Part 21 Report - 1997-370
ACCESSION #: 9702030199
LICENSEE EVENT REPORT (LER)
FACILITY NAME: Clinton Power Station PAGE: 1 OF 5
DOCKET NUMBER: 05000461
TITLE: Failure of Nuclear Fuel Supplier to Analyze Turbine
Pressure Regulator Downscale Failure Event in the Off-
Rated Condition Results in Operation in an Unanalyzed
Condition
EVENT DATE: 01/03/97 LER #: 97-001-00 REPORT DATE: 01/28/97
OTHER FACILITIES INVOLVED: None 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) & OTHER
LICENSEE CONTACT FOR THIS LER:
NAME: R. W. Chickering, Engineering TELEPHONE: (217) 935-8881,
Projects Extension 3334
COMPONENT FAILURE DESCRIPTION:
CAUSE: SYSTEM: COMPONENT: MANUFACTURER:
REPORTABLE NPRDS:
SUPPLEMENTAL REPORT EXPECTED: NO
ABSTRACT:
Because of a nuclear fuel supplier error, the Turbine Pressure Regulator
Downscale Failure (PRDF) event for 40 to 80 percent of rated thermal
power had not been quantitatively analyzed during past operation. The
fuel supplier issued a revision to the power-dependent operating limit
for the cycle 7 Minimum Critical Power Ratio (MCPR) to correct the
previous limit which was not adequate for conditions between 40 and 80
percent of rated thermal power for the PRDF event. Utility engineers
reviewing the documentation identified that there was some potential to
exceed the Safety Limit MCPR if the PRDF event had occurred during any of
the past 5 fuel cycles. The engineers identified that the plant had
operated in an unanalyzed condition during fuel cycle 6 and may have
operated in unanalyzed conditions during fuel cycles 2, 3, 4, and 5. The
cause of this event is attributed to an error by the nuclear fuel
supplier in determining which events were the limiting anticipated
operational occurrences that required analysis for the fuel design.
Corrective action includes implementing corrected power-dependent
operating limits for the MCPR. This event is also reportable under
10CFR, Part 21.
END OF ABSTRACT
TEXT PAGE 2 OF 5
DESCRIPTION OF EVENT
On January 3, 1997, the plant was in Mode 5 (REFUELING) and the sixth
refueling outage (RF-6) was in progress. Reactor [RCT] coolant
temperature was being maintained between 75 and 185 degrees Fahrenheit
and pressure was atmospheric.
Because of a nuclear fuel supplier error, the Turbine Pressure Regulator
Downscale Failure (PRDF) event for 40 to 80 percent of rated thermal
power had not been quantitatively analyzed during past operation for fuel
cycles 2, 3, 4, 5, and 6. The PRDF event leads to a larger change in the
power-dependent operating limit Minimum Critical Power Ratio (MCPR) than
any of the other Anticipated Operational occurrence. This condition is
unique to the Boiling Water Reactor (BWR)-6 reactor type because a single
failure may cause the pressure regulation system to fail downscale.
The fuel supplier issued a revision to the power-dependent operating
limit for the MCPR for fuel cycle 7 to correct the previous limit which
was not adequate for conditions between 40 and 80 percent of rated
thermal power in the PRDF event. Utility engineers were performing an
approval review of the fuel supplier documentation for the fuel cycle 7
Supplemental Reload Licensing Report and the core performance monitoring
computer [CPU] [IO] data bank. ,The review identified that there was
some potential to exceed the Technical Specification Safety Limit MCPR if
the PRDF event had occurred during any of the past 5 fuel cycles.
At about 1520 hours, while comparing fuel cycle 6 actual operating data
with the new limits for fuel cycle 7, the engineers identified that the
plant had operated in an unanalyzed condition during fuel cycle 6 and may
have operated in unanalyzed conditions during fuel cycles 2, 3, 4, and 5.
Investigation of the condition identified that the PRDF event should have
been analyzed for power levels between 40 and 80 percent of rated thermal
power during fuel cycles 2, 3, 4, 5, and 6 because the impact of PRDF is
more limiting than the other events used for establishing the operating
limit for MCPR. Because the standard margins for uncertainty land
instrument error for the calculations were not maintained, if a PRDF
event occurred while operating near the operating limit for MCPR, the
Safety Limit MCPR could have been violated.
During fuel cycle 6, non-conservative power-dependent operating limits
for the MCPR were used to monitor the reactor. On several occasions
during reactor startups, the reactor was in a condition that placed the
MCPR on a few lead fuel bundles close to the power-dependent operating
limit for the MCPR. The power-dependent operating limit for the MCPR
would have been exceeded if it had been correctly calculated for fuel
cycle 6.
The error in the analysis of the power-dependent operating limit for the
MCPR has been applicable since the first refueling outage (RF-1) when the
Maximum Extended Operating Domain (MEOD) modification was implemented.
The MEOD modification eliminated the conservative Total Peaking Factor
requirements and replaced them with the power-dependent operating limit
for the MCPR.
The Operations Shift Supervisor was notified about the non-conservative
power-dependent operating limit for the MCPR at about 1545 hours.
TEXT PAGE 3 OF 5
Condition Report 1-97-01-030 was initiated to track a cause and
corrective action determination for this event.
No automatic or manually initiated safety system responses were necessary
to place the plant in a safe and stable condition. No 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 of this event is attributed to an error by the nuclear fuel
supplier, GE Nuclear Energy, in determining which events were the
limiting Anticipated Operational Occurrences that required analysis for
the fuel design. The error occurred in the generic design of MEOD which
was completed long before its installation at Clinton Power Station
(CPS). Previous CPS reviews of the MEOD modification and fuel design
changes did not identify the GE error. The fuel supplier has informed
CPS that it plans to perform a root cause analysis of the error.
CORRECTIVE ACTION
Corrected power-dependent operating limits for the MCPR will be
implemented in the core performance monitoring computer and incorporated
into the Core Operating Limits Report of the CPS Operating Manual after
the fuel cycle 7 Supplemental Reload Licensing Report is approved.
ANALYSIS OF EVENT
This event is reportable under the provisions of 10CFR50.73(a)(2)(ii)(A)
due to the plant being in an unanalyzed condition that could have
compromised plant safety.
An assessment of the safety consequences and implications of this event
indicated that this event had potential nuclear safety significance. The
potential to exceed the Safety Limit for the MCPR in fuel cycles 2, 3, 4,
5, and 6 due to a PRDF event was not conservatively analyzed for
conditions between 40 and 80 percent of rated thermal power. If a PRDF
event had occurred while operating near the non-conservative
power-dependent operating limit for the MCPR in those fuel cycles, the
potential would have existed to exceed the Safety Limit for MCPR for fuel
bundles that were near the power-dependent operating limit for the MCPR.
However, CPS has not experienced any Turbine Pressure Regulator Downscale
Failure events while operating between 40 and 80 percent of rated thermal
power during fuel cycles 2, 3, 4, 5, or 6. Additionally, at low power
levels and at near 100 percent rated thermal power, the power-dependent
operating limit for the MCPR was adequate. Further, the reactor was not
operated for long periods of time close to the power-dependent operating
limit for the MCPR. Following completion of RF-6, and during fuel cycle
7, the power-dependent operating limit for the MCPR will be correct.
TEXT PAGE 4 OF 5
ADDITIONAL INFORMATION
No equipment or components failed during or as a result of this event.
CPS has not issued LERs for similar events in recent history; however, GE
Nuclear Energy has reported similar fuel design errors regarding the
Safety Limit MCPR under the provisions Of 10CFR, Part 21.
For further information regarding this event, contact R. W. Chickering,
Engineering Projects, at (217) 935-8881, extension 3334.
10CFR, PART 21 REPORT 21-97-003
While performing an approval review of GE Nuclear Energy documentation
for the fuel cycle 7 Supplemental Reload Licensing Report and core
performance monitoring computer data bank, Illinois Power (IP) determined
that there was some potential during the past 5 fuel cycles to exceed the
Safety Limit MCPR if a PRDF event had occurred. Review of fuel cycle 6
actual operating data identified that CPS had operated in an unanalyzed
condition during fuel cycle 6 and may have done so in fuel cycles 2, 3,
4, and 5 as well. The cause of this condition is an error in the MEOD
analysis performed by GE Nuclear Energy, the nuclear fuel supplier for
CPS.
IP has evaluated 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.
(i) Wilfred Connell, Vice President of Illinois Power Company,
Clinton Power Station, Post Office Box 678, Clinton, Illinois,
61727, is informing the Commission by means of this report.
(ii) The basic component involved in this report is the reload core.
The core was to be designed to operate with adequate margins
during all conditions as described by the CPS Updated Safety
Analysis Report (USAR). This includes the conditions of the
MEOD. one of the conditions the core design Must meet is
operating limits for MCPR that provide margin to the Safety
Limit MCPR for all Anticipated Operational occurrences between
40 and 80 percent of rated thermal power. The PRDF event is a
limiting transient for a region of the MEOD.
(iii) The reload core designs with the MEOD for fuel cycles 2, 3, 4,
5, and 6 were supplied by GE Nuclear Energy.
TEXT PAGE 5 OF 5
(iv) As discussed in the DESCRIPTION OF EVENT portion of this
document, the nature of the defect is the failure of the fuel
supplier to include the PRDF event for 40 to 80 percent of
rated thermal power in the MEOD analysis. If the PRDF event
had occurred during any of fuel cycles 2, 3, 4, 5, or 6, while
operating near the non-conservative power-dependent operating
limit for the MCPR, the potential would have existed to exceed
the Technical Specification Safety Limit MCPR on fuel bundles
that were at or near the power-dependent operating limit for
the MCPR.
(v) GE Nuclear Energy notified CPS about the deficiency in the MEOD
analysis in a letter dated December 22, 1996. The letter
reported that the GE evaluation of reportability under 10CFR,
Part 21, concluded that the condition was not reportable. On
January 3, 1997, while comparing fuel cycle 6 actual operating
data with the new limits for fuel cycle 7, IP engineers
identified that the plant had operated in an unanalyzed
condition during fuel cycle 6 and may have operated in
unanalyzed conditions during fuel cycles 2, 3, 4, and 5 as
well. This event was determined to be potentially reportable
under the provisions of 10CFR, Part 21 at that time.
(vi) The GE Nuclear Energy letter reports that the deficient reload
core analysis applies to Clinton Power Station and other BWR-6
reactor types.
(vii) The corrective action that IP is taking for this event is
discussed in the CORRECTIVE ACTION section of this document.
(viii) IP expects that GE Nuclear Energy will notify or has notified
affected reactor owners and has no additional advice to offer.
ATTACHMENT TO 9702030199 PAGE 1 OF 1
Illinois Power Company
Clinton Power Station
P.O. Box 678
Clinton, IL 61727
Tel 217-935-5623
Fax 217-935-4632
WC-075-97
January 28, 1997 Wilfred Connell
Vice President
ILLINOIS
POWER U-602685
2C.220
Docket No. 50-461 10CFR50.73
10CFR21.21
Document Control Desk
Nuclear Regulatory Commission
Washington, D.C. 20555
Subject: Clinton Power Station - Unit 1
Licensee Event Report No. 97-001-00
and 10CFR, Part 21 Report.No. 21-97-003
Dear Madam or Sir:
Enclosed is Licensee Event Report (LER) No. 97-001-00 and 10CFR,
Part 21 Report No. 21-97-003: Failure of Nuclear Fuel Supplier to Analyze
Turbine Pressure Regulator Downscale Failure Event in the Off-Rated
Condition Results in Operation in an Unanalyzed Condition. This report
is being submitted in accordance with the requirements of 10CFR50.73 and
10CFR21.21.
Sincerely yours,
Wilfred Connell
Vice President
RSF/krk
Enclosure
cc: NRC Clinton Licensing Project Manager
NRC Resident Office, V-690
Regional Administrator, Region III, USNRC
Illinois Department of Nuclear Safety
INPO Records Center
GE Nuclear Energy
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