ML20037B425
| ML20037B425 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/03/1978 |
| From: | Ziemann D Office of Nuclear Reactor Regulation |
| To: | Reed C COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8009260708 | |
| Download: ML20037B425 (6) | |
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DISTRIBUTION Doc ket TBAbernathy NRC PDR JRBuchanan Local PDR ACRS (16)
Dockrt No. 50-10 ORB #2 Reading VStello KRGoller IN Commonwealth Edison Company t
ATTN: fir. Cordell Read OISE (3)
Assistant Vice President P. O. Box 767 DLZiemann PWO'Connor Chicago, Illinois 60690 SNowicki Gentlemen:
DE e ut In response to the NRC Order of June 22, 1976, the Commonwealth Edison Company provided a description and' analysis of certain proposed modifications to the protection system for Dresden Unit 1 to bring it into compliance with IEEE Std 279-1958, single failure and changed independence requirements. These modifications involve complete replacement of the existing two-out-of-two channel reactor protection system with a one-out-two-twice system. He have reviewed the infomation submitted to date, and find that the additional infomation identif&ed in the enclosure to this letter is required to continue our evaluation.
Please provide within 20 days a sch,edule for complete respo.nse to F
this request.
Sincerely,.
oris' " i '
pi3 u.
Dennis L. Zicmann, Chief Operating Reactors Branch !2 Division of Operating Reactors'_
Enclosure:
Request for Additional Infomation cc w/ enclosure:
See next page
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Mr. John W. Rowe Isham, Lincoln & Beale Counselors at Law One First National Plaza, 42nd Floor
- Chicago, Illinois 60603 Mr. B. B. Stephenson Plant Superintendent Dresden Nuclear Power Station Rural Route #1 Morris, Illinois 60450 O
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_ REQUEST FOR_ ADDITIONAL INF_0RMATION.
REGARDING THE PLANT PROTECTION SYSTEMS' SUSCEPTIBILITY TO DISAB_ LING SINGLE FAILURES y
1.
The'information you have provided to' date is not sufficient for os to verify that the actuation system for the engineered safety features is not susceptible to disabling single failures.
Please provide com-plete logic and schematic diagrams for all plant protection systems instrumentation and controls which produce initiation signals to start the engineered safety features equipment (i.e., Containment Isolation, Emergency Condenser, Core Spray, High Pressure Core Injection and Post Incident System) or control safety related interlocks (e.g., interfaces between high pressure and low pressure systems).
The logic and schematic diagrams provided should describe the instrumentation and controls from the process sensors to the engineered safety features equipment actuation device (e.g., circuit breakers and pilot valves).
In addition, provide a failure modes and effects analysis of the engineered safety features actuation system
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keyed to the logic and schematic diagrams to demonstrate that the system and its supporting systems (e.g., control relay power, instrument air, and HVAC) are not susceptible to disabling single failures.
2.
Provide an analysis to demonstrate that all of the plant protection systems (e.g., reactor protection, engineered safety features t.ctua-tion, and safety related interlocks systems) equipment are protected
! from physical hazards such as missiles, flooding, pipe breaks and severe extremes of their operating environment such as high temperature, 6
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humidity and radiation, which could disable redur. dant components.
The analysis should consider each separate area of the plant where safety related instrumentation and control equipment is located ano describe the physical protection design features for that area.
3.
The information provided in your letters, dated September 30, 1976 and May 31, 1977, regarding separation of redundant protection system channels and sphere penetrations is not sufficient to demon-strate adequate separation.
Please provide layout drawings with redundant protection system eq:, ment, including, but not limited to, sphere penetrations and cable routing, ' clearly marked to show both verticle and horizontal separation.
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'.55 The following items deal with specific statements made in Attachment B of your September 30, 1976 letter:
a.
Clarify your statement in paragraph 2.2.3.3 that, "Every effort will be made to route redundant wire ways as far apart as practical or to interpose an existing barrier".
Is the separation criteria given in paragraphs 2.2.3.3.1 and 2.2.3.3.2 intended to be the minimum separation for redundant equipmer' not separated by barriers?
b.
Describe the construction of the conduit referred to in paragraph 2.2.3.4 that will be used with a minimum one inch separation distance between redundant protection system channels.
Identify all locations where the one-inch separation criteria will be used and provide an analysis-to demonstrate that no single event (e.g., fire, either from
- =z cable failure or other causes) can result in damage to redundant safety equipment and simultaneously cause:51 condition (i.e.,
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Clarify your statement in paragraph 2.2.5, " Instrument piping c.
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necessary to reconnect a relocated ~ instrument shall be installed
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without considering separation criteria."
4.
In paragraph 2.2.6 of Attachment B to your September 30, 1976 letter,-.
you state that additional neutron monitoring system signals required for the four channel RPS will be obtained from electronic assemblies '
of the neutron monitoring cabinets.
Provide an expanded discussion of-the proposed modifications to this portion of the reactor protec-tion system to demonstrate that the independence of redundant instrument channels is maintained from detector to actuation device.
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In. addition, clarify your statement in paragraph 2.4.2 that separation criteria will be applied to the neutron monitoring system "where practical".
5.
Provide a schematic piping and instrumentation diagram of the scram control system, indicate the proposed modifications, and state the
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reason for each modification.
6.
Attachment C of your September 30, 1976 letter provided updated tables listing equipment located in the containment required to fH operate during and after a LOCA.
Solenoid valves SV 562, SV 553, SV 573, SV 574, SV 576, 50 30, 50 31, 50 32 were delted from the eariler list provided with your June 30, 1975 letter.
Justify the deletion of these valves.
7.
Verify that plant protection system equipment is not located in areas of the plant where a single failure within the heating, 9
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ventilating or air conditioning system could have an adverse effect on protection system equipment, i.e., result in a loss of functional capability of the protection system.
8.
Identify all cases where portions o{ the plant protection systems receive inputs from, or provide outputs to, other redundant portions of the systems or non-safety related equipment.
For all such cases, describe the isolation devices that will be used to assure that no single failure of either safety related ur non-safety related equip-ment will disable redundant portions of the plant' protection systems.,'
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