ML19329B083: Difference between revisions
StriderTol (talk | contribs) (Created page by program invented by StriderTol) |
StriderTol (talk | contribs) (Created page by program invented by StriderTol) |
||
| Line 18: | Line 18: | ||
=Text= | =Text= | ||
{{#Wiki_filter:- - - .- | {{#Wiki_filter:- - - .- | ||
. . . e s .. s . . . . | |||
. . . e | |||
s .. s . . . . | |||
. y x . . . . | . y x . . . . | ||
) , | ) , | ||
sms/ | sms/ | ||
TOLEDO | TOLEDO | ||
:l . | :l . | ||
. EDISON | . EDISON | ||
. . . LOWEu. E. ROE | . . . LOWEu. E. ROE | ||
.., .c. | .., .c. | ||
..- ,. . w.. ,,.w. | ..- ,. . w.. ,,.w. | ||
p.u.a. o...-. ' | p.u.a. o...-. ' | ||
~ | ~ | ||
. . . .t ..= ..., . .~. | . . . .t ..= ..., . .~. | ||
. um ese.sa<a October 19, 1976 '- . | |||
. um ese.sa<a | |||
October 19, 1976 '- . | |||
. f. ,, . ."- . | . f. ,, . ."- . | ||
.. . . .e .. | .. . . .e .. | ||
. . . : . , ' 9_.r:.; . . | . . . : . , ' 9_.r:.; . . | ||
Serial No.131 '.~' '. # | Serial No.131 '.~' '. # | ||
,. "; .,,'..: | ,. "; .,,'..: | ||
, Docket No. 50-346 . . | , Docket No. 50-346 . . | ||
... ' ',a. .. . . | ... ' ',a. .. . . | ||
. ..~. . | . ..~. . | ||
c | c | ||
.- s. | .- s. | ||
. . .. ; . .. . . | . . .. ; . .. . . | ||
.' Mr. James G. Keppler li - . | .' Mr. James G. Keppler li - . | ||
~ | ~ | ||
: y. Regional Director, Region III . | : y. Regional Director, Region III . | ||
.Dir'ectorate of Regulatory Operations - | .Dir'ectorate of Regulatory Operations - | ||
C | C | ||
. ., U.S. Nuclear Regulatory Commission , | . ., U.S. Nuclear Regulatory Commission , | ||
\ " | \ " | ||
el 799 Roosevelt Road J.. . "- | el 799 Roosevelt Road J.. . "- | ||
's-Glen Ellyn, Illinois | 's-Glen Ellyn, Illinois | ||
. 60137 - | . 60137 - | ||
3 ...; | 3 ...; | ||
==Dear Mr. Keppler:== | ==Dear Mr. Keppler:== | ||
: y. . vC'.O. . | : y. . vC'.O. . | ||
~ .... | ~ .... | ||
.~.... | .~.... | ||
. . : .{ . .,'.f [''t ' . ', , | . . : .{ . .,'.f [''t ' . ', , | ||
. r. | . r. | ||
' Th'is letter is submitted in accordance with 10 CFR 50.55(e) as a con- | ' Th'is letter is submitted in accordance with 10 CFR 50.55(e) as a con- | ||
.. .* smnmation of the Interim Report dated August 6,1976 regarding defi- | .. .* smnmation of the Interim Report dated August 6,1976 regarding defi- | ||
. ciencies in the Davis-Besse Nuclear Power Station Unit No. 1, General | . ciencies in the Davis-Besse Nuclear Power Station Unit No. 1, General | ||
. Electric, type AK-3-25 and AK-3-50 480 volt AC circuit breakers, power | . Electric, type AK-3-25 and AK-3-50 480 volt AC circuit breakers, power sensors and supplies. ., . , | ||
sensors and supplies. ., . , | |||
.. c ., | .. c ., | ||
Description of the Deficiency | Description of the Deficiency | ||
.~ -- | .~ -- | ||
General Electric identified a failure mode of the zener diode in the power supply circuit. Diode failure could occur when simultanecusly the~ ' | |||
' breaker load current was less than 15-20% frame size current rating and 5 ' | |||
the gate current of the shunting SCR's (silicon controlled rectifiers) was in the medium to upper range of the specification limits. With . | |||
these two conditions existing, the thermal rating of the diode is ex-ceeded, which may lead to failure of the zener. | |||
General Electric identified a failure mode of the zener diode in the | |||
power supply circuit. Diode failure could occur when simultanecusly the~ ' | |||
' breaker load current was less than 15-20% frame size current rating and | |||
5 ' | |||
these two conditions existing, the thermal rating of the diode is ex- | |||
ceeded, which may lead to failure of the zener. | |||
8001300[[h | 8001300[[h | ||
. . v. . | . . v. . | ||
n . | n . | ||
. c= | . c= | ||
. 2 O | |||
* O .- | |||
. 2 | |||
O | |||
O .- | |||
. Corrective Aceion . | . Corrective Aceion . | ||
. .'. .. t , . . .... . . . .. . | . .'. .. t , . . .... . . . .. . | ||
.. 7 . ,. | .. 7 . ,. | ||
General Electric redesigned the power supply circuit t:o eliminate the - - | General Electric redesigned the power supply circuit t:o eliminate the - - | ||
stated failure mode. The Applicant has arranged to replace all subject | stated failure mode. The Applicant has arranged to replace all subject | ||
* ** power supplies and power sensors at Davis-Besse Unit I and is presently -- -- | * ** power supplies and power sensors at Davis-Besse Unit I and is presently -- -- | ||
" . having General Electric rework the breakers. Each reworked breaker will, | " . having General Electric rework the breakers. Each reworked breaker will, | ||
. be required to pass pre-operational testing under the Applicant's test | . be required to pass pre-operational testing under the Applicant's test | ||
. program before being considered acceptable for use. | . program before being considered acceptable for use. | ||
Safety Implications ' | Safety Implications ' | ||
- 5 .'.'"': ~.A. . . | - 5 .'.'"': ~.A. . . | ||
~ ~ ~ | ~ ~ ~ | ||
* If the above conditions had gone uncorrected, the zener diode coulci have . | * If the above conditions had gone uncorrected, the zener diode coulci have . | ||
* " failed. | * " failed. | ||
* If the diode had shorted, insufficient trip voltage would have ~ | * If the diode had shorted, insufficient trip voltage would have ~ | ||
- .j | - .j | ||
.been available. The consequence would have been failure to protect t | .been available. The consequence would have been failure to protect t | ||
associated essential electrical equipment during an electrical fault. | associated essential electrical equipment during an electrical fault. | ||
With the diode opened, excessive control voltage would be available in e the power supply and power sensor circuits. In this latter c.ase, no * | |||
-'' immediate safety consequence would have necessarily occurred, however electrical fault protection of associated essential electrical equipment | |||
With the diode opened, excessive control voltage would be available in | * could have been adversely affected should the high voltage have caused the power sensor to fail. . | ||
, ,,.7 A The scheduled repair of the affected breakers and acceptable pre-oper- | |||
e the power supply and power sensor circuits. In this latter c.ase, no * | |||
-'' immediate safety consequence would have necessarily occurred, however | |||
electrical fault protection of associated essential electrical equipment | |||
* could have been adversely affected should the high voltage have caused | |||
the power sensor to fail. . | |||
, ,,.7 | |||
A The scheduled repair of the affected breakers and acceptable pre-oper- | |||
'( , | '( , | ||
'ational testing of the devices prior to station operation assures that - - - | 'ational testing of the devices prior to station operation assures that - - - | ||
the health and safety of the public are not jeopardized. . . . | the health and safety of the public are not jeopardized. . . . | ||
. . . . . . , ; ., .. ' | . . . . . . , ; ., .. ' | ||
~:,;= . | ~:,;= . | ||
.Yo.urs very truly. | .Yo.urs very truly. | ||
. . .,: s | . . .,: s | ||
.. .:... . . + . ~ . .: . . . ... . .. ....- | .. .:... . . + . ~ . .: . . . ... . .. ....- | ||
. . c.. | . . c.. | ||
: z. . . .. | : z. . . .. | ||
. . .. . s. . | . . .. . s. . | ||
; . , . .. = | ; . , . .. = | ||
^ | ^ | ||
~ | ~ | ||
p( ,. /. .- ^ ~- .< vr " * | p( ,. /. .- ^ ~- .< vr " * | ||
,. r & :.:. u.-'; . .. ' | ,. r & :.:. u.-'; . .. ' | ||
w i . | w i . | ||
~. . . . .: s. .. . . | ~. . . . .: s. .. . . | ||
; .:- . | ; .:- . | ||
pc/29 - | pc/29 - | ||
- -~ - | - -~ - | ||
._ .};:,..{,'', [ . | ._ .};:,..{,'', [ . | ||
- ; - . , | - ; - . , | ||
.; . .. . | .; . .. . | ||
cc: .. | cc: .. | ||
,Dr. Ernst Volgenan, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D. C. 20555 . | |||
,Dr. Ernst Volgenan, Director | |||
Office of Inspection and Enforcement | |||
U.S. Nuclear Regulatory Commission | |||
Washington, D. C. 20555 . | |||
, .i . | , .i . | ||
.; . | .; . | ||
. ;. . | . ;. . | ||
1 ' | |||
y | y | ||
, . e ,. | , . e ,. | ||
: t. . | : t. . | ||
8 o}} | |||
8 | |||
o}} | |||
Revision as of 22:35, 31 January 2020
| ML19329B083 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 10/19/1976 |
| From: | Roe L TOLEDO EDISON CO. |
| To: | |
| Shared Package | |
| ML19329B081 | List: |
| References | |
| 131, NUDOCS 8001300674 | |
| Download: ML19329B083 (2) | |
Text
{{#Wiki_filter:- - - .-
. . . e s .. s . . . .
. y x . . . .
) ,
sms/ TOLEDO
- l .
. EDISON
. . . LOWEu. E. ROE
.., .c.
..- ,. . w.. ,,.w.
p.u.a. o...-. '
~
. . . .t ..= ..., . .~.
. um ese.sa<a October 19, 1976 '- .
. f. ,, . ."- .
.. . . .e ..
. . . : . , ' 9_.r:.; . .
Serial No.131 '.~' '. #
,. "; .,,'..:
, Docket No. 50-346 . .
... ' ',a. .. . .
. ..~. .
c
.- s.
. . .. ; . .. . .
.' Mr. James G. Keppler li - .
~
- y. Regional Director, Region III .
.Dir'ectorate of Regulatory Operations -
C
. ., U.S. Nuclear Regulatory Commission ,
\ "
el 799 Roosevelt Road J.. . "-
's-Glen Ellyn, Illinois
. 60137 -
3 ...;
Dear Mr. Keppler:
- y. . vC'.O. .
~ ....
.~....
. . : .{ . .,'.f [t ' . ', ,
. r.
' Th'is letter is submitted in accordance with 10 CFR 50.55(e) as a con-
.. .* smnmation of the Interim Report dated August 6,1976 regarding defi-
. ciencies in the Davis-Besse Nuclear Power Station Unit No. 1, General
. Electric, type AK-3-25 and AK-3-50 480 volt AC circuit breakers, power sensors and supplies. ., . ,
.. c .,
Description of the Deficiency
.~ --
General Electric identified a failure mode of the zener diode in the power supply circuit. Diode failure could occur when simultanecusly the~ '
' breaker load current was less than 15-20% frame size current rating and 5 '
the gate current of the shunting SCR's (silicon controlled rectifiers) was in the medium to upper range of the specification limits. With . these two conditions existing, the thermal rating of the diode is ex-ceeded, which may lead to failure of the zener. 8001300[[h
. . v. .
n .
. c=
. 2 O
- O .-
. Corrective Aceion .
. .'. .. t , . . .... . . . .. .
.. 7 . ,.
General Electric redesigned the power supply circuit t:o eliminate the - - stated failure mode. The Applicant has arranged to replace all subject
* ** power supplies and power sensors at Davis-Besse Unit I and is presently -- --
" . having General Electric rework the breakers. Each reworked breaker will,
. be required to pass pre-operational testing under the Applicant's test
. program before being considered acceptable for use.
Safety Implications '
- 5 .'.'"': ~.A. . . ~ ~ ~
- If the above conditions had gone uncorrected, the zener diode coulci have .
* " failed.
- If the diode had shorted, insufficient trip voltage would have ~
- .j
.been available. The consequence would have been failure to protect t
associated essential electrical equipment during an electrical fault. With the diode opened, excessive control voltage would be available in e the power supply and power sensor circuits. In this latter c.ase, no *
- immediate safety consequence would have necessarily occurred, however electrical fault protection of associated essential electrical equipment
- could have been adversely affected should the high voltage have caused the power sensor to fail. .
, ,,.7 A The scheduled repair of the affected breakers and acceptable pre-oper-
'( ,
'ational testing of the devices prior to station operation assures that - - -
the health and safety of the public are not jeopardized. . . . . . . . . . , ; ., .. '
~:,;= .
.Yo.urs very truly.
. . .,: s
.. .:... . . + . ~ . .: . . . ... . .. ....-
. . c..
- z. . . ..
. . .. . s. .
; . , . .. =
^
~
p( ,. /. .- ^ ~- .< vr " *
,. r & :.:. u.-'; . .. '
w i .
~. . . . .: s. .. . .
; .:- .
pc/29 -
- -~ -
._ .};:,..{,, [ .
- ; - . ,
.; . .. .
cc: ..
,Dr. Ernst Volgenan, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D. C. 20555 .
, .i .
.; .
. ;. .
1 ' y
, . e ,.
- t. .
8 o}}