ML19336A504
| ML19336A504 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 10/14/1980 |
| From: | Parker W DUKE POWER CO. |
| To: | Harold Denton, Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8010230459 | |
| Download: ML19336A504 (3) | |
Text
1 Duxz POWER COMPANY Powra Bun.ntxo 422 Sourn Cauncu Srazzr, CRAR1DTTz, N. C. 28242 wiwAu o. Pannen.sn.
October 14, 1980 WCE PetSio(NT TCL(9mCNC; AAE4 7C4 Stram Pacouct$om 373-4083 Mr. H. R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention:
Mr. B. J. Youngblood, Chief Licensing Projects Branch No. 1 Re: McGuire Nuclear Station Docket Nos. 50-369 and 50-370
Dear Mr. Denton:
Mr. B. J. Youngblood's letter of July 9, 1980 discussed potential design deficiencies in bypass, override, and reset circuits of Emergency Safe-guard Features. The letter established a new NRC Staff position on this issue for all near-term operating license applicants and requested a McGuire design review to determine the degree of conformance to this new position. Duke Power Company's response to Mr. Youngblood's letter is attached.
Very truly yours, 9hE-a P L p William O. Parker, Jr.
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J DUKE POWER COMPANY MCGUIRE NUCLEAR STATION i
Response'to July 9, 1980 letter from
- Mr. B. J. Youngblood to Mr. W. O. Parker l
NRC Staff Position
.1)
The overriding of one type of safety actuation signal (e.g., particulate radiation) should not cause the blocking of any other type of safety 4
actuation signal (e.g., iodine radiation, reactor pressure) for those valves that have no function other than containment isolation.
2), Physical' features (e.g., key lock switches) should be provided to ensure adequate administrative controls.
- 3) A system level annunciation of the overridden status should be provided for every safety system impacted:when any override.is active.
(See Regulatory Guide 1.47).
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Response
i.
The high radiation and safety injection ' actuation signals to the containment ventilation isolation logic do have a common reset circuit. Thus, if the reset is used to override a high radiation signal, subsequent safety injection actuation signals.would be blocked from reinitiating containment vent isolation.
Administrative controls are in place which do not allow resetting of a high
-radiation actuation signal until the high radiation input has cleared.
In addition, circuit modifications will be made to separate these resets, thereby assuring that resetting of a high radiation signal cannot result in the blocking of a' safety injection actuation signal to the containment ventilation isolation
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logic. This modification will be implemented prior to fuel loading.
I NRC Staff Position
- 4) The following diverse signals should be provided to initiate isolation of the containment purge / ventilation system: containment high radiation, safety injection actuation, and containment high pressure (where contain-ment high pressure'is not a portion of safety injection actuation).
- 5) The instrumentation systems provided to initiate containment purge ventilation isolation should be designed and qualified to Class IE criteria.
Response-Both high radiation and. safety injection actuation signals are provided to initiate' isolation of the containment-ventilation system. The safety injec-tion, actuation system includes high containment pressure actuation and is
' designed and qualified to. Class lE criteria. Although not considered Class 1E, fthe high radiation instrumentation used to initiate-containment ventilation
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isolation is a highly reliable system which derives its power-from battery-backed
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and diesel' generator backed sources. A further description of this radiation i
monitoring system is'provided in the McGuire FSAR Section 11.4.
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7 NRC Staff Position
- 6) The overriding or resetting of the ESF actuation signal should not cause any. equipment to change position.
Response
A review of the electrical schematics of all McGuire electrical components receiving an ESF signal has been performed. This review revealed the following four areas where design _ changes will be made to prevent the resetting of an ESF actuation signal from causing any equipment to change position.
1.
The auxiliary' building air haLdling units are aligned to filter units upon receipt of an ESF signal. These filter units would be bypassed upon clearing of the ESF signal. The controls to the filter unit dampers will be modified so that the ESF signal will be sealed l
in, and manual reset will be required to clear the signal. This modification will be complete before fuel loading.
I 2.
The hydrogen skimmer and containment air return fans / dampers are i
switched on/open upon receipt of an ESF signal. The fans / dampers will automatically stop/close upon clearing of the ESF signal. The-controls to these fans / dampers will be modified so that the ESF signal will be sealed -in, and manual reset will be required to clear the signal. This modification will be complete before fuel icsding.
3.
The turbine driven auxiliary feedwater pump automatically starts upon receipt of either a low-low steam generator level signal or a station blockout signal. This pump will automatically stop upon clearing of'the either.of the above signals. The controls to this pump will be modified so that.the low-low steam generator level-signal and the station blockout signal are sealed in thus requiring manual shutdown of the pump _after an automatic start.
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L This modification will be completed after startup. The current control design does not prevent an automatic restart of the pump after the actuating signals reset.
t 4.
The main ~ steam isolation and isolation bypass valves close upon receipt of a main steam' isolation signal. These valves may reopen after both trains main steam isolation signals reset. The main steam isolation' signal to each main steam isolation and isolation
' bypass valve will be sealed in such that following reset of this signal-each valve remains in the emergency mode until-the associated controls are manually reset. Elis modification will be completed-after startup. TLe current design seals in this signal at the system level.
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-Containment isolation valve control systems are designed such that resetting i
of the= containment isolation signal will not cause any containment isolation valveJto automatically reposition. Deliberate. operator action is required to reposition a containment isolation valve following reset of a containmeat Lisolation' signal. Further description of the containment isolation provisions l-are' discussed in the document " Duke Power Company, McGuire Nuclear Station, Response'to TMI Concerns."
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