ML20065G739

Details Evaluation of Discrepancy Between Electronically Simulated Reactor & Channel Periods Revealed in Calibr Test Performed on Log-N-2 Channel.No Unsafe Condition Existed & No Tech Spec Violation Occurred

ML20065G739
Person / Time
Site:	Lynchburg Research Center
Issue date:	09/27/1982
From:	Olsen A CONSOL, INC. (FORMERLY CONSOLIDATION COAL CO.)
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8210040214
Download: ML20065G739 (3)

Text

. -. - = - -

f 4 ,

Research & Development Division Babcock & Wilcox ,

tynennore n rcn c.ni.,

4 a McDermott company P.O. Box 239 I Lynchburg, Virginia 24505 September 27, 1982 (804) 384 5111 i

i i

l Standardization & Special Projects Branch t

Division of Licensing Office of Nuclear Reactor Regulation i U. S. Nuclear Regulatory Commission l Washington, DC 20555 4

License: CX-10, Docket 50-13

Reference:

Letter to Robert W. Reid, Chief From A. F. Olsen, May 18, 1981 Centlemen:

J The referenced letter informed the NRC that a calibration test i

performed on the Log-N-2 channel of the CX-10 revealed a discrepancy between the value of an electronically simulated reactor period and i

the period indicated on the channel's period meter. In the refer-ence, the NRC was advised that the facility would not be operated until the discrepancy was resolved and that the NRC would be informed of the resolution. The purpose of this letter is to advise the NRC

of the resolution of this problem.

Our evaluation of this problem focused on three areas:

1. Determination of whether an unsafe condition had been present or not.

2. Determination of whether or not a violation of the facility's j Technical Specifications had occurred.

j 3. Repair of the channel so that true period and indicated period j correspond.

We concluded from our evaluation that no unsafe condition had existed

and that no violation of the Technical Specifications had occurred.

{ The channel was repaired so that true period and indicated period

corresponded. The evaluation is discussed in detail below.

i 1.0 Safety Considerations

, 1.1 Normal' Operations i I The Log-N-2 period instrument provides a shutdown function only.

It is not used by the operator to track the approach to criticality or to monitor the reactor period. This information is provided by the OW Log N startup channel.

i 8210040214 820927 4

PDR ADOCK 05000013 i P PDR

._ _ _. _ . ~ _ _ _ _ - - . . . _ _ . _ _ _ . - _ _ _ _ _ - __. - - . - . -

• 2 9

1.2 Maximum Credible Accident None of the safety analyses in the Hazards Evaluation Reports prepared for the license or amendment applications assume operation of the period safety channel. Termination of uncontrolled reactivity excursions during the postulated maximum credible accidents depend mainly on internal shutdown mechanisms, i.e., Doppler broadening of the epithermal absorption resonances. The one Hazards Evaluation (Amendment #11) that does assume operation of the external safety system takes credit for scram initiation by one of the two redundant linear safety channels. Even in this case, the period channels are not assumed to function and the effects of the external shutdown system take place only after doppler broadening has already terminated the initial excursion. No credit is taken fer the mitigating effects of the period channel activation during any accident analysis because the calculated consequences and effects of the accident would not be changed by a change in the Log-N-2 period channel setting.

2.0 Technical Specifications The CX-10 facility does not have technical specifications per se.

However, Title 10, Code of Federal Regulations, Part 50, 550.36(d)(1) states that if a facility license was issued prior to January 16, 1969, and does not have technical specifications, the entire safety analysis report is considered to be the technical specifications. In the case of CX-10, this would include several documents because t umerous license amendments have been applied for and granted since the license was initially issucd.

These documents specify the use of four safety channels (two linear safeties and two period safeties) at all times during reactor operation.

There is no question that all four safety channels have been operational since each one is tested every day that the reactor is run. Only the settings (scram and setback) of Log-N-2 are in question.

The requirements for the Log-N-2 scram and setback settings specified in the license applications that comprises the Safety Analysis Report are vague. BAW-1245 (application for amendment #5 authorizing operation with the 2.5% enriched fuel) incorporates by reference the safety system described in BAW-1211 (application for amendment #3). BAW-1211 states that Log-N-2 initiates scram and setback signals at pre-set levels which are usually set at 13 and 20 seconds, respectively. There is no apparent license restriction that prohibits these settings from being changed to any particular value.

In view of these considerations, it was concluded that no violation of the technical specifications had occurred.

3.0 Instrument Repair The final step was to repair the instrument so that the true period and the period meter reading matched. This was accomplished so that the meter could be used to confirm the Log-N-2 scram and setback settings during the Log-N-2 channel checks performed each day prior to reactor operation. The repair was accomplihsed by adjusting the capacitance of 1 i ,

a condenser that differentiates the Log N amplifier output and provides j the input signal for the Log-N-2 safety preamplifier. After the repair, proper calibration of the channel was experimentally confirmed both with an electronically simulated period and with a true reactor period uti-lizing the Lynchburg Pool Reactor (R-47) . The channel was also tested for proper scram and setback operation before being restored to service.

~

All these actions.have been reviewed by the Lynchburg Research Center's, Safety Review Committee. The instrument has operated properly since the repair has been completed.

4 Very truly yours, BABCOCK & WILCOX Lynchburg Research Center

! ,rne F. Olsen Senior License Administrator I AF0/jhc 4- cc: Director, Region II i

)

1 l

I i

i 5

i t

i I

1 4

- -.- - -- - - - . - , .,r-,, , nnn--,------, - s--, .. .,--n., -.v..-,-,. .-..--.,n,. . . . .. - - - -n--.- - - , - ,,- - - -- , - ------ ---