ML20059H310

Revised Safety Evaluation Clarifying Individual Rod Position Indication Testing Exception & Bases for Approving Test Exception

ML20059H310
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	09/06/1990
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20059H301	List: ML20059H298 ML20059H310
References
NUDOCS 9009170103
Download: ML20059H310 (4)

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1. "'*4 UNITEO STATES 8

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s' REVISED SAFETY-EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION E

RELATED TO AMENDMENT NO.127 TO FACILITY OPERATING LICENSE NO. DPR-61 CONNECTICUT YANKEE ATOMIC POWER COMPANY HADDAM NECK PLANT

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DOCKET NO. 50-213 J

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1. 0 INTRODUCTION 1

Pursuant to 10 CFR 50.90, Connecticut Yankee Atomic Power Company (CYAPCO) has

'l proposed to amend Operating License No. DPR-61 for Haddam Neck Plant. By Established|letter dated March 14, 1990]] CYAPC0 proposed to amend the Technical Specifications (TS)

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by adding a Special. Test Exception 3.10.4, Position Indication System-Operating.

This-will allow testing of the individual rod position indication (IRPI) system during power operation of the Haddam Neck Plant. The proposed Technical 3

Specification (TS) will allow suspension of the following limiting conditions i

for operation (LCOs) for a maximum of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> for each cycle during the performance of the test:

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Movable Control Assemblies 3.1. 3.1 Position Indicating Systems-Operating 3.1.3.2 l

Shutdown Rod. Insertion Limit 3.1.3.5

-Control Group Insertion Limits (4 Loops) 3.1.3.6.1 3

1-Control Group Insertion Limits (3 Loops) 3.1.3.6.2 l

DISCUSSION-Individual rod position is obtained by a linear variable differential transformer (LVDT) on each of the 45 control rod housings. The rod drive shaft acts asta permeable core for the transformer. Thus, as the rod position changes, l

the magnetic coupling between the primary and secondary windings will also change. As the shaft moves higher within the housing, the magnetic coupling increases causing an increase in the transturmer secondary voltage. The 1

secondary voltage is fed to an AC to DC converter which provides a DC signal

'i proportional to rod _ position. A digital voltmeter is calibrated to read out individual indication of rod position in steps.

The IRPI system drif t due to temperature changes has been an observed phenomena since early operation of the plant. The TSs require that the IRPIs be recalibrated whenever any of the IRPIs drifts outside of the TS limits. The proposed test would allow the IRPI to fluctuate with temperature and not L

require the IRPI to be recalibrated to show compliance with the TS during the 1.

test. The control rod position indications will be recorded and used to establish a correlation between temperature and control rod position indication.

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1. i The IRPI system consists of 45 control rods in four banks (A,B,C and D). Banks j

C and D are the shutdown banks and contain 8 and 12 rods respectively. Banks A and B are the control banks and contain 17 and 8 rods respectively. To perform the test, three conditions must be met: 1) Each control rod in Banks A, C and D will be verified to be withdrawn to at least 317 steps (full out-of-core i

position) within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> prior to the start of the test, 2) Banks A C and D will not be moved during the test, and 3) The Group Position Indication (GPI) system is-operable during the performance of the test. In addition, with any

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movement of rods in Banks A, C or D the Action statement will require that the j

test be terminated and that the IRPI be restored to operable status within 1 l

hour or be in at least hot standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

L The test will be to vary the reactor power from 100% to 65% using control Bank B and boron concentration. Control Bank B and boron are the usual means for controlling power. By varying reactor power from 100% to 6g%, the tegt will cover the entire temperature range of power (T from 562 F to 535 Fg This i

isbecausetheplantoperatesisothermalfrom059to 65% power (T

=535 F, see l

figure 1)0 Theprocedurelimitspowerdescensionto2.5MWE/minuM9or approxi-mately.4 F/ minute. The plant has determined based on previous observations with this rate of temperature change that there is no delay time between reactor coolant temperature change and IRPI fluctuation. The test will be to record the temperature and IRPI during the power descension and ascension.

Based on these observations a correlation between temperature and rod position indication will be developed for each control rod in Banks A. C and D over the entire temperature range of power operation. Because Bank B rods were moved

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during the test, Bank B IRPI will not be corrected based on this test data.

Bank B IRPI will be adjusted based on previous data. The test will not require J

a new procedure as the plant currentiv performs a load reduction from 100% to 65% power every 31 days to test the turbine-generator control valve. Therefore, the IRPI test procedure'will only require recording the IRPI and temperature during the turbine generator control valve test with some noted precautions.

EVALUATION The IRPI system does not provide any input to any automatic safety or control system function at the plant. The IRPI system is important to safety because it is used to assure that all rods are withdrawn equal to or greater than the required rod insertion limits. The rod insertion limits are maintained by the TS and assure that the minimum shutdown margin is maintained. The rod bottom bistables, which are part of the IRPI, are unaffected by the test and will continue to provide input to the turbine runback feature during the test. The automatic turbine runback feature is strictly for plant control and has no safety function.

Banks A, C, and D will be fully withdrawn and verified to be within their respective rod insertion limits prior to the test. The control rod control system will be switched to the manual mode prior to the test. Therefore any control rod movement would require an operator to manually move the rods and as noted above the TS will not allow any motion of Banks A, C, or D during i

the test. The test exception is needed because TS Sections 3.1.3.1, 3.1.3.2, 3.1.3.5, 3.1.3.6.1 and 3.1.3.6.2 could be violated as the indicated position may change during,he test and exceed TS limits even though the actual position y

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i has not. During the test, rod position will continue to be monitored by the Group Position Indica'. ion (GPI) system. Control Bank B must also remain within it's rec insertion limits as required by TS Sections 3.1.3.6.1 and 3.1.3.6.2.

j In addition, the TS wi'1 limit the use of the test exception to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> each I

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The TS change would allow the plant to perform a test to provide a more accurate indication of control rod position. This TS change does not change any l

of the current TS requirements for the operability of the IRPI system.

The plant'will have both indications available and use the existing control rod L

position indication algorithm until the new algorithm has been verified. In i

addition the use of the new algorithm even if it were less accurate than the I

current algorithm would have no effect on safety because it would cause the

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plant enter an ACTION statement earlier, which would require limiting movement j

of the control rods and restoring the rod position indication to operable i

l status.- Based on the above the staff has determined that the proposed TS changes will have no adverse impact on plant safety and will maintain the L

intent of the current TS. Therefore, the staff concludes that the proposed TS-I changes are acceptable.

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ENVIRONMENTAL CONSIDERATION L

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The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in l

10 CFR Part 20.

The staff has determined that the amendment involves no significant. increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.

The Commission has previously published a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding.

Accordi C, the amendment meets the eligibility criteria for categorical exclu At forth in 10 CFR 51.22(c)(9).

Pursuant to 10 CFR 51.22(b), no environmentai m et statement or environmental assessment need be prepared in connection with

,.e issuance of the amendment.

CONCLUSION We have concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be-inimical to the common defense and security or to the health and safety of the public.

Dated: -September 6, 1990 Principal Contributor:

A. Wang

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