ML20215M943

Forwards Addl Info Re Steam Line Rupture Detection/Isolation Sys Supervisory Capabilities in Response to NRC Concern Re Surveillance Frequencies Specified in 860604 Tech Spec Request & Discussed in 861020 Telcon

ML20215M943
Person / Time
Site:	Fort Saint Vrain
Issue date:	10/27/1986
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Berkow H Office of Nuclear Reactor Regulation
References
P-86605, TAC-60421, NUDOCS 8611030513
Download: ML20215M943 (6)

Text

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2420 W. 26th Avenue, Suite 1000, Denver, Colorado 80211 October 27, 1986 Fort St. Vrain Unit No. 1 P-86605 Director of Nuclear Reactor Regulation V. S. Nuclear Regulatory Commission Washington, D.C. 20555 Attention: Mr. H. N. Berkow, Director Standardization and Special Projects Directorate Docket No. 50-267

SUBJECT:

SLRDIS Technical Specification Request for Additional Information

REFERENCE:

1) PSC Letter Walker to Berkow, dated June 4, 1986 (P-86227)

Dear Mr. Berkow:

Public Service Company of Colorado (PSC) submitted in a letter dated June 4, 1986 (referenced above) a proposed Technical Specification change request for the Steam Line Rupture Detection / Isolation System (SLRDIS).

This letter submits (Attachment 1) the additional information on the SLRDIS system supervisory capabilities discussed with and requested by the NRC Staff in a telecommunication conference on October 20, 1986. This information is in response to the NRC Staff's concern related to the surveillance frequencies specified in the above referenced Technical Specification request.

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P-86605

. Pagn 2 October 27, 1986 i Should you have any questions concerning this matter, please contact

. Mr. M. H. Holmes at (303) 480-6960.

Very truly yours, 8

8 8. /YwJ l D. W. Warembourg, M r Nuclear Engineering Division I - DWW/JS:pa

!- Attachment I

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, Attachment 1 to P-86605 Each SLRDIS logic rack contains a microprocessor as the control unit.

The control unit continuously and automatically monitors critical circuitry and internal components. The control unit transmits a status request message (8 bit word transmitted serially) to each detection . module and in return each detection module sends back a status message. This ' process requires approximately one (1) millisecond to complete and is performed at intervals of about one (1) second. This state-of-the-art supervision system continuously monitors the following:

• Integrity of the interconnecting circuitry between each control unit and each thermistor assembly.

• Integrity of each thermistor assembly (open or shorts).

• Integrity of the circuitry to the shutdown relay coils.

• Integrity of each shutdown relay coil.

• All critical components within the logic rack and each detection module.

• Integrity of the circuitry between the logic rack and each detection module.

• The presence of the appropriate printed circuit cards within the logic and detection modules.

• The position of the trip inhibit switches.

• Status of individual sensor circuit test modes, i.e. status of the equipment in test.

Status of the power to each individual rack and total power of the system.

Status of the printer, including trouble and out of paper.

!~ . Attachment 1 j

• to P-86605

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F For any - trouble condition other than the status on the integrity of each thermistor. assembly, the following response will occur:

1. The system normal indicator on the specific detection rack

. or logic rack initiating the trouble response will turn off

! (For data transmiss' ion failure the system normal indicator

j. of the associated logic rack turns off.)

2. The annunciator output contacts on both logic racks will transfer if the trouble condition is . initiated by any detection rack. The annunciator output contact controlled

- from only the specific logic rack will transfer if the logic rack initiates the trouble response.

3. Except for microprocessor halts, printer. trouble (including

! printer cut of paper), or total power failure, the event will be logged on the system printers. For detection rack initiated troubles , both printers will operate. For trouble; associated with a logic rack, only the printer on that rack will operate.

! 4. If not disabled, the trouble audibles on the specific rack j in' trouble will sound.

i The trouble response above when caused by the following conditions will reset automatically when the trouble conditions is corrected:

1. Data transmission failure, j 2. Power supply or power failure.

{ 3. Microprocessor halt or malfunction.

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,+ Attachment 1

• to P-86605 The trouble response above when caused by the following conditions will reset when the trouble condition is corrected and the logic rack reset pushbuttons are then pressed:

1. Shutdown relay trouble.

2. Printed circuit card trouble.

3. Test mode position changes.

If the trouble response is still present when the system is reset, it will reoccur after approximately a 10 second reset delay.

When any sensor open circuit is detected, the control unit responds as follows:

1. A white sensor trouble indicator annunciating the specific circuit begins flashing.

2. The system normal light on the detection rack initiating the response turns off.

3. The event is printed on both logic rack printers.

4. If not disabled, the trouble audible in the initiating detection rack sounds.

5. The annunciator output contacts transfer (or reflash if previously transferred from another event).

The sensor open circuit response is latching and must be reset by clearing the open circuit and then pressing both logic rack reset buttons. If the open circuit is still present when the system is reset, the open circuit response will reoccur after a reset cycle lasting approximately 10 seconds.

4 Attachment 1

• to P-86605 When any sensor short circuit is detected, the control unit responds as follows:

1. A white sensor trouble indicator annunciating the specific circuit begins flashing.

! 2. The system normal light on the detection rack initiating the response turns off.

3. The event is printed on both logic rack printers.

4 4. If not disabled, the trouble audible in the initiating

, detection rack sounds.

5. The annunciator output contacts transfer (or reflash if previously transferred from another event).

The sensor short circuit response will automatically reset when the short is cleared after approximately 10 seconds. If a short circuit is still present when the system is reset, the short circuit response will reoccur after a reset cycle lasting approximately 10 seconds.

As discussed above, the supervision system continuously monitors critical circuitry and internal components. Alarms and printouts are given for the trouble conditions as noted above. The system normal indicators provide status of the SLRDIS and thus the integral supervision system.

j The supervisory system immediately alerts the operator of any anomalies within SLRDIS; whereas, without such a system, these same anomalies would not be detected until surveillance testing was performed.

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