ML17201P582
| ML17201P582 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 11/20/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17201P539 | List: |
| References | |
| TASK-07-01.A, TASK-7-1.A, TASK-RR NUDOCS 8903010226 | |
| Download: ML17201P582 (2) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, 0. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE SYSTEMATIC EVALUATION PROGRAM IPSAR TOPIC VII-1.A.
1.0 *INTRODUCTION COMMONWEALTH EDISON COMPANY DRESDEN STATION UNIT 2 DOCKET NO. 50-237 By letters dated August 15, 1983 and January 9, 1987 Corrmonwealth Edison submitted their commitments to resolve SEP Topic VII-1.A.
The proposed changes involve providing electrical isolation between the RPS and the non-safety recorders and compu_ter.
2.0 DISCUSSION AND EVALUATION SEP Topic VlI-1.A is subdivided into ~ections 4~24.1, 4.24.2, and 4.24:3~
Section 4.24.1 concerns the electrical isolation of the Class lE nuclear flux monitoring system intermediate range.monitors (IRMS), local power
- range monHors (LPRMS) and average power range monitors (APRMS) from the non-Class lE process recorders and indicating meters.
To prevent common-mode.electrical faults in the control room process recorders from affecting the flux monitoring system, the licensee proposed to install Class lE signal isolation devices at the inputs to each recorder.
The licensee has also stated that they are evaluating the-possibility of installing Class lE recorders which would eliminate the need for electrical isolation devices.
Section 4.24.2 concerns the electrical isolation between the APRM and the process computer. The APRM scram function is derived from relay actuation resulting for amplified analog signals sensed by those relays. The ampli-fied analog signals are input directly to the process computer.
The licensee has modified the.... ioputs to include "flying capacitors" which are switched by relay contacts from the input signals to the process computer. There is always an open contact between.either the capacitor and. the computer or
' the capacitor and the input.
The. commitment made by the licensee for Section 4.24.3 was found acceptable in NUREG-0823, the Integrated Plant Safety Assessment Evaluation Program, February 1983.
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- 3. 0 CONCLUSION The staff has concluded that the proposed methods to meet the electrical separation requirements are acceptable.
For section 4.24.1 either the Class lE isolation devices or the installation of Class lE recorders is acceptable to the staff. The licensee is requested to submit the test results or evaluation which demonstrate the ab11 ity of the specific components selected for installation to meet the separation requirements.
The NRC staff cr1ter1a for reviewing isolation devices is lis~ed below.
- a.
For the type of device used to accomplish electrical isolation, describe the spec1f_1c testing performed to demonstrate that the device is accepta-ble for 1ts application(s). This description should include elementary diagrams which are necessary to indicate the test configuration and how the maximum credible faults were applied to the devices.
- b.
- c.
d *.
- e.
Data to verify that the maximum credible faults applied during the test were the maximum voltage/current to which the device could be exposed,.
and define how the maximum voltage/current was detennined
- Data to verify that the maximum credible fault was applied to the output of the device 1n the transverse mode (between signal and return) and other faults were considered (1.e ** open and short circuits).
Define the pass/fail acceptance criteria for each type of device.
Provide a corrmitment that the 1solat1on devices comply with the environ-ment qualifications (10 CFR 50.49) and w1th the seismic qualifications which were the basis for plant licensing *.
- f.
Provide a description of the measures taken to protect the safety systems from electrical interference {1.e., Electrostatic Coupling, EMI, Corrmon Mode and Crosstalk) that may be generated by the SPDS.
- g.
Provide infonnation to verify that the Class lE isolator is powered from a Class lE source.
Pr1nc1pal Contributor:- J. Stewart Date: