ML20116E392

Submits Addl Info Re Generic Ltr 82-33 Re Spds,Per J Miller .Hot Leg Temp Displayed in Primary Reactor Coolant Temp Trend Display.Steam Line Radiation Variables Will Be Added to Top Level Primary Heatup/Cooldown Display

ML20116E392
Person / Time
Site:	Prairie Island
Issue date:	04/17/1985
From:	Musolf D NORTHERN STATES POWER CO.
To:	Office of Nuclear Reactor Regulation
References
GL-82-33, NUDOCS 8504300277
Download: ML20116E392 (3)

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e O Northem States Power Company 414 Nicollet Mall Minneapolis. Minnesota 55401 Telephone (612) 330-5500 April 17, 1985 Director Office of Nuclear Reactor Regulation U S Nuclear Regulatory Commission Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License'Nos. DPR-42 50-306 DPR-60 Additional Information Related to Generic Letter No. 82-33; Safety Parameter Display System (SPDS)

The purpose of this letter is to provide, ter the information of the NRC Staff, additional information related to Generic Letter No. 82-33, Safety Parameter Display Systems (SPDS). This information was requested in a letter dated February 14, 1985 from James R. Miller, Chief, Operating Reactors Branch No. 3, Division of Licensing US NRC.

The following information is provided in response to Mr. Miller's February 14, 1985 letter:

Item IIIB Additional Requested Variables

1. Hot Leg Temperature Hot Leg Temperature is displayed in the lower level primary RC Temperature Trend Display. The critical safety functions for core cooling utilize core exit thermocouples as a decision variable.

Core exit thermocouple highest value is displayed on the top level primary displays and on various lower level primary trend displays. In addition, plans are to have a core thermocouple map display as a lower level primary display.

2. Steam Line Radiation Steam line radiation variables (one monitor per steam line located upstream of the main stream isolation valves) will be added to the top level primary heatup/cooldown display and to the top level primary normal operations display.

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Containment-Isolation

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. One-_of-the functions of the ERF computer is to provide indication of containment-isolation'on the secondary CRT's. This display is

. a default type of display, ie., will indicate if containment

s-_ isolation didn't take place and will list components that didn't 7,, -isolate. A message dicplay will appear on each of the primary 1 displays in the message area alerting the operator to a containment isolation malfunction..

-4'.h Containment Hydrogen Concentration

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Containment hydrogen concentration variables (two monitors per con-

' tainment) will be added to the lower level primary containment trend l graph display.

$i, Item IIIE Electrical and Electronic' Isolation y The computer driven SPDS for Prairie Island has electrical input signals from plant sensors and plant instrumentation and control circuits terminated in remote multiplexer units. Type 1 remote multi-

• plexing units are qualified by type testing to meet.the requirements for Class IE qualification and are powered from plant Type 1 power ~

i sources 1by suitably qualified electrical wiring.

All remote multiplexer units communicate with Type 3 non-safety related

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- computer equipment by means of fiber optic cable. The result of this system design is that the remote multiplexer units are optically iso-lated from each other, from the computer systems and from surrounding equipment. The fiber optic cable is performing the function of isola-tion, between safety related and non-safety related equipment.

.The non-safety related portions of the SPDS, therefore,.are considered suitably isolated from being able to cause: electrical and electronic I interference with equipment and sensors used for safety systems for the

following reasons

, 1. Safety re' lated'inputsIfor the SPDS are terminated in Class 1E

.qualifi_ed remo'te multiplexer units using safety grade cabling. l 7

2. All components comprising a Type 1 remote multiplexer unit are j seismically and environmentally qualified as safety related -

. equipment (10 CFR 50.49).

. ~3. ~ Type 1 remote multiplexer units are powered from plant Type 1

power sources by suitably qualified cabling.

i w i 4. Safety related-plant input signals wired to Type 1 remote multi-

! :plexer units use safety grade cabling.

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5. The interface between non-safety circuits and safety circuits is by fiber optic cable whichlis inherently: immune to electrical and

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electronic interference.

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In addition the electric isolation devices described in USAR section 7'4.1.2.6 and referenced as items 3 and 4 in USAR section 7.11 are used to

,3,i isolate the multiplexer inputs from the reactor protection end engineered safety feature actuation circuits. ,

Please. contact us if you have any questions related to the additional infor-mation we have provided.

-D D k ws David Musolf Manager - Nuclear Sup rt Services ,

c: Resident Inspector, NRC Regional Administrator-III, NRC '

NRR Project Manager, NRC G. Charnoff E

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