ML17292A803
| ML17292A803 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 04/11/1997 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML17292A800 | List: |
| References | |
| 50-397-97-04, 50-397-97-4, NUDOCS 9704170093 | |
| Download: ML17292A803 (16) | |
See also: IR 05000397/1997004
Text
NCLOSURE 2
U.S. NUCLEAR REGULATORY COMMISSION
REGION I.V
Docket No.:
License No.:
Report No.:
Licensee:
Facility:
Location:
Dates:
Inspectors:
Approved By:
50-397
50-397/97-04
Washington Public Power Supply System
Washington Nuclear Project-2
3000 George Washington Way
Richland, Washington
February 10-14, 1997
G. W. Johnston,
Senior Project Inspector
D. G. Acker, Senior Project Inspector
H. J. Wong, Chief, Reactor Projects Branch E
Attachment:
Supplemental
Information
9704K 70093 97041 i
ADOCK 05000397
8
EXECUTIVE SUMMARY
Washington Nuclear Project-2
NRC Inspection Report 50-397/97-04,
~En ineerin
~
A nonconservative
and erroneous
plant modification record (PMR) resulted in a
violation.
Design personnel failed to consider, during initial design, the safety
requirements
associated
with ensuring service water (SW) Pump 1A and the low
pressure
core spray (LPCS) pump would operate when required.
The licensee did
not act on available technical information which indicated that the associated
instantaneous
overcurrent (IOC) trips were set too low (Section E8.1).
~
After issuing the PMR, engineering
personnel twice noted conflicts with the UFSAR,
but took no action to review th'e PMR for additional conflicts, until one was noted
by the inspector (Section E8.1)
~
~
The installation of replacement
High Pressure
Core Spray (HPCS) initiation drywell
pressure switches without the required substitution evaluation was a violation .of
facility procedural requirements
(Section E8.2).
~
The'licensee staff had several opportunities to identify the deficient conditions for
both the overcurrent trip setpoints
and the replacement
HPCS initiation drywell
pressure switches.
These opportunities reflect on'the ability of licensee staff to
'ecognize
potential problems prior to their occurrence
(Sections
E8.1 and E8.2).
~
..
The licensee's
immediate corrective actions for both issues were prompt
(Sections E8.1 and E8.2).
Re ort Details
This inspection involved review of two events:
(1) the tripping of Standby Service Water
Pump 1A due to an incorrect overcurrent relay setting; and 2) the installation of drywell
pressure instruments which were not properly vented and resulted in degraded
performance.
III. E
ineerin
Miscellaneous Engineering Issues (92902)
E8.1
Closed
Licensee Event Re ort
LER 50-397 96-009:
miscalculation of
instantaneous.overcurrent
relay settings resulting in inoperability of safety-related
equipment.
The licensee identified that the supply circuit breaker to the motor for Standby
Service Water (SW) Pump 1A tripped on December 20, 1996, during a routine
attempt to start the pump.
The licensee determined that the circuit breaker was
tripped due to actuation of the circuit bre'aker's
IOC relay.
The licensee determined
that the setpoint for the IOC relay had.been
reset in
November 1996 based on calculations using an ina'ccurate locked rotor current and
nonconservative
selection of.a multiplication factor.
Between November 1996,
when the IOC was reset, and the December 20, 1996; failure, the pump had been
successfully started seven times.
Postmaintenance
testing included bench
testing'f
the, relays and a successful
pump start,
The licensee reset the IOC relay trip
setpoint and successfully started the pump.
The licensee identified the root cause
as use of inappropriate design input for
determining the IOC setpoint.
As a result of the trip of SW Pump 1A, the licensee requested
and,the NRC
approved the use of enforcement discretion to discontinue repetitive testing of
This'approval was documented
in a letter to the
licensee dated Decemb'er 24, 1996.
a.
Ins ection Sco
e
The inspector reviewed the LER, the plant modification associated
with the initial
change
in the IOC relay setpoint, associated
calculations and circuit breaker
coordination studies, industry standards for selection of IOC setpoints,'he
licensee's operability and root cause evaluations,
and discussed
this information
with licensee employees.
b.
Observations
and Findin s
The inspector noted that normal plant electrical protective device coordination
requires IOC relays for tripping individual pump circuit breakers for pump and cable
faults.
Proper coordination requires that the IOC relays be set to trip the pump
0
-2-
circuit breaker before circuit breaker(s) supplying the entire bu's trips.
However, the
IOC relays needed to be set high enough to ensure that they did not trip during
starting of the pump.
Starting current for pumps is normally estimated
using vendor
locked rotor test data, general motor design data, or actual starting current
measurements.
Based on past licensee evaluations.and
NRC inspections,
the licensee determined
that the coordination of their plant circuit breakers could be improved.
On
January 30, 1996, the licensee approved
PMR 85-0528-0, "Protective Relay
Coordination Study and Installation," to reset or change
a number of protective
relays to improve overall plant protection from electrical faults.
This PMR was
based
on calculations issued in 1993.
The licensee stated that they received locked rotor current test data from General
Electric (GE) for a number of plant pumps.
Some of this data was'locked rotor
current for a test at 20 percent of rated voltage, some of it was locked rotor current
data at 80 percent voltage, and some of the data was GE's projecte'd locked rotor
current at full voltage based
on tests and an unspecific'd multiplication factor.
For the SW Pump 1A, GE'provided
a locked rotor current (LRC) value at
approximately 20 percent rated voltage.
The licensee extrapolated the locked rotor
current at 100 percent voltage by multiplying the current at 20 percent voltage by a
linear factor and de'termined the LRC was 960 amps.
Motor starting c'urrent is dependent
on the locked rotor current and additional
variables such as direct current offset and line voltage.
Therefore,
IOC trips 'are set
at some value above locke'd,rotor current that will ensure that the IOC trips "willnot
activate during pump starting.'merican-National
Standards
Institute/Institute of
Electrical and Electronics Engineers
(IEEE) C37.96-1988,
"IEEE Guide for AC
[alternating current] Motor Protection," recommends
th'at the IOC trips be set at
locked rotor. current multiplied by 1.65 to 1.875.
Other technical guides
'ecommend
use of locked rotor current multiplied by.1.7 to 1.8.
The licensee chose
to use 1.65 times locked rotor current for their safety-related
and balance-of-plant
pumps.
As noted above, SW Pump 1A tripped on IOC during a routine start
attempt after its IOC relay trip value was lowered.
Data was available to the licensee which indicated that the setting chosen by the
licensee co.:ld be too low including:
"IEEE Standard Test Procedure for Polyphase
Induction Motors and Generators,"
states that locked rotor current taken at
low voltage levels could not simply be multiplied by a linear factor to
determine locked rotor current at 100 p'ercent voltage due to changes
in"
reactance.
3
The motor nameplate
and design drawings provided for the SW Pump 1A
motor indicated locked rotor current was 1330 amps or approximately
'0
per'cent higher than the value calculated by the licensee.
The value of locked rotor current calculated by the licensee provided
a ratio
of locked rotor current to running'current which was approximately 4.5, a
very low value for this size and type of motor.
The licensee was operating the motors at 4160 volts nominal, while their
calculated lock rotor current was based on 4000 volts.
Since the starting
current will increase with increased
voltage, the calculated IOC.trip point
was based
on a voltage which was approximately five percent low.
The licensee was using the lowest multiplication factor (1.65) recommended
by industry.
The inspector reviewed the above information with the licensee,
The licensee
acknowledged that they had information which could have alerted them to the
potential for improper setting of the SW Pump 1A IOC relay.
However, licensee
representatives
stated that they believed the primary root cause of the problem was
that in attempting to provide the best circuit breaker coordination, they lost sight of
fhe fact that the important safety function of SW Pump 1A was to operate
and that
they should have set the IOC at a higher industry recommend
value, which would
also provide adequate
circuit breaker coordination.
The inspector agreed that this
was an important contributor to the event.
I
The licensee subsequently.
measured
the starting current for SW Pump 1A.and
determined that it was approximately 1350 amps,
The inspector determined that IOG trip setting was incorrectly set in that the setting
would not always ensure that SW Pump 1A would start when required, and had
caused the pump.to fail and be declared inoperable on December 20, 1996.
Failure
to correctly set the'OC relay to ensure SW Pump 1A operability is a violation of
10 CFR Part 50, Appendix B, Criterion III, Design Control (Violation 50-397/97-04-
01).
The inspector noted that the IOC for the LPCS Pump was set as low as SW
Pump 1A and was potentially susceptible to tripping during pump starting.
The
licensee reset the IOCs.
There were no other IOCs for. safety-related
pumps set as
low as these two pumps, partly since no safety-related
pump IOCs had been 'reset
for Train B safety-related
pumps.
The inspector reviewed circuit breaker
coordination associated
with the SW 1A and LPCS pumps and concluded, that the
, new IOC settings provided adequate
circuit breaker coordination with bus supply
~
circuit breakers.
-4-
After the trip, the licensee had reset the IOC for SW Pump 1A to 2100 amps;
approximately 1.5 times the measured
locked rotor current of 1350 amps.
The
inspector reviewed the UFSAR and determined that Section 8.3.1.1 stated that the
IOCs were set to trip at approximately two times locked rotor current.
The
inspector considered that this was not the sa'me as described
in the UFSAR.
The
IOC for the LPCS Pump was also set lower than two times locked rotor current.
The inspector reviewed PMR 85-0528-0 and the licensee's
design control
procedures
and determined that the design control procedures
required a.review of
'he
UFSAR to determine if the design affected anything in the UFSAR; however, in
January 1996 licensee personnel checked
a step in'dicating that the UFSAR was not
affected by the PMR. The inspector considered that since the licensee's objective
on thesetpoint change was to provide improved breaker coordination, lowering the
IOC setpoint would be an expected result. At most, a more complete review of the
UFSAR would have most likely resulted in only an updated
UFSAR page and not a
more accurate calculation of the IOC setpoint.
The inspector reviewed changes
associated
with the PMR and noted that two
separate
changes,
issued in 1996, identified two other conflicts between the PMR
and the UFSAR, which the licensee resolved.
The inspector discussed
review of the
UFSAR with licensee personnel.
The licensee issued
a problem evaluation
request
(PER) to compare the PMR to the UFSAR and resolve any differences.
c.
Conclusion
The inspector concluded that the present IOC setpoints for SW Pump 1A and the
LPCS Pump were coordinated with upstream circuit breakers, but were
nonconservative
with respect to motor testing currents.
The inspector concluded that the original PMR was flawed in that licensee design
personnel failed"to consider, during initial design, the safety requirements
associated
with ensuring SW Pump 1A arid LPCS pumps would 'operate when required and did
not act on available technical information which indicated that the associated
IOC
trips were set too low. Failure to establish appropriate circuit breaker trip setpoints
to ensure reliable operation of SW Pump 1A is a violation of 10 CFR Part 50,
Appendix B, Criterion III, Design Control.
'n
addition, after initial issue of. the PMR, engineering
personnel twice n'oted
conflicts with the UFSAR, but took no action to review the PMR for additiorial
conflicts, until one was noted by the inspector.
In summary, the inspector concluded that engineering
performance associated
with
this PMR was weak.
-5-
E8.2
Closed
LER 50-397 96-008:
failure.to comply with a Technical Specification
action requirement for the emergency
core cooling system actuation instrumentation
due to unidentified inoperability condition.
The licensee identified that drywell pressure switches, designed to initiate the High
Pressure
Core Spray (HPCS) on high drywell pressure,
had exceeded
their Technical
Specification allowable values on several occasions
during the period from June'10
through November 24, 1996.
The original pressure switches had been replaced by newer models in April 1996,
during
Refueling'Outage
R11.
The switches that were installed had a loss-of-
coolant accident (LOCA) seal and a vent plug installed on the instrument housing.
The vent plug had not been removed as required for the instaflation.
It was
subsequently
determined that the failure to remove the vent plug allowed
temperature
variations in the reactor building to affect the setpoint of the pressure
switches.
The licensee determined the root cause of the event to be an administrative
deficiency in the control on the issuance
o'f the p'ressure switches for use.
A PMR
had been initiated in 1984 that would have initiated the engineering
analysis of the
replacement
pressure switches; however, the PMR was cancelled in 1989.
With no
process tie between the PMR and the pressure switches, the installation in 1996
went forward without an engineering
ev'aluation of the substitution.
ao
Ins ection Sco
e
The irispector reviewed the LER, the'MR associated
with the installation of the
,. drywell pressure switches, the substitution evaluations performed, design
documents,
work packages
associated
with the installation of the pressure
switches, the licensee's
operability and root cause evaluations,
and discussed
this
information with licensee employees.
b.
Observations
and Findin s
The licensee performed an evaluation of setpoint drift on December 5, 1996, related
to drywell Pressure
Switches MS-PS-47B and 47C (used for actuation of HPCS on
high drywell pressuie).
The evaluation was prompted by several instances where
the switches failed administrative calibration limits during surveillance tests and
were required to be recalibrated.
The evaluation was documented
in PER 296-
0829.
The PER determined that 'the drywell pressure switches were installed with
the instrument cover vent plugs left in place.
The PER also determined that the
switches were operable at the time of the evaluation.
However, the PER indicated
they had possibly been inoperative during several periods since their installation;
Due to that evaluation,
LER 50-397/96-008 was issued.
-6-
In 1984,'PMR 8'4-1125-0 was written to replace
a Static 0-Ring (SOR)
12NAA5X10TT.(referred to hereafter as TT) pressure switch installed as a drywell
pressure switch for actuation of the HPCS System.
The TT switch could not be
procured as a Quality Class
1 component.
However, SOR Pressure
Switch 12N6BB4NXCIAJJTTX6 (referred to hereafter as X6) was available as a
- Quality Class
1 component.
The primary difference between the switches was the
provision for a loss-of-coolant accident seal or an air tight conduit connection
and a
vent plug installed on'the instrument case for the X6 switch.
In 1988, SOR
Corporation issued
a I art 21 notification"for the X6 switch due to
process'ermeation
through the kapton diaphragm that affected setpoint drift. A revised
version of SOR 12N6BB4NXCIAJJTX12 (hereafter referred to as X12) replaced the
kapton diaphragm with a stainless steel diaph'ragm.
March 9, 1989, Substitution Evaluation 567, Revision.0; was issued to evaluate the
difference between the'stook of X6 switches and the newer X12 model.
The
.
evaluation noted that a PMR was re'quired to install the X12 version.
No procedural
requirement existed at that time to place
a limitation on use in the Material
Management
System (MMS)..
Subsequently,
on August 3, 1989, PMR 02-84-1125-0 was voided.
A note on the
PMR states
"SOR being revised to SS diaph. per RFTS 89-03-094" and "will
address switch replacement
as required."
No reason was given for cancellation of
the PMR.
Later, on February
1'2, 1990, a purchase
order was issued to return three
X6 switches, have them modified to X12 versions, and acquire eight new X12
, switches.
On June 'l5, 1991, Procedure
SPES-1, Section 7.47; was issued, requiring that a
limitation on use be placed on any item being procured as part of a PMR prior to a
Basic Design Change being approved.
This would place in.the MMS a notation that
the item required an engineering review prior to its use in the plant.
This procedure
change would, under current circumstances,
require that any equipment proc'ured
~ for replacement stock that was not identical to the installed equipment be restricted
with a limitation on use.
On December, 8, 1995, four X12 switches were issued for replacement of installed
, drywell pressure switches under work orders (WO) YT4401 and WO YT4501.
These WOs were generated
on April 17, 1996, as routine replacement for
environmental qualification requirements.
The inspector examined the WO,
identifying that the task required
a replacement of flexible conduit for the
'nstallation
of the new switch.
This is becaus'e the TT model installed in the plant
does not have a sealed electrical conduit connection.
The inspector noted that the
WOs requirement for extra work, specifically the conduit. replacement,
provided an
opportunity for the preparer to identify'the possible need for an engineering
evalu'ation.
-7-
Two more opportunities occurred in June 1996 for identifying the need for
engineering
evaluations.
June 4, 1996, Substitution Evaluation 2293, Revision 0,
was issued to address the replacement of the now obsolete X12 pressure switch
with an newer version.
This substitution evaluation was released for review
January 30, 1996.
While recognizing that the preparer was not required to evaluate
prior substitution evaluations
or review previous limitations on use, had the'preparer
of this substitution evaluation noted that Substitution Evaluation 567 required a
PMR for installation, the necessity for a limitation on use in the MMS may have
become apparent.
Further,
a revision to setpoint Calculation E/I-02-92-1072 for
the'PCS
drywell pressure switches, was issued on June 6, 1996, that reflected
changes
due to the replacement of the pressure switches.
The previous calculation
(for the installed switches) stated that the switches were subjected to a walkdown
to verify a vent path existed.
The licensee noted that although the walkdown
comment was included in the revision barred section of the calculation, no
verification walkdown was conducted.
Although the configuration of the original
pressure switches included the vent plug, a walkdown may have noted the need for
a vent path due to the inclusion of the LOCA seal in the replacement
switches'.
Therefore
a walkdown may have resulted in the identification of the need to vent
the instrument housing.
WO YT4401 was signed off as completed. for installation April 29; 1996, for
Instruments MS-PS-47A and 47C.
Final signoff occurred June 6, 1996.
WO YT4501 for installation of Instruments MS-PS-47B and 47D signed as
completed on April 26, 1996, and final sign off occurred July 7, 1996.
The
inspector examined the WOs and fou'nd them to be complete:
Initial calibrations
were done for both sets of switches'with no notations of a problem in either case.
There was no information supplied in either package of a substitution evaluation.
Further, it appeared
that no reliance was made of prior substitution evaluations.
The requirement to perform substitution evaluations
is described
in Plant Procedure
Manual (PPM) 1.15.12, Section 8.4, Revision 0, "Substitution Evaluation," and a
subtier Procedure
SPES-1, Sect)on 6.7, Revision 1, ".Substitution Evaluations."
PPM 1.15.12 states,
in part, under 8.4.2, "Determination of Need," "Where
desirable or necessary
to procure or use substitute items, it is the responsibility of
the user to request an evaluation by. Material, Technical and Quality prior to
procurement or use
~ .." Further, Procedure
SPES-1, Section 6.7.A, states,
in part,
that "Substitution evaluations
are performed on safety-related
and augmented
quality class (other than'Flag 1M) items per PPM 1.15.12 to assure the alternative
replacement
item is an acceptable
substitute."
Contrary to this, a substitution
evaluation was not requested
to be performed for the installation on April26 and
29, 1996, of replacement
HPCS drywell pressure Switches MS-PS-47A, 47B, 47C,
and 47D. This is a violation of the requirements of Technical Specification 6.8.1a
for failure to implement the requirements
of PPM 1.15.12 (Violation 50-397/97-04-
02).
0
0
-8-
Following installation of the X1.2 replacements,
the switches were subjected
periodic surveillance tests in accordance
with Surveillance Procedures
7.4.3.3.1.53
"HPCS Initiation Drywell Pressure
High A & C - Channel Function Test/Channel
Check (CFT/CC)," and 7.4.3.3.1.54
"HPCS Initia'tion Drywell Pressure
High B 5, D-
CFT/CC." These procedures
had administrative limits of 38.0 to 49.0 inches of
water (1.37 psi and 1.77 psi respectively), with a nominal setpoint of 45.7 inches
of water (1.65 psi).
T. S. 3.3.3 specifies an allowable actuation setpoint of
1.85 psig.
For the period from April 1996 through November 1996 there were six
. occasions
when a switch failed to meet the administrative limits. In four of those
occurrences,
a switch failed to meet the administrative limit by being over the
acceptance
criteria.
On two occasions the switches were below the acceptance
criteria.
Only one occurrence
on June 30, 1996, involving Switch MS-PS-47C, was
over the Technical Specification requirement of 1.85 psi, at 1.899 psi ~
Corrective Actions - Following the determination on December 5, 1996, that the
reliability of the HPCS drywell pressure switches was.questionable,
the licensee
took immediate action to remove the vent plugs. from the instrument cases
and
verify the setpoints in'accordance with the Channel Functional Test Surveillance
Procedures
7.4.3.3.1.53
and 7.4.3.3.1.54.
The licensee's
actions restored the
~
instrument to their intended configuration.
Other instruments
in the facility were
also inspected to assure the proper venting for similar instruments;
none were
deficient.
PER 296-0829 and,the corrective action'plans associated
with the, PER were
reviewed by the 'inspector to de'termine the adequacy
of the scope of the evaluation
of the event and the long term corrective actions.. The licensee indicated that all
open or voided PMR's, which required procurement of c'omponent level materials to
implement, will be reviewed to determine if there were materials requiring
substitution evaluations that were not captured
in the, Material Management
System
with limitations on use.
These actions appear to address the significant issues
related to the installation of replacement components
by ensuring that similar
circumstances
are not repeated.
P
Conclusion
The inspector concluded the licensee had several opportunities to.capture the fact
that replacement
HPCS initiation drywell switches had not been subjected to
engineering
analysis for substitution.
These opportunities reflect on the ability of
licensee staff to recognize potential problems prior to their occurrence.
The installation of replacement
HPCS initiation drywell pressure switches without
the required substitution evaluation was a violation of procedure
PPM 1.15.12.
The licensee's
immediate corrective actions were prompt and effective.
Long-term
corrective actions'appear
to provide assurance
that possible similar situations will
'be appropriately identifiqd.
1
-9-
IV. IVlana ernent IVleetin s
X1
Exit Meeting Summary
The inspectors presented
the inspection results to members of licensee management
after
the conclusion of the.inspection on March 19, 1997.
The licensee acknowledged
the
.
findings presented.
The inspectors
asked the licensee whether any materials examined during the inspection
should be considered
proprietary.
No proprietary information was identified.
ATTACHMENT
Supplemental
Information
PARTIAL LIST OF PERSONS CONTACTED
Licensee
P. Bemis, Vice President for Nuclear Operations
R. Webring, Vice President Operations Support
L. Fernandez,
Licensing Manager
B. Pfitzer, Licensing Engineer
G. Smith, Plant General Manager
J. Swailes, Engineering Director
D. Swank, Regulatory Affairs Manager
INSPECTION PROCEDURES USED
Followup - Engineering
ITEMS CLOSED
LER 50-397/96-008
LER 50-397/96-009
LIST OF ACRONYMS USED
CFT/CC
IOC
'LER
NRC
'PER
PMR
WNP-2
channel functional test/channel
check
Final Safety Analysis Report
'eneral Electric
high pressure
instantaneous
licensee event report
low pressure
material management
system
U.S. Nuclear Regulatory Commis'sion
problem evaluation request
plant modification record
plant procedure
manual
Updated Final Safety Analysis Report
Washington Nuclear Project-2
work order