United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #:  9801070010

                       LICENSEE EVENT REPORT (LER)



FACILITY NAME:  Clinton Power Station                     PAGE: 1 OF 5



DOCKET NUMBER:  05000461



TITLE:  Plant Outside Design Basis Due to Inadequate Tornado

        Missile Protection Caused by Design Error



EVENT DATE:  09/29/86   LER #:  97-032-00   REPORT DATE:  01/02/98



OTHER FACILITIES INVOLVED:                          DOCKET NO:  05000



OPERATING MODE:  5   POWER LEVEL:  000



THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR

SECTION:

50.73(a)(2)(ii)



LICENSEE CONTACT FOR THIS LER:

NAME:  D. L. McMillan,                 TELEPHONE:  (217) 935-8881

       Corrective Action Team Lead                 Extension 3902

       Engineer



COMPONENT FAILURE DESCRIPTION:

CAUSE:      SYSTEM:       COMPONENT:       MANUFACTURER:

REPORTABLE NPRDS:



SUPPLEMENTAL REPORT EXPECTED:  NO



ABSTRACT:



On December 2, 1997, at approximately 1840 hours, Plant Operations

determined that portions of the High Pressure Core Spray (HPCS) pump

suction piping, Reactor Core Isolation Cooling (RCIC) pump suction

piping, and RCIC tank level instrumentation standpipe, located outside of

a missile protected building, were not designed to withstand missiles

generated by a design basis tornado.  The Updated Safety Analysis Report

(USAR) identifies that these components should be designed to withstand

the effects of a missile generated by a design basis tornado.  Because

portions of the HPCS and RCIC pump suction piping and the RCIC tank level

instrumentation standpipe are not provided missile protection, the design

of these systems was not in accordance with the design basis of the

plant.  The cause of this event was determined to be design engineering

oversight.  The corrective actions for this event include providing

missile protection for the portions of the HPCS and RCIC pump suction

piping, and RCIC tank level instrumentation standpipe located outside a

missile protected building, and investigating other portions of the plant

for similar tornado missile design deficiencies.  This condition is also

reportable under 10CFR21.



END OF ABSTRACT



TEXT                                                          PAGE 2 OF 5



DESCRIPTION OF EVENT



On December 2, 1997, at approximately 1840 hours, Clinton Power Station

(CPS) was in mode 4 (COLD SHUTDOWN), and reactor [RCT] coolant

temperature was being maintained between 100 and 120 degrees Fahrenheit

(F) at atmospheric pressure.  The sixth refueling outage was in progress.

Plant Operations determined that portions of the High Pressure Core Spray

(HPCS) [BG] pump [P] suction piping, Reactor Core Isolation Cooling

(RCIC) [BN] pump suction piping, and RCIC tank [TK] level instrumentation

standpipe were not designed to avoid damage from the effects of a design

basis tornado missile.  Section 6.3.2.2.1 of the Updated Safety Analysis

Report (USAR) identifies HPCS components and piping as being positioned

to avoid damage from the physical effects of design-basis accidents, such

as pipe whip, missiles, high temperature, pressure, and humidity.

Additionally, section 3.1.2.1.4 of the USAR identifies that structures,

systems, and components important to safety are designed to withstand the

effects of missiles from events and conditions outside the nuclear unit.

Because portions of the HPCS and RCIC pump suction piping and the RCIC

tank level instrumentation standpipe are important to safety and not

provided missile protection for a design basis tornado, their design was

not in accordance with the design basis of the plant.  This condition has

existed since September 29, 1986, when the plant was in Mode 5

(REFUELING) for initial fuel loading, and reactor coolant temperature was

ambient and pressure was atmospheric.



On October 10, 1997, at approximately 0945 hours, a station engineer was

performing a walkdown in the RCIC storage tank room to investigate if

missile protection was provided for RCIC instrumentation.  This walkdown

was prompted by information that another facility found safety-related

components unprotected from tornado generated missile hazards.  During

the walkdown, the engineer identified that portions of the HPCS pump

suction piping, RCIC pump suction piping and RCIC tank level

instrumentation standpipe outside a missile protected building appeared

to be unprotected from missile hazards.  Condition Report (CR)

1-97-10-184 was written to investigate and track this issue.  The

Operations Shift supervisor was informed of this issue and he directed

Nuclear Station Engineering to evaluate this concern and report the

results to the operations Shift Supervisor.



The HPCS and RCIC PUMPS Supply reactor grade water to the reactor vessel

from the RCIC tank during postulated accident conditions.  In the event

that the RCIC storage tank water supply becomes exhausted or is not

available, the RCIC tank level instrumentation provides input to

automatically transfer the water source from the RCIC tank to the

Suppression pool.  This capability assures a closed cooling water supply

is available for continuous operation of the HPCS and RCIC systems.

Portions of the HPCS and RCIC system suction piping, and the RCIC tank

level instrumentation standpipe are contained in the RCIC storage tank

building located between the RCIC storage tank and the Fuel Building.

The RCIC storage tank building is not designed to withstand Missiles

generated by a design basis tornado, however, the HPCS and RCIC systems

are required to have missile protection.  Therefore, on December 2, 1997,

Plant operations determined that these systems were not in accordance

with the design basis of the plant and entered a restraint from changing

modes until this issue was resolved.



No automatic or manually initiated safety system responses were necessary

to place the plant in a safe and Stable condition.  This event was not

affected by other inoperable equipment or components.



TEXT                                                          PAGE 3 OF 5



CAUSE OF EVENT



The cause of this event is oversight by design engineers who failed to

provide a design that protects the HPCS and RCIC pump suction piping, and

RCIC tank level instrumentation standpipe from missile hazards generated

by a design basis tornado.  Illinois Power did not recognize this design

discrepancy during initial plant design review.



CORRECTIVE ACTIONS



Prior to plant startup, missile protection will be provided for the

portions of HPCS and RCIC pump suction piping and RCIC tank level

instrumentation standpipe located outside of a missile protected

building.



IP is investigating other portions of the plant for similar tornado

Missile design deficiencies.



ANALYSIS OF EVENT



This event is reportable under the provisions of 10CFR50.73 (a) (2) (ii)

(B) due to the HPCS and RCIC piping and RCIC standpipe not having tornado

missile protection in accordance with the design basis of the plant.



The HPCS and RCIC components and piping were not positioned to avoid

damage from the physical effects of missiles generated by a design basis

tornado.  Two accident scenarios are postulated which result in the HPCS

and RCIC systems not being capable of performing their safety-related

functions.  In the first scenario, a tornado missile could pinch the RCIC

tank level instrumentation standpipe closed, preventing the level

instrumentation from sensing a low level in the RCIC tank during a design

basis accident.  The pinched standpipe would prevent the automatic

transfer of supply water from the RCIC tank to the suppression pool.  As

a result the HPCS and/or RCIC pump would loose suction pressure,

interrupting the water supply to the reactor vessel, and damaging the

pump(s) if not promptly diagnosed and corrected by control room

operators.  The second scenario postulates that a tornado missile severs

the unprotected HPCS and/or RCIC PUMP suction piping without a failure of

the RCIC tank or RCIC tank level instrumentation standpipe.  In this

scenario the pump(s) would continue to operate without sufficient suction

flow or net positive suction head until sufficient water was lost from

the RCIC storage tank through the ruptured line(s) to reach the low level

trip for the system(s) transfer to the suppression pool water supply.

This condition could also interrupt the water supply to the reactor

vessel during a design basis accident and damage the pump(s).



An assessment of the safety consequences and implications of this event

identified this condition as potentially safety significant.  A loss of

either the HPCS and/or RCIC system operability is a significant

contributor to risk in the Probability Risk Assessment.  However, the

probability of the failure of these lines due to tornado Missiles is

expected to be considerably smaller than other failure mechanisms for the

HPCS and RCIC systems.



TEXT                                                          PAGE 4 OF 5



ADDITIONAL INFORMATION



No equipment or components failed as a result of this event.



Clinton Power Station reported a similar event regarding inadequate

missile protection for safety-related equipment in LER 88-027.



For further information regarding this event, contact D.  L.  McMillan,

Corrective Action Team Lead Engineer, at (217) 935-8881, extension 3920.



10CFR21 REPORT 21-97-057



On December 2, 1997, IP determined that portions of the HPCS and RCIC

pump suction piping, and the RCIC tank level instrumentation standpipe

were not designed to withstand missiles generated by a design basis

tornado.  This condition was determined to be potentially reportable

under the provisions of 10CFR21 on December 5, 1997.  IP has completed an

evaluation of this issue and conclude that it is reportable under the

provisions of 10CFR, Part 21.



IP is providing the following information in accordance with 10CFR21.21

(c) (3) within 2 days of the date the responsible officer approves this

report.



(i)       J.  G.  Cook, Senior 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

          portions of the HPCS and RCIC pump suction piping, and the RCIC

          tank level instrumentation standpipe for protection against

          design basis tornado generated missiles.



(iii)     The design for the HPCS/RCIC pump suction piping, and the RCIC

          tank level instrumentation standpipe was supplied by Sargent

          and Lundy.



(iv)      As discussed in the DESCRIPTION OF EVENT portion of this

          report, the nature of the reportable condition is a portion of

          the HPCS and RCIC pump suction piping, and the RCIC tank level

          instrumentation standpipe are not designed to withstand

          missiles generated by a design basis tornado as required by

          USAR sections 6.3.2.2.1 and 3.1.2.1.4.  As discussed in the

          ANALYSIS OF EVENT portion of this report, the safety hazard

          created is a loss of supply water for the RCIC and/or HPCS

          pump(s).



(v)       On December 2, 1997, IP identified that portions of the HPCS

          and RCIC pump suction piping, and the RCIC tank level

          instrumentation standpipe were not designed to withstand

          Missiles generated by a design basis tornado.  This issue Was

          determined to be potentially reportable under the provisions of

          10CFR21 on December 5, 1997.



TEXT                                                          PAGE 5 OF 5



(vi)      This issue affects the design of the HPCS and RCIC systems at

          CPS.  IP is aware of the Perry Nuclear facility having similar

          missile protection issues.  IP has no information regarding the

          applicability of this issue to any other purchasers or

          licensees.



(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 ***







Page Last Reviewed/Updated Thursday, March 29, 2012