ML20197C286
| ML20197C286 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 10/30/1986 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | Harold Denton, Lear G Office of Nuclear Reactor Regulation |
| References | |
| CON-NRC-86-104 VPNPD-86-443, NUDOCS 8611060036 | |
| Download: ML20197C286 (3) | |
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i WUSCORSin Electnc eowra coue>~r 231 W. MICHIGAN. P O. BOX 2046, MILWAUKEE.Wl 53201 (414)277-2345 VPNPD-86-443 NRC-86-104 October 30, 1986 Mr. H. R. Denton, Director Office of Nuclear Reactor Regulation U. S. NUCLEAR REGULATORY COMMISSION Washington, D.
C.
20555 i
1 Attention:
Mr. George. Lear, Director PWR Project Directorate 1 Gentlemen:
4 DOCKETS 50-266 AND 50-301 ISOLATION DEVICES FOR SAFETY ASSESSMENT SYSTEM POINT BEACH NUCLEAR PLANT This is to confirm the recent telephone conversations between i
Mr. Steven Schellin of my staff and Mr. Tim Colburn and others of your staff regarding the electrical isolation devices for the Point Beach Nuclear Plant (PBNP) Safety Assessment System (SAS).
As discussed, the potential for faulted conditions in the SAS to challenge the isolation devices between the SAS and the safeguards and protection system electrical inputs has been considered in the design of the Plant Process Computer System (PPCS).
We believe that the equipment and configuration of the SAS will not result in failure of the isolation devices or i
cause a disturbance cn: perturbation within the plant's safeguards, protections, or' control circuitry.
-Those components of the PPCS which provide the SAS functions i
have-been specified to meet the environmental conditions for the areas where they are installed.
Since these areas are in the control building, specifically the control roo:m and the computer room / reactor engineering office, the design criteria were basically seismic and electrical.
We have met the seismic criteria through the purchase of equipment or components which provide the input signal processing, multiplexing, data transmission,.and display that are seismically qualified or tested.
The electrical criteria for the isolation of process c
instrumentation input signals and contact inputs have been met through the purchase of_ Distributed Input / Output Controllers C
8611060036 861030 ho PDR ADOCK 05000266 iO P
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Mr. H. R. Denton October 30, 1986 Page 2 from Computer Products, Incorporated (CPI) for multiplexing the inputs to the computers.
Other appropriate isolation also exists in addition to that provided by this equipment.
1 Those process instrumentation inputs which were part of the original (pre-TMI) plant configuration typically have two levels of isolation between the initial signals used for plant safeguards and protection system inputs and the final output signal to the CPI equipment used for the input multiplexing to the SAS/PPCS.
The first level of isolation is provided by Foxboro H-Line current to current repeater modules (M/668BC-0) between the safeguards and protection signals and the signals used for the control board displays, control system inputs, and/or computer inputs.
This isolation meets the original i
plant design requirements.
The second level of isolation is provided by the use of resistor-type computer input isolation blocks between the control board display or control system signals and the computer system inputs.
These isolation blocks were also installed as part of the original plant design.
For other process instrumentation signals, the instrument loop is connected directly to the resistor-type computer input isolation block and then to the computer input equipment.
l Three exceptions to these typical process instrumentation input l
configurations occur.
For thermocouples going to the computer, the field wires are connected directly to CPI uniform temperature reference (UTR) plate assemblies in the multiplexor racks and then to the computer input equipment which provides the isolation.
Where these thermocouple signals provide inputs j
to other equipment, the required inputs are wired in parallel j
with the field wiring from the UTR to a separate reference junction in the other equipment..None of these thermocouple signals provide inputs to the safeguards or protection systems.
1 For the rod position indication system (RPIS), computer outputs paralleled off the remote indicator circuitry were provided as i
part of the original equipment design and installation.
These outputs from the RPIS are wired directly to the CPI equipment I
for input to the SAS/PPCS.
The RPIS does not provide any inputs to the safeguards or protection systems.
i l
For the nuclear instrumentation system (NIS), isolated computer outputs were provided as part of the original equipment design a
]
and installation.
These outputs from the NIS are wired i
directly to the CPI equipment for input to the SAS/PPCS.
Two signals from the NIS for which computer outputs were not originally provided are to be added as inputs to the SAS.
These are the source and intermediate range start-up rates.
These new NIS outputs to the computer input equipment will ixt voltage signals paralleled off local indicators in-the NIS equipment.
Mr. H. R. Denton October 30, 1986 Page 3 Isolation of the instrumentation, which was added as a result of the post-TMI regulatory requirements and Wisconsin Electric-instituted upgrades, is achieved through the use of Foxboro SPEC 200 instrumentation output isolation modules (N-2AO-VAI) for each output signal.
The outputs from these. modules are then connected to the computer input equipment.
Contact inputs to the CPI multiplexors are first isolated through the use of auxiliary " dry" contacts on existing relays or an interposing isolation relay.
Typically the relay is initially isolated from the instrumentation loop signal by a bistable module which provides the appropriate setpoint for the relay actuation and contact closure.
Here the separation is contact-to-coil or contact-to-contact, and the sensing signal is supplied by the computer input equipment.
Each CPI computer input multiplexor interfaces with a seismically qualified Perkin-Elmer 3205 computer (located in the same seismic multiplexor rack) which provides the communication to the host computers, other multiplexors, and remote displays via interconnecting fiber optic cables.
The fiber optic cabling provides complete electrical isolation between multiplexors, between each multiplexor and the redundant host computers, and between the multiplexors and the remote displays in the control room.
We believe that this meets, or exceeds, the isolation and separation criteria for a Safety Parameter Display System (SPDS) as required in NUREG-0737, Supplement 1.
As a result of our conversations with your staff, however, we will further examine the faulted conditions considered in the design of the CPI multiplexors and the equipment qualification documentation provided by the supplier to verify that these devices are acceptable in the configuration described above.
We will also assemble the documentation relative to the testing and vendor qualification of the equipment used in the SAS for inspection at PBNP or our corporate offices, as appropriate.
The examination and collection processes will begin following the conclusion of the present Unit 2 refueling outage and should be available for your inspection after the first of the year.
1 We understand your safety evaluation report on the SAS has been j
prepared and will be transmitted to us shortly.
Please contact I
us if you have any further questions regarding these matters.
Very tru y
- ours,
{,
j C. W.
Fay (
Vice President Nuclear Power Copy to Resident Inspector
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