ML20049J529

LER 82-021/01T-0:on 820217,during Startup,Shutdown Rods in Shutdown Bank a Exceeded Plus/Minus 12 Steps of Actual Position on Indicators.Caused by Misinterpretation of Limiting Condition for Operation 3.1.3.3.Rods Recalibr

ML20049J529
Person / Time
Site:	Sequoyah
Issue date:	03/02/1982
From:	Carver A, Harding M TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20049J527	List: 05000328/LER-1982-021, Forwards LER 82-021/01T-0 05000328/LER-1982-021-01, /01T-0:on 820217,during Startup,Shutdown Rods in Shutdown Bank a Exceeded Plus/Minus 12 Steps of Actual Position on Indicators.Caused by Misinterpretation of Limiting Condition for Operation 3.1.3.3.Rods Recalibr ML20049J529
References
LER-82-021-01T, LER-82-21-1T, NUDOCS 8203180311
Download: ML20049J529 (3)

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["o'TT] l Unit 2 in mode 3, with RCS temperature and pressure at 500 degrees F and 1900 psig. I gol3; l During unit startup, shutdown rods in shutdown bank A were in excess of 112 steps of f o 4 l actual rod position as indicated by rod position indicators. This event and previous l o 3 l occurrences require'd entry into LCO 3.1.3.3. There was no effect on public health l lo is l 17r' saf e ty. (Circumstances for possible previous occurrences are outlined in the l go;7l { attachment submitted.) -

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p o .o LER SUPPLEMENTAL INFORMATION Event Description During unit 2 startup with the reactor in mode 3, RCS temperature at 500 degrees F and RCS pressure at 1900 psig, shutdown rods were in excess of 12 steps of actual rod position as indicated by the rod position indicators. In addition, fods P-4 ,,

and M-14 were in excess of 112 steps of other rods within the same bank. At various times during startup of units 1 and 2 since initial operation, the requirements of Technical Specification 3.1.3.3 have not been met due to a misinterpretation and misunderstanding of the specification requirements.

Sequence of Events and Background Information On February 17, 1982, it was discovered by the NRC Resident Inspector on unit 2 that the rod position indicators of two rods (P-4 and M-14) in shutdown bank A were indicat ,g greater than 12 steps with respect to the other rods in the banks.

The inspectot 'iscussed this situation'with the Shift Engineer and it was concluded that the exist. g situation was in violation of LCO 3.1.3.3. The Shift Engineer then directed the unit operator to open the reactor trip system breakers, thereby complying with the action statement.

Investigation revealed that the rod position indicators for P-4 and M-14 had been calibrated to cold conditions while the other rods in bank A were calibrated to hot conditions. This resulted in the rod position indicators indicating different values. The rod position indicators were recalibrated after the system attained normal operating temperature.

Prior to this event, Sequoyah had been routinely maintaining the shutdown control rods fully withdrawn with the unit in mode 3, 4, or 5, regardless of system temperature, to provide additional safety in the event of a boron dilution or similar inadvertent criticality event. The individual rod position indicators are calibrated with the system at normal operating temperature. Due to their sensitivity to system temperature, the rod position indicators will vary from demand position indication (actual position) when system temperature is less than 541 degrees F. For these reasons, 3.1.3.3 was interpreted to be met l

if individual rod position indicators were within 12 steps of each other.

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On February 18, 1982, this event and technical specification 3.1.3.3 interpretations were discussed between Operations personnel and the Operations supervisor. It was

! discovered that there were differing opinions on the interpretation of 3.1.3.3 and some confusion existed. It became apparent that no unified clear interpretation l of 3.1.3.3 existed among the Operations personnel contacted.

A second interpretation that surf aced during these discussions was that the RPI had to indicate within 12 steps of actual rod position.

Because of the existing confusion and the possibility that this second interpretation was correct, the shutdown rods on unit 1 were inserted and the NRC Resident Inspector was contacted. The NRC regional office was notified, and a conference call was held with Nuclear Reactor Regulations (NRR) technical specification specialists on February 18, 1982, concerning the interpretation of 3.1.3.3. NRR stated that the requirements of 3.1.3.3 are met if the rod position indicator indicates actual rod position within 112 steps with reactor trip system breakers

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in'the close'd position. NRR was aware of the effects of temperature on the .

rod position indicators and made a suggestion that a technical s'ecification p change be l submitted.

The results of this conversation were discussed with the NRC Inspector.concerning

' Sequoyah~ units 1 and 2 being less conservative that the requirements given in 3.1.3.3 at various times during startup since initial operation.

Conclusions and Corrective Actions It appears that both units have been operating at various times less conservatively.

than the requirements of Technical Specification 3.1.3.3 as interpreted by the NRR.

This was due to a misinterpretation of specification 3.1.3.3 and the operating procedures reflecting this misinterpretation Since the unit 2 startup event of February 17, 1982, the requirements of 3.1.3.3 have been met on both units by keeping shutdown ods fully inserted until operating temperature has been reached. -This has been achieved by placing a statement to this effect in the night order book.

A technical specification change . request will be prepared and submitted to allow l the shutdown rods to be withdrawn in modes 3, 4, and 5. Appropriate procedural changes will also be made once the specification change has been approved.

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