Part 21 Report - 1998-041
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.
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