ML20140C717

Safety Evaluation Supporting Interim Operational Use of SPDS Until Design & Installation of computer-based SPDS Completed

ML20140C717
Person / Time
Site:	Peach Bottom
Issue date:	03/12/1986
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20140C700	List: ML20140C695 ML20140C717
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-1.D.2, TASK-TM NUDOCS 8603250462
Download: ML20140C717 (5)

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f jog UNITED STATES g NUCLEAR REGULATORY COMMISSION O g('(:: np WASHINGTON, D. C. 20555 v 4,o8 SAFETY EMLUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION _

PEACH BOTTOM ATOMIC POWER STATION, UNITS 2 AND 3 INTERIM SAFETY PARAMETER DISPLAY SYSTEM (NUREG-0737, I.D.2)

DOCKET NOS. 50-277 AND 50-278 I. BACKGROUND In response to the requirements for a Safety Parameter Display System (SPDS) identified in Supplement 1 to NUREG-0737, a Safety Analysis (Ref.1) on the Peach Bottom SPDS was submitted for staff review. The staff reviewed the Safety Analysis and also conducted an audit of the Peach Botton SPDS. The results from these efforts served as the basis of the staff's Safety Evaluation Report (SER), Reference 2.

The SER stated the staff was unable to confirn that Peach Botton SPDS met NRC requirements. The Philadelphia Electric Company's (licensee)

SPDS consisted of existing instruments located at various points in the control room, but did not incorporate acceptable human factors engineering principles, and did not include an effective means to validate data. In addition, the staff raised questions on the need to monitor additional variables and the need for information on the adequacy of the isolation devices. The licensee requested a meeting to discuss these findings and conclusions, and on June 14, 1985, met with the NRC. Minutes of the meeting are presented in Reference 3.

During the June 14, 1985 meeting, the licensee provided the staff with additional information on the SPDS. The licensee identified plans to install a new, process-control computer at the plant and associated computer assisted SPDS. The licensee also discussed modifications to the existing SPDS to have it serve as an interim SPDS during the design, development, and installation of a computer-based SPDS. The NRC staff stated that further review of the Peach Bottom interim SPDS t.as warranted, and we requested the licensee to docket information on the status of the new process computer, which the licensee did (Ref. 4).

II.

SUMMARY

The staff's review of the licensee's existing SPDS concludes that the system is acceptable for operational use as the interim SPDS until the design.and installation of the computer-based SPDS is completed. All of the interim SPDS instruments conforn to the category 1 criteria of Regulatory Guide 1.97, except for Neutron Flux. The SPDS indication for -

neutron flux is a non-safety recorder. The isolation device used at the interface between the flux sensor and the recorder is a fuse and voltage -

divider. This device was reviewed and found acceptable during the 3250462 860312 p ADOCK 05000277 PDR 3

licensing review of Peach Bctton, therefore, we conclude that this _

device is acceptable for the interim SPDS. However, during the des ~ign, .

development, and installation of the new computer-based SPDS, qualified isolation devices must be installed at this interface.

III. EVALUATION Human Factors Engineering Principles The staff's initial review of the Peach Bottom SPDS design concluded that it did not incorporate human facters engineering principles so as not to mi, lead operators during accidents. During the June 14, 1985 meeting with the staff, the licensee stated that the ongoing Control

. Room Design Review (CRDR) will evaluate the specific human factors concerns identified by the staff on the interim SPDS.

In Reference 4, the licensee states that since the analog-based SPDS will be replaced with a computer-based SPDS, specific human factor concerns addressed in the Control Room Design Review will be addressed from the viewpoint of an indicating SPDS instrument. The licensee also states that a task analysis of the SPDS function and major hardware changes to resolve the human factors concerns related to the SPDS function will be deferred since the new computer-based SPDS will receive its own human factors evaluation as required by Supplement 1 of f;UREG-0737. Design specifications for the new process-control computer are currently being developed by the licensee. Based on current outage schedule projections, the computer-based SPDS should be operational on Unit 2 by late 1989, and on Unit 3 by mid-1990.

During the June 14, 1985 meeting with personnel from Peach Bottom, the staff requested information on the cost and effort to install an SPDS independent of the new process-control computer. The licensee's response (Ref. 4) states that an SPDS independent of the process-control cceputer would add nearly two million dollars to the total cost of these modifications. The additional expense associated with incorporating the SPDS feature into the process computer is approximately 0.5 million dollars. The cost-benefit is in favor of incorporating the SPDS into the process-control computer.

During the interval between now and operation of the new computer-based SPDS, the licensee proposed that existing control room instruments serve as the-interim SPDS system with the following justifications:

. the system includes the key parameters needed by control room personnel for assessing whether abnormal conditions warrant corrective action by operators to avoid a degraded core; -

i the operators have been thoroughly trained on a simulator to -

respond to transients and emergency conditions using existing control room instruments and redundant instruments on other panels in the control room; n- . .. . - . - - - . - _ - _ - . . .

u -

- following completion of the upcoming Unit 3 outage, all SPDS sensors will be environmentally and seismically qualified in accordance with the licensee's commitment on Regulatory Guide 1.97.

Based on this information, the staff concludes that the interim SPDS is acceptable until the new computer-based SPDS consistent with the stated schedule is installed and declared operational. However, we request the licensee submit for staff review the human factors program used in the design of the computer-based SPDS. In addition, the results from the task analysis of the SPDS function should also be submitted for staff review.

Data Validation The staff's initial review of the interim SPDS concluded that the design did not include an effective means to validate data. During the June 14, 1985 meeting, the licensee stated that for most variables within the interim SPDS, the instrument loops are safety-related circuits. It was further stated that all sensors except one in Unit 3 are environmentally and seismically qualified, and this one remaining sensor is being replaced with a qualified sensor (to meet Regulatory Guide 1.97 requirements) during the current Unit 3 refueling outage.

The use of instruments that meet Regulatory Guide 1.97 requirements make the interim SPDS a reliable system. The staff's audit of the interim SPDS found that the redundant instruments used to validate the readings from the principal instruments of the interin SPDS were not located near the principal instruments. The lack of a concise display was the basis of our conclusion that the design does not include an effective means to validate data.

The relocation of the redundant instruments to a position near.the 1 principal instruments to facilitate data validation is not a practical  !

solution. The operators have been thoroughly trained to respond to transients and emergency conditions using the interim SPDS and redundant instruments. Based on this training, the staff concludes that these practices should serve to validate data from the interim SPDS.

In the. design of the computer-based SPDS, the staff recommends the licensee use signals from redundant sensors for a process variable in validating data prior to display. Furthermore, the licensee should submit.'for staff review a description of the algorithm to be used in ,

valida&ing data. Also, the licensee should submit for staff review the . l design verification and validation program to be used in the design and l development of the computer-based SPDS. The staff will review this .

information to confirm that the data displayed are valid and to ensure the development of a reliable display system. The results from our review will be presented in a future SER. l

Parameter Sele: tion The NRC staff's evaluation (Ref. 2) of the Peach Bottom SPDS included followup items regarding the addition of a more direct indication of neutron flux and radioactivity release rate. In its August 9, 1985 letter, the licensee stated that the current Source Range Monitor (SRM) indication will be designated as part of the interim SPDS. The licensee also designated the APRMs as part of the interim SPDS. For the Radioactivity Control Critical Safety Function, the licensee has identified offgas and vent stack radiation indication and drywell high-range radiation as part of the interim SPDS. The staff concludes that the commitnent to include these additional variables is responsive to the staff and is acceptable. We note that the interim SPDS includes only Group I (Main Steam) isolation valves in the containment isolation status display. We recommend that the licensee include additional 1 isolation valve groupings in the development of the new, computer-based SPDS. By monitoring the status of all isolation. valves, there is assurance that known process systems pathways have been secured.

! Electrical and Electronic Isolation The staff's review of the licensee's interim SPDS was incomplete because of insufficient information on the adequacy of the isolation devices within SPDS design. In the August 9, 1985 submittal, the licensee states that several instruments selected for the interim SPDS are treated as safety-related circuits from the sensors up to and including the interim SPDS indicators. No isolation devices are'used in these circuits to separate the interim SPDS from the sensors.

All of the interim SPDS instruments conform to the category 1 criteria of Regulatory Guide 1.97, except for Neutron Flux. -The SPDS indication for neutron flux is a non-safety recorder. The isolation device used at the interface between the flux sensor and the recorder is a fuse and voltage divider. This device was reviewed and found acceptable during the licensing review of Peach Bottom, therefore, we conclude that this device is acceptable for the interim SPDS. However, during the design, development, and installation of the new computer-based SPDS, qualified isolation devices must be installed at this interface.

In the. licensee's design of the computer-based SPDS, the staff will require data on the isolation devices used in the design. The staff plans to review the data to determine if the SPDS is suitably isolated from electrical or electronic interference with equipment and sensors that awe in use for safety systems (Supplement 1, NUREG-0.737). The ,

results from the staff's review will be presented in a future SER.

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Dated: March 12,1986 l Principal Contributor: L. Beltracchi l L

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IV. REFERENCES ,

1.

Letter from J. W. Gallagher, Philadelphia Electric Cempany, to D. G ,Eisenhut, NRC,

Subject:

Safety Parameter Display System, Peach Bottom Atomic Power Station, dated September 28, 1983.

2. Letter from H. L. Thompson, NRC, to E. G. Bauer, Jr., Philadelphia Electric Company,

Subject:

Review of Philadelphia' Electric Company's Safety Analysis and the NRC Staff's Audit of the Peach Bottom Safety Parameter Display System, dated April 3, 1985.

3. Letter from G. E. Gears, NRC, to Licensee: Philadelphia Electric Company, Facility: Peach Bottom Atomic Power Station, Units 2 and 3,

Subject:

Summary. of Meeting With Philadelphia Electric Company Proposed Safety Parameter Display System (SPDS) At the Peach Bottom Facility, dated July 2,1985. ,

4 Letter from J. S. Kemper, Philadelphia Electric Company, to H. L. Thompsco, NRC,

Subject:

Peach Bottom Atomic Power Station Units 2 and 3, Safety Parameter Display System, dated August 9,1985.

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