United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #:  9711210231

                       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 #:  97-022-01   REPORT DATE:  11/13/97



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:  NO



ABSTRACT:



The diesel generator (DG) room ventilation system was designed based on

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 the area

extreme high temperature identified in the USAR.  The cause for this

condition was design engineers, oversight.  During the investigation,

annunciator power supplies located in the DG rooms were identified as not

meeting Class 1E qualification due to improper implementation of a design

modification.  Corrective actions include revising procedures, evaluating

components for increased room temperature, installing a temporary

modification to reduce temperature inside a control panel, design changes

to the DG Direct Current (DC) electrical distribution system, reviewing

other ventilation systems for the design deficiencies, correcting the

USAR, correcting the DG DC annunciator power supply Class 1E deficiency,

evaluating the effects of outside air temperature extremes and verifying

Class 1E deficiencies do not exist in other control panels.  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 12 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 (EK] Room Heating, Ventilating, and Air

Conditioning (HVAC) system [VJ] fan [PAN] 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 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 is not operating.  These design requirements

were based on an outside air temperature range of minus 2 degrees F,

winter minimum temperature, and 96 degrees F, Bummer maximum temperature,

or 1 percent and 99 percent of the 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.  Due to the

limitations of the original design requirements, it was determined the

diesel generator room ventilation subsystems may not b 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.



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 was 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.

This was based on an engineering evaluation which 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.



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 9000.01 D001, "Control Room

Surveillance Log - Mode 1, 2, 3," and CPS 9000.01 D002, "Control Room

Operator Surveillance Log - Mode 4, 5 Data Sheet," were revised to

require monitoring of outside air temperature.  If outside ambient

temperature was not within the required temperature range for the

respective diesel generator (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 9000.01

D001 and 9000.01 D002 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 were acceptable for Division I and II diesel generator

rooms; however, to ensure conservative operation, CPS  procedures were

not revised to reflect the higher temperature.



As a long-term solution to the Diesel Generator area extreme high

temperature issue, an evaluation was performed to determine the maximum

temperature that the diesel generator rooms could reach during the area

extreme high outside air temperature of 112 degrees F.  The evaluation

determined that the diesel generator room temperature could be maintained

at or below 140 degrees F during this condition.  Engineering then

commenced an evaluation to ensure that all diesel generator supporting

components were operable for temperatures up to 140 degrees F.



On August 21, 1997, at about 1730 hours, during the evaluation, engineers

determined that temperatures within the Division 3 diesel generator

control panel (located within the Division 3 DG room) could reach 23

degrees F higher than room temperature.  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 which could cause the

control power [JC] circuit breaker [BKR] in the DG Direct Current (DC)

Distribution Panel to open, shutting down the diesel generator.  It was

determined that outside air temperatures greater than 91 degrees F could

cause temperatures in the annunciator control panel to exceed 140 degrees

F (140 degrees F, minus 26 degrees F room temperature rise, minus 23

degrees F panel temperature rise, equals 91 degrees F outside air

temperature), thereby exceeding the maximum design temperature of the DC

annunciator power supply.  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 associated with the

Division 1 and Division 2 diesel generators on August 29, 1997, found

that they too were only qualified to 140 degrees F.  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 for these diesels could also

result in DG shutdown.



TEXT                                                          PAGE 4 OF 7



Also on August 29, 1997, engineers discovered the annunciator power

supplies for the 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 [EJ].  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 analysis for

Non-Class 1E isolation.  Engineers determined that Division 1 and

Division 2 diesel generator annunciator power supplies did not have Class

1E isolation and there was no justification provided.  At this time both

Division 1 and Division 2 diesel generators were inoperable for other

reasons.  A Limiting Condition for Operation Action Statement (Technical

Specification [TS) 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 were corrected prior to declaring the Division 1 and

Division 2 diesel generators operable.  CR 1-97-09-201 was written to

investigate and track this issue.



The design of the diesel generator room ventilation subsystems was

determined not to be in accordance with the licensing basis of the plant.

The design deficiency in the diesel generator ventilation subsystems had

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 DGs

were also not in accordance with the licensing basis of the plant.  This

condition had existed since February 20, 1991, for the Division 1 DG and

January 29, 1992, for the Division 2 DG.



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 high temperatures was due to design engineers,

oversight.  The cause for the DC annunciator power supplies for Division

1 and 2 diesel generators not meeting Class 1E qualification requirements

was determined to be improper implementation of a plant modification.  A

review during the modification process identified that provisions should

be made for Class 1E use; however, this requirement was never implemented

prior to final approval.



CORRECTIVE ACTION



An engineering evaluation for outside area extreme low temperatures has

determined that the diesel generator rooms can be maintained within the

design limits for the diesel generator.



An engineering evaluation was performed to verify diesel generator

support equipment operability during outside area extreme high

temperature.  It was determined that all diesel generator components

remain operable up to the corresponding room and cabinet temperature

associated with the area extreme high temperature, with the exception of

the DC annunciator power supplies.



TEXT                                                          PAGE 5 OF 7



Electrically coordinated class 1E fuse protection will be provided for

the DC annunciator power supplies in Division 1, 2 and 3 diesel generator

control panels.  This protection will prevent a low impedance fault of

the DC annunciator power supplies from tripping the diesel generator

control power.  This design change also satisfies proper class 1E

isolation requirements for the Division 1 and 2 DGs in accordance with

USAR Section 8.3.1.4.1.4 for connections between non-Class 1E components

and Class 1E systems.  The coordinated fuse protection has been installed

in Division 1 Diesel Generator and will be installed in Division 2 and 3

Diesel Generators prior to plant start up.



Surveillance procedures CPS 9000.01 D001 and CPS 9000.01 D002 have been

revised to monitor outside air temperature.  If outside temperature is

not within the required temperature 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 generator(s).

These temperature monitoring requirements and limitations will be

discontinued once class 1E fuse protection is installed.



A Temporary Modification was installed on the Division 3 DG control panel

to remove the panel doors allowing the temperature inside the panel to

equalize with DG room temperature.  This temporary modification will be

withdrawn after the Class 1E electrically coordinated fuse protection is

installed for the DC annunciator power supply.



Other safety-related HVAC systems with very high outside air flow rates

and/or low thermal inertia with short air changes were reviewed to

identify if similar issues to those discussed in this event exist.  No

other deficiencies were found.



The CPS USAR will be revised to accurately identify the diesel generator

room temperature limitations.



Other class 1E panels with the same DC annunciator power supply as those

in the Division 1 and 2 DG control panels were evaluated for compliance

with USAR section 8.3.1.4.1.4.  No deficiencies where identified.



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 in the event of a concurrent

loss of offsite power.  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

10CFRR50.73(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



TEXT                                                          PAGE 6 OF 7



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 high 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 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 NRC Operations Center in accordance

with 10CFR21.21(c)(3) within 2 days of the date the responsible officer

approves this report.



TEXT                                                          PAGE 7 OF 7



(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.



(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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