ML20137A669

Observations & Comments,Initial Reactor Startup & Low Power Reactor Physics Tests,Palo Verde Nuclear Generating Station,Unit 1,NRC Region V Enhanced Insp

ML20137A669
Person / Time
Site:	Palo Verde
Issue date:	06/21/1985
From:	Peterson L LAWRENCE LIVERMORE NATIONAL LABORATORY
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ML20137A500	List: IR 05000522/2006005 IR 05000523/2006005 ML20137A569 ML20137A592 ML20137A617 ML20137A641 ML20137A669
References
NUDOCS 8508210456
Download: ML20137A669 (5)

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Observations and Comments Initial Reactor Startup and Low Power Reactor Physics Tests Palo Verde ~ Nuclear Generating Station, Unit 1 NRC Region V Enhanced Inspection by L. Rolf Peterson, P.E.

Lawrence Livermore National Laboratory June 21, 1985 Backcround I participated as a consultant member of the NRC Region V Enhanced Inspection Team at Palo Verde Nuclear Generating Station, Unit 1 (Palo Verde 1), from May 22 through May 31, 1985. During this inspection I reviewed the procedures for initial criticality and low power physics tests, observed the performance of reactor test and reactor operations personnel during reactor startup and low power operation, and evaluated the preliminary results of the low power reactor physics tests.

The initial startup of Palo Verde 1 was conducted using Arizona Public Service Co. (APS), Palo Verde Nuclear Generating Station Manual, Procedure 72IC-1RX02, Initial Criticality, Revision 1, dated May 20, 1985. Startup and initial criticality was performed with the primary reactor coolant system (RCS) at 320 degrees F temperature and 600 psia pressure. Initial criticality was achieved at 0145 on May 25, 1985.

Low power reactor physics tests were conducted using APS Procedure 72PY-1RX30, Low Power Physics Test, Revision 0, dated May 22, 1985.

Initial low power physics tests were conducted at RCS temperature /

pressure = 320 degrees F / 600 psia. Final low power physics tests were conducted at RCS t em pera t u re / pressure = 565 degrees F / 2250 psia.

The low power physics tests commenced on May 25, 1985, and were concluded on June 1, 1985.

On May 22, 1985, I attended.a briefing by David Hoppes, the supervising APS reactor test engineer, and Frank Philpott, the lead Combustion Engineering (CE) reactor engineer on site for the Palo Verde 1 startup.

The briefing summarized the plans for initial criticality and low power physics tests and reviewed the major evolutions included in the procedures cited.above.

Initial Criticality I reviewed in detail Procedure 721C-1RX02, Initial Criticality. Seven properly approved Procedure Change Notices (PCNs) corrected minor discrepancies in the original Initial Criticality Procedure. I found that the procecure, including the PCNs, was complete and incorporated good operating practices for a safe approach to initial reactor criticality.

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t The procedure included adequate precautions to prevent an unanticipated criticality and to ensure proper detection of the neutron multiplication during startup. The procedure established safe initial conditions for reactor startup with a high boron concentration and all control el em en t assembly ( CEA ) groups fully withdrawn except for CEA. Group 5, which was withdrawn to half insertion.

, The procedure for boron dilution to approach criticality was cautious and orderly. It provided for periodic sampitng and laboratory analysis of the RCS and pressurl=er boron concentra J.ons and for monitoring RCS tboronometer readings during boron dilution and mixing. The procedure called for Inverse Count Rate Ratio (ICRR or 1/M) plots versus boron concentration and versus time during boron dilution and mixing to assist in the prediction of conditions for initial criticality. The preceiure also required verification of at least one decade of nuclear instrumentation response overlap between the startup channels anc the log safety channels during the final portions of the approach to critical.

I observed operations in the control room during early stages of boron dilution on May 24, 1965, and I observed the final two hours of the approach to initial criticality. Initial criticality was declared at 0145 hours0.00168 days <br />0.0403 hours <br />2.397487e-4 weeks <br />5.51725e-5 months <br /> ( 1 : 45am ) , May 25, 1985. All operations were safely ar.d competently performed in accordance with the Initial Criticality Procedure.

The predicted RCS boron concentration for initial criticality with CEA Group 5 halfway withdrawn and all other CEAs fully withdrawn was 1063- ppm ( q 100 ppm ) . The actual measured boron concentration at initial criticality in this configuration was 1054 ppm. This value was well within the acceptable uncertainty of the predicted critical boron concentration.

Low Power Physics Tests After Palo Verde 1 initial criticality was established, APS entered Procedure 72PY-1RX30, Low Power Physics Test, Revision O. Tests included in this procedure were:

l Critical boron concentration measurements with different control rod configurationsi Isothermal temperature measurements with different control rod configurations; Reactivity worth measurements of regulating CEA Groups 5, 4, 3, 2, and 1 insertions with no overlap at RCS 320 degrees F / 600 psia and withdrawals with no overlap at RCS 565 degrees F / 2250 psia;

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, Reactivity worth measurement of shutdown CEA Group B insertion at RCS 320 degrees F / 600 psia; Reactivity worth measurement of insertion of Shutdown CEA Group A minus one CEA (Group A- 1 ) at RCS 320 degrees F / 600 psia, simulating highest reactivity worth element CEA 77 stuck in the i fully withdrawn position;

' Pseudo-ejected CEA reactivity worth measurement at RCS 565 degrees F / 2250 psia; Reactivity worth measurements of pseudo-dropped CEA, Part Length CEA (PLCEA), and-PLCEA Subgroup at RCS 565 degrees F/

2250 palai CEA reactivity worth symmetry checks at RCS 565 degrees F/

2250 psia; Reactivity worth measurement of PLCEA Group P ( an- optional measurement for information only);

CEA reactivity worth ~ measurements by exchange of reactivity between CEA groups ( optional measurements ) .

I reviewed APS Procedure 72PY-1RX30, Rev 0, Low Power Physics Test, prior to and during the time that I observed the low power physics tests at Palo Verde 1. The procedure was modified by four PCNs to correct minor discrepancies and to change the frequency of boron sampling during long periods of boron stability. I found that the procedure was-complete'and explicit for all physics test activities. The procedure established prerequisites for low power physics testing that included comprehensive personnel indoctrinationi pretest briefing of operations personnel; equipment availability, calibration, and configuration requirementsi and special surveillance requirements. Initial conditions for entery into the procedure were clearly stated. Special precautions-to be observed during the procedure were provided.

I observed in the control room representative portions of all activities and measurements during the low power physics tests. All tasks were performed in accordance with the test procedure.and approved PCNs.

During the low power physics tests, the normal shift test. crew was an APS Responsible Engineer,.two assistants, and a Combustion Engineering representative. I-observed that the reactor test and reactor operating crews properly followed test procedures throughout the tests. The APS and Combustion Engineering reactor test personnel had a good basic understaning of the_ measurements being made and used proper test techniques to er.ture that valid data was obtained. I also observed close cooperation between the APS reactor test personnel and the Combustion Engineering representatives.

The APS reactor test pe.rsonnel were noticeably dependent upon the advice of the more experienced Combustion Engineering representatives during the approach to initial criticality and during early portions of the low power physics tests. I noted a definit ~e increase in confidence and independence of the APS reactor test personnel as they gained experience during the course of the low power physics tests.

During the low power physics tests I reviewed raw data and observed the APS data analysis process. All experiment data was analyzed by at least two people to detect errors and minimize interpretive variation. Good records were kept of all raw data for future reference. I found the data analysis effort was well planned and adequately staffed. I did not observe any discrepancies that went undetected or uncorrected. I believe that the' data obtained was gocd and that the final results of data analyses were accurate.

In all cases except one, the measured parameters conformed to predicted

' design values that were provided by Combustion Engineering and incorporated into the APS procedure. The predicted worth for insertion of CEA Group A minus one CEA withdrawn to simulate a stuck rod assembly (CEA Group A-1 ) was -0.37 %Dk/k with an acceptance range between -0.47 and -0.27 %Dk/k. The measured reactivity worth of CEA Group A-1 was

-0.55 %Dk/k. The larger than expected negative reactivity of CEA Group A-1 is not a safety problem since it indicates that more shutdown reactivity than was predicted is available frem insertion of this CEA group when one of the highest worth CEAs in the group is stuck in the fully withdrawn position.

APS test p.arsonnel generated a Test Exception Report (TER) for the CEA Group A-1 11easurement and initiated an Engineering Evaluation Request (EER). The APS Test Results Review Group (TRRG) reviewed the TER on May 30. The TRRG made an interim determination that the higher than expected r.egative reactivity worth of CEA Group A-1 did not impact safety in Mode 1 below 20% power. The TRRG referred the EER'to Combustion Engineering for final evaluation of the impact of exceceding the expected negative reactivity worth. I agree with the TRRG evaluation and disposition of this deviation from predicted test results.

CONCLUSIONS I found that Arizona Public Service had adequate and complete procedures in place to safely conduct the startup to initial criticality and the low power physics tests at Palo Verde Nuclear Generating Station, Unit 1.

The Palo Verde 1 operating crews and reactor test personnel that I observed on shift in the control room during initial startup and throughout the performance of low power physics tests followed established procedures.

I observed that the Palo Verde 1 reactor operating crews and reactor test personnel performed the appt nach to initial criticality and all low power physics tests competently. I also observed good cooperation and assistance from Combustion Engineering representatives on shift during the Palo Verde 1 startup and low power physic's tests.

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I observed representative portions of the data acquisition and analysis activities by the reactor test personnel during initial criticality startup and low power physics tests. Accurate data was obtained for all startup and test evolutions. I concur with the test data analyses and evaluaticns made by Arizona Public Service and Combustion Engineering personnel. No deviations from expected nuclear design characteristics that would adversely affect safety of operations of Palo Verde 1 were observed during the initial reactor startup and the low power physics test program.

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L. Rolf Peterson, P.E.

Nuclear Systems Safety Program Lawrence Livermore National Laboratory

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