ML20045D574

Responds to 930305 Request for Clarification of Statement, Re Generic Weakness Identified During Operating Exam,That Appeared in Initial Exam Rept 50-002/OL-92-03

ML20045D574
Person / Time
Site:	05200002
Issue date:	06/24/1993
From:	Boger B Office of Nuclear Reactor Regulation
To:	Burn R MICHIGAN, UNIV. OF, ANN ARBOR, MI
References
NUDOCS 9306290163
Download: ML20045D574 (4)

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WASHINGTON, D.C. 20555 4 001 JUN 2 41993 Mr. Reed R. Burn, Reactor Manager The University of Michigan Phoenix Memorial Laboratory Ford Nuclear Reactor Ann Arbor, Michigan 48109-2100

SUBJECT:

INITIAL EXAM REPORT NO. 50-002/0L-92-03 This letter responds to your letter _ dated March 5,1993, to Mr. Vick requesting clarification of the statement, "A generic weakness was identified during the operating exam concerning the difficulty that each of the candidates exhibited when asked to explain the relationship between reactor power instrument readings and actual reactor power," that appeared in Initial Examination Report No. 50-002/0L-92-03 dated February 2, 1993. On March 24, 1993, the University of Michigan Ford Nuclear Reactor (FNR) experienced an over-power event and a decision was _made not to respond to your letter until the event evaluation had been completed.

Following the enforcement conference held in Region III on April 26, 1993, concerning the March 24, 1993, over-power event and a telephone conference call between yourself, members of your staff (Gary Cook and Robert Touchberry), and NRC staff members (Jim Caldwell, Warren Eresian, Larry Vick and Ted Michaels) on May 3, 1993, the NRC staff has a better understanding of the complexities associated with the FNR's method of achieving and controlling reactor power at or below its license limit.

During the conference call you explained the use of the rod shadow curve and' core differential temperature for making reactor power, nuclear instrument set-point, and nuclear instrument position adjustments to compensate for the effects of xenon-induced flux shift as seen by the nuclear instruments. Also during the conference call you stated that because of the placement of the related sensors, there are no nuclear instrument power indications in the control room which indicate actual reactor power to the operator. The operators rely on the facility's operating procedures to ensure that reactor power is at or below the license limit.

During the initial license examinations conducted by the NRC on December 16, 1992, the Chief Examiner noted that each of the candidates had difficulty explaining the relationship between the control room reactor power instrument readings and actual reactor power.

While the reactor was operating at an indicated power in excess of 100%, the examiner asked each candidate the following questions:

(1) What is the actual reactor power, and.(2) Explain how you can determine actual reactc power? The questions were asked to determine the candidate's understa;, Jing of the relationship between reactor power instrument readings and actual reactor power.

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JUN 2 41993 Mr. Reed R. Burn.

The candidates answered that reactor power was 2 MW, which is the facility license limit for the Ford Nuclear reactor.

The candidates also described how to use the facility's operating procedures to reach the expected 2 MW reactor power.

Each candidate explained in very general terms the procedure for performing a calorimetric at 1 MW thermal power prior to increasing the reactor to 100% power.

However, none of the candidates adequately described how the relative reactor power instrument readings, which can read anywhere from 95% to 105% for the same actual reactor power, could be used to determine actual reactor power or how they knew that the license power limit of 2 MW had not been exceeded.

The candidates did not discuss the basis and function of the rod shadow curves, which are used to adjust reactor power upward during the xenon-induced flux shift.

In addition, the candidates did not explain how core differential temperature is used to verify that the adjustments made while using the rod shadow curves have not caused actual reactor power to increase above the license limit. Also, the candidates did not describe how core differential temperature is affected by the operation of various facility components and ambient conditions or when the differential temperature can and cannot be used to verify that the license power limit has not been exceeded.

These concepts, which are essential in explaining how reactor power is controlled at your facility, were not communicated to the examiner during the operating test for initial license examinations conducted on December 16, 1992.

In the conference call with the NRC on May 3,1993, you stated that following the March 24, 1993, over-power event, you developed a procedure that explains the method of compensating for the xenon-induced flux shift, by using the rod shadowing power effect curve, a newly developed table and a core differential temperature operating band.

You also explained similar information in-an internal memorandum to your reactor operations staff dated February 15, 1993.

In addition, you indicated that you will be upgrading your training program to provide more training to the operators concerning the use and basis of the rod shadow curves and the core differential temperature.

These actions should provide the operators with the necessary knowledge to enable them to properly diagnose problems with reactor power and recognize when abnormalities exist.

In summary, although the examiner understood that the candidates could follow the facility's operating procedures for achieving 100% reactor power, he was not provided with the information necessary to verify that the candidates understood the relationship between indicated power and actual power.

The generic weakness, in the examination report, 50-002/0L-92-03, served to

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Mr. Reed R. Burn identify the incomplete responses of the candidates to the question concerning the relationship between indicated reactor power and actual reactor power.

If you have any questions, please call Jim Caldwell at (301) 504-1042.

Sincerely, Original.sigred by:

Bruce A. Boger, Director-Division of Reactor Controls and Human Factors Office of Nuclear Reactor Regulation 1

DISTRIBUTION:

' Central Files

• OLB RF PDR/LPDR LVick SGuenther AMendiola JCaldwell DJLange DMcCain RGallo/BBoger SWeiss

• See previous concurrence

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0FFICIAL RECORD COPY DOCUMENT NAME:

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JUN 2 41993 q

s Mr. Reed R. Burn.

identify the incomplete responses of the candidates to the question concerning the relationship between indicated reactor power and actual reactor power.

If you have any questions, please call Jim Caldwell at (301) 504-1042.

Sincerely, Origir.11 signed by:

Bruce $.Boger, Director Division of Reactor Co'4trols and Human Factors Office of Nuclear Reactor Regulation DISTRIBUTION:

Central Files OLB RF PDR/LPDR LVick SGuenther AMendiola JCaldwell DJLange DMcCain RGallo/BBoger SWeiss

• See. previous concurrence HOLS:DRCH HOLB:DRCH HOLB:DRCH HOLB:DRCH ONDD: DORS DIR:DRCH D LVick:rc AMendiol a JCaldwell DLange SWeiss RGallo B ger 05/06/93* 05/11/93* 05/11/93* 05/28/93 06/10/93*

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/gp3 0FFICIAL RECORD COPY DOCUMENT NAME:

G:\\CALDWELL\\BURNLTR3.FNR

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