ML20023C941

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Safety Evaluation Supporting Amends 84 & 67 to Licenses DPR-53 & DPR-69,respectively
ML20023C941
Person / Time
Site: Calvert Cliffs  Constellation icon.png
Issue date: 05/05/1983
From:
Office of Nuclear Reactor Regulation
To:
Shared Package
ML20023C940 List:
References
NUDOCS 8305180607
Download: ML20023C941 (4)
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NOS. 84 AND 67 TO FACILITY OPERATING LICENSES NOS. DPR-53 AND OPR-69 BALTIM0RE GAS AND ELECTRIC COMPANY CALVERT CLIFFS NUCLEAR POWER PLANT UNIT NOS. 1 AND 2 DOCKET NOS. 50-317 AND 50-318 Introduction By app.lication for License Amendment dated March 15, 1983, Baltimore Gas and Electric Company (BG&E) requested changes to Calvert Cliffs Units 1 and 2 Technical Specification (TS) 3/4.1.3, " Movable Control Assemblies - Full Length CEA Position," and 3/4.1.3.3, " Position Indication Channels." The purpose of the proposed TS changes is to allow periodic testing of control element assemblies (CEAs) with inoperable reed switch stack system.

Discussion Three separate CEA position indication systems are used by the Calvert Cliffs Unit Nos. 1 and'2 to monitor CEA positions. The Pulse Counting System infers the position of each CEA by maintaining a record of the raise and lower control pulses used to actuate the magnetic jack mechanisms. This system is incorporated into the plant computer which feeds control board digital displays and an output typewriter. The plant computer also provides deviation informaticn.

If the de-viation in position between the highest and the lowest CEA in any group exceeds setpoints of 3.75 and 7.5 inches, the computer provides an alarm and initiates a printout of the actual positions of all CEAs within the affected group. The Reed Switch Stack system utilizes a series of magnetically actuated reed switches, spaced at 1.5 inch intervals along the CEA housing and arranged with precision resistors in a voltage divider network, to provide signals propor-tional to CEA pcsition. The signals are displayed in bar chart form by the metrascope on control board 1C05. A backup readout is provided which can be utilized to read the output of any reed switch voltage divider. The metra-scope logic package uses the reed switch positions to generate various alarms associated with misaligned or overinserted CEAs. These alarms also prevent further CEA insertion by generating a CEA Motion Inhibit (CMI). The third indication system uses Reed Switches independent of those on the reed switch stack. These switches actuate lights on a CEA mimic display on control board 1C05. On this display ' red lights indicate " Full-out" CEAs, green lights indicate " Full-in" CEAs, amber lights indicate Dropped CEAs, and white lights indicate CEAs between the upper and lower limits.

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. Recent operating experience at Calvert Cliffs indicates that new reed switch stacks installed in both Units 1 and 2 during the last outages are experiencing higher than previous failure rates of the previous reed stack design.

The current failures result in loss of reed switch stack indication for the affected CEA and consequently a continuous CMI signal regardless of CEA position.

In accordance with TS 3.1.3.3, the affected CEAs have been with-drawn until the " Full-out" indication was received.

In order to provide the CMI function for other CEAs, the defective stack input to the metrascope has been replaced with a 10 VDC signal consistent with the affected CEA's full out position. A relay operated off the " full-out" reed switch was also installed so that loss of the " full-out" indication opened a contact in the temporary 10 VDC signal to the metrascope. This arrangement will annunciate improper alignment of the affected CEA and prevents-the movement of other CEAs should such misalignment occur. These modifications ensure all CMI functions are operable for all CEAs except when the affected CEA is being moved between

" full-in" and " full-out" during startup and shutdown. The licensee presently expects to replace the failed reed switch stacks and remove the 10 VDC source during the next~ refueling outage.

The failure of the reed switch stacks has, however, resulted in a conflict in the TS. This conflict involves TS 3.1.3.3 which requires CEAs with an inoperable posjtion-indicating channel to be maintained in a fully inserted or fully withdrawn position

  • and TS 4.1.3.1.2 that requires that CEAs not fully inserted be tested.by inserting them at least 7.5 inches at least once per 31 days.

To resolve this conflict, BG&E has proposed the following changes to the TS:

(1) Action Statement 3.1.3.1.h is established to define the requirement for insertion of a CEA with an inoperable CEA position indicating channel. Proposed TS 3.1.3.1.h states that, "For the purpose of performing the CEA operability test of TS 4.1.3.1.2, if the CEA has an inoperable position indication channel, the alternate indication system (pulse counter or voltage dividing network) will be used to monitor position.

If a direct position indication (full out read switch or voltage dividing network) cannot be restored within ten minutes from the commencement of CEA motion, or CEA withdrawal exceeds j

I the surveillance testing insertion by > 7.5 inches the position of the CEA shall be assumed to have been > 15 inches from its group at the commencement of CEA motion." Existing TS 3.1.3.1.f provides re-quirements for remedial action when a CEA is misaligned by a distance equal to or greater than 15 inches.

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  • This requirement assures that the CEA position is known via the " Full-out" i

or " Full-in" reed switches.

During full power operation, no CEAs are fully inserted.

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y (2) Proposed change to TS 3.1.3.3.c.2 is also required-to allow motion df a CEA, being maintained fully withdrawn due to an inoperable CEA 4

position indicating channel *, to be inserted for the purpose of CEA motion testing. The proposed TS 3.1.3.3.c.2 change is as follows:

"This requirement is exempted during CEA motion required for.

surveillance testing pursuant to Technical Specification 3.1.3.1."

(3).Froposed change to TS 3.1.3.3.c.3 provides a reference to TS 3.1.3.1 for the requirements applicable to testing of CEAs with inoperable position indicating channels. This change is administrative in nature in that.it does not impact any system important to safety, it is provided only as a convenience in that it refers to another requirement. This change is therefore acceptable.

In addition to the above TS changes, changes ~are proposed to the Bases for TS 3/4~.1.3 to reflect the requirements for CEA motion testing with an inoperable CEA position indication channel.

Evaluation As indicated above, the CEA position indication between the full-out and full-in limits is monitored by the reed switch stack and_ pulse counting systems. The reed switch stack system is preferred since it' indicates the actual location of the CEA. The pulse counting system measures the demand position in that is shows the " requested" location of the CEA. The actual location and the demand location of a CEA may be different due to binding of the CEA or slipping within the CEA drive mechanism. For this reason, TS

'that would allow CEA motion with an inoperable position indicating channel would be more limiting.with an inoperable reed switch stack system, with i -

position being monitored by the pulse counting system, due to the uncertainty associated with the actual CEA position.

For the case of proposed TS 3 1.3.1.h'and 3.1.3.3.c.2, with-an inoperable reed switch stack system, the CEA motion test of TS 4.1.3.1.2 would be con-ducted using the pulse counting system to monitor CEA position. Even in the unlikely event that the actual CEA position immediately differed from the position indicated by the pulse counting system, the actual position would have to be. reestablished via the full-out reed switch or reed switch stack system, within 10 minutes.

If CEA position could not be reestablished, the proposed TS would require that the maximum CEA misalignment (equal to or.

greater than 15 inches) be assumed to have occurred with initiation of CEA 1

motion. Existing TS 3.1.3.1.f requires remedial action to be taken within one hour in the event that a CEA is misaligned by a distance that is equal 4

to or greater than 15 inches. Moreover, the proposed TS would require that the total time that the actual CEA position is unknown be incorporated in the one-hour time limit for remedial action under TS 3.1.3.1.f in the event that actual CEA position cannot be reestablished. We conclude, therefore, that the proposed TS would require that remedial action, if needed, be taken within the-time limitations of existing TS. Accordingly, we conclude that the l

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. proposed TS fall within the range of consequences which are already con-sidered in the TS bases, will not increase the hazards potential associated with misaligned CEAs and are, the efore, acceptable.

Environmental Consideration We have determined that the amendments do not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this determination, we have further concluded that the amendments involve an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact statement or negstive declaration and environ-mental impact appraisal need not be prepared in connection with the issuance of these amendments.

Conclusion We have concluded, based on the considerations discussed above, that:

(1) because the amendments do not involve a significant increase in the probability or consequences of an accident previously evaluated, do not create the possibility of an accident of a type different from any evaluated greviously, rqJ do not involve a significant reduction in a margin of safety, the amendments do not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.

Date: May 5, 1983 Principal Contributor:

D. H. Jaffe J

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