United States Nuclear Regulatory Commission - Protecting People and the Environment


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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