ML20154N437
| ML20154N437 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/03/1986 |
| From: | Lester Tripp NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML20154N432 | List: |
| References | |
| 50-271-86-08, 50-271-86-8, NUDOCS 8603170324 | |
| Download: ML20154N437 (15) | |
See also: IR 05000271/1986008
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U.S. NUCLEAR REGULATORY COMMISSION
REGION I
Report No.
86-05
Docket No.
50-271
License No. DPR-28
Licensee:
Vermont Yankee Nuclear Power Corporation
RD 5, Box 169, Ferry Road
Brattleboro, Vermont 05301
Facility:
Vermont Yankee Nuclear Power Station
Location:
Vernon, Vermont
Dates:
February 9-27, 1986
Inspectors:
William J. Raymond, Senior Resident Inspector
Glenn W. Meyer, Project Engineer
Approved by:
. h.
ps4 0
8 8b
LR E. Tripp/,fChief, Reactor Projects Section 3A
' D' ate
Inspection Summary:
Inspection on February 9-27, 1986 (Report No. 50-271/86-05)
Areas Inspected:
Special, unannounced inspection on day time and backshifts of
the events associated with the discovery during surveillance testing on February
8, 1986, that the Standby Liquid Control System was inoperable.
The inspection
involved 61 total hours by the Senior Resident Inspector and a Project Inspector.
Results: One apparent LCO violation was identified for the SLC system being in-
operable from July 14, 1984 to October 3, 1985 when required to be operable.
Con-
cerns were also identified with the SLC system continuity monitoring circuitry,
the apparent loss of configuration control in the SLC firing circuit wiring, and
the apparent inability to detect a manufacturing error during preservice tests.
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1.
Summary...............................................................
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2.
Purpose...............................................................
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3.
Event, Initial Evaluation, and Notification...........................
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4.
SLC System Description................................................
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5.
Primer Wiring Change.........................................
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6.
SLC Continuity Monitoring Change......................................
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7.
.SLC Surveillance Testing..................................-............
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8.
Previous Circuit Der,ign Changes.......................................
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9.
Previous Maintenance Activities.......................................
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10.
Licensee Conclusions..................................................
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11.
Inspection Findings...................................................
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12.
Persons Contacted and Management Meetings.............................
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1.
Summary
During a February 8,1986 surveillance test, Vermont Yankee found that the
SLC system was inoperable due to the inability to actuate the explosive squib
valves.
The prior successful actuation of the squib valves had occurred dur-
ing a July 11, 1984 surveillance test.
The licensee found that the replace-
ment squib valve explosive primers, installed following the July test and
presumed to be electrically the same as the primers successfully fired, were
electrically different due to a changed connector pin to bridgewire configura-
tion. The primer wiring change was a manufacturing error unknown to the vendor,
Conax Corp., and had not been detected by the licensee during receipt inspec-
tion or preservice testing.
The continuity monitoring circuit for the firing
circuit was incapable of detecting the problem.
Although the inspection found that the principal reason the squib valves
failed to fire was due to the primer manufacturing error, irregularities were
also found in the firing circuit.
The inspection found that the firing cir-
cuit (external to the primer) had been modified in 1977 as a result of GE SIL
186.
The licensee determined that the as-found firing circuit wiring differed
from the wiring design drawing. Apparently, this difference occurred when
difficulties encountered during installation resulted in a needed field modi-
fication to the firing circuit. This field modification did not go through
the normal required review process and therefore was not reflected in a change
to the as-built drawing of the firing circuit.
Ironically, it was found that if the firing circuit field modification had
not been made, the improperly manufactured primers would have fired the squib
valves and allowed the SLC to function as designed.
However, since the field
modification would have been approved in 1977 if properly submitted, the pri-
mary cause of the SLC system failure remains the primer manufacturing error
and the failure of the manufacturer and the licensee to detect this error.
The licenste was reviewing corrective actions including firing circuit design
changes, revised surveillance testing, and additional pre-installation checks
at the end of this inspection.
2.
Purpose
The purpose of the special inspection was to review the failure of the Standby
Liquid Control (SLC) system during the February 8, 1986, refueling surveil-
lance test and to identify the factors that caused the SLC system to be in-
The reactor was in a cold shutdown, defueled condition to support
the replacement of the reactor recirculation system piping.
The SLC syt, tem
was not required to be operable when the discrepant condition was discovered.
3.
Event, Initial Evaluation, and Notification
During the SLC surveillance testing per OP 4114 and 4203 on February 8, 1986,
both primer charges for the 14A squib valve failed to fire at 9:45 A.M. when
SLC System I was actuated.
The parallel 148 squib valve was not tested as
part of the System 1 testing, and its firing was deferred pending further
investigation of the A circuit.
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Licensee investigation of the System 1 firing circuit determined that the
primer charges were miswired (when compared to Control Wiring Diagram (CWD)
191301, Sheet 1200) by having both 120 VAC high side leads wired to the A-B
primer bridgewires, and both neutrals wired to the C-D primer bridgewires.
The wiring was found rolled (i.e., interchanged) at a local terminal box (TB)
mounted immediately above the squib valve.
Instead of the white-black green-
red sequence (W-Bk-G-R) required by the CWD, entering and leaving the TB, the
sequence into the TB was Bk-G-W-R, and the sequence leaving the TB was W-G-
R-Bk.
The firing circuit worked properly when tested at 4:19 P.M. after the
TB was rewired per Maintenance Request (MR).86-0278 to agree with the CWD.
The TB wiring for the System 2 squib valve was inspected and also found mis-
wired as follows: sequence into the TB was R-W-G-Bk, and the sequence out of
the TB was Bk-R-G-W.
Although different in appearance, the terminal boxes
were electrically the same (e.g. , black connected to white, white connected
to red, etc.).
Even though the SLC system was not required to be operable for the existing
plant mode, licensee personnel deemed it probable that the SLC system would
not have been functional during the last operating cycle (XI) which ended in
September 20, 1985.
The licensee notified the NRC Duty Officer per
50.72(b)(2)(iii) at 4:40 P.M. on February 8, 1986, of the potential loss of
function for the SLC system.
Following the appointment of a lead engineer to systematically investigate
and evaluate the as-found SLC conditions, the licensee attempted to perform
OP 4114 on System 2 at 3:15 P.M. on February 11, 1986. The B pump started and
injected into the reactor vessel during the test (through the already open
A valve), but squib valve 11-148 failed to fire.
A second notification was
made to the NRC Duty Officer per 10 CFR 50.72(b)(2)(iii).
Reviews completed during this inspection (discussed further below) identified
no modification, maintenance, or testing activities that would have made the
SLC system inoperable following the July 11, 1984 test.
As noted below, the
squib valves most likely became inoperable following the installation of new
primer charges during the 1984 test. The inspector concluded that the SLC
system was inoperable from July 11, 1984 until February 8, 1986.
The SLC
system was required by Technical Specification 3.4.A to be operable whenever
the reactor had fuel and the mode switch was not in the shutdown position,
i.e., from July 14, 1984 to October 3, 1985.
The failure to meet these con-
ditions is a violation of Technical Specification 3.4.A (VIO 86-05-01).
4.
SLC System Description
The SLC system consists of two redundant pumps that take suction from a tank
containing sodium pentaborate solution and inject into the reactor vessel
through two normally sealed, closed squib valves mounted in parallel on the
pump discharge line.
To initiate SLC injection, the reactor operator turns
a key locked switch on control room panel (CRP) 9-5 to either the System 1
or System 2 position.
Turning the switch to the System 1 position causes the
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A pump to start and the A squib valve to open.
Should either component in
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System 1 fail, the B pump and B squib valve would then be activated by turning
to the System 2 position. When the system is in a standby mode, a relay
circuit monitors the electrical continuity of the valve firing circuit and
lights a light bulb on CRP 9-5 for each valve when the circuit has continuity.
The wiring configuration for the System 2 firing and monitoring circuits,
which is typical for System 1, is shown in Figure 1.
The mechanical details
of the squib valve and explosive chamber are shown in Figure 2.
The squib
valve is opened by shearing the cap on the inlet fitting mounted in the valve
flow path.
The cap is sheared off by the trigger assembly that is actuated
by two explosive charges in the primer subassembly.
Either primer charge is
sufficient to shear the inlet fitting plug.
The primer charges are ignited
by concurrently applying 120 VAC to bridgewires embedded in the charges.
Turning the CRP 9-5 control switch to the System 2 position closes contacts
2, 4, 6, and 8, which starts the B pump, applies voltage to the bridgewires
in the B valve primer change, and shunts around control relay 11-678 of the
continuity monitoring circuit.
Once actuated, the primer, the trigger assem-
bly, and the inlet fitting cannot be reused and must be replaced.
The as-found wiring of System 2 is shown in Figure 3.
5.
Primer Wiring Change
The ifcensee's investigation of the February 8, 1986 event identified a primer
wiring change as the primary cause of the incident.
The vendor supplied two
types of primer assemblies with the same part number and drawing number, but
with different wiring between the connector pins and the firing circuit.
The squib valves ere supplied by the Conax Corp. of Buffalo, New York, and
are described in GE Specification 21A5468 and Conax Instruction DS 1832-2,
Rev C dated June 18, 1970.
The trigger assembly part number is 1617-139-01.
Revision E of this Conax drawing dated August, 1970 shows a connector pin to
bridgewire grouping of A&B and C&D.
The primer subassembly part number is
1621-186-01.
Revision E of this drawing dated August, 1970, also shows pin
wiring with the same bridgewire/ configuration.
However, Revision K of drawing
1621-186-01 dated Noveraber 2,1982, showed a pin to bridgewire grouping of
1&4 and 2&3 with a labeling convention in the counterclockwice (CCW) direction.
The initial information from the vendor on Feburary 13, 1986 indicated that
the two connectors are electrically equivalent, and further, that only one
type of connector had been produced since 1980.
The licensee completed bench continuity measurements on February 13, 1986 of
two primer subassemblies taken from the 17 items currently available in stores.
The tested subassemblies are labeled type A and B Tor this narrative.
The
type A primer (S/N 254) was manufactured in May, 1982 and was obtained under
purchase order 18163.
Two primers from this group were installed in the SLC
system squib valves in 1983 under material issue slip 4V0277.
When tested
on February 13, 1986, the primer had a pin to bridgewire grouping of 1&4 and
2&3, measured with a CCW rotation, which agreed with Rev K of drawing 1621-
186-01.
The type B primer (S/N 557) was manufactured in October,1983, and
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was obtained under purchase order 21182.
Two primers from this group were
installed in the SLC squib valves following the July 11, 1984 testing, under
material issue slip 7V543. When tested on February 13, 1986, the type B
primer had a pin to bridgewire grouping of 1&2 and 3&4 when measured in a CCW
rotation, which disagreed with the vendor drawing.
It is notable that primers of either type would have fired in the VY SLC squib
valves if the external circuits were wired in the neutral-hot-neutral-hot
sequence on the CWDs.
However, in the as-found hot-neutral-neutral-hot wiring
sequence, only the type A (manufactured in 5/82) primers will fire.
To demon-
strate this latter assertion, the licensee performed an in-situ test of a 5/82
primer in the B valve on February 14,19e6 with the wiring in the configura-
tion as-found on February 8, 1986, and demonstrated that the squib valve fired.
The licensee notified the Conax Corp of the above findings on February 14,
1986.
Based on these results and their own review, the vendor indicated an
error had occurred internally that would have affected the production of
primer assemblies (i.e., a reversal in pin labeling from a CCW to a CW rota-
tion during a change in manufacturing facilities in 1983).
The Conax Corp.
made an oral report to NRC Region I per 10 CFR Part 21 on February 14, 1986.
The vendor's written report will be reviewed by the NRC at a later date.
This
item is open pending further NRC review of the vendor report and the licen-
see's actions to determine whether the licensee properly reviewed and used
information supplied by the vendor, or if the vendor did not properly control
and/or document changes to his product (UNR 86-05-02).
6.
SLC Continuity Monitoring Circuit
The continuity monitoring circuit, mentioned above, continuously confirms that
the fuses, resistors, wires and bridgewires in each firing circuit are intact
and lights a panel 9-5 light for each valve to confirm this.
It does this
by closing a contact in series with the panel light when control relay 11-678
is energized (picked up).
The relay is normally energized when 120 VAC is
supplied to one side of the coil, and a path to ground exists through the
following circuit: ISK resistor R1B, fuse F28, primer bridgewire AB, resistors
R3B1-R4B1-R4B2-R382, primer bridgewire CD, fuse F38, ISK resistor R28, and
neutral (see Figure 1).
The inspector noted that in the as-found condition on February 8, 1986,
neither squib valve was capable of perf orming its intended function, yet all
indications available ta the reactor operator indicated that continuity of
the ignition circuit existed.
The monitoring circu'.t indicated continuity existed, even though it would not
fire because the following closed circuit existed (shown for "B" side - typi-
cal for both; see Figure 1): 120 VAC was provided through fuse F1B to one side
of the coil for relay 11-67B; a path to ground existed through resistor R18,
F2A, terminal point FF 54, primer coil BA, terminal point FF 55, fuse F38,
resistor R2B, terminal point FF 53, and to neutral. Only one primer bridge-
wire was included in the monitoring circuit, instead of two for each squib
valve, as is normally the case.
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This item is significant because the configuration at Vermont Yankee is be-
lieved to be typical of the standard circuit design recommended by the vendor.
This item will be reviewed further by the NRC to determine for generic applic-
ability and appropriate followup actions (IFI 86-05-03).
7.
SLC Surveillance Testina
Refueling surveillance testing of the SLC system is performed under OP 4114,
SLC System Surveillance, and OP 4203. Maintenance and Testing of SLC Squib
Valves.
SLC pump capacity testing is also conducted per OP 4114 on a monthly
basis.
For the refueling surveillances, OP 4114 governs the overall sequence
for the conduct of the test and establishes the required plant and system
valve lineup conditions.
OP 4203 is performed in conjunction with OP 4114
and provides for bench and simulated in-system electrical testing of the ex-
plosive charges.
The major objective of the tests is to meet the refueling surveillance re-
quirements of the technical specifications, including manual initiation of
the system except the explosion valves, injection of demineralized water into
the reactor vessel, and explosion of one of three charges in a batch to verify
proper function. Accordingly, the tests verify an operable flow path to the
reactor vessel by manually actuating the system using the normal controls from
the control room.
Additionally, the tests verify that the explosive charges
installed in the system and to be removed following the test were capable of
being fired using the actual system wiring configuration.
Finally, the tests
demonstrate that the batch of charges from which the two replacement primers
will be taken is acceptable by exploding one charge from the batch on a bench
test set-up.
The combined OP 4114 and OP 4203 testing sequence is generally as follows:
remove the inlet fitting from the A valve and reassemble the valve
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body to establish an open flow path to the vessel.
install the existing primer in a test block mounted adjacent to the
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fire the A valve primer in place with the system wiring when System
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1 is actuated.
install the existing B primer in a test block mounted adjacent to
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the squib.
fire the B valve when System 2 is actuated.
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install new primers in the A and B squibs valves.
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bench test a new primer with the inlet fitting removed from the A
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valve to verify the explosive primer batch is acceptable, and the
charge is capable of shearing the cap.
install a new inlet fitting in the A squib.
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The bench test of the new primer is completed using a type C or D battery
connected across two of the primer electrical pins. It should be noted that
no rewiring of electrical circuits is required to complete the OP 4203 steps.
The firing circuit is disconnected from the in-situ primers by disconnecting
the connector at the primer.
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The last time prior to the 1995-86 outage that the SLC system was tested using
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the above procedures was on July 11, 1984.
Both squib valves fired as re-
quired during that test.
8.
Previous Circuit Design Changes
The last documented design change on the SLC firing circuitry was PDCR 77-2
on September 17, 1977, to enhance the circuit reliability by adding a second
neutral line (a common neutral existed previously) and to improve the monitor-
ing capability so that the circuit resistors were included in the monitoring
circuit.
The changes were made based on General Electric (GE) Services In-
formation Letter (SIL) No. 186, dated July 30, 1976. The inspector reviewed
the nature and scope of the design changes and determined the changes were
appropriate to accomplish the intended objectives.
Further, the changes recorded in the PDCR documentation package would have
prevented the February 8, 1986 event, as it would have resulted in the hot
leads alternating on the primer connector even though the CWD showed an in-
correct connector wire to primer pin configuration.
However, it is possible
that the unrecorded deviation from the CWD configuration occurred in 1977
during the PDCR and remained in place as noted in 1983, on January 6, 1986,
and following the 1986 test.
During implementation of PDCR 77-2, a circuit
problem was noted that apparently prevented the successful firing of the B
squib valve the first time it was attempted on September 11, 1977.
The cir-
cuit problem was corrected by rolling (i.e. interchanging) two wires some
place in the circuit.
The evidence for this is a hand written note on the
PDCR Installation and Test Procedure (reference Page 7, Step 45).
Based on
an interview with the electrical worker who completed the PDCR wiring, there
are no further details as to what the problem was, what wires were moved, or
whether the circuit wiring drawings were updated.
The worker involved with
the job in 1977 did not recall having to roll the wires in the local tbs to
the as-found configuration.
The worker further felt that such a change would
have been documented had it been necessary at the time.
He supposed that the
wires rolled would have more likely been some of the non-color coded 9-5 panel
wires.
It should also be noted that the licensee identified another deviation between
the as-built conditions and the wiring configuration called for in CWD 191301,
Sheet 1201.
The four conductors of cable C11201 were found to terminate at
points DD-89, 90, 94, and 95 in CRP 9-5.
The circuit is then carried through
to the intended termination points of FF 54, 55, 56, and 57 using gray bench-
board (SIS) wire.
It was these SIS wires the electrician supposed may have
been rolled during PDCR 77-2.
Continuity checks completed by the licensee
on February 11, 1986 confirmed that this wiring configuration did not contri-
bute to the test failure on February 8, 1986.
The as-built wiring is recorded
on CRP 9-5 panel drawings 5920-3738, Rev. 22 and 5920-3703, Rev. 27.
However,
the wiring configuration was recorded on those drawings during an as-built
update of the prints in 1984.
There apparently was no attempt made in 1984
to compare the updated panel diagrams with the CWDs. The deviaticn between
the as-found wiring, the CWDs and the panel diagrams most likely existed prior
to 1984,
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The discrepancy between the as-found circuit wiring and the approved de.iign
drawings represents a potential loss of configuration control that is of sig-
nificant concern to the NRC.
This matter warrants further review by the lic-
ensee and the NRC to determine whether the wiring configuration noted on
February 8, 1986 resulted from an approved design change. This item is un-
resolved and will be reviewed further on a subsequent NRC inspection (UNR
86-05-04).
9.
Previous Maintenance Activities
Maintenance requests (MRs) for the SLC system were reviewed by the licensee
and the inspector to determine which involved the electrical circuits and to
possibly identify a repair activity that may have altered the wiring at the
local terminal boxes. The inspector's review included the following MRs:
83-1303, 83-0450, 83-0500, 83-1064, 83-1180, 83-1136, 84-1185, and 85-2635.
The following items warranted further followup.
Work completed under MRs 83-0450 and 0500 in March-April,1983 resulted in
the change-out of the pigtails (connectors and short length of cable) from
the local terminal boxes to the squib valves.
Based en interviews with the
I&C technician who performed the work, the replacement was one-for one, wire-
for-wire.
The technician noted at the time that the wiring sequence did not
match the CWD.
No further actions were taken since it was noted that the
existing wiring sequence worked based on previous satisfactory performance
of system testing, and the only repair activity was a one-for-one replacement.
The observations by the technician while performing the work under MRs 83-
450/500 indicate that the wiring configuration observed to fail on February
8,1986 was in place prior to the satisfactory test performed per OP 4114 in
July, 1984.
Maintenance was performed per MR 84-1185 on the A squib valve continuity
circuitry on July 13, 1984, two days after performance of the OP 4114 testing.
The problem, loss of squib valve A continuity, was corrected by replacing fuse
F2A.
The operability testing completed following the repair consisted of
verification that normal indication and continuity meter readings returned.
While it appears that more rigouous testing following MR 83-1185 may have de-
tected a change in the monitoring circuits, the scope of the actual testing
completed, in the inspector's opinion, was not inappropriate for the nature
of the work completed.
MR 85-2634 was submitted by a reactor operator on December 29, 1985, to in-
vestigate the intermittent occurrence of the squib valve loss of continuity
alarm.
The alarm apparently occurred, even though the circuit trickle current
of 0.25 mamp was above the alarm setpoint of 0.1 mamp.
The problem appeared
to occur concurrent with a lower voltage condition on the 345 KV grid.
How-
ever, no direct association between the two events has been establishe.d.
Troubleshooting activities under MR 85-2634, consisted of visual inspections
and continuity measurements and were completed on January 6, 1986, eten though
the problem had cleared and no further symptoms were present.
During this
effort, the I&C technician (who also happened to complete the work under MRs
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83-0450/0500) again noted that the local terminal box wiring did not match
that required by the CWD.
The technician further noted that the continuity
readings across the primer bridgewires indicated that the squib valves could
not possibly fire as wired.
No wires were moved.
After consulting mainten-
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ance personnel to confirm the satisfactory system testing on July 11, 1984,
I&C supervision decided to take no further actions to investigate the anomaly
until after the 1986 SLC testing per (OP 4114), as the system was not required
to be operable, either then or prfor to the test.
Based on the above, the inspector concluded that SLC system maintenance acti-
vities within the scope of the above review did not appear to have contributed
to the wiring configuration noted on February 8, 1986.
It also appears that
a minor intermittent problem in the monitoring circuit remains to be investi-
gated and resolved.
The licensee should review the monitoring circuit to
assure curent loops are appropriately balanced.
This item is open pending
completion of a review by the licensee of the monitoring circuit design and
function and subsequent review by the NRC (IFI 86-05-05).
10.
Licensee's Conclusions
The licensee issued Plant Information Report (PIR) 86-03 on February 24, 1986
covering the SLC failure.
Under the PIR system, the PIR will be reviewed by
plant management, concurred on by the PORC, and approved by the Plant Manager.
Accordingly, the PIR reviewed by the inspector represented the licensee's
preliminary conclusions and recommendations.
The licensee concluded that the SLC system was inoperable from July 11, 1984
until February 8,1986, and that the primary cause of the event was the in-
advertent, undetected manufacturing error by the vendor, Conax, which changed
the wiring between primer pins and explosive charge bridgewires. The licensee
concluded that the as-found wiring of the firing circuit was a contributing
factor to the event in that its configuration permitted a primer failure with
the inadvertently revised primers.
However, the licensee concluded that the
as-found wiring was an acceptable design when utilized with the as-designed
primer and had properly fired the primers many times when correct primers had
been installed.
The as-found wiring met the design specified in SIL 186.
The licensee concluded that the difference between the as-found wiring and
the CWD occurred during the installation of the 1977 wiring design change,
and the CWD was never revised to reflect the as-built wiring.
The licensee
concluded that such a design change / drawing revision process would have been
unlikely to realize the potential problem and unlikely to result in a differ-
ent wiring.
The licensee concluded that the as-found wiring had existed since the 1977
wiring design change based on the lack of any records of design change or
maintenance activities which would have changed the wiring subsequent to 1977.
Further, PDCR 77-2 and the resultant CWD were not correct, in that the pigtail
cable between the primer connector and the local terminal box was misrepre-
sented (e.g., the black lead connected to pin A, whereas the white lead ac-
tually connects to pin A). The licensee hypothesized that the electricians
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realized this misrepresentation during the installation and revised the wiring
in the terminal box to provide a workable wiring.
This field change was then
never implemented on the drawing or approved in the drawing change process.
The PIR contained recomended corrective actions, as follows:
Revise testing procedure OP 4203 to include pin to pin continuity tests
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and a test of new primers using the firing circuit.
Revise terminal box wiring such that hot leads alternate around the con-
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nector and either primer type will fire.
Revise CWD to as-built configuration.
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Revise procurement program to specify latest drawings are sent with parts.
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Review other surveillance procedures which test performance of components
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following use to determine whether additional testing and design changes
are appropriate.
Retest SLC system following completion of other recomendations.
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The PIR recomended that no additional changes be made to the design change
and configuration control program, as revisions to these programs since 1977
have instituted administrative controls to ensure that field changes are pro-
perly reviewed and approved and that as-built drawings are completed.
NRC review of the approved PIR 86-03, including the recomended corrective
actions including changes to OP 4203, is an open item (86-05-06).
11.
Inst.ection Findings and Conclusions
A.
As documented throughout the report, the inspector identified the fol-
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lowing:
86-05-01; Violation for inoperable SLC system.
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86-05-02; Unresolved item for evaluation of the Conax manufacturing
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error and the licensea's failure to find it prior to use.
86-05-03; Open item for design of continuity monitoring circuit.
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86-05-04; Unresolved item for loss of configuration control.
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86-05-05; Open item for repetitive maintenance of continuity moni-
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toring circuit.
86-05-06; Open item for review of PIR recomended changes.
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B.
The inspector agreed with the conclusion of the PIR that the primary
cause of the inoperable SLC system was the manufacturing error in the
primer charges.
Concerning the as-found firing cit c91t wirk.g, which permitted the re-
vised primers to fail, the inspector agreed the that this probably re-
sulted during the installation of the 1977 design change and that the
as-found wiring represented an acceptable design implementation of SIL
186.
C.
The inspector noted that the Traversing In-core Probe (TIP) shear valves
also incorporate an explosive primer which actuates the valve.
The in-
spector's preliminary evaluation of the firing circuit and the primer
component found that the firing circuit was similar to SLC and the primer
also used a four pin connector. Accordingly, the licensee's evaluation
of the applicability of the SLC corrective actions to the TIP shear
valves is an open item (86-05-07).
D.
The inspector noted that the licensee had 17 primers in stock following
the incident.
As the design life of the primer is five years and only
three primers are used per operating cycle (if the batches are good),
the 17 primers in stock appeared to be excessive. The licensee's shelf
life program, which should prevent usage of outdated primers, is under
development.
Also, there appeared to be no provision in the primer in-
sta11ation procedure to ensure the primer's useful life would not expire
during its use.
Therefore, the licensee's action to ensure that primers
are installed which will be within their useful life during their use
is an open item (86-05-08).
E.
The inspector noted that the February 8, 1986 incident constituted the
first example wherein an apparent vendor supplied product deficiency was
not detected by the licensee's receipt inspection program or post-in-
sta11ation preservice testing, and which rendered a plant safety system
12.
Persons Contacted and Management Meetings
Interviews and discussions were conducted with members of the licensee staff
and management during the inspection to obtain inforriation pertinent to the
areas inspected.
Preliminary inspection findings were discussed with the
Acting Plant Manager on February 14, 1986, and final inspection findings were
discussed with the Plant Manager on February 27, 1986.
The contacted person-
nel included the following people.
Mr. P. Donnelly, Maintenance Superintendent
Mr. J. Halvey, I&C Assistant
Mr. D. McElwee, Senior Engineer - Operations
Mr. M. Stone, Electrician
L.
_.
_ _ _
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