87.5 87.0/87.5 87.5/87.5 Group 8, %WD 31.9/34.4 25.0/25.0 20.9/21.9 Core Burnup, EFPD 0.6/2.0 2.1/3 0 5.2/4.0 Boron Concentration, ppmB 1044/NA 919/NA 845/NA Axial imbalance, %FP
-0.53/-0.49
-0.33/-1.19
-1.77/-2.59 Max Incore Quadrant Power Tilt, %FP 3.85/<2 91 0.64/<2 91 0.86/<2.91 Minimum DNBR 10.29/>1.30 3.23/>1.30 2.01/>1.30 Worse Case LHR, Kw/ft 6.11/<15.80 9.761/<17.14 12 986/< 16.80 Max Radial Power Peak 1.441/1.461 1.429/1.380 1.430/1.369 Hax Total Power Peak 1.765/1.734 1.671/1.599 1.689/1.614 Max Peak at Core Grid / Level L-14/2 K-11/5 L-14/3 Equilibrium Xenon Yes, 3D Yes, 3D Yes, 3D Acceptable for Power Escalation Yes Yes Yes Extrapolations done to, %FP 85 105.5 105.5 Acceptance criteria which applies to the radial and total peaking factors is +5% and +7.5% respectively when compared to the predictions for the peak assembly at the'75% and 100% power plateaus. All acceptance criteria was met 2
and escalation based upon this test data proved to be conservative.
The measured..DNBR (8) l l
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.2 Power imbalance Detector Correlation Test This test is performed at 75% FP for the purpose of establishing the relationship between the out-of-core nuclear instrumentation and the full set of in-core sel f powered neutron detectors.
In the August 29 submittal to the commission, this test was described as making use of the "APSR Scan" technique for inducing the necessary imbalance.
Since that time, it was determined that an alternate method would provide the same information without imposing high transient heat rates in the fuel assemblies containing the APSR's. The revised method amounted to a deboration from equilibrium conditions which brought the controlling rod group into its maximum insertion position at 75% FP.
This created the maximum desired imbalance then a boration returned the control rods to their normal position.
Subsequent transient Xenon effects induced the desired maximum positiva Imbalance.
The results corresponding to the maximum and minimum imbalance conditions are shown here:
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Power, %FP 73.51 73.15 Imbaiance, %FP
+5.61
-19.16 Maximum Til t, %FP
+0.67
+1.81 DNBR, Minimum 3.22 3.45 Maximum LHR, Kw/ft 10.23 11.93 Extrapolated DNBR 1.45 2.17 Extrapolated LHR, Kw/f t 14.42 17.55 The test results met all acceptance criteria with minimum DNBR values at greater than 1.30.
Maximum linear heat rates remained below the center line fuel melt linear heat rate limit of 20.4 kw/ft.
The, nuclear instrumentation correlation with in-core offset data is as follows:
Correlation NI Channel Slope Nl-5 1.123 NI-6 1.092 NI-7 1.089 NI-8 1.098 NOTE:
O f fset is imbalance divided by power level.
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Cycle 2 safety analysis assumes that the correlation slope is greater than or equal to 1.000.
As the above data shows, this corre-lation criteria is satisfied on all protective channels. At the same time that this data was obtained, the relationship between the full set of incore instrumentation and those on the backup recorde.s was determined to meet its acceptance criteria. The relationship between the incore and out-of-core instrumentation is shown to be conservative.
Thus the Reactor Protection System will protect the core from exceeding maximum linear heat rates and DNBR limits.
A gain factor of 3.70 is set into the Nuclear Instrumentation differential amplifier circuitry for this cycle, and as shown here, is adequately conservative.
3 Power Doppler Coefficient of Reactivity From equilibrium conditions at near 100% FP, the power doppler coefficient was determined by the method described in the August 29 letter. The value obtained was -1.293x10-4 ok/k/%FP, compared to the vendor predicted value of -1.23x10-4 ak/k/%FP. The acceptance criteria for this parameter was that the value shall always be more negative than
-0.55x10-" ak/k/%FP.
This criteria is therefore satisfied.
.4 Temperature Coefficient of Reactivity at Power The "at power" temperature coefficient was measured by the method described in the August 29 letter, while operating the Reactor at equilibrium conditions and 99.8%FP.
Measurements determined the (11)'
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coefficient to be -0.921x10-4 Ak/k/F* compared to a vendor predicted value of -1.33x10-4 ok/k/F*.
The acceptance criteria for this parameter is that it shall not be " positive" for Reactor operations above 95%FP. This condition for operation is satisfied for Cycle 2.
5 Dropped Control Rod Power Distribution Verification With the Reactor established at the 40% FP plateau and in its normal control rod configuration, that is, Group 7 controlling near 85%
withdrawn and all other control rod assemblies fully withdrawn from the core, the rod predicted to be the highest worth " dropped rod" is located in control rod Group 6.
This rod was then inserted fully into the core, and the resulting power distribution data obtained.
Diffi-culty was experienced in obtaining a three dimensional power map from the on-line computer, thus approximately four hours operation with the " dropped rod" was required to obtain the necessary data. This time period allowed for redistribution of the local Xenon effects and caused slightly higher than anticipated peaking factors to be observed in the test results. The test results at 40% FP and the measurement condition
+8.57% imbalance; 5.31 minimum DNBR; 7.47 kw/ft worse case linear were:
heat rate; with a maximum total peak of 2.405 in a core location symmetric to the desired.
Extrapolating these values to 100%FP gives a minimum DNBR of 1.6 using the BAW-2 Critical Heat Flux correlation, a maximum linear heat rate of 18.59 kw/ft, and a maximum Imbalance of +17.82%.
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1 in addition to the above core parameters, the correct functioning of the asynnetric "faul t".and asymmetric "alarnf' conditions of the control rod drive system were veri fied as the " dropped -rod" lef t its group average position. All acceptance criteria was met and operation at full power is deemed appropriate by these results.
SECTION V - CONCLUSION The results of testing and the conclusions summarized in this report demonstrate that Rancho Seco Unit 1, Cycle 2, has been properly designed; and the unit can be operated in a manner that will not endanger the health and safety of the pubile.
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