ML17252A271
| ML17252A271 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 04/21/1977 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | Kappler J NRC/RGN-III |
| References | |
| 50-249/1977-9 | |
| Download: ML17252A271 (3) | |
Text
Commonwe4t Edison Dresden Nuclear Power Station R.R. #1 Morris, Illinois* 60450 Telephone 815/942-2920 BBS Ltr. # 334 April 21, 1~77 Mr. James G. Keppler, Regional Director Directorate of Regulatory Operation - Region JI I U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, 111 inois 60137 Enclosed please find Reportable Occurrence report number 50-249/1977-9.
This report is being submitted to your office in accordance with the Dresden Nuclear Power Station Technical Specifications, Section 6.6.B.
Stephenson tation Superintendent Dresden Nuclear Power Station BBS:skm Enclosure cc:
Director of Inspection & Enforcement Director of Management Information & P~ogram Control Fi 1 e/NRC APR 2 G 1977
L l1
\\
.. *CONTROL BLOCK: l 1
LICENSE.E EVENT REPORT 91 I I I I
~I I I LI 0 1 '-~
11135 1 31 I 01 ° 1.:... I 0 I 0 I 0 I 0 I 0 1-1° I 0 I.14 *1 1 11 I 1 I 1 I I 0 1 11 7
89 14 15 25 26 30
- 31 32 CATEGORY REPORT.
REPORT*
TYPE SOURCE DOCKET NUMBER EVENT DATE REPORT DATE
@TI]coN'T I I I L!J L!:J I 01 s 1 o 1~1 o 12 14 I 9 I I 0 I 4 1 1 I o I 71 7 I I 01 4j 212117 17 I 1 * *0 57 58 59 60 61 68 69 74 75 80 EVENT DESCRIPTION
[filfil I During control rod withdrawal operations at approximately 44% power, the unit 7
8 9 lo131 I 013erato.r discovered that Rod Block Monitor (RBM) channels 7 and 8 were automatically 81 7 8 9!:-'.---------------------------------~....;._----------__.J*
lol41.!;l __
.b_y.;..p_a~s_s_e~d=-a_n_d_i_n_d_i_c_a_te_d_
1_
1 e_d_g_e__,r_o_d_s_e_l_e_c_t_ed_
1_
1
_w_h_e_n_i_n_t_e_r_i_o_r_c_o_n_t_r_o_1_ro_d_B_-_s_w_a_s _____
8
~l (q{5j *j!;.
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__ r_c_o_n_t_r_o_l_r_o_d_s_w_e_re_t_h_e_n_s_e_l,....e_c_t_e_d_t_.o_c_h.,...e_c_k_t_h_e_f:..,.u_n_c_t.:....* i-'o_n_i_n_g--
8
~1 7
8 9 lo Isl~ ~I __.,..,.o_f.__t_h_,e_R_B_M_.--* _c_o_n_t_r_o_l _ro_d_B.;..-_7_w_a_s_t_h_e_o_n_l _y_o_t h_e_r __
i n_t_e_r_i_o_r_c_o.;..n_t.._r_o_l _r_od __
t h_a.,..t_w __ a __ s ____
s_Jl 7
8' 9 PRIME.
(continued) 80
. SYST.EM CAUSE COMPONENT.
COMPONENT COOE
.. COOE COMPONENT CODE SUPPUER MANUFACTURER VDLATlJN
(§0 I I I B I LlJ I II N I s I Tl R I u I
~
I G I 0 I 8 I 0 I
~
7 8 9 10 11 12 17 43 44 47 48 CAUSE DESCRIPTION (olal I Investigation revealed that a shorted diode in the control rod select circuitry I
7 8 9 80 lolsl 1~*--w_a_s ___ t_h_e....,....c_a_u_s_e_.~o-f_t_h_e_._s... pu ___
r_ro_u~s--R_B_M_b_y_p_a_s_~_a_n_d ___
1 1
e_d_g_e_r_o:..,.d __ s_e_1_e_c_t_e __ d_
11_i_nd-ic_a_t_io_n_f_o_r ____
~I j1ioj j~_b_.~_*t_h __ c_o_n_t_r_o_l_r_o_d_s_B_-_7_a_n_d_B_-_s_. __
T_h_e_d_e_f_e_c_t_iv_e_d_io_d_e_._w_a_s_r_e_p_l_a_c_e_d_,_a __
nd_p_r_o_p_e_r_R_B_M ___
8
~l 7
8 9 80 FACIUTY METHOD OF.
('continued)
- . STATUS POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION l_Ll I 0 I 4 I 4 I
- 1.___N_A ____ -"
~ I See 11Eve*nt Descr i pt i on 1
1 EE1 7.a.
9 10.
12 13 44 45 46 80
.FORM OF
.ACTIVITY CONTENT RELEASED OF RELEASE AMOUNT. OF ACTIVITY
~ ~ l~_NA-.,,.;-----....J' 9
10.
11 44 rn 7
8 NA LOCATION OF RELEASE 45 80 PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION
[ill] I. o L ol 01 L.fJ
.-=---*-N_A. _________________
__;.....;...__~--_J 7
8 9 11 12
- 13.
BO PERS.ONNEL
- 1NJURIES NUMBER OESCRl°PTION
[ill] I 0 I 01 01.';::-* -* __._NA_*---------------~---~--~
7 a*s 11 12 00 OFFSITE, CONSEQUENCES
. E~L NA 7
8 9 80 LOSS OR DAMAGE TO FACILITY TYPE
. DESCRIPTION EID lLl NA 7
8 9 10!::--------------------'--....--....;._--------------......:.--------8~0 PUBLICITY
[fill NA
. 7 8 9 80 ADDITIONAL FACTORS Eifil 7
8 9
- N 60
~
~
7 B.9~.----,.-----------.--.------~~----------------....:...------_..:.....:... __....... "--~
.. NA-'\\1E~.~. _,_ __ J_e_f_f_e_r_y....,.R_. _w_o_J_* n_a_r_o_w""'s_k_i -------- PHONE: __
E_x_t_. _\\..;;;~23);;;;;2;;;.___
GPO a 111.* a 117
EVENT DESCRIPTION (continued) found to cause :a oypass of the RBM system.
Withdrawal of control rods B-7 and B-8 was suspended and an investigation was initiated.
The safety significance of this event was minimal because the RBM backs up p~ocedural rod selections.
Although the Tech Specs require the RBM to be
- operab 1 e above 30% power, the Tech Spec bases indicate that the RBM function is not necessary below 70% power.
The significance was further mitigated by the core location of B-7 and B~8, since both control rods are located one position i~side the core periphery.
This is not a repetitive occurrence.
(50-249/1977-9)
CAUSE DESCRIPTION (continued) operation was verif1ed before further withdrawals of control rods B-7 and B-8 were performed.
All other interior control rods have been successfu(ly checked for similar problems.
This is the first rep0,r_ted failure of any of these diodes.
No further corrective action was deem~d~)warranted. The Rod Block Monitoring system. was supplied by the General Electric Company.