ML20004D427
| ML20004D427 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 06/04/1981 |
| From: | Jackie Cook CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 12229, NUDOCS 8106090386 | |
| Download: ML20004D427 (5) | |
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James W Cook
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kJ J;d,43i Vice Pressdent - Projects, Engsneersng and Constructson oenerei offices: 1945 weet Pernell Road Jackson, MI 492ot e (5171788o453 June 4, 1981 Harold R Denton, Director Office of Nuclear Reactor Regulation Division of Licensing US Nuclear Regulatory Commission Washington, DC 20555 MIDLAND PROJECT DOCKET NOS 50-329, 50-330 RESPONSES TO REQUESTS FOR ADDITIONAL INFORMATION CONCERNING CONTROL SYSTEM FAILURES FILE: 0485.11 UFI: 70*01*11 SERIAL:
12229 Enclosed herewith are responses to Requests for Additional Information transmitted to Consumers Power Company by letters from Robert L Tedesco to J W Cook dated April 16, 1981 and May 12, 1981.
These responses will also be included in the volumes " Responses to NRC Questions" in the next normal revision to the Midland FSAR.
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Racp:n030 to NRC Quactienc Midicnd 1&2 Question 030.56 Identify those control systems whose failure or malfunction could seriously impact plant safety.
Response
Those safety grade control systems whose failure or malfunction could seriously impact plant safety are described in Section 7.1.
The effects of failure or malfunction of non-safety grade control systems have been taken into account in the safety analyses of the plant where it is recognized that the effects have more serious conse-quences on the accident results, and have been found not to seriously impact plant safety.
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RO poncoo to NRC Qucotienc Midicnd 1&2 Quystion 030.57 Indicate which, if any, of the control systems identified in the response to Request 030.56 receive power from common The power sources considered should include power sources.
all power sources whose failure or malfunction could lead to failure or malfunction of more than one control system and should extend to the ef fects of cascading power losses due to the failure of higher level distribution panels and load centers.
Response
Redundant trains of the control systems described in Section 7.1 are powered from independent power sources.
Onsite power systems are described in Section 8.3.
Design bases for power systems are described in Subsection 8.1.4.
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Racpon0cc to NRC Quasticno Midland 1&2 Question 030.58 Indicate which, if any, of the control systems identified in the response to Request 030.56 receive input signals from common sensors.
The sensors considered should include, but should not necessarily be limited to, common hydraulic headers or impulse lines feeding pressure, temperature, level or other signals to two or more control systems.
Response
No common sensors are used to feed redundant trains of safety grade control systems.
However, due to design limitations on the number of instrument taps, reactor coolant system flow and auxiliary feedwater suction pressure sensors share a common tap for different channels.
For steam generator wide and narrow range level sensors and reactor coolant system wide and narrow range pressure sensors, the instruments for different systems share a
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common tap for the same channel.. Additional details of control' system's identffled in'Q&R 030.~56'are provided in' Chapter 7.
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RO pon 20 to NRC Qusatienc Mid1cnd 1&2 Question 030.59 Provide justification that any simultaneous malfunctions of the control systems identified in the responses to Requests 030.57 and 030.58 resulting from failures or malfunctions of the_ applicable common power source or sensor are Lo-;nded by the analyses in Chapter 15 and would not require action or response beyond the capability of operators or safety systems.
Response
Any simultaneous malfunctions of the control systems described in Q&R 030.57 and Q&R 030.58 are bounded by the analyses in Chapter 15.
These analyses include assumptions such as loss of offsite power, failure of a diesel to start, and single active failures, and do not require action or response beyond the capabilities of operators or safety systems.
Additional details of control systems analyses and evaluations are discussed in Chapter 7.
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