ML17252A291

License Event Report - Rod Withdrawal at Approx. 44% Power, Discovered Rod Block Monitor Channels 7 and 8 Automatically Bypassed

ML17252A291
Person / Time
Site:	Dresden
Issue date:	04/22/1977
From:	Commonwealth Edison Co
To:	Office of Nuclear Reactor Regulation
References
Download: ML17252A291 (3)

Text

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..,_ "1esCRIPTION

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

7 as a.:..:

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7 8 9 SYSTEM CAUSE ~JENT COMPONENT (cell ti "~ 8 ~8M bv JJ4..rJ,c, CODE COOE COMPONENT COOE 5lJPPIJER MANUFACTIJRER vtlLATllN fr

[§0 I r I s I .LlJ I II NI sI Tl R I u I ~* IG Io I8 Io f L!J 1 as 10 11 12 * .11 *

• 43 44 47 48 CAUSE OESCFHPTION .

~I hwasti9atioa revealed tRa-tA shorted diode in the contrrol rod select circuitry

. 7 8 9 SC (ojsj *~I__wa u_se__o_f_t_h_e_s_pu_r_io~u_s__R_B_M_by_p_a_s_s._a_n_d_'_'e_d_g_e_r_o_d_se_le_c_t_e_d__i....

........s,..-t_h_e__c_a... nd_ic_a_t_i_o_n_,~-----'

7 8 9 a. f BG

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1 a~ METHOO OF ('continued) ec

'ACIUTY .. OTHEA STATUS

• . STATUS OISCOVERY DISCOVERY OESCRIFTION

. EE L£J

' POWER Io I 4 I 4 I NA ~ I See E'>>'ent Description" 7.8 9 10 12 13 44 45 46 80

• FOAM~OF ACTMTY CONTENT RELEASED OF REl.£ASE AMOUNT. OF ACTIVITY: LOCATION. OF RELeASI:

7 rn 8 9

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10 l.__NA_ _ _ ___,J 11 44 45 NA 80 PERSONNEL EXPOSURES *.

NUMBER TYPE OESCRIPTION *

(!El_ I o I oI 01 W NA 1 8 s 11 . 12 13 SC PERSONNa INJURIES NUMBER* OESCRlPTION fIE] I o I oj oj ~-*-NA~-------------_;.._ _ _ _ _--..;.._.;,..__ _...l

. 7 8 9 11 12 SC OFFSITE CONSEQUENCES

• 1 EE8 s NA SG LOSS OR

• OAMAGE TO FACILITY TY1'£ OESCRIPTION 7

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PUBUCITY

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(,, 7f:052001 :3 1 8 s ADOmONAL FACTORS i.

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SQ 7lillJ 89~--------------------,..-------------------------~

NAME:-- Jeffery R. Wojnarowski PHCN~ ____E_x_t_.___ 43_2___

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--* ',J EVENT DESCRIPTION (continued)

• 175"13 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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1 0 UC EN SEE L.CENSE EVENT

. NAME LICENSE NUMBER TYPE I f PE

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EVENT OESCRIPTION c..,..I. -'*' , ' iJ 1 '.i II:; l 11

/oj 2J I During control rod withdrav1al operations at .~i~p~ dximately 44% pmver, the unit 1

7 8 9

! 0 13 1 ._I__o_!)_e_ra_to_r_d_i_sc_o_v_e_re_d__ t h_a_t_R_o_d_B_lo_c_k_M_o_n_*_,t_o_r_(_R_B_M_)_c_h_a_n_n_e_r_s_7_a_n_d_8_w_e_r_e_a_u_t_o_m...a_t_i_c_a_1_1_y_*.

., 8 9 lal 4 j l~_b_*_fP_a_s_s_e_d_a_n_d__i n_d_ic_a_t_e_d_'_'e_d_g_,e_r_o_d_s_e_l_e_c_t_e_d_'_'_w_h_e_n_i_n_t_e_r_i_c_r._c_o_n_t_r_o_i_r_o_d_B_-_a_w_a_s_ _ _ _ .~

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9 8 9 PRME (continued) s sYSTI:M CAUSE COMPONENT COMPONENT COOE . CODE COMPONENT cooe SUPPIJER MANUFACTU;:l(R VOLATON

~ I I I B I Ll.I I I I N I sI Tl R I u I ~ IG I 0 I8 I 0 ~ 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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METHOO OF ('continued)

FACUTY STATUS ' POWER OTHER .STATUS DISCOVERY DISCOVERY OESCRIPTION ill LLl Io I 4 I 4 I NA

~ See 11

[-i. en t Description

' a 9 10 12 13 44 45 46 9, FORM OF ACTIVITY CONTENT

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. a RaEASEO l2.I 9

PERSONNEL .EXPOSURES OF RELEASE L.:J 10 '----------J 11 NA AMOUNT OF ACTIVITY 44 45 NA LOCATION OF RELful.SE s*

NUMBER TYPE DESCRIPTION ill)lololol W NA as 11 12 13 PEF1SONNEL INJURIES NUMBER OESCRIPTION

~lo! 8 9 Oj OI11 '::---N_A--------------------~--~-------------------------

12 OFFSrTE CONSEQUENCES ill) NA as LOSS OR OAMAGE TO fACILITY TYPE DESCRIPTION

~LI 89 NA 10:-------------------------------------------------------------.;__~

PUBLICITY iE)

• tlA aa AOOITIONAL FACTORS

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