ML20057A131
| ML20057A131 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 09/08/1993 |
| From: | Phillips M, Twigg R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20057A125 | List: |
| References | |
| 50-155-93-10, NUDOCS 9309130096 | |
| Download: ML20057A131 (6) | |
See also: IR 05000155/1993010
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U.S. NUCLEAR REGULATORY COMMISSION
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REGION III
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Report P . 50-155/93010(DRP)
Docket No.
50-155
License No. DPR-6
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Licensee:
Consumers Power Company
212 West Michigan Avenue
Jackson, MI 49201
facility Name:
Big Rock Point Nuclear Plant
inspection At:
Charlevoix, Michigan
Inspection Conducted:
August 9 through August 20, 1993
Inspector:
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R. L/Twigg
Approved By
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. P. Phillips, Chief
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Reactor Projects Section 2B
lospection Summary
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inspection on August 9 throuah Auaust 20. 1993. (Recort No. 50-155/93010(DRP))
A_reas Inspected: A special, unannounced safety inspection by the reactor
engineer of the conditions surrounding the event of July 8, 1993, in which.
your staff identified that both containment high pressure sensors were outside
of the allowable Technical Specification tolerances due to an installation
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error.
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Results:
Of the area inspected, one non-cited violation was. identified in
paragraph 2.
The violation involved the setpoints of two containmer.t high
pressure sensors being outside of the Technical Specification limits.during
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certain atmospheric conditions, at which time there would have been a'small
delay in the automatic actuation of Primary Containment Spray. . The root -
causes of the violation involved the failure of engineering personnel
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associated with the installation of these pressure sensors to recognize the'
affect of temperature changes on the setpoint and the failure to communicate
the unique characteristics of installation to the vendor to determine whether
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the vendor's recommendation concerning venting the reference leg was no longer
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valid.
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9309130096 930908
ADOCK 05000155
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DETAILS
1.
Persons Contacted
Consumers Power Company
P. Donnelly, Plant Manager
E. Bogue, Chemistry / Health Physics Manager
G. Boss, Systems and Project Engineering Manager
D. Turner, Maintenance Manager
G. Withrow, Plant Safety and Licensing Director
M. Bourassa, Senior Licensing Technologist
L. Chase, Instrumentation and Controls, Acting supervisor
C. Petitjean, Nuclear Performance Specialist
All of the above personnel attended the exit interview conducted on
August 20, 1993.
The inspector also talked with and interviewed several other licensee
employees, including members of the technical and engineering staffs;
reactor and auxiliary operators; shift supervisors; and electrical,
mechanical, and instrument maintenance personnel.
2.
Event Description
In October 1990 the licensee replaced two containment pressure sensors,
PS-7064A and PS-7064B, due to age degradation.
The two sensors
constituted one of two pairs in the actuation logic (one of two taken
twice) for Primary Containment Spray.
The sensors were upgraded to meet
environmental qualification requirements using sealed units (S382) from
Static-0-Ring (SOR), the vendor.
The sensors were located in a small
building attached to the outside of the containment sphere.
This
environment would have experienced high radiation and a gradual
temperature increase during a loss of coolant acci 'ent (LOCA) or steam
line break (SLB).
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Information provided by SOR indicated that under high temperature
conditions, such as those occurring during a LOCA, the sensors could
experience a drift in their setpoints in a e.onconservative direction;
therefore, under those conuitions, SOR recommended that the reference
vent for the sensors be vented to outside air or the sen or be set
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conservatively.
Given the location of the sensors, no significant
temperature changes would occur due to a LOCA cr ElB before the sensors
comple 'ed their function; therefore, the licensee installed the sensors
with tne reference vents capped.
The licensee failed to recognize that
increased atmospheric temperatures during the summer months could affect
the building temperature and subsequently, the setpoint of the sensors
if capped. The licensee did not communicate with the vendor to
determine if the sensors could be affected by significant atmospheric
temperature changes because the sensors would be located 31 a non-
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control
environment, unlike the installation normally provided at
most other facilities.
As a result, on July 8,1993, with outside temperatures on the order of
90 F, the setpoints were found to exceed Technical Specification (TS)
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3.5.1.E.
The TS required the setpoints to be less than or equal to 2.2
psig. Sensor PS-7064A was observed to trip at 2,79 psig and Sensor PS-
7064b was observed to trip at 2.87 psig. TS II.3.3.4.b states, in part,
that if during power operation, one of the containment spray systems is
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inoperable, a normal orderly shutdown shall be initiated within' 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />
and the reactor shall be shut down as described in Section 1.2.5(a)
within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and shut down as described in Section l'.2.5(a) and (b)
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within the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. During the summer days from 1991 to-
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1993, the setpoints for the two sensors were unknowingly in violation of
the TS limit and the Primary Containment Spray was technically
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3.
Event Peview
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The containment spray system consists of primary and secondary spray
headers sharing a common supply with the Emergency Core Cooling System.
Both the primary and secondary containment spray headers are located
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high in the containment with numerous fog nozzles that would spray into
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containment and the steam drum cavity. Automatic initiation of the
primary spray was required when containment pressure reached 2.2 psig.
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The secondary spray required remote-manual initiation from the control
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room and would have been used in the event of primary spray failure.
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Prior to 1982, the actuation of primary containment spray at 2.2 psig
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containment pressure only-initiated a 15 minute delay relay for
containment spray. With core spray and containment spray sharing a
common suction header, the delay ensured sufficient core spray was
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available at the beginning of a LOCA or SLB. The containment spray was
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used for iodine washout ano was not used for containment pressure
control. An analysis of various LOCA and SLB scenarios demonstrated
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that containment pressure would not exceed the design limit of 27 psig,
even without containment spray,
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In 1982 the licensee identified that with a single phase, superheated
SLB, containment temperature could rapidly rise to as much as-343 F with
an Electrical Equipment Qualification (EEQ) requirement of 260 F.
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corrective actions taken by the licensee at that time were to eliminate
the 15 minute delay of Primary Containant Spray actuation and, to
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ensure sufficient core spray, reduce the size' of the spray nozzles.
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The inspector reviewed the calibration data for these two sensors
subsequent to the October 1990, replacement and' determined the
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following:
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April 14, 1992 - PS-7064A showed a conservative drift of 0.03 psig
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(to 2.06) and PS-7064B.showed a conservative drift of 0.02 psig
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(to 2.07) from .the previous calibration. The drift was not-
considered abnormal and no adjustments to the setpoints were made.
December 11, 1992 - PS-7064A showed a conservative drift of
0.52 psig (to 1.54) and PS-7064B silowed a conservative drift of
0.75 psig (to 1.32) from the April readings. The licensee did not
consider the drift to be an indication.that the TS limit would be
challenged since the drift was conservative and new, more accurate
testing equipment had been used. 'The licensee failed to recognize
that this drift could be due to an installation error, or that the
drift could be non-conservative when outside temperatures were
high.
The setpoints were reset at that time to 2.03 and 2.01-
respectively.
July 8, 1993 - PS-7064A showed a nonconservative drift of
0.84 psig and PS-7064B showed a nonconservative drift of 0.78 psig.
from the December 1992 as-left setpoints.
The drift resulted in
the setpoints being at 2.87 and 2.79 respectively, which exceeded
the TS limit of 2.2 psig. The licensee reset the setpoints and
notified the NRC via the Emergency Notification System and
subsequently issued LER 93-003, dated August 4, 1993.
4.
Licensee Actions
The licensee was proactive in contacting SOR for assistance and
immediately implemented SOR's recommendation to remove the cap from the
vent on the sensors
The licensee performed a review of the plant and
detarmined that there were no additional sealed pressure sensors
susceptible to temperature changes. The licensee did not initiate
corrective actions to address the engineering efforts or vendor
communication needs associated with the installation of these sensors.
5.
Evaluation of Root Causes
Due to the unique design of the facility, the pressure sensors were
located in an environment that would be relatively unaffected by changes
in conditions due to severe accidents, but would be susceptible to
atmospheric temperature changes. This environment would be different
than where these sensors are normally installed at other reactor
facilities.
Since the licensee did not recognize the potential for
temperature changes affecting the pressure setpoints, it also failed to
implement the vendors recommendations concerning high temperature
conditions, namely, that the setpoints would drift-in a nonconservative
direction and that the reference vent be vented to outside air.
Any
temperature change would affect the function of the pressure sensors if
the reference side was sealed. Two causal factors contributed to the
event; nt.nely
a lack of experience on the part of licensee engineering personnel
with sealed pressure units; and
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inadequate communication by the licensee with the vendor
concerning the uniqueness of how these sensors would be installed
at Big Rock Point and what implications that location would have
on operational characteristics of these sensors.
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6.
Safety Sionificance
The containment spray system was not required to prevent exceeding the
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containment design pressure of 27 psig during a LOCA or SLB.
In the
Final Safety Analysis Report, section 6.3.1.3.3 stated, "the enclosure
or containment spray system serves to maintain containment temperatures'
below the Electrical Equipment Qualification (EEQ) temperature envelope
in the event of a LOCA which releases steam to containment." Since a
SLB would release superheated steam into containment and a LOCA would
release saturated steam, the most severe accident affecting containment
temperature would be the'SLB.
The FSAR analysis considered a range of'
SLBs.
The capability of the Containment Ventilation System to remove
air was sufficient to prevent containment pressure from rising to 2.2
psig for a small SLB. Therefore, automatic actuation of Primary
Containment Spray was not relied upon in the FSAR analysis for a small
SLB.
In a large SLB accident, containment pressure would reach 2.2 psig
within approximately 3 seconds.
The delay in actuatian of Primary Containment Spray due to the pressure
sensors being out-of-tolerance by .69 psig on July 8,1993 would have
been approximately I second. The FSAR analysis assumed flow to the
containment spray nozzles would commence 75 seconds after Primary-
Containment Spray actuated. Therefore, given there was only a 1 second
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delay, the safety significance of the pressure sensors being out-of-
tolerance is minimal.
In addition, fluctuations of atmospheric
temperatures over the summer days of 1991 through 1993 would not have
added significantly to the 1 second delay.
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7.
Conclusions
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The licensee violated the requirements of TS 3.5.1.E regarding the
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setpoint whenever outside air tempe atures were sufficiently high to
raise the setpoint pressure to greater than 2.2 psig.
The potential to
exceed the setpoint significantly did not exist in that a significant
increase in outside temperatures to greater than 110 F. would only result
in a small increase in the setpoint above that found during the
July 1993 surveillance. The safety significance of the condition was
minimal in that the increase in setpoint would have a negligible effect-
on the initiation of primary containment spray for the analyzed accident
where it was required.
In that case, the delay in initiation would-be
on the order of I second, where the FSAR assumed 75 seconds from
initiation to spray flow.
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The root causes of the violation involved the failure of engineering
personnel associated with the installation of these pressure sensors to
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recognize the affect nf temperature changes on the setpoint and the
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failure- to communicate the unique characteristics of installation to the
vendor to' determine whether the vendor's recommendation concerning
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venting the reference leg was no longer valid.
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Although corrective actions were prompt and adequately addressed the'
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specific problem associated with these_ transmitters, the corrective
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actions failed to ensure.that future engineering efforts associated with
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equipment replacements will involve adequate review of'the intended use
and coordination with the vendor to ensure proper operations given the
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unique design and operational needs of the Big Rock Facility.
8.
Exit Interview
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The inspectors met with licensee representatives (denoted in
paragraph 1) at the conclusion of the inspection on August 20, 1993.
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The inspector summarized the purpose and scope of the inspection and the
findings. The inspectors also discussed the likely informational
content of the inspection report, with regard to documents or processes
reviewed by the inspectors during the inspection. The licensee did not
identify any such documents or processes as proprietary.
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