ML17252A291

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License Event Report - Rod Withdrawal at Approx. 44% Power, Discovered Rod Block Monitor Channels 7 and 8 Automatically Bypassed
ML17252A291
Person / Time
Site: Dresden  Constellation icon.png
Issue date: 04/22/1977
From:
Commonwealth Edison Co
To:
Office of Nuclear Reactor Regulation
References
Download: ML17252A291 (3)
v • d • e


Text

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._ CONT~O~ BLOCK:~QI,'715J_ /I 3J (P. PRINT AU s:lEQUIRED INFORMATiO:

LICENSEE NAME

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la13j j operator discovered that Rod Block Monitor~- charineTis 7 and 8 were automatically 6

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NAME:-- Jeffery R. Wojnarowski PHCN~ ____ E_x_t_. ___

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',J 175"13 EVENT DESCRIPTION (continued) found to-~ause-a bypass of the RBM system.

Withdrawal of control rods 8*7 and B-8 was suspended and an investigation was initiated.

The safety significance of this event was minimal because the RBM backs up procedural rod selections. Although the Tech Specs require the RBM to be operable above 30% power, the Tech Spec base? indicate that the RBM function is not necessary below 70% power.

The significance was further mitigated by the core locati-0n of B-7 and B-8, since both control rods are located one position inside the core periphery.

This is not a repetftive occurren~e.

(50-249/1977-9)

CAUSE DESCRIPTION (continued) operation was verified before further withdrawals of control rods B-7 and B-8 were performed.

All other interior control rods have been successfully checked for similar problems.

This is the first reported failure of any of these diodes.

No further corrective action was deemed warranted.

The Rod Block Monitoring system was supplied by the General Electric Company.

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EVENT OESCRIPTION c..,..I. -'*', ' iJ 1

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/oj 2J I During control rod withdrav1al operations at 11

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1dximately 44% pmver, the unit 7

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8 9 PRME (continued) s sYSTI:M CAUSE COMPONENT COMPONENT COOE.

CODE COMPONENT cooe SUPPIJER MANUFACTU;:l(R VOLATON

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l1J a s 10 11 12 17 43 44 41 48 CAUSE DESCRIPTION

~ ajsj I Investigation revealed that a shorted diode in the contr.ol rod select circuitry 8 9 s

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' a FACUTY STATUS LLl 9

POWER Io I 4 I 4 I 10 12 FORM OF ACTIVITY CONTENT OTHER.STATUS NA 13 44 RaEASEO OF RELEASE l2.I L.:J '----------J AMOUNT OF ACTIVITY NA

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10 11 PERSONNEL.EXPOSURES NUMBER TYPE ill)lololol W DESCRIPTION NA a s 11 12 13 PEF1SONNEL INJURIES NUMBER OESCRIPTION 44 METHOO OF

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DISCOVERY DISCOVERY OESCRIPTION

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See 11 [-i.. en t Description

45 46 9,

NA LOCATION OF RELful.SE 45 s*

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NA as LOSS OR OAMAGE TO fACILITY TYPE DESCRIPTION

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PUBLICITY iE)

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