IE Circular No. 81-03, Inoperable Seismic Monitoring Instrumentation
SSINS No.: 6830
Accession No.:
8008220271
IEC 81-03
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
March 2, 1981
IE Circular No. 81-03: INOPERABLE SEISMIC MONITORING INSTRUMENTATION
Description of Circumstances:
On November 8, 1980, an earthquake occurred off the coast near Eureka,
California. The earthquake was reported to have a magnitude of 7.0 on the
Richter Scale at the epicenter, approximately 25 to 75 miles from the
Humboldt Bay Power Plant facility. There were 12 separate seismic events
above a magnitude of 3.5 that occurred within 24 hours of the earthquake,
the largest event measuring 5.2. Reported damage to structures included
several houses that were moved off supporting posts, various chimneys that
were knocked down, one highway overpass that collapsed, and unspecified
damage that occurred at two pulp mills. There were three potentially
different sources of plant response data: three sets of magnetic tape
triaxial accelograph recorders; three sets of triaxial film recorders
(passive device); and one set of triaxial response spectrum recorders
(passive device). A review of the records from these instruments indicated
the following: the magnetic tape triaxial recorders did not produce useful
records due to a degraded low-voltage power supply in the recording system
(previously scheduled for routine servicing one week after the earthquake);
a buildup of dirt and dust appeared to make inoperable six of the nine film
recorders (the readings from the other three are considered highly
unreliable and were not obtained from the same set of triaxial recorders);
the triaxial response spectrum recorder was the only instrument believed to
produce reliable data.
On January 24, 1980, an earthquake measuring 5.5 on the Richter Scale
occurred about 10 miles north of Lawrence Livermore Laboratory (near San
Francisco, California). Numerous aftershocks also occurred with one
measuring 5.2 on January 26. The damage to civil structures was considered
minor. Rancho Seco Nuclear Plant, located approximately 45 miles northeast
of the earthquake area, reported no physical damage, although plant
personnel felt slight building motion.
Rancho Seco was shutdown for refueling during these earthquakes. During this
period, the electrical seismic instrumentation system was inoperable because
portions of the system were out for calibration. For the other instruments,
power was not being supplied due to electrical cable problems. Whether the
seismic instrumentation would have activated or not is unclear because the
U.S. Geological Survey equipment close to the site did not trigger. Records
from a passive recorder showed peak accelerations from 1 to 1.5 g and 0.1 g
.
IEC 81-03
March 2, 1981
Page 2 of 3
for the January 24 and 26 events respectively, which are in excess of values
which might be attributed to the seismic event. These indications are not
believed to be accurate values since the recorder was in an area in which it
could be easily jarred by personnel.
An earthquake measuring 3.6 to 4.1 on the Richter Scale occurred about 15
miles from the Maine Yankee site on April 17, 1979. Personnel in the control
room felt the earthquake motion, but it was not felt by others inside the
containment. An inspection of the strong-motion accelographs (Kinemetrics
SMA-l) on April 19, 1979 revealed that one instrument was inoperable
apparently because leakage of corrosive fumes from the rechargeable
batteries destroyed the battery connection. Inspection of the seismic
instruments on August 1, 1979 again revealed the corrosion problem as found
before but occurring on both instruments. Based on this, a shorter
inspection interval was initiated. Recent discussions with the
manufacturer's representative indicate that the battery corrosion problem
appears to be limited to the SMA-l units because the SMA-2 and SMA-3 units
have not exhibited a corrosion problem. Those facilities that may have SMA-l
units include Turkey Point Unit 3, Pilgrim, Maine Yankee, Vermont Yankee,
Point Beach Unit 1, Fort St. Vrain, and Browns Ferry Unit 1.
The experiences at the Humboldt Bay, Rancho Seco, and Maine Yankee
facilities are of concern because, if a significant earthquake had occurred,
important data relating to the plant response would not have been obtained.
The experiences point out that (1) calibration or testing of the seismic
instrumentation should not disable a major portion of the seismic
instrumentation system for long periods of time; (2) the necessity for
periodic surveillance and calibration of the entire seismic monitoring
system; (3) the necessity to assess the adequacy of the
surveillance/calibration interval; and (4) the necessity to detect those
areas where accidental impact or high background vibrations may mask the
actual seismic response. In addition, Licensee Event Reports (LERs)
submitted to the NRC have revealed various problems relating to seismic
instrumentation. The problems involve not only the electrical time-history
instrumentation, but also the passive peak acceleration recorders. A
description of the problems is enclosed. Note that the first problems
identified in Attachment 1 could have prevented the recording of the plant
seismic response if a significant earthquake had occurred. The remainder are
instances of less significant malfunctions.
The requirements for seismic instrumentation are described in Appendix A to
10 CFR Part 100 and Regulatory Guide 1.12. The instrumentation serves to
enable a prompt review of the actual seismic response of plant features
important to safety in comparison with that used as the design basis. This
information can be used to determine whether a plant should be shutdown, or
can continue to be safely operated, and to permit appropriate, timely
action. If an earthquake were to occur near a nuclear facility, the most
useful information of the plant's response would be from the onsite seismic
instrumentation. Evaluation of the plant response due to a seismic event
.
IEC 81-03
March 2, 1981
Page 3 of 3
and evaluation of continued operation of the facility would be difficult
without accurate and reliable data. Based on the above discussion, the
following action is recommended.
Recommended Action for Holders of Operating Licenses and Construction
Permits:
It is recommended that holders of operating licenses and construction
permits review for applicability the specific items presented in the
"Description of Circumstances" and the enclosure to the Circular. It is
further recommended that the surveillance testing and calibration programs
for the seismic instrumentation system be reviewed and revised as necessary
to detect and prevent the malfunctions described herein and to limit the
potential for having or making the entire seismic monitoring system (active
and passive components) inoperable during all plant modes of operation.
No written response to this Circular is required. If you require additional
information regarding these matters, please contact the Director of the
appropriate NRC Regional Office.
Attachments:
1. Seismic Instrumentation Malfunctions
2. Recently Issued IE Circulars
.
Attachment 1
IEC 81-03
March 2, 1981
SEISMIC INSTRUMENTATION MALFUNCTIONS
PLANT LER NUMBER/ EVENT DESCRIPTION
DOCUMENTATION
Beaver Valley Power 78-028 Magnetic tape
Station, Unit 1 recorder (Teledyne
Geotech Model
MTS-100), was
found inoperable
during surveillance
test; replaced with
new instrument
D.C. Cook Nuclear Plant, 75-56 One channel was found
Unit 1 during surveillance
testing to have a
severe amplifier
balance shift; the
amplifier board was
replaced
76-19 Movable masses on the
peak recording
accelerometers were
against the stops;
the units were
replaced; initiated
shortened
surveillance interval
76-50 Cassette tape (Kine-
metrics) on
monitoring
system was found
sticking during
surveillance testing;
the sticking tape was
replaced
Davis-Besse Nuclear 77-13 Spurious activation
Power Station of seismic trigger;
unit was replaced
79-111 Excessive noise in
recorded tape
prevented reading of
accelerometer traces
during surveillance
test
(Teledyne-Geotech
Model 37200); part of
problem was due to
one lead of AC input
line on playback
monitor was not
connected
.
IEC 81-03
March 2, 1981
- 2 -
PLANT LER NUMBER/ EVENT DESCRIPTION
DOCUMENTATION
Hatch Nuclear Plant, Letter from Georgia One channel of the
Unit 1 Power to NRC dated Triaxial Time-History
6/25/80 Accelerometer
(Kinemetrics) had
shifted its sensiti-
vity by 47% and
natural frequency by
12%.
Humboldt Bay NRC Reconnaissance Magnetic tape time-
Power Plant Report dated 1/19/81 history
accelerometers
(TERA Technology)
were found inoperable
due to a degraded low
voltage power supply;
6 of 9 film recorders
(TERA Technology)
were inoperable
because of dirt and
dust buildup
Maine Yankee Inspection Report Corrosion of connec-
Atomic Power 50-309/79-11 tions to the
Plant batteries
on Kinemetrics
SMA-l units made the
units inoperable;
increased testing
frequency initiated
Rancho Seco Nuclear Inspection Report Seismic monitoring
Generating Station 50-312/80-03 instrumentation was
inoperable due to
calibration and
power supply problems
with electrical
cable; passive
accelerometers
placed in area
susceptible to
impacts by passing
traffic
.
IEC 81-03
March 2, 1981
- 3 -
PLANT LER-NUMBER/ EVENT DESCRIPTION
DOCUMENTATION
Less Significant Occurrences -
Beaver Valley Power 76-53 Control room seismic
Station 78-040 alarm indicated
spuriously due to
misaligned reed
switches; the
recording scribes on
the Engdahl response
spectrum recorders
remained operable;
the reed switches
were adjusted
Calvert Cliffs Nuclear 77-79 The motor on the
Plant, Unit 1 tape playback unit
(Kinemetrics Model
No. SMP-l) was found
sticking; the motor
was replaced
North Anna Power 78-060 Alarms from the
Station, Unit 1 78-118 (Engdahl) response
spectrum recorders
indicated spuriously
on four separate
occasions
Three Mile Island 78-002 A defective recording
Nuclear Station, plate was found in
Unit 2 the spectrum
recorder; the
plates were replaced
Page Last Reviewed/Updated Tuesday, March 09, 2021
Page Last Reviewed/Updated Tuesday, March 09, 2021