ML20066B239

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Control Rod Worth Analysis
ML20066B239
Person / Time
Site: Comanche Peak  Luminant icon.png
Issue date: 12/31/1990
From: Denise Edwards, Janne R, Killgore M
TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:
Shared Package
ML20066B230 List:
References
RXE-90-005, RXE-90-5, NUDOCS 9101070014
Download: ML20066B239 (44)
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I CONTROL ROD WORT 11 ANALYSIS I DECEMBER 1990 DEBORAll J . EDWARDS I

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Reviewed: dd&L

'Micg6y,[R.[#j/ILet/- _ _.._ Date: /1 TA[fp Killtfore Supervibor, Reactor Physics

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Approved: '- -

Date: /2 90 V Ran L,. Janne Manag Nuclear Fuel Approved: fL'bCWh.h~IWTw' Date,* ilh4/70 Aus6f Husain Director, Reactor Engineering L _

I DISCLAIMER The information contained in this report was prepared for the specific requirements of Texas Utilities Electric Company (TUEC), and may not be appropriate for use in situations other than those for which it was specifically prepared.

TUEC PROVIDES NO WARRANTY HEREUNDER, EXPRESSED OR IMPLIED, OR STATUTORY, OF ANY KIND OR NATURE WHATSOEVER, REGARDING THIS REPORT OR ITS USE, INCLiiDING BUT NOT LIMITED TO ANY WARRANTIES ON MF.RCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

,I By making this report available, TUEC does not authorize its use by others, and any stch uso is forbidden except with the prior written approval of IvEC. Any such written approval l

shall itself be deemed to incorporate the disclaimers of l5 liability and disc. aimers of warranties provided herein. In

! no event shall TUEC have any liability for any incidental or consequential damages of any type in connection with the use, authorized or unauthcrized, of this report or the information l in it.

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TABLE OF CONTENTS L

PAGE L

DISCLAIMER . . . . . . . . . . . . . . . . . . . . . 11 TABLE OF CONTENTS . . . . . . . . . . . . . . . . iii LIST OF iABLES . . . . . . . . . . . . . . . . . . . Vi Cl! APTER

1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . 1-1
2.

SUMMARY

, . . . . . . . . . . . . . . . . . . . . . 2-1

3. ANALYTICAL METHODOLOGY . . . . . . . . . . . . . . . 3-1 3.1 Core Model . . . . . . . . . . . . . . . . . . 3-1 3.2 Delayed Neutron Parameters . . . . . . . . . . 3-1 3.2.1 Selection of Delayed Neutron Parameters . . . . . . . . . . . . . . . 3-1 3.2.2 Determination of Core Average Delayed Neutron Parameters . . . . . . . 3-2
4. CONTROL ROD BANK REACTIVITY DETERMINATION . . . . . 4-1 4.1 Boron Dilution . . . . . . . . . . . . . . . . 4-1 4.1.1 Measurement Technique . . . . . . . . . 4-1 4.1.2 Analytical Technique . . . . . . . . . . 4-1 4.2 Control Rod Swap . . . . . . . . . . . . . . . 4-2 4.2.1 Measurement Technique . . . . . . . . . 4-2 4.2.2 Definitions . . . . . . . . . . . . . . 4-3 4.2.3 Description of the Rod Worth Parameter . 4-4 iii

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4.2.4 Measurement Corrections . . . . . . . 4-5 4.3 Rod Worth Tests . . . . . . . . . . . . . . . . 4-9 4.3.1 Measured Rod Worth Parameter . . . . . . 4-9 4.3.2 Calculated Rod Worth Parameter . . . . 4-10 4.3.3 Data Reduction and Evaluation . . . . 4-11

'.3.4 Other Considerations . . . . . . . . . 4-12

5. METHODOLOGY VALIDATION . . . . . . . . . . . . . . . 5-1 5.1 Background . . . . . . . . . . . . . . . . . . 5-1 5.2 Prairie Island Comparisons . . . . . . . . . . 5-2 5.2.1 Core Description . . . . . . . . . . . . 5-2 5.2.2 Analytical Approach . . . . . . . . . . 5-2 5.2.3 Comparisons to Plant Data . . . . . . . 5-3 5.3 Catawba Comparisons . . . . . . . . . . . . . . 5-3 5.3.1 Core Description . . . . . . . . . . . . 5-3 5.3.2 Analytical Approach . . . . . . . . . . 5-4 5.3.3 Comparison; to Plant Data . . . . . . . 5-4 5.4 Comanche Peak Comparisons . . . . . . . . . . . 5-5 5.4.1 Core Description . . . . . . . . . . . . 5-5 5.4.2 Analytical Approach . . . . . . . . . . 5-5 5.4.3 Comparisons to Plant Data . . . . . . . 5-5 5.5 Summary of Results . . . . . . . . . . . . . . 5-5
6. REVIEW AND ACCEPTANCE CRITERIA FOR MEASUREMENTS . . 6-1 6.1 Evaluation of Test Results . . . . . . . . . . 6-1 6.2 Lovel 1 (Review) Criteria . . . . . . . . . . . 6-2 i 6.3 Level 2 (Acceptance) Criteria . . . . . . . . . 6-3 iv I

I I 6.4 Additional Constraints . . . . . . . . . . . . 6-3

7. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . 7-1
8. REFERENCES . . . . . . . . . . . . . . . . . . . . . 8-1 I

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LIST OF TABLES TABLE PAGE 5.1 Control Rod Worth Comparisons for Measurements with Boron Dilution, Prairie Island Unit 1, Cycles 5 Through 7 and Cycle 9, HZP . . . . . . . . 5-7 5.2 Control Rod Worth Comparisons for Measurements with Rod Swap, Prairie Island Unit J, Cycles 9 g and 10, HZP . . . . . . . . . . . . . . . . . . . . 5-8 3 5.3 Control Rod Worth Comparisons for Measurements g with Boron Dilution, Catawba Unit 1, Cycle 1, HZP . 5-9 g 5.4 Control Rod Worth Comparisons for Measurements with Rod Swap, Catawba Unit 1, Cycle 2, HZP . . . 5-10 5.5 Control Rod Worth comparisons for Measurements with Rod Swap, Comanche Peak Unit 1, Cycle 1, HZP 5-11 5.6 Summary of Control Rod Bank Worth Comparisons . . 5-12 I

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I CHAPTER 1 I INTRODUCTION I

A steady state reactor physics methodology has been developed by TU Electric to be utilized in support of reload design, licensing, and operation of Comanche Peak Steam Electric Station (CPSES) Units 1 and 2. The generalized methodology is documented in Reference 1. As described in that report, TU Electric has selected W, ate-of-the-art computer codes and has focused on application of the codes using modeling I details appropriate for power reactors. This methodology has been extended to the calculation of control rod worth. The applicability of the methodology is demonstrated by comparison of calculated control rod bank worths to control rod bank worths measured with the boron dilution technique and with the control rod swap technique.

I Included in Refarence 1 are the results of pre-startup l calculations for CPSES Unit 1, Cycle 1 using the TU Electric methodology. After the issuance of Reference 1, TU Electric elected to incorporate the flexibility of utilizing control rod swap as an alternative method of measuring control rod worth. In order to maintain such flexibility.for reload 1-1 I

E cycles, TU Electric develooed an analytical methodology to support control rod worth measurements using either the boron dilution technique or the control rod swap technique. The TU Electric control rod swap methodology was provided in Reference 2 along with pre-test predictions of CPSES Unit 1, Cycle 1 control rod bank worths to be compared to control rod bank worths measured with the control rod swap technique. In order to clearly demonstrate the capability of the I methodology when applied in the predictive modo, Reference 2 was issued prior to the CPSES Unit 1, Cycle 1 startup physics testing.

This report presents comparisons of calculated and measured control rod bank worths for several power reactors. CPSES Unit 1, Cycle 1 results are included. The test procedures are summarized for both measurement techniques and, in addition, test review and acceptance criteria are identified.

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I CHAPTER 2 1

SUMMARY

I The steady state reactor physics methodology described in Reference 1 has been extended to includa calculation of control rod bank worths. To that end, TU Electric has developed an analytical methodology to support control rod bank worth measurements at CPSES using either the boron dilution technique or the control rod swap technique.

I Presented in this report are the analytical methodology for evaluation of control rod bank worth and the validation of the methodology by comparisons between calculated results and measured data for large power reacters (Catawba Unit 1, Prairie Island Unit 1, and CPSES Unit 1). The methodology was applied to eight cycles of operation: Catawba Unit 1, Cycles 1 and 2, Prairie Island Unit 1, Cycles 5 through 7 and Cycles 9 through 10, and CPSES Unit 1, Cycle 1. For five of these cycles, the boron dilution technique was utilized to measure the control rod bank worths. For four cycles the control rod swap technique was utilized. Prairie Island Unit 1, Cycle 9 control rod bank worths were measured using both techniques.

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I Control rod bank worths calculated with the methodology presented in this report show good agreement with measured values. For measurements made with the boron dilution technique (23 control rod banks in 5 cycles), the average difference between ca.'.culated and measured control rod bank worths is 2.32% with a standard deviation of 4.04%. The average difforence between calculated and measured worth of the sum of the banks is 2.08% with a standard deviation of I 2.40%. For measurements made with the rod swap technique (28 control rod banks in 4 cycles), the average difference between calculated and measured control rod bank worths is 0.501, with a standard deviation of 6.03%. The average difference between calculated and measured worth of the sum of the banks is 0.664 with a standard deviation of 5.74%.

All results are well within the review and acceptance criteria for control rod bann worth measurement tests.

It is concluded that the TU Electric control rod worth analysis methodology accurately predicts control rod worths as demonstrated by comparisons to control rod bank worths measured by both the boron dilution technique and the control rod swap technique. Further, it is concluded that the test formulations presented herein can be utilized by TU Electric to measure control rod bank worth by either the boron dilution or the control rod swap technique. The analytical 2-2 I

I methodology will be used in the design, licensing, and operation of CPSES while the test criteria wil.' be applied for control rod worth measurements.

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I CHAPTER 3 ANALYTICAL METHODOLOGY I

3.1 Core Model The TU Electric three-dimens.ional core model was employed to calculate the control rod bank worths. The nodal model is described in Reference 1 and utilizes the computer codes MICBURN-3, CASMO-3, TABLES-3, and SIMULATE-3.

3.2 Delaved Neutron Paratteters Control rod bank worths are measured with a reactivity I

computer. Core average delayed neutron parameters are required as input to the reactivity computer which then determines reactivity through the Inhour equation.

3.2.1 Selection of Delaved Neutron Parameters I

The basic delayed neutron data currently coded into CASMO-3 is derived from ENDF/B-V. However, the ENDF/B-V delayed neutron parameters are being re-evaluated at the Oak Ridge National Laboratory while the conversion from delayed neutron 3-1 I

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I I yield per fission to delayed neutron fraction of total fission neutrons is being re-evaluated by Studsvik. t Revisions to ENDF/B-V and subsequently to CASMO-3 are anticipated, but several years may elap.se before the revisions are released for general use.

I Because of the uncertainty associated with the ENDF/B-V delayed neutron parameters, alternative delayed neutron parameter data sets were reviewed to identify the data to be employed in the TU Electric methndology. As a result of the review, the delayed neutron parameters originally encoded in CASMO-2 were selected to replace those in CASMO-3. These I delayed neutron parameters are based on ENDF/B-III and g therefore rely heavily on the work of Keepin (Reference 3).

3.2.2 Determinfttien of Core Averace Delaved Neutron Parameters-With SIMULATE-3, the core effective delayed neutron parameters are determined using two-group adjoint flux weighting of assembly average parameters calculated with CASMO-3. However, the CASMO-3 assembly depletions required for the control rod worth caculations reported herein were completed before the selected delayed. neutron data set described in Section 3.2.1 had been installed in CASMO-3.

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Therefore, for this report, the measured control rod bank worths have'been corrected based on a power and volume weighting of assembly average delayed neutron parameters. In future applications, the coro average values will be determined directly from SIMULATE-3.

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I I CHAPTER 4 CONTROL ROD BANK REACTIVITY DETERMINATION i

I 4.1 Boron Dilution 4.1.1 Measurement Technicue

.I control rod bank worth has traditionally been measured using

the boron dilution technique. When that technique is employed, the contro3 rod bank is stopped in with the boron concentration being ;ontinuously diluted. System temperature and pressure are ma.ntained constant. The control rod bank worth is obtained by summing the incremental worths output from the reactivity computer.

l 4.1.2 Analytical Techniaue The control rod bank worth is calculated as the change in f reactivity between the control rod bank fully withdrawn statepoint and the control rod Max fully inserted I statepoint. In additir., the differential and integral worths can be determined as a function of control bank 4-1 lI

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pot by performing a series of statepoint calculations at the positions of interest.

4.2 gontrol Rod Swan 4.2.1 Measurement Technicuq To evaluate control rod bank worths using the control rod swap technique, two measured quantjties are required the -

reference bank worth and the reference bank critical position with each test bank fully inserted. The measurements proceed as follows. The reference bank worth is measured by boron dilution. Before beginning the rod swap maneuvers, the reactor is stabilized with the reference bank fully inserted, all other banks fully withdrawn, and the boron concentration such that the reactor is just critical. Then the reference bank is incrementally withdrawn while a test bank is incrementally inserted, maintaining nominal criticality.

When the test bank is fully. inserted with the reactor critical, the position of the reference bank is recorded.

The procedure is repeated until all test bank measurements.

are completed.

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I 4.2.2 Definitions I Reference bank - the highest worth control rod bank, measured by the traditional boron dilution method.

Test bank - the control rod bank which is swapped with the reference bank.

MCP (Measured Critical Position) - position of the reference bank when the test bank is fully inserted and the reactor is just critical, including corrections as required.

R - total worth of reference bank, inserted alone.

I T - total worth of test bank, inserted alone.

I AR - worth of reference bank from MCP to fully withdrawn, inserted alone.

I Tu (rod worth parameter) - test bank worth, with reference bank inserted to the MCP.

AR, - worth of reference bank from MCP to fully withdrawn,

-with test bank inserted.

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I Superscripts "M" and "C" may be included on the last five defined quantities to denote " measured / inferred" and

" calculated," respectively.

4.2.3 Description of the Rod Worth Parameter I

I There are two rodded statepoints at which criticality is established: 1) reference bank in, all other rods out, and I

2) test bank fully inserted, reference bank at the MCP for that test bank. The total not change in reactivity associated with transitioning from one state to another is zero and is independent of the path. From a:. analytical point of view, two paths can be addressed: 1) withdraw the reference bank, insert the test bank, insert the reference bank to the MCP, and 2) withdraw the reference bank, insert the reference bank to the MCP, insert the test bank. Writing equations for the two paths:

-R + T + AR 7 =0 (1)

-R + AR + T g =0 (2)

From those two equations, three relationships can be determined:

R = T + AR, (3)

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I R = AR + T,, (4)

T + A R, = A R + T,, (5)

With the control rod swap technique, values of R and AR are measured by boron dilution, so a measured value of T,, can be determined from equation (4). Equation (4) is then rearranged as:

I TM ,, = RM -

ARM (6)

As noted above, T",, is the measured / inferred rod worth parameter.

I 4.2.4 Measurement Cofrectiong Although every effort is made to maintain the plant conditions constant during the control rod bank worth measurements, it is possible that the boron concentration or moderator temperature could drift clightly, or that the reactor could be other than exactly critical either at the MCP or at the reference bank inserted condition. In addition, it is possible that the reference bank could be less than fully inserted at the start of the test. A deviation in any of these parameters affects the reactivity balances of equations (1) through (6). The rod worth 4-5 I

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parameter can be corrected for deviations in plant conditions by correcting the MCP to what it would have been had the plant conditions not changed.

Effects to be accounted for includo drifte in temperature or I

boron concentration. Since the isothermal temperaturo coefficient (ITC) is generally negativo, an increase in temperature results in a negative reactivity insertion.

Similarly, an increase in boron concentration also results in a negativo reactivity insertion. If temperature or boron concentration increases during the test, then the insertion required of the reference bank to maintain criticality is less than it would have been had there been no increase.

Thus, the MCP corrected for temperature and boron concentration drift will be lower in the core than the actual measured critical position. The MCP corrected only for temperature and boron concentration drift is:

I MCP = MCP* - (AT*ITC + AB*BW)/(or /Ah) (7) where MCP is the critical position corrected for temperature and boron changes, 4-6 I

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MCP* is the measured critical position, AT is.the change in temperature during the test, ITC is the reference-bank-in isothermal temperature coefficient, AB is the change in boron concentration during the test, BW is the boron worth, and Ap/Ah is the differential worth of the refersace bank in the vicinity of the MCP.

ITC, BW, and Ap/Ah are typically negative.

Much of the time, the reference bank may not be fully inserted at the start of the test. In that case, a reactivity correction is needed, since R" in equation (6) requires that the reference bank be fully inserted. The correction can be applied to the MCP:

MCP = MCP* - [AT*ITC + AB*BW + RM)/(Ap/Ah) i (8) where R"i is the reactivity worth of the reference bank from the initial configuration to the bottom of the core. The reactivity bias can be thought of as equivalent to an increase in boron concentration, and R; is negative.

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I The temperature correction is usually negligible. In addition, the boron concentre ion measurement has an uncertainty of approximately 10 ppm, so a small drift in the boron concentration during the test might not be detected.

Unless there is a very large change in boron concentration during the test, the boron concentration correction provided in equations (7) and (8) should not be used. The largest correction term in equation (8) is anticipated to be RM,g I

l which accounts for the reference bank not being fully inserted at the start of the control rod swap test. f I

If the reference bank is swapped for the test bank after the determination of each MCP, drift in boron concentration and temperature can be determined from the difference in the initial and final reference bank positions, where initial and final refer to the configuration with the reference bank >

inserted alone before and after swap with a test bank.

Assuming that the reactivity computer shows the plant to be critical at the initial, final, and MCP statopoints, and further recognizing than the reactivity change due to drifting core conditions is typically quite small, the following approximation is made:

I R", + 2 ( AT*ITC + AB*BW) = R", (9) 4-8 I

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I where R", is the worth of the reference bank from its final position to fully inserted (a negative value), and AT and AB are defined as in equation (7), between the initial and MCP statepoints. Thus, drift in the boron concentration and l

temperature in equation (8) can be replaced by the quantity (R", - R",), Icading to I MCP = MCP* - [ (R", + R"j))/(Ap/6h) (10)

I If the referenco bank is re-swapped for the test bank following determination of the MCP, equation (10) can be used to correct the MCP for drifting core conditions; otherwise I equation (8) should be used.

I 4.3 Rod Worth Tests I

4.3.1 geasured Rod Wor _th Parameter i

R" is available upon completion of the reference bank worth measurement by boron dilution. Following each rod swap maneuver, the MCP is available. The value of AR" can then be obtained from the reference bank worth measured data.

Equation (6) is used to define the measured rod worth parameter for each test bank.

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I 4.;.2 Calculated Rod Worth Parameter i The calculated reactivity change between the initial li '

statopoint and the MCP statopoint is zero only if the calculated critical position is identical to the measured l critical position. Therefore, equations (3) and (4) Inay not be applicable. However, equation (5) can be utilized in the evaluation of the calculated rod worth para [ncter, leading to: I TC g = Te + ARC 7 -

arc (ii)

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Using the three-dimensional core model, the worth of the reference bank is calculated prior to testing as a function of rod position, which permits the value of ARC to be extracted once the MCP is determined. The worth of each test bank, TC , is also calculated prior to testing. In addition, the integral worth of the reference bank in the presence of l the test bank is calculated for reference bank positions l about the calculated critical position, once the MCP is established, equation (11) is used to determine the calculated rod worth parameter.

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I 4.3.3 Data Reduction and Evaluation I For a given test bank, the procedure for determining the calculated and measured rod worth parameters is as follows:

1. Obtain the MCP, corrected for changes in core conditions, using equation (8) or equation (10).
2. From the measured reference bank integral worth data, obtain AR" and R".

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3. Determine the measured rod worth parameter T"3, using equation (6).

I 4. Obtain ARC from the calculated reference bank worth curve, reference bank inserted alone.

5. Obtain arc from the calculated reference bank worth 3

curve with the test bank inserted.

6. Obtain T C.

I 7. Determine the calculated rod worth parameter Tc g using equation (11),

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The calculated and measured rod worth parameters are compared to verify that the plant is performing as expected.

4.3.4 Other considerations It is possible that the calculated reference bank will not be the highest worth bank if any other centrol rod bank has a similar worth. Under those circumstances, when the highest worth bank is swapped with the reference bank, the reference bank will be fully withdrawn before the test bank is fully inserted. In that case, after the reference bank has been fully withdrawn, the test bank should be fully inserted and the incremental worth measured with the reactivity computer. I The measured rod worth T"a will be R" + A p , where op is the incremontal worth of the test bank after the reference bank has been fully withdrawn. The calculated rod worth remains Tc, I

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I CHAPTER 5 ,

I METHODOLOGY VALIDATION I

5.1 Backaround e

I Prior to CPSES Unit 1, Cycle 1 startup testing, TU Electric methodology for control rod worth analysis was validated through comparisons with measured data from Prairie Island Unit 1, Cycles 5 through 7 and Cycles 9 through 10, and Catawba Unit 1, Cycles 1 and 2. Although the CPSES Unit 1, I Cycle i startup testing was supported with analytical results provided by Westinghouse, analyses (including control rod cwap) were also performed utilizing the TU Electric methodology. TU Electric predictions for the CPSES startup tests except the control rod swap measurements were documented in Reference 1. The TU Electric control rod swap l pre-test predictions were documented in Reference 2.

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5.2 Prairie Island Comparisons 5.2.1 Core Descrintion Prairie Island Unit 1 is a Westinghouse two-loop, 1650 MWth I

pressurized water reactor. The core consists of 121 fuel acsemblies, each with a 14x14 fuel pin array. Each assembly has 16 guide tubes and one off-center instrument thimble.

Fuel assemblies manuf acturcd by Westinghouse '-'re used in the initial core and jn the first three reloads. In Cycles 5 through 10, fuel assetrblies fabricated by Advanced Nuclear Fuels (ANF) were loaded in the core. In the ANF supplied  ;

reloads, burnable absorNrs in the - fot... :" gadolinia blended in uranium dioxide 'Nre employed. Natural uranium axial blankets, 6 inches top and bottom, were incorporated into the Cycles 7 through 10 reload desigTs. These reload designs- .

also had a higher water-to-fuel ratio than-did previous-reload fuel.

5.2.2 Analytical Approacjl I

I Each cycle was depleted at het full power (HFP) with all rods out (ARO). Plant coastdown was modeled, as well as tirsion product decay after shutdown. Coastdown was utilized at the g' C

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end of Cycles 5, 6, 7, and 9. Calculations of control rod bank worths at hot zero power (HZP) were compared to treasured control rod benx worths provided by Northern States Power Company.

5.2.3 Comparisons to Plant Data I Control rod bank worths were measured using the boron dilution technique for Cycles 5 through and with the rod swap technique for Cycles 9 and 10. Rosalts of the bontr$1 rod worth compariscns for Prairie Ti vJa are presented in Tacic 5.1 for measurements using the be,ron dilution technique I e and in Table S ' for measurements which employed the control rod swap tech- iue .

tf 5.3 Catawba ('omnarisons 5.3.1 Core Description -

I Cacawba Unit 1 is a 4-loop Westinghouse plant rated at 3411 MWtb. The core contains 193 fuel assemblies each' with a 17x1/ fue) pin array. Cycles 1 and 2 utilized Westinghouse optimized Fuel Assembly (OFA) fuel, standard burnable g absorbers, and Bp control rods. The burnable absorbars in ej 5-3 9

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I the cycle 1 assemblies were removed prior to Cycle 2 operation.

5.3.2 Analytical Annroach Each cycle was depleted at hot full power (HFP) with all rods out (ARO) Coastdown at the end of Cycle 1 was modeled, as well as fission product decay after shutdown. Removal of the burnable absorbor clusters between Cycles 1 and 2 was accounted for in the ani.lysa. Hot zero power (HZP) calculated control rod bank worths were compared to measured control rod bank worths provided by Duke Power Company.

5.3.3 Comparie ns to Plant Data control rod bank worths were measured using the boron dilution technique in Cycle 1 and by the rod swap technique in Cycle 2. Results of the control rod worth comparisons for I Catawba are presented in Table 5.3 for measurements using the boron dilution techt.ique and in Table 5.4 for measurements made with the control rod swap technique.

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I-I 5.4 Comanche Peak Comparisons i

!I 5.4.1 Core Description CPSES Unit 1 is a 4-loop Westinghouse plant rated at 3411 l$5 MWth. Cycle .L utj:tzes Westinghouse standard fuet with 17x17 j pins per assembly, standard burnable absorbers, and Ag-In-Cd control rods. The core contains 193 assembli 3.

I 5.4.2 Analytical Approach As this was a fresh core, no depletion calculations were required. The control rod bank worth calculations were initiated directly from the beginning-of-life core model.

5.4.3 Comparisons to Plant Data Control rod bank worths were measured by the rod swap te hnique. Comparisons of calculatect and measured rod worth paramet.ers are given in Table 5.5.

lI 5.5 Summary of Results I

The comparisons of calculated and measured contro: rod bank I

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worths are summarized in Table 5.6. As shown, the average difference in individual control rod bank worths is -0.77%

with a standard deviation of 5.37%. With respect to the sum of the control rod bank worths, the average difference is

-1.45% with a standard deviation of 3.97%. The comparisons of calculated and measured control rod bank worths show very good agreement for individual control rod banks as well as for the sum of the banks.

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I Table 5.1 g Control Rod Worth Comparisons for Measurements g with Boron Dilution Prairie Island Unit 1, Cycles 5 Through 7 and Cycle 9, HZP Rods SIM M M-3 Measured' Dif f er,e,nce Cycle (pcm) (pcm)

Inserted (%)

5 D 657 665 - 1.20 CD 1078 1087 -

.83 I BCD ABCD 621 1789 633 1794

- 1.90

.28 tota 4145 4179 -

.81 6 D 729 736 -

.95 1283 1319 I CD BCD ABCD 773 1575 740 1570

- 2.73 4.46

.32 total 4360 4365 -

.11 7 D 961 1068 -10.02 I CD BCD 1126 860 1229 870

- 8.38

- 1.15 ABCD 1174 1167 .60 total 4121 4334 - 4.91 I 9 A BA DB.T 1292 977 750 1356 1024 778

- 4.72

- 4.59 3.60 I CDBA total 1734 4753 1817 4975

- 4.57

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+ corrected for delayed neutron parameters

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Control Rod Worth comparisons for Measurements with Rod Swap Prairie Island Unit 1, Cycles 9 and 10, HZP SIMULATE-3 Measured

  • Rod Worth Rod Worth Differ,e,nce Cycle Rod Bank Parameter Param>ter (%)

(pcm) (pcm) 9 A* 1292- 1356 - 4.72 g' B 588 653 - 9.95 3-C 947 1009 - 6.14 D 860 915 - 6.01 .

total 3687' 3933 - 6.25 10 A* 1197 1261 - 5.08 B 590 544 8.46 C 1007 1050 - 4.10 '

D 706 691 2.17 648 641 SA 1.09 SB 652 650 .31 total 4800 4837 -

.76

+ corrected for delayed neutron parameters

  • Reference Bank .

( c-m m +100)

I:

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I-I I Tablo 5.3 Control Rod Worth Comparisons for Measurements with Boron Dilution Catawba Unit 1, Cycle 1, HZP SIM E-3 Meusured' D H fer,a,nce Rods Inserted (pcm) (pcm) (%)

I D CD 792 1201 797 1217

.63 1.31 I BCD ABCD ABCD+SE 1263 509 430 1185 554 466 6.58 8.12 7.73 743 781 4.87 I ABCD+SE+SD -

ABCD+SE+SD+SC 1136 1112 2.16 total 6104 6112 -

.13

.I

  • corrected for delayed neutron parameters

( c-m +100)

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g e-e I

I Table 5.4 Control Rod Worth Comparisons for Measurements with Rod Swap Catawba Unit 1, Cycle 2, HZP SIMULATE-3 Measured' l Rod Bank Ftod '4 rth Rod Worth Differ,e,nce W sarameter Parameter (%)

(pen! (pcm)

D 537 499 7.62 C' 1014 979 3.58 B 823  : 750 9.73 l

m A 260 259 3.86

,0 365 334 9.28 g Cr? 461 426 8.22 g SC 459 421 9.03 SB 815 754 8.0'9 SA 532 496 7.26 cotal 5275 4918 7.26 5 _

  • corrected for delayed neutron parameters
  • Reference Bank

( 1*m

  • 10 0 )

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5-10 g I

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I I Table 5.5 Control Rod Worth Comparisons for Measurements with Rod Swap I Comanche Peak Unit 1, Cycle 1, HZP I Rod Bank SIMULATE-3 R d Worth Parameter Measured

  • Rod Worth Parameter Differ,e,nce

(%)

(pcm) (pcm)

I 699 D G93 -

.86 I C B

A 802 810 322 826 817 333

- 2.91

.86-3.30 SE 363 380 I SD SC 461 461 489 496 4.47 5.73 7.06 SB* 850 884 - 3.85 SA 624 622 .32 total 5386 5546 - 2.88

+ corrected for delayed neutron parameters

  • Reference Bank

( c-m m *100)

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5-11 I l l

I Table 5.6 Suramary of Control Rod Bank Worth Coaphrisons I

Difference standard

"""#"9 (*)* deviation (%)

Individual Control Rod Banks Dilution Measurements - 2.32 4.04 Rod Swap Measurements .50 6.03 Combined -

.77 5.37 Sum of Control Rcd Banks 5

Dilution Measurements - 2.08 2.40 Rod Swap Measurements -

.66 5.74 Combined -

1.45 3.97

< ~m .1 e o , I I

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I 5-12 g I

I CHAPTER 6 I REVIEW AND ACCEPTANCE CRITERIA FOR MEASUREMENTS I

6.1 Evaluation of Test Results I Two levels of critoria are utilized for the evaluation of control rod worth measurement test results. Level 1, or review criteria, is defined for global evaluation anc has no direct safety significance. Level 2, or acceptance criteria, is related to assumptions which form the basis of the safety

I analysis.

I If a test result fails to meet the Level 1 criteria, it is reviewed in combination with the balance of the plant startup data. The impact of the discrepancy on the cycle safety analysis is then resolved within 60 Effective Full Power Days (EFPD) following completion of the tests. If a test result fails to meet the Level 2 criteria, a similar resolution must be achieved within 30 EFPD of test completion. In the case of an acceptance test failure, the failure and resolution must be reported to the NRC within 45 EFPD of test I completion.

) 6-1

.I

I l' 1 6.2 Level 1 (Review) Criteria Il For control rod worth measurement using either measurement technique,

1. For all measured banks, either
a. the absolute value of the percent difference between inferred and predicted integral worths must .

be $ 15 percent, or I

b. the absolute value of the reactivity difference .

between inferred and predicted integral worths must be 5 100 pcm, .

whichever is greater.

2. The sum of the measured bank worths must be s 110 percent of the sum of the predicted bank worths.

In addition, when using the control rod swap raeasurement technique,

3. The absolute value of the percent difference between 6-2 I

I measured and predicted integral worth for the reference bank must be s 10 percent.

I .

6.3 Level 2 (Accentance) Criteria For control rod worth measurements using either measurement technique,

1. The sum of the measured bank worths must be 1 90 percent of the sum of the predicted bank worths.

I In additiori, when using the control rod swap measurement technique, I 2. The absolute value of the percent difference between the measured and predicted integral worths for the reference bank must be 5 15 percent.

Additional Constraints I 54 When using the boron dilution measurement technique, at least four control rod banks should be measured. Typically, Control Banks D, C, B, and A are chosen, and are measured in sequential insertion.

6-3

l l When implementing the control rod swap technique, all Control Banks and Shutdown Banks should be measured.

When determining percent differences between measured and calculated control rod worth parameters, the calculated values are used as the bases.

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I 6-4 1

I-I I CHAPTER 7 CONcL119?ONS ,

I The TU Electr.ic steady state reactor physics methodology has I been shown to accurately predict control rod worths.

applicability of the methodology has been 'emonstrated d by The comparicons to measurements performed with the boron dilution technique and with the control rod swap technique. Further, the control rod bank worth measurement requirements have been defined for employment of either the boron dilution technique g or the control rod swap technique. Both techniques have been demonstrated to be appropriate by comparisons to applicable startup test results including those obtained for Comanche )

Peak Unit 1, Cycle 1. All results are well within-the

{'

2cc..N
au zawew and acceptance criteria for control rod

>I bank worth measurement tests.

I I i l I l

l 7-1 l

.l I

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CHAPTER 8 REFERENCES I

1. " Steady State Reactor Physics Methodology," TU Electric, RXE-89-003-P, July, 1989. ,
2. Letter, W. J. Cahill, Jr. to U. S. Nuclear Regulatory _

Commission, " Comanche Peak Steam Electri c Station -

(CPSES) Docket Nos. 50-445 and 50-446 kuload Analysis ~.

Methodology (Control Rod Swap Methodology)," TXX-90083, "

March 23, 1990.

3. Keepin, G. R., Physics of Nuclear Kinetics, Addison- g Wesley Publishing Co., Reading, Mass., 19FF. g I

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