ML20062J984
| ML20062J984 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 08/18/1993 |
| From: | Rueger G PACIFIC GAS & ELECTRIC CO. |
| To: | |
| References | |
| OLA-2-I-MFP-054, OLA-2-I-MFP-54, NUDOCS 9311190416 | |
| Download: ML20062J984 (7) | |
Text
-
- Ol A ?h
~
ff fg f
93 Widd)-
~
Pacific Gas and Electric Company 77 Beale Street Room 1451 Gregory er PO Box 770000 m,ni ;i Senior Vice Presi0ent and San Francisco CA 94177
%hF. GeneralManager 415/973-4684 Nut! ear Power Generahon Fax 415/973-2313 April 5, 1993 PG&E Letter No. DCL-93-076 U S. Nuclear Regulatory Commission
~ ~ " "
r/'
ATTN: Document Control Desk
.-y/t Washington, D.C.
20555
~12 Re:
Docket No. 50-323, OL-DPR-82 Diablo Canyon Unit 2 j
Licensee Event Report 2-93-003-00 Technical Specification 3.9.4 Requirement for Containment i
Equipment Hatch Closure During Refueling Core Offload Not Met Due j
to Personnel Error j
Gentlemen:
PG&E is submitting the enclosed Licensee Event Report pursuant to 10 CFR 50.73(a)(2)(1)(B) and 50.73(a)(2)(v)(C) concerning fuel movement during refueling core offload with tha containment equipment hatch not fully closed due to personnel error.
i This event has in no way affected the health and safety of the public.
Sincerely, 4
n l
4 I
4 p,9 Giegory M. Rueger i
j cc.
Ann P. Hodgdon Jotfn B. Martin
+-
1 Mary H. Miller Sheri R. Peterson CPUC J
Diablo Distribution l
INP0 t
\\
DC2-93-MM-N013 nucun eccur,RY COVMCSUN Enclosure 0"h' *
' 3 2 C" N.N3 W
^
wr e unwu et RM <<4C_h+S Clnd 5~0c%' l'c 1085S/85K/JCN/2246 v
, w 7n Ni l' ' A
..~....._.---_...I)
tw.m /
i
. u,e _
2 EM S,. _b,f05 e. 2df ~Y 3 9311190416 930818
/
i PDR ADOCK 05000275
~-
cou O
PDR RU"b b.d C!):l 4
LICENSEE EVENT REPORT (LER)
DIABLO CANYON UNIT 2 0l5l0l0l013l2l3 Il 'l 6 l TECHNICAL SPECIFICATION 3.9.4 REQUIREMENT FOR CONTAINMENT EQUIPMENT HATCH CLOSURE DURING -
mum REFUELING CORE OFFLOAD NOT MET DUE TO PERSONNEL ERROR EVENT DATE ft)
LDI NLAdaEM IS)
REPORT DATE (7) oTHER FACILITIES INVOLVED (8)
,AO 8 DAY YM YM SEQUEN HAL R&MaaON MON DAY YM DOCKET 8eUMam (86 Ntmasm Nuusm O'
5 0
0 0
03 11 93 93 0l0l3 0l0 04 05 93 0
5 0
0 0
RA THis REPORT Is SUBMITTED PURsVANT TO TMC REQUIREMfMis DF 10 cFat (11) 6 L EL x
10 CFR 50.73(e)(2)(i)(B) and 50.73(a)(2)(v)(c) 0] Ol 0 (2 1 OTHER -(Specify in Abstract below end in text, WRC Form 366A)
UCEN$tt CONT AcT POR T642 Lim (121
^" ' '
DAVID P. SISK, SENIOR REGULATORY COMPLIANCE ENGINEER 805 545-4420 COMPLETE ONE UNE POR EACH COMPONENT F AILURI DESC75 SED IN Tras REPORT 0 3) caust sesitM coMPoNENr FAc.
R po t
caust sysTtM COMPONENT FAC.
R C E
I
!II III I
III lll l
lll llI I
III III suPnsMENTat asPOni txPecTED o*'
EXPECTED
'E^"
SUBMI5510N DATE W l l YEs (if yes, complete EXPECTED SUBMIS$10W DATE) lX l NO sssTRAct (16)
On March 12, 1993, at 1416 PST, with Unit 2 in Mode 6 (Refueling), the Limiting Conditions for Operation of Technical Specification 3.9.4 were not met when a visible gap in the seal of the conta:...aent equipment hatch was identified.
Core offload had been in progress and was immediately suspended.
On March 12, 1993, at 1615 PST, PG&E made a four-hour, non-emergency notification to the NRC in accordance with 10 CFR 50.72(b)(2)(iii)(C).
Immediate corrective actions taken included suspension of core offload and the installation of additional bolting on the containment equipment hatch followed by verification of hatch sealing.
The root cause of the event was personnel error (cognitive), failure to follow procedure.
The corrective actions are to counsel personnel involved with the containment equipment hatch closure, to enhance the procedure to reduce the possibility of misinterpretation, and to brief Mechanical Maintenance personnel on the necessity for procedural adherence.
10T25S/85K
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION ham m
.. m
- u. q.g m o n
- u. m DIABLO CANYON UNIT 2 0lSl0l0l0l3l2l3 93
- 0l0l3 0l0 2 l"l 6 TDT (17)
I.
Plant Conditions Unit 2 was in Mode 6 (Refueling) at 0 percent power.
11.
Descriotion of Event A.
Sumary:
Technical Specification (TS) 3.9.4, which requires containment equipment hatch closure, was not complied with on March 12, 1993, at 1416 PST, when the Refueling Senior Reactor Operator (SRO) observed i
that the Unit 2 containment equipment hatch (NH)(DR) had a visible, l
approximately 1/2-inch gap in 25 percent of the upper portion of its sealing area.
Core (AC) offload had been in progress and was immediately suspended.
i On March 12, 1993, at 1615 PST, PG&E a completed a four-hour, non-emergency notification to the NRC in accordance with 10 CFR j
50.72(b)(2)(iii)(C).
j B.
Background:
TS 3.9.4 requires: "The equipment door closed and held in place by a minimum of four bolts,...," during core alteration.
l Maintenance Procedure (MP) M-45.1, " Containment Equipment Hatch Door Opening and Closing," requires installation of four equally-spaced bolts and a visual inspection from outside of containment (NH) to ensure there is no gap between the equipment hatch and containment.
In MP M-45.1, each of these requirements must have a signature certifying its completion.
C.
Event
Description:
On March 10, 1993, a Mechanical Maintenance tailboard was conducted prior to the Unit 2 containment equipment hatch closure; however, only the number of bolts to use to.close the equipment hatch was emphasized during the discussion.
On March 10, 1993, two Mechanical Maintenance journeymen closed the Unit 2 equipment hatch with four bolts installed.
The four bolts were at approximately the two, four, eight, and ten o' clock positions about the equipment hatch (there are 48 total bolts). The lead journeyman erroneously believed the positions of the bolts met the requirements of MP M-45.1 for the bolts to be "... equally spaced."
After installing the bolts, the lead journeyman performed a visual inspection of the equipment hatch to ensure there was no air gap in the hatch seal.
This inspection was performed from the inside of 1085S/85K m
i
{
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION m
.= m u ua y a racion.- m ooc m = m m l
DIABLO CANYON UNIT 2 0l5l0l0l0l3l2l3 93 0l (, l 3 0l0 3 l'l6 trat ( m containment instead of from the outside of containment as required by MP M-45.1.
From inside of containment, the lead journeyman was unable to see the air gap in the top portion of the equipment hatch seal.
Since the portion of the equipment hatch seal the lead journeyman could see had no air gap, he believed that the equipment hatch was adequately closed.
Had the lead journeyman performed the equipment j
hatch seal inspection from the outside of containment as required by the procedure, the air gap that existed ia the top portion nf the 4
hatch seal would have been observed and additional hatch bolting could i
have been installed as required to seal the hatch.
The lead journeyman signed the MP M-45.1 data sheet certifying that four equally-spaced bolts had been installed and that no air gap was visible in the equipment hatch seal as viewed from outside of i
containment.
The lead journeyman informed the foreman that the hatch closure was.omplete and the foreman also signed the M-45.1 procedure 1
certifying closure of the containment equipment hatch based on the verbal assurance of the lead journeyman.
No additional verification of the containment equipment hatch closure was required.
On March 11,1993, at 1408 PST, Unit 2 core offload commenced.
A discharge permit was in effect at this time and containment ventilation fans E-3 and S-3.(VA)(FAN) were running continuously with the plant vent radiation monitor (VL)(MON) in operation.
The i
containment ventilation fans maintain the pressure inside containment i
below ambient atmospheric pressure to prevent uncontrolled airborne i
out-flow from containment in the event of an accident. The plant vent radiation monitor provides a containment ventilation isolation function if monitored containment ventilation exhaust activity exceeds acceptable limits.
On March 12, 1993, at 1416 PST, the Refueling SR0 reported that the i
Unit 2 equipment hatch had a visible, approximately 1/2 inch gap in i
25 percent of the upper portion of its sealing area as observed from outside of the containment.
Core offload had been in progress and was immediately suspended (122 of the 193 fuel assemblies had been removed from the core).
I On March 12, 1993, at 1430 PST, Mechanical Maintenance was advised of the equipment hatch condition; an additional eight hatch bolts were i
installed and torqued. Mechanical Maintenance verified that there was no visible gap at the hatch sealing area as viewed from outside the containment.
On March 12,199?, at 1547 PST, core offload resumed.
On March 12, 1993, at 1615 PST, PG&E completed a four-hour, non-emergency notification to the NRC in accordance with 10 CFR 50.72(b)(2)(iii)(C).
1085S/85K
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION
,j oocagt utesta (r) ten ennera es)
Pant (3)
' b. Fac;L;77 Mwet (2) vua sa w
mveca 0l0l3 0l0 4 l'l6 DIABLO CANYON UNIT 2 0l5l0l0l0l3l2l3 93 nu tv>
D.
Inoperable Structures, Components, or Systems that Contributed to the Event:
None.
E.
Dates and Approximate Times for Major Occurrences:
1.
March 10, 1993:
The Unit 2 containment equipment hatch was closed with four bolts in place.
2.
March 11, 1993, at 1408 PST:
Event date.
Unit 2 core offload commenced.
3.
March 12, 1993, at 1416 PST: Discovery date. The Refueling SRO reported that the Unit 2 equipment hatch had a visible, approximately 1/2-inch gap in upper portion of its seal. Core offload was immediately suspended.
4.
March 12, 1993, at 1430 PST: Mechanical Maintenance installed and torqued an additional eight hatch bclts when informed of the equipment hatch condition and then verified that there was no visible gap at the hatch sealing area as viewed from outside the containment.
4.
-March 12, 1993, at 1615 PST:
PG&E completed a. four-hour, non-1 emergency notification to the NRC in accordance with 10 CFR 50.72(b)(2)(iii)(C).
F.
Other Systems or Secondary Functions Affected:
None.
G.
Method of Discovery:
The Refueling SRO identified the equipment hatch sealing area gap during the performance of a normal shift equipment observation tour.
H.
Operator Actions:
Core offload was immediately suspended, 1085S/85K
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION
~~
Ft.cILITT MMt (1) cocKtt muMata (2) tra munste is) pau m e..,,.
DIABLO CANYON UNIT 2 0l5l0l0l0l3l2l3 93 0l0l3 0l0 5 l 'l 6 g
ttat (17) l l
1.
Safety System Responses:
h None required.
1 III. Cause of the Event A.
Immediate Cause:
The immediate cause of this event was inadequate closure of the containment equipment hatch.
B.
Root Cause:
The root cause of the event was determined to be personnel error (cognitive), in that plant non-licensed personnel failed to follow the procedure to verify the absence of a containment equipment hatch seal gap from the outside of containment.
C.
Contributory Causes:
1.
Independent verifications were not required or performed for the 1
containment equipment hatch closure prior to core offload, although they had been performed as an optional activity for this evolution in the past.
2.
The Mechanical Maintenance tailboard prior to the containment equipment hatch closure activity was not adequate. The~ equal spacing of the haten bolts and visual verification that there was no gap at the hatch sealing area from outside of containment was not discussed during the tailboard.
IV.
Analysis of the Event An analysis of the consequences of an accident during core offload was performed, based on the estimated flow rate out of the equipment hatch under post-accident conditions with the gap that was observed in the equipment hatch. The estimate of the flow rated included an assumed difference between the inside containment atmosphere and ambient temperatures throughout the postulated event and resulted in a calculated leak rate of 34 cubic feet per minute (CFM).
This result was combined with the design basis fuel handling accident source term and meteorological assumptions to calculate postulated site boundary doses estimates.
The resulting dose estimates are less than 10 percent of the 10 CFR 100 limits.
Consequently, the analysis of the postulated fuel handling accident with the containment equipment hatch seal breached as occurred in this event has shown that the resulting site boundary dose wo'uld be bounded by the results of accidents analyzed in the FSAR Update.
10855/85K x
a
a LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Y f4CILITT HAME (1) oocr.tf nuMata (t) tra to to) par.t (3) muussa sannosa DIABLO CANYON UNIT 2 0l5l0l0l0l3l2l3 93-0l0l3 0' l 0 6 l"l6 ftIf (??)
Thus, the health and safety of the public were not adversely affected by this event.
V.
Corrective Actions A.
Immediate Corrective Actions:
1.
Core offload was immediately suspended.
The installation torque for the four bolts positioning the,l, 2.
containment equipment hatch was verified and eight additiona equally-spaced bolts were installed and torqued. The sealing area of the equipment hatch was inspected and the absence of a gap was verified from outside of containment.
3.
Quality Control (QC) has implemented hold-points on the remaining Unit 2 fifth refueling outage containment equipment hatch closure activities.
B.
Corrective Actions to Prevent Recurrence:
1.
Personnel involved in the closure of the Unit 2 containment equipment hatch, including the pre-activity tailboard, have been counseled in accordance with the PG&E positive discipline program on the need to review and follow procedures involving eq>ipment whose function could affect personnel a..d plant safety.
2.
MI M-45.1 will be revised to include visual, independent verification from the outside of the containment by QC hold-point inspection that the containment equipment hatch _ seal has no visible gaps.
3.
This event was discussed at a departmental level meeting for Mechanical Maintenance personnel with emphasis on the necessity for procedural adherence.
VI.
Additional Information A.
Failed Components:
None.
8.
Previous Similar Events:
None.
1085S/85K
)
.