ML20059D124
| ML20059D124 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/21/1993 |
| From: | Shiffer J PACIFIC GAS & ELECTRIC CO. |
| To: | |
| References | |
| OLA-2-I-MFP-147, NUDOCS 9401070020 | |
| Download: ML20059D124 (8) | |
Text
'*hh2
& 275 33 - DL R&
T Nfl#'lf? g1 y y y
~
Pacific Gas and Electric Compang g
C'19. IVj @,
r
' P:.ita',
j
, ac 93 0F 28 P 5 :50 -
August 13, 1991 PG&E Letter No. DCL-91-202 q
d' Q M U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555 Re:
Docket No. 50-323, OL-DPR-82 Diablo Canyon Unit 2 Licensee Event Report 2-98-001-00 Containment Ventilation Isolation Resulting From a Voltage Transient Due to Personnel Error Gentlemen:
Pursuant to 10 CFR 50.73(a)(2)(iv), PG&E is submitting the enclosed Licensee Event Report (LER) concerning a containment ventilation isolation system actuation.
This actuation constitutes an Engineered Safety feature (ESF) actuation.
This event has in no way affected the health and safety of the public.
Titterely,
/
f., ), [
NUCLEAR REGULATOW cowuieging J.'D.'
Shi f r Decket No.509'75<4L omai E uo MF#- /M7 in the ma+ttr cf [Od/f/C _8 Ab IIf1CP bdNI[d C
John B. Martin
""" y cc:
Ann P. Hodgdon
- """'---"""3 Phillip J. Morrill suciw _
Paul P. Narbut r
Harry Rood cwam;EM[7[Mmt_gg-fa e -,..ay f CPUC Diablo Distribution othe wituu t/
koc/
nenrter DC2-91-TI-N062 r
Enclosure RECElVED 3 4 lbSI 54455/0085K/ALN/2246 e e...., $,1..,,,.
9401070020 930821 hDR ADOCK 05000275 i
PDR l
s LICENSEE EVENT REPORT (LER) 175452
)
,- a., - o,
-. n et,,. <,,
. a., o DIABLO CANYON UNIT 2 0l5l0l0l0l3l2l3 1l' 7
inu m CONTAINMENT VENTILATION ISOLATION RESULTING FROM A VOLTAGE TRANSIENT DUE TO PERSONNEL ERROR (UEMI DATE (5)
Lie etsefR (6)
RE pcuR1 Daft U)
O f **f 8 r ACILit!Es !=wCLv[D (B)
SON DAT TR TB St AL Rv ON BEJM 04Y TB DDcEti staeth (s) 0 5
0 0
0 07 15 91 91 0l0l1 0l0 08 13 91 0
5 0
0 0
o sa-tais atmost is sve-iitto evessani to int acoulstat=Ts or so cra: pa) 1 LtItY x
10 CFR
- 50. 73Je)(2)t iv) 1l01 0 OTnER.
~
(Specify in Abstract below and irt telt, htC For1R 366A)
LTCIsr5f t copriaci rom YHis t.IR M,)
,ne.= w -.r.
MARTIN T. HUG, SENIOR REGULATORY COMPLIANCE ENGINEER 805 545-4005 l
ccee>trir out ting som rAcu conspontut FAntuur otscalero su tuts arsomt on e o t
o E
8 Ca ht sisit" Ccewo=t=1 mags,s ac.
coast s*sta=
ccreo th-ma s' aj.
1 i lI III l
i II III I
III III I
III III suretoemtAL espost (settito (3a) esco.1.s Da, etaa EXPECTED
$UBMIS$10N
'f5 (if yes, cornplet e EXPECTED SUBu!SSION DATE)
!X l WO DATE (15) cesisa:t 06)
~
On July 15, 1991, at 1416 PDT, with Unit 2 in Mode 1 (Power Operation) at approximately 100 percent power, a spurious Containment Ventilation Isolation (CVI) actuation l
occurred. This constitutes an Engineered Safety feature (ESF) actuation.
A four-hour, i
non-emergency report was made to the NRC in accordance with 10 CFR 50.72(b)(2)(ii) on July 15, 1991, at 1725 PDT.
An Instrumentation and Controls (l&C) technician inadvertently dropped a screw on the l
power switch for power supply NM51 while performing maintenance.
This resulted in a voltage transient to the output relays of radiation monitors RM-ll and RM-12, which caused a solid state protection system (SSPS) Train B CVI actuation.
The root cause for the CVI was determined to be personnel error, inattention to detail, in that the I&C technician did not establish a temporary electrical barrier while working above the energized switch.
The corrective actions to prevent recurrence will include:
(1) counseling of the technician involved regarding the necessity for establishing a temporary electrical barrier when working around energized equipment, when practical, and (2) issuance of a maintenance bulletin that describes this event and discusses current policies and procedures applicable to performing work on energized equipment.
l 5H5S/0085K
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION 175452
,e o, u.y
,uun. - w
-n -n w DIABLO CANYON UNIT 2 0l5l0l0l0l3l2l3 91 0l0l1l-- 0l0 -2 l 'l 7 Test 07) 1.
Plant Conditions Unit 2 was in Mode 1 (Power Operation) at 100 percent power.
II.
Descriotion of Event A.
Event:
On July 15,1991, at 1416,JT, a Train B Containment-Ventilation Isolation (CVI) actuation occurred. This event occurred when an Instrumentation and Controls (I&C) technician dropped a screw onto the switch (IG)(JS) for power supply (IG)(JX) NM51 during routine maintenance.
The screw fell off of a " holding" screwdriver (a tool l
designed to hold the screw while it is being inserted), fell through i
the cabinet (IG)(CAB), and came in contact with unused contacts on the switch.
The screw caused a voltage transient to the instrument AC power supply (EF)(JX) for the output relays-(IL)(RLY) of radiation monitors _
(IL)(MON) RM-ll and RM-12.
This transient resulted in the solid state protection system (SSPS) (JG) initiating a Train B CVI actuation.
SSPS Train B actuation' caused the containment ventilation isolation system (CVIS) (JM) valves (VA)(ISV) outside.of containment-(NH) to close as designed.
Operators postulated that SSPS Train A did not actuate due to the l
short duration of the voltage transient. They, verified that.a valid high radiation alarm would actuate both trains of the SSPS by testing with a radioactive source.
Subsequent investigation determined that the output relays of RM-ll and RM-12 are of a rotary type that will actuate Train B first, then Train A uper 'ull travel.
The voltage l
transient caused the relay to travel far enough to actuate only Train B.
On July 15,1991, at 1512 PDT, operators returned the CVIS to normal operating mode after verifying that no actual high radiation condition existed. A four-hour, non-emergency report was made to the NRC in accordance with 10 CFR 50.72(b)(2)(ii) at 1725 PDT.
l l
B.
Inoperable Structures, Components, or Systems that Contributed to the Event:
None.
C.
Dates and Approximate Times for Major Occurrences:
1.
July 15, 1991, at 1416 FDT:
Event / Discovery date - spurious CVI actuation.
54455/0085K l
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION' 175452Ik
,u m,,.- m
-.,..m u.
-u.,.,
0l0l1 0l0 3 l 'l 7 DIABLO CANYON UNIT 2 0 l 5 l 010 l 0 l 31,2 l 3 91 Test (17)
I 2.
July 15, 1991, at 1512 PDTi Operators returned CVIS to normal configuration.
3.
July 15, 1991, at 1725 PDT:
A four-hour, non-emergency report was made to the NRC in accordance with 10 CFR 50.72(b)(2)(ii).
D.
Other Systems or Secondary Functions Affected:
The voltage transient momentarily affected the fuel handling building ventilation system (FHBVS) (VG} logic panel POV1 (VG)(PL), which caused the FHBVS to shift from normal mode to the iodine removal mode and the auxiliary building' ventilation system (VF) to switch from normal mode to safeguards mode.
E.
Method of Discovery:
The event was immediately apparent to licensed operators-due to alarms and indications received in the-control room.
F.
Operators Actions:
1.
After operators determined that no radiation monitors were in the alarm condition, the operators reset the CVIS isolation l
logic.
2.
The operators verified that a valid high radiation alarm would actuate both trains of the SSPS by testing with a radioactive source, and restored the CVIS to its normal mode of operation.
G.
Safety System Responses:
The CVIS isolation valves outside of the containment building closed.
111.
Cause of the Event A.
Immediate Cause:
The immediate cause of the CVI was determined to be a voltage i
transient on an instrument AC power supply.
B.
Root Cause:
l j
l The root cause for the CVI was determined to be personnel error, i
i inattention to detail, in that the 1&C technician did not establish a l
temporary electrical barrier while working above the energized switch.
it is common practice for technicians to establish temporary 54455/0085K i
)
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION 175452 l
F&Clk]TT NAMC (1)
DOCS.[i kVMBER (2)
LER kVM0fa (6)
DAGE 13) 1.-
~
g g
l DIABLO CANYON UNIT 2 0l5l0l0l0l3l2l3 91
- 0l0l1 0l0 4 l 'l 7 T[sf (17) electrical barriers when working on or near energized equipment, when practical.
l IV.
Analysis of the Event A.
Safety Analysis:
A CVI is a conservative actuation regardless of plant conditions.
All plant equipment functioned as designed, and would have isolated l
the CVIS had an actual high radiation condition existed. Therefore, this event did not adversely affect the health and safety of the l
public.
V.
Corrective Actions A.
Immediate Corrective Actions:
1.
After it was determined that a high radiation condition did not exist, the CVIS was returned to normal configuration.
B.
Corrective Actions to Prevent Recurrence:
1.
The technician involved in the event will be counseled regarding the necessity for establishing a temporary electrical barrier when working around energized equipment, when practical.
2.
An I&C maintenance bulletin will be issued describing the event and discussing current 1&C policies and procedures with~ respect to temporary barriers when working on energized equipment.
VI.
Additional Information A.
Failed Components:
l
- None, l
B.
Previous LERs on Similar Problems-1.
LER l-87-021-00 Actuation of Building Ventilation System Engineered Safety Features (Containment, Fuel Handling, and Auxiliary Building Ventilation Systems) Due to inadvertent Grounding of Electrical Components The event in LER l-87 021-00 is similar to the recent event in that a CVI was caused by an 1&C technician.
The root cause was determined to be a personnel error in that the technician failed to realize that the circuit was energized. The corrective actions included training the I&C department technic-ians on the l
54455/0085K l
l l
LICENSEE EVENT REPORT (LhH) t hXI UUNilNUAllVN 175454 FACIL]TV hAML (1)
Doct[T NW4819 (I)
LIS NLDe6(S 16) w iG[ (3)
DIABLO CANYON UNIT 2 0l5l0l0l0l3l2l3 91 0l0l1 0l0 5 l 'l / i YERT (37) event. This corrective action would not have prevented the recent event as the technician was aware that the circuit was energized.
2.
LER 2-88-004-00 CVI Due to Power Supply Transient and Failure of CVI Protection Train A Valves to Close Due i
to Installation Error and Procedural Deficiency Ihis event is similar to the recent event in that a tran:':nt to the power supply of a radiation monitor caused an actuation.
The root causes of the event were determined to be inaccurate wiring instructions from the vendor and an inaccurate vendor diagram of connection, which led to a procedure deficiency.
The corrective actions included correcting the appropriate diagrams and revising procedures to provide instructions on disabling the CVI inouts for testing.
As the root cause for this LER was the result of drawing and procedure deficit.cies, the corrective actions would not have prevented the recent event.
3.
LER l-89-011-00 Inadvertent CVI Due to Personnel Error i
1 This event is similar to the recent event in that a voltage transient resulted in a safety system actuation.
The root cause of this event was determined to be personnel error in that a technician inadvertently connected the power lead to the neutral i
lead.
The corrective actions included:
(1) counseling the technician regarding the precautions necessary when working on energized equipment; and (2) issuing a maintenance bulletin to i
reemphasize tha need fnr caution when working on energized equipment.
In the recent event, use of a " holding" screwdriver indicates adherence to work practices regarding caution when working near energized equipment.
However, based on this recent event, additional re-emphasis is warrante'.
i 4.
LER 1-90-002-00 Manual Reactor Trip Due to Main Feedwater Pumps Tripping Due to Unknown Cause Though the root cause of this event is unknown, this event may be similar to the recent event because one potential root cause considered was that I&C technicians working in the SSPS racks may have dropped metallic debris onto contacts in the cabinet.
Corrective actions included a cautionary tailboard of I&C technicians regarding the potential hazards of test equipment use during SSPS testing.
In the recent event, use of a
" holding" screwdriver indicates adherence to work practices regarding caution when working near energized equipment.
However, based on this recent event, additional re-emphasis is warranted.
54455/0085K
//
D U
CENSEE tm IABLO CANYON ENT EV UNIT R
T(L E)T R
w LER w
c 29 m
EXT na 00 0
m CONTINU 040 5
0 0
Th 0
ATIO tr is Co 0
ev Ha ntai 3
~
N an per si ent lodndl nime 2l
- a. m"e%. n e
a so 3
nt i
Du i s
neg nt n
te nn V
91 17k and st el res si Re Buil nt ring Tr e
w (1
a pr er ul mi movdi il 0
l (2 ) i ted a ob ror ne al ng Vat r
o Ow e
(3 ) r io 0
utral o n in to ubl ss t
i Mode ui n
1 e
cha)ge a
th sho e
e nt Is that vi ng l sl Du ilat ol
,0 C
ev Ve i
e n
al win a e
I r
oti ad p, wh n.
e e
i at ec u
m n
a i
I&C he nt ng to on io 0
ai.
er at g Te act gi impl ng the nte T
i P Sn 6
he ch ivi at z
nan co a
r yste nd ev e
co te r em de ev c
prionta cau t
io o
e sonn m s ch ot nt e
F ct ies. n nt si ent e r
Suh el r
i bul ct ed nici aus e
c in of ed gn 6
e el v
r ed ift n
l iv a an e
e that Er b
Ho pa in chan qu eti e sho i
of nt. corry t rt st r
w or to LER ct he al ge a ev rte n a
e r ct rt nadv th v
a er of l
s i
l9 iv s
00 a
ew hetheedto rl ega o
b e
i ol c,t a
r n etw rte e
s ta ty r
he tr d s in ev ing 1
cti in de eab po een ntl e ge c
Thi 90 aining;t w
cluded:n a y nt er po in on the ner tr s he w
al wlas et s
0 co er an ev ul re gi du wi ener co nt Actu ev wi ntrsi e tch ab ai nd ent; gi ed ow c
d ce z ri e
e si e at ot nt ati ng t
nt is D
n th act r
n z
hat et ed u
er on m
i ha ev r
a ai to on or f el s w.
T e ul mi nt,s acco iuse v
e wi nte ul he l
ct ted a P
of e
o t
dep rda t
pr r
er a ch nan n
b ri d
d Co ev c
i t
s l
hat n
o onn nt e nd w ce wi artm al el si n
ck.i o
as th e ce an a
th el ain nted the th ow gn act the nt wi if i
CVe Er me r
Tn nt he ef e de-he he adv 1 ec r
i f th t
r t
cr on o
s f or ew s
or V
r e wi rte Aent s
r e
ev s
iuse w ta el ro c,t tch e
e e
Ge ev ntil nt. to cl n
nd e bol rkiard ot r
ntlner e
nt h e
ece ctr r
ud e
wicci us br al nt at o
Tevi ed ck ng a y nt h
i o
Co in o
As ev e ew m
i hol ay o
e n
rk an n
pr hadof ugh nst that is "Noi s nt,c e
or pr di ener di n
a th t r
e ol e
vi ng ot is hru a
at LERse cus si ctiv tai ah giz ct taped e is cti v
ou i
i LE Rsed nce e
m rR l 8 edu e ed ce s
on l v pl o ol v
i n (G)tage s
i a
ai bo o
c e
ad l8 60 ct n the cti nte rd th nt ab u er C
a ccur ise io P i
7 0
ets,d e w
Na s
70 n G&E 1&Cns an u ati003 n
o n
m r
by to as in s
1 T
l ce et ed ol p e
ed on te W ul b in. T el he ier co a
t sk et b
m 0,L r
nta 1
ER F te n
so e
chni o
ct y ul gs l
he e ni, "po lor DCL an ha ns d
nn I&C el ct r
ed iv po ctri to w8ce ci not eti wi l b e w
c r
thor c
e 60 Fi89 was e
r r
s y
a er ing hu cti tr ha al GrCect co 1
n v
v tr 40 al 254 u
an e
m ons si cau si pr el a
ev nd iv an of an ancet e nta 1
Re sin ev a
e:
e e, L po, dated pr ; a he V r (1)nts nt I ct r
s pr nted to&
ER rt g
e ed nts r
C Co ogr i
(t nd(3)I ; (2)traininei erl 8 ega s
r s
f bev af O
ope t
t a
r he th
'c hat m f
6 0 rd ctob to s
i u
e to in ad ng al cti ui 1
i tr is r
ni ct V ng 50 g n
er ol g to ad C i
d n in g y
l epl ti o
dr Is. CV 1 2, 1 s.
m es aceati du CVrI edu ed ReduI r,l odis ess a
98 e ng ri e nd fisen 9,
si xi a ng ryp po b
ce by ci ated cati t st r
n iv in ad ad aiss n
o e
g i
w sevg CVI er at alr to r ati s
er io wi n
t tr adion al s
e an ady el che e atimo mo ni ni s si i ctri on e
m to to to nts mpl c
r al oni rin all eme tog ow nt n ed oise. s wisyste r
r thm edu The ces time
//-
ff g# 0 s
- 's' f," S
_f'(s
$+ / /*s
~'
i.
swf7 f
- s *s v
/,/, ss,g e
ev a #b' i
- p' f,s
$*/, * $* / 9,$* ',a s,s#$' # " '
64 4;e* /b*e,. * * ' <,
&'Y<'
ts
(
- s
$sc e*'ji/.$'$'sls+',s*$$s
\\
h6 4:
fe
' N
- };,$4g.
m.
4~
~:sc/.fxy.k:;'
3.R
.-A, <e
+/
s !I$
s.
hl g%
.st 9
+'
~
~
r LICENSEE EVENT REPORT (LER) TEXT CONTINUATION 175452 c Litu sAME (p pocagv m ega (2) tre e ste m par.t b DIABLO CANYON UNIT 2 0l5l0l0l0l3l2l3 91
- 0l0l1 0l0 6l"l7 TEAT (17) 5.
LER 2-90-004-00 Containment Ventilation-ation and Fuel Handling Building Ventilau n System Shift to Iodine Removal isode Due to Personnel Error During Troubleshooting This event is similar to the recent event in that a voltage transient resulted in a CVI. The root cause of this event was personnel error in that an I&C technician inadvertently allowed a test probe to slip, which caused a short between an energized and a neutral lead.
The co.rettive actions included:
(1) issuing a maintenance bulletin regarding the event; (2) reviewing the event in quarterly training; and (3) evaluating design changes to the power cabinet. The design change implemented installed a power switch that would allow de-energization of part of the cabinet during maintenance activities.
However, the de-energization switch was the switch contacted by the screw in the recent event, and therefore, the prior corrective action could not have prevented the recent event.
6.
LER l-90-019-00 Actuation of Containment Ventilation Isolation Due to Personnel Error This event is similar to the recent event in that a voltage transient resulted in a CVI.
A General Construction (GC) contract electrician inadvertently brought his pliers in contact with a fuse block.
The root cause of this event was personnel error in that if the electrician had taped the tool in accordance with standard work practices used by the I&C department for working in energized cabinets, electrical contact with the fuse block may not have occurred. The corrective actions included holding tailboard meetings with GC and 1&C crews to review previous maintenance bulletins relevant to this event.
The corrective actions n uld not have prevented the recent event, since the I&C technician was using proper tools.
7.
As discussed in PG&E letter DCL-89-254, dated October 2, 1989,
" Noise Reduction Task Force Final Report regarding LER l-86-007-01, LER l-86-014-01, LER l-86-015-01, and LER l-87-003-01," power transients affecting CVI-related radiation monitors have caused several CVis.
Reducing CVIs caused by power transients is being addressed by several corrective actions:
(1) training to reduce power transients caused by human error; (2) adding CVI bypass switches to allow disabling of the CVI function during radiation monitor maintenance; and (3) initiating a radiation monitoring system upgrade program to replace existing radiation monitors with equipment that is less sensitive to electrical noise.
The time delay circuitry modification already implemented reduces 4455/0085K
4 LICENSEE EVENT REPORT (LER) TEXT CONilNUAllVN 1(M,
no o n aw m man -en m
___. an -so s ___
.s na me,mn umu DIABLO CANYON UNIT 2 0l5l0l0l0l3l2l3 91
- 0l0l1 0l0 7 l 'l 7
toi on spurious CVis caused by noise on the signal input; however, the output relays of the monitors are still sensitive to transients on their power supply (such as in the recent event).
C.
Remarks:
In summary, PG&E has implemented several corrective actions to minimize recurrence of inadvertent CVIs:
1.
The installation of the power switch permits the de-energization of sensitive equipment in this cabinet that is not absolutely necessary for plant operation.
2.
The continued use of insulated and holding tools when working near energized equipment, as well as establishing temporary electrical barriers when practical, will reduce the number of inadvertent CVis due to personnel error.
3.
The radiation monitoring system noise reduction program appears to have eliminated inadvertent CVis due to spurious electrical noise.
4.
The counseling of technicians and training on maintenance bulletins will continue to sensitize plant personnel to the potential consequences of working near energized equipment.
While these actions are designed to reduce the number of inadvertent CVis, PG&E recognizes that it is impossible to completely eliminate personnel errors.
54455/0085K l
l
-