Part 21 Report - 1997-721
ACCESSION #: 9709300310
LICENSEE EVENT REPORT (LER)
FACILITY NAME: Clinton Power Station PAGE: 1 OF 7
DOCKET NUMBER: 05000461
TITLE: Design of Diesel Generator Ventilation Subsystems Outside
Design Basis as a Result of Failure to Include Minimum
and Maximum Outside Air Temperature Extremes Due to
Design Error
EVENT DATE: 09/29/86 LER #: 97-022-00 REPORT DATE: 09/22/97
OTHER FACILITIES INVOLVED: DOCKET NO: 05000
OPERATING MODE: 4 POWER LEVEL: 000
THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR
SECTION:
50.73(a)(2)(i), 50.73(a)(2)(ii), 50.73(a)(2)(v), 50.73(a)(2)(vii) & OTHER
LICENSEE CONTACT FOR THIS LER:
NAME: M.M. Gandhi, Engineering Projects TELEPHONE: (217) 935-8881,
Engineer Extension 4082
COMPONENT FAILURE DESCRIPTION:
CAUSE: SYSTEM: COMPONENT: MANUFACTURER:
REPORTABLE NPRDS:
SUPPLEMENTAL REPORT EXPECTED: YES EXPECTED SUBMISSION DATE: 11/17/97
ABSTRACT:
The diesel generator (DG) room ventilation system was designed for an
outside air temperature range of -2 degrees Fahrenheit (F), winter
minimum temperature, and 96 degrees F, summer maximum temperature. The
Updated Safety Analysis Report (USAR) identifies temperature extremes of
-22 degrees F and 112 degrees F based on surrounding area temperature
data. Analysis determined that the DG ventilation system is unable to
maintain DG room temperature within the design limit during temperature
extremes identified in the USAR. The cause for the DG ventilation system
being inadequate is design engineers oversight. During the
investigation, DC annunciator power supplies were identified as not
meeting Class 1E qualification. The cause for this condition has not
been determined. Corrective actions for this event include revising
procedures, evaluating components for increased room temperatures,
installing a temporary modification to reduce temperature inside a
control panel, evaluating design changes to prevent DC power supplies
from tripping due to high temperature, reviewing other ventilation
systems, correcting the USAR, correcting the DG DC annunciator power
supply Class 1E deficiency, and evaluating low outside air temperature
extremes. This condition is reportable under 10CFR21.
END OF ABSTRACT
TEXT PAGE 2 OF 7
DESCRIPTION OF EVENT
On July 24, 1997, the plant was in Mode 4 (COLD SHUTDOWN) for the sixth
refueling outage (RF-6). Reactor (RCT) coolant temperature was being
maintained within a band of 100 to 120 degrees Fahrenheit (F) and
pressure was zero pounds per square inch. Engineers were investigating
condition report (CR) 1-97-06-302 which identified an issue involving
increased Emergency Diesel Generator Room Heating, Ventilating, and Air
Conditioning (HVAC) system [VJ] fan [FAN] horsepower consumption during
low outside ambient temperature conditions.
At about 0745 hours, during the investigation, questions were raised
about the design of the diesel generator room ventilation subsystems.
The room ventilation subsystems are designed for an outside air
temperature range of minus 2 degrees F, winter minimum temperature, and
96 degrees F, summer maximum temperature, based on the 1 percent and 99
percent temperature extremes for Central Illinois. The diesel generator
ventilation system was designed in accordance with the American Society
of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)
Fundamentals Handbook chapter on weather data and design conditions.
However, the Clinton Power Station (CPS) Updated Safety Analysis Report
(USAR) identifies surrounding area extremes of minus 22 degrees F
(Springfield, IL) and 112 degrees F (Springfield, IL). Actual Clinton
Power Station extremes documented in the USAR are minus 19.8 degrees F
and 95.4 degrees F. Therefore, due to the design limitations, it was
determined the diesel generator room ventilation subsystems may not be
adequate to support operability of the diesel generators during extreme
outside temperatures that exceed the recommended levels in the ASHRAE
Fundamentals Handbook.
The operations Shift Supervisor was notified about this issue at 0830
hours and he directed that Engineering perform further evaluations.
The diesel generator room ventilation subsystems were designed to limit
the temperature in the diesel generator room to 130 degrees F with the
diesel generator operating and between 65 degrees F and 104 degrees F
when the diesel generator in not operating. However, the engineers
determined that when outside temperatures are below 5 degrees F or above
102.7 degrees F for the Divisions 1 and 2 diesel generator rooms, and
below 5 degrees F or above 104 degrees F for the Division 3 diesel
generator room, the DG HVAC system may not maintain the temperature in
these rooms within design limits. Further evaluation of the effects of
the area extreme low temperature is in progress.
CR 1-97-07-250 was initiated to investigate and track the extreme
temperature issue. On July 25, 1997, at approximately 0051 hours, an
operability determination completed by the Operations Shift Supervisor
concluded that the outside ambient temperature band required for proper
operation of the Diesel Generator Room HVAC system is 5 degrees F to
102.7 degrees F for the Divisions 1 and 2 diesel generator rooms, and 5
degrees F to 104 degrees F for the Division 3 diesel generator room.
TEXT PAGE 3 OF 7
The operations Shift Supervisor implemented interim actions to ensure
continued operability of the emergency diesel generators. On July 25,
1997 surveillance procedures CPS 9000.01D001, "Control Room Surveillance
Log - Mode 1, 2, 3," and CPS 9000.01D002, "Control Room Operator
Surveillance Log - Mode 4, 5 Data Sheet," were revised to require
monitoring of outside air temperature. If outside ambient temperature
for the respective diesel generator was not within the required
temperature range (5 to 102.7 degrees F for Divisions 1 and 2, or 5 to
104 degrees F for Division 3), appropriate actions in accordance with CPS
Technical Specifications for the inoperable diesel generators) were to be
taken. On August 4, 1997, CPS surveillance procedures 9000.01D001 and
9000.01D002 were revised again to require actions in accordance with CPS
administrative procedure 1014.06, "Operability Determination," and the
CPS Technical Specifications for the inoperable diesel generators).
Further analysis showed that temperatures higher than 102.7 degrees F are
acceptable for Division I and II diesel generator rooms; however, to
ensure conservative operation, CPS procedures were not revised to reflect
the higher temperature. For long-term solutions, Engineering is
evaluating all diesel generator supporting components to ensure they are
operable for temperatures up to 140 degrees F. This is based on the
results of an engineering evaluation showing that the rooms can be
maintained below 140 degrees F for outside air temperatures up to the
area extreme high temperature of 112 degrees F.
On August 21, 1997, at about 1730 hours, during investigation of CR
1-97-07-250, engineers determined that the Division 3 diesel generator
would not be operable when outside air temperature was greater than 91
degrees F. The basis for this determination was a postulated 23 degrees
F temperature differential between the Division 3 diesel generator room
temperature and the Division 3 diesel generator control panel. An
annunciator power supply [JX] within the Division 3 diesel generator
control panel was not qualified for temperatures above 140 degrees F.
Overheating of the annunciator power supply could result in a low
impedance fault. The result of such a fault could cause the control
power [JC] circuit breaker [BKR] in the DG Direct Current (DC)
Distribution Panel to open, shutting down the diesel generator. CR
1-97-08-204 was initiated to investigate and track this issue. The
original operability determination was revised as a result of this
finding and a temporary modification was initiated to remove the control
panel doors to equalize room temperature and control panel temperature.
This temporary modification restored the Division 3 diesel generator to
an operable status.
Investigation of the DC annunciator power supplies on Division I and
Division 2 diesel generators on August 29, 1997, found that they too were
only qualified to 140 degrees P. These power supplies are located in
control panels similar to Division 3 where temperatures inside the panel
could be 23 degrees higher than room temperature. A low impedance fault
on the DC power supplies in these diesels could also result in DG
shutdown.
Also on August 29, 1997, engineers discovered the annunciator power
supplies for Division 1 and Division 2 diesel generators were not Class
1E qualified. These power supplies do not perform a safety related
function, however, they are connected to the Class 1E DC diesel generator
electrical distribution system. Section 8.3.1.4.1.4 of the USAR requires
Non-Class 1E, non-division associated components, be electrically
isolated from Class 1E systems by an acceptable Class 1E isolation device
or have an adequate justification and
TEXT PAGE 4 OF 7
analysis for Non-Class 1E isolation. Engineering determined that
Division 1 and Division 2 diesel generator annunciator power supplies did
not have Class 1E isolation and no justification existed for Non-Class 1E
isolation. At this time both Division 1 and Division 2 diesel generators
were inoperable. A Limiting Condition for operation, 3.8.2, was entered
to ensure that the Non-Class 1E power supply issue and the high
temperature issue for Division 1 and 2 diesel generators are corrected
prior to declaring the Division 1 and Division 2 diesel generators
operable.
The design of the diesel generator room ventilation subsystems is not in
accordance with the licensing basis of the plant. The design deficiency
in the diesel generator ventilation subsystems has existed since initial
plant operation on September 29, 1986, when the plant was in Mode 5
(REFUELING) for initial fuel loading. At that time, reactor coolant
temperature was ambient and pressure was atmospheric. The Non-Class 1E
DC annunciator power supplies for Division 1 and 2 DG are also not in
accordance with the licensing basis of the plant. It has not been
determined how long this condition has existed.
No automatic or manually initiated safety system responses were necessary
to place the plant in a safe and stable condition. No other equipment or
components were inoperable at the start of this event to the extent that
their inoperable condition contributed to this event.
CAUSE OF EVENT
The cause for the diesel generator ventilation system being inadequate
during extreme ambient temperatures was due to design engineers'
oversight. Why the DC annunciator power supplies for Division 1 and 2
diesel generators do not meet Class 1E qualification has not been
determined and is under investigation.
CORRECTIVE ACTION
Surveillance procedures CPS 9000.01D001 and CPS 9000.01D002 have been
revised to monitor outside air temperature, and if temperature is not
within the minimum and maximum (5 to 102.7 degrees F or 5 to 104 degrees
F) design operating range for the respective diesel generator,
appropriate actions will be taken in accordance with CPS administrative
procedure 1014.06, operability Determination", and the CPS Technical
Specifications for the inoperable diesel generators). However, further
evaluation for area maximum high and low outside air temperatures remains
to be completed to determine impact on the operability of the diesel
generators. Based on the results of the evaluation, appropriate actions
will be taken to ensure equipment operability. IP will revise this LER
to include the results of the evaluations for area high and low
temperature extremes. IP expects to issue the revision by November 17,
1997. Additional corrective actions include the following:
A Temporary Modification was installed on Division 3 control panel to
remove the panel doors allowing the temperature inside the panel to
equalize with DG room temperature.
Design changes will be initiated and implemented to provide protective
isolation for the DC power supplies to prevent the DC distribution panel
from tripping.
TEXT PAGE 5 OF 7
Other safety related HVAC systems with very high outside air flow rates
and/or low thermal inertia with short air changes will be reviewed to
identify issues similar to those discussed in this event.
The CPS USAR will be revised to accurately identify the diesel generator
room temperature limitations.
Design changes will be initiated and implemented for the DC annunciator
power supplies in Division I and II to ensure Class 1E compliance in
accordance with USAR Section 8.3.1.4.1.4.
The cause for the improper Class 1E DC annunciator power supplies for
Division 1 and Division 2 diesel generators is under investigation. The
results of this investigation will determine if other corrective actions
are required. IP will include the cause for the improper power supplies
and any additional corrective actions in the revision to this LER.
ANALYSIS OF EVENT
This event is reportable under several criteria or provisions of
10CFR50.73. The event is reportable under the provisions of
10CFR50.73(a)(2)(ii)(B) because the design of the diesel generator room
ventilation subsystems, and the design of the Division 1 and 2 DC
annunciator power supplies, are not in accordance with the design
requirements of the plant. The diesel generators are required to
mitigate the consequences of an accident. Failure of the DC annunciator
power supplies could have prevented the diesel generators from fulfilling
their safety function, therefore this event is reportable under
10CFR50.73(a)(2)(v). This event is also reportable under the provisions
of 10CFR50.73(a)(2)(vii) because a single condition caused the three
subsystems of the emergency diesel generator HVAC system to become
inoperable. Finally, due to the previously unrecognized potential for
the diesel generators to be rendered inoperable from the effects of high
temperature on required equipment in the diesel generator rooms (when
outside air temperatures exceed levels that are not improbably high),
this event is also reportable under the provisions of 10CFR50.73
(a)(2)(i)(B) as a condition or operation prohibited by the Plant
Technical specifications. This is based on the fact that, to date, there
have been many occasions or periods of time when outside air temperatures
exceeded 91 degrees F. During those times, all three diesel generators
were inoperable (but were not declared inoperable since the condition was
unknown). Having three diesel generators inoperable at the same time
requires entry into Technical Specification (TS) 3.0.3. A condition or
operation requiring entry into TS 3.0.3 constitutes a condition or
operation prohibited by the plant Technical Specifications.
An assessment of the safety consequences and implications of this event
identified that this event has potential nuclear safety significance.
The failure of the diesel generator room ventilation subsystems to
perform their design functions during outside air temperature extremes
could cause common mode failure of the divisional emergency diesel
generators to perform their functions of supplying sufficient power to
safety-related equipment. Specifically, extremely high outside air
temperatures could increase the diesel generator room temperature to
above the design limits and cause a power supply failure and
TEXT PAGE 6 OF 7
subsequent trip of the DC main feed circuit breaker to the diesel
generator control panel. A loss of power to the control panel could
prevent the diesel generator from performing its design function.
ADDITIONAL INFORMATION
No equipment or components failed as a result of this event.
Clinton Power Station has not reported similar events regarding
inadequate HVAC design and failure to provide proper Class 1E electrical
isolation in recent history.
For further information regarding this event, contact M. M. Gandhi,
Engineering Projects Engineer, at (217) 935-8881, extension 4082.
10CFR21 Report 21-97-036
On July 24, 1997, during investigation of condition report (CR)
1-97-06-302 which identified an issue involving increased Diesel
Generator Room Heating, Ventilating, and Air conditioning system fan
horsepower consumption at low temperature and the effect on diesel
generator loading and electrical load distribution system, questions were
raised about the design of the HVAC system. These questions resulted in
an evaluation of the DG ventilation system for adequacy during extreme
high and low outside ambient air temperatures. Due to design limitations
on the diesel generator room ventilation subsystems, it was determined
adequate cooling capacity may not be available to support operability of
the diesel generators if outside temperatures exceed levels that are not
improbably high for the summer season. This issue was determined to be
potentially reportable under 10CFR21. IP has completed an evaluation of
this issue and concludes that it is reportable under the provisions of
10CFR, Part 21.
IP is providing the following information in accordance with
10CFR21.21(c)(4). Initial notification of this matter will be provided
by facsimile of this letter to the URC Operations Center in accordance
with 10CFR21.21(c)(3) within 2 days of the date the responsible officer
approves this report.
(i) Wayne D. Romberg, Assistant Vice President of Illinois Power
Company, Clinton Power Station, Highway 54, 6 Miles East,
Clinton, Illinois, 61727, is informing the NRC of a condition
reportable under the provisions of 10CFR21 by means of this
report.
(ii) The basic component involved in this report is the design of
the diesel generator room ventilation subsystems.
(iii) The design for the diesel generator room cooling subsystems was
supplied by Sargent & Lundy.
TEXT PAGE 7 OF 7
(iv) As discussed in the DESCRIPTION OF EVENT portion of this
report, the nature of the defect is the diesel generator room
ventilation subsystems are not designed to address the
temperature extremes of the area surrounding CPS and may not
perform their design functions during those extremes.
As discussed in the ANALYSIS OF EVENT portion of this report,
failure of the ventilation subsystems to perform their design
functions during temperature extremes could cause failure of
the diesel generators to perform their functions of supplying
sufficient power to safety-related equipment.
(v) On July 24, 1997, IP identified that the diesel generator room
ventilation subsystems may not be designed to include the
temperature extremes of the area surrounding CPS and IP
determined that this issue was potentially reportable under
10CFR21.
(vi) This issue affects the design of the diesel generator room
ventilation subsystems for the Divisions 1, 2, and 3 emergency
diesel generators. IP is not aware of other facilities that
would be affected by this issue.
(vii) The corrective action that IP is taking for this event is
discussed in the CORRECTIVE ACTION section of this report.
(viii) IP has no additional information to offer.
*** END OF DOCUMENT ***
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