Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
ACCESSION #: 9612270138
LICENSEE EVENT REPORT (LER)
FACILITY NAME: Clinton Power Station PAGE: 1 OF 5
DOCKET NUMBER: 05000461
TITLE: Incorrect Torque Value for Control Rod Drive Hydraulic
Control Units Was Specified by Supplier Causing
Inoperability of Control Rod Drive System
EVENT DATE: 10/14/81 LER #: 96-018-00 REPORT DATE: 12/17/96
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)
50.73(a)(2)(v) &
Other
LICENSEE CONTACT FOR THIS LER:
NAME: Nguyen Le, Engineer TELEPHONE: (217) 935-8881,
Extension 4066
COMPONENT FAILURE DESCRIPTION:
CAUSE: SYSTEM: COMPONENT: MANUFACTURER:
REPORTABLE NPRDS:
SUPPLEMENTAL REPORT EXPECTED: NO
ABSTRACT:
On November 19, 1996, the plant was in Mode 5 (Refueling), engineering
determined that the wrong torque value was used on the 3/8 inch bolts
that connect the 145 Control Rod Drive (CRD) Hydraulic Control Units
(HCU) to structural supports in the containment building. This torque
value exceeded the minimum yield strength for these bolts causing the CRD
HCUs to not Meet seismic qualifications, and therefore, they were not
operable. The CRD HCU operation would only be affected if a seismic
event occurred during plant operation. This condition has existed since
initial licensing of the plant. The cause of this event is a failure of
Sargent and Lundy Engineering to provide the proper torque values due to
a lack of attention to detail and a questioning attitude on the part of
their engineers. Also, Illinois Power and General Electric failed to
recognize this error during their review of this information. Corrective
action for this event is to replace all of the 3/8 inch hold down bolts
on the CRD HCUs and torque them to the proper value. This event is also
reportable under 10CFR, Part 21.
END OF ABSTRACT
TEXT PAGE 2 OF 5
DESCRIPTION OF EVENT
On November 19, 1996, the plant was in mode 3 (Refueling) with the
reactor pressure vessel [RCT] head removed and the pool over the reactor
pressure vessel being maintained at greater than 23 feet above the
reactor pressure vessel flange, reactor coolant temperature was being
maintained in a range from 80 to 90 degrees Fahrenheit. Utility
mechanical maintenance personnel were performing maintenance on the
control rod drive (AA) (CRD) hydraulic control units [HCU] (HCU) using
Clinton Power Station procedure 8221.01, "CRD Hydraulic control Unit
Maintenance." Part of the maintenance work was to retorque the hold down
bolts for the CRD HCUs. These hold down bolts attach the General
Electric (GE) supplied CRD HCUs to structural steel supports designed by
Sargent and Lundy Engineering, the architect engineer for the
construction of the power station. During performance of section 8.15 of
the procedure maintenance personnel questioned the use of the same torque
value for both the 1/2 inch and 3/8 inch diameter bolts. Engineering
determined that the torque value that was given in the procedure was
correct for the 1/2 inch bolts but the torque value for the 3/8 inch bolt
exceeded the bolts minimum yield strength and therefore, was
unacceptable.
Engineering reviewed the records for the original installation of the
bolts and determined that when the 3/8 inch bolts were originally
installed the incorrect torque value, which exceeded the bolts minimum
yield strength, was used to install the CRD HCUs. Engineering concluded
that because the bolts minimum yield strength had been exceeded for the
bolts when the CRD HCUs were initially installed, that all 145 CRD HCUs
were Inoperable. This determination was made because the improper torque
value used for torquing the 318 inch bolts would cause the bolts to be
overstressed and therefore, not able to fulfill the seismic qualification
requirements' for restraining the CRD HCUs during a design basis
earthquake. There are seven 3/8 inch bolts in each of the 145 CRD HCUs
for a total of 1015 total bolts that are improperly torqued.
The history of the determination of the torque values for the 3/8 inch
bolts was reviewed by engineering personnel. The results of that review
showed that on October 5, 1981, Field change Request (FCR) 11732 was
submitted to request torque values for the 3/8 inch and 1/2 Inch bolts on
the CRD HCUs. The request for a torque value for the 3/8 inch bolts was
reviewed, and dispositioned by Sargent and Lundy Engineering based on
GE's recommendation for 1/2 inch bolts used on the CRD HCUs. Illinois
Power (IP) concurred with this disposition. on October 14, 1981, FCR
11732 was completed and Sargent and Lundy Engineering concluded that the
same torque value should be used for the 3/8 inch bolts and the 1/2 inch
bolts because they were made of the same material. This assumption was
incorrect since a different torque value should have been specified
because the bolts were not the same diameter. On November 4, 1981, a
request was made, using Nonconformance Report (NCR) 5720, to allow a
lower torque value to be used for 3/8 inch bolts that were not readily
accessible to be retorqued to the higher torque value specified in FCR
11732. The request to use a lower torque value was approved by IP and
concurred with by GE. However, this lower torque value specified for the
inaccessible bolts was still higher than the minimum yield strength for
the 3/8 inch bolts. Also, GE did not recognize that the 3/8 inch CRD HCU
hold down bolts were not within the Scope of GE design and therefore,
Sargent and Lundy Engineering was responsible for providing the input.
TEXT PAGE 3 OF 5
On September 1, 1982, FCR 17063 was dispositioned by IP with GE
concurrence to allow a range of the higher and lower values specified in
FCR 11732 and NCR 5720 to alleviate any confusion caused by specifying
two different torque values for the bolts on FCR 11732 and NCR 5720.
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 THE EVENT
The cause of this event is attributed to a lack of a questioning attitude
and attention to tail by Sargent and Lundy when determining the proper
bolt torque for the HCU hold down its. Also, IP and GE failed to
recognize this error during their review of this information. On three
separate occasions either Sargent and Lundy or GE reviewed the torque
values for the 3/8 inch CRD HCU hold down bolts and the error contained
in the imposition of the first document requesting proper torque values
was not corrected during subsequent reviews.
CORRECTIVE ACTION
All of the 3/8 inch CRD HCU hold down bolts have been replaced with new
bolts and retorqued o the proper value. Also, a sample of the 3/8 inch
bolts that were removed from the CRD s will be tested to determine
whether or not they would have boon able to withstand a design basis
earthquake when installed on the CRD HCUs. The results of these teat
results ill be used to determine past operability of the CRD HCUs.
ANALYSIS OF EVENT
This event is reportable under the provisions of 10CFR50.73(a)(2)(ii) and
10CFR50.73(a)(2)(v). This event is reportable under 10CFR50.73(a)(2)(U)
because the inoperability of the CRD HCUs since initial plant licensing
places the plant in a condition here it is degraded. This event is
reportable under 10CFR50.73(a)(2)(v) because the inoperabIlity of the CRD
HCUs places the plant in a condition that alone could have prevented the
CRD system from fulfilling its safety function to shutdown the reactor
and maintain it in a safe shutdown condition.
If the results of the toots on the CRD HCU hold down bolts determine that
they would have an unable to withstand a design basis earthquake, the
safety consequences and implications of this event would be considered to
have low safety significance. Although he ability of the control rod
drives to safely shutdown the reactor may have been affected ring a
design basis earthquake, the reactor could have been shutdown using the
standby liquid control system (BR] from rated power at any time during
core life as stated in section 9.3.5.1 of the updated Safety Analysis
Report.
TEXT PAGE 4 OF 5
Therefore, the function of the control rod drive system to shutdown the
reactor would have been accomplished through the use of the standby
liquid control system when it was operable. During periods when both
trains of the standby liquid control system were unavailable and a design
basis earthquake occurred and the CRD HCUs failed to operate this
condition would have safety significance. Because the unavailability
time for the standby liquid control system is low, particularly since
only one of the two trains of the system would be required to function to
shutdown the reactor, and the probability of a design basis earthquake
occurring during that unavailability time is low, the overall safety
significance for this event is low.
The control rod drive system may have been inoperable since initial plant
licensing.
ADDITIONAL INFORMATION
Clinton Power Station has not reported other failures by outside
engineering groups to provide correct information which affected the
operability of systems in recent history.
For further information on this event contact Nguyen Le, Engineer, at
(217) 935-8881 at extension 4066.
10CFR21 Report No. 21-96-032: Incorrect Bolt Torque Specified By Sargent
and Lundy For CRD HCUs
On November 19, 1996, IP identified that the torque value specified by U
for the 3/8 inc hold down bolts for the CRD HCUs exceeded the minimum
yield strength of the bolt material causing the CRD HCUs to be inoperable
because the torque value did not meet seismic qualification requirements.
The concern was determined to be potentially reportable under the
provisions of 10CFR21. Based on an evaluation of this matter, IP in
providing the following information in accordance with the requirements
of 10CFR, Part 21.21(b)(3).
(i) Wilfred Connell, Vice President of Illinois Power Company,
Clinton Power Station, P. O. Box 678, Clinton, Illinois, 61727,
is informing the Commission by means of of this report.
(ii) The basic component involved are the torque requirements for
the 3/8 inch hold dow bolts for the CRD HCUs.
(iii) Sargent and Lundy Engineering provided the incorrect torque
specification for the 3/8 inch hold down bolts used in the CRD
HCUs.
(iv) The torque value specified exceeded the 3/8 inch hold down
bolts minimum yield strength and made the CRD HCUs inoperable.
Because the hold down bolts were overstressed the bolts could
potentially fail in a design basis earthquake causing the
control rods to fail to Insert Into the reactor core when
required.
TEXT PAGE 5 OF 5
(v) IP identified the condition as a potential defect on November
20, 1996.
(vi) This condition involves 7 hold down bolts on each of the 145
CRD HCUs for a total of 1015 bolts installed at Clinton Power
Station.
(vii) Corrective actions for this matter are discussed in the
CORRECTIVE ACTION section of this report.
(viii) IP does not have any advice to other purchasers or licensees
related to this report.
ATTACHMENT TO 9612270138 PAGE 1 OF 2
POWER REACTOR EVENT: 31477
FACILITY: CLINTON REGION: 3 NOTIFICATION DATE: 12/18/96
UNIT: [1] [ ] [ ] STATE: IL NOTIFICATION TIME: 15:15 [ET]
RX TYPE: [1] GE-6 EVENT DATE: 12/17/96
EVENT TIME: 14:30 [CST]
NRC NOTIFIED BY: MATT STOOKEY LAST UPDATE DATE: 12/18/96
HQ OPS OFFICER: DICK JOLLIFFE NOTIFICATIONS
EMERGENCY CLASS: NOT APPLICABLE
10 CFR SECTION:
CCCC 21.21 UNSPECIFIED PARAGRAPH VERN HODGE NRR
UNIT SCRAM CODE RX CRIT INIT PWR INIT RX MODE CURR PWR CURR RX
MODE
1 N N 0 REFUELING 0 REFUELING
EVENT TEXT
-INOP CRD SYSTEM DUE TO INCORRECT TORQUE VALUE OF CRD HCU HOLD
DOWN
BOLTS-
ON 11/19/96, WITH THE PLANT IN A REFUELING OUTAGE, THE LICENSEE
IDENTIFIED THAT THE TORQUE VALUES SPECIFIED BY GENERAL ELECTRIC FOR
THE
3/8 INCH HOLD DOWN BOLTS FOR THE CONTROL ROD DRIVE (CRD) HYDRAULIC
CONTROL UNITS (HCUs) EXCEEDED THE MINIMUM YIELD STRENGTH OF THE
BOLT
MATERIAL. THIS CAUSED THE CRD HCUs TO BE INOPERABLE BECAUSE THE
TORQUE
VALUE DID NOT MEET SEISMIC QUALIFICATION REQUIREMENTS FOR
RESTRAINING THE
THE CRD HCUs DURING A DESIGN BASIS EARTHQUAKE. THE CRD HCU
OPERATION
WOULD ONLY BE AFFECTED IF A SEISMIC EVENT WERE TO OCCUR DURING
PLANT
OPERATION.
THERE ARE SEVEN 3/8 INCH BOLTS IN EACH OF THE 145 CRD HCUs FOR A TOTAL
OF
1015 BOLTS. THESE BOLTS ATTACH THE GENERAL ELECTRIC SUPPLIED CRD
HCUs TO
STRUCTURAL STEEL SUPPORTS IN THE CONTAINMENT BUILDING WHICH WERE
DESIGNED
BY SARGENT AND LUNDY ENGINEERING, THE ARCHITECT ENGINEER FOR THE
CONSTRUCTION OF THE POWER STATION. THIS CONDITION HAS EXISTED SINCE
INITIAL LICENSING OF THE PLANT IN 1987.
ALL OF THE 3/8 INCH CRD HCU HOLD DOWN BOLTS HAVE BEEN REPLACED WITH
NEW
BOLTS AND RETORQUED TO THE PROPER VALUE. ALSO, A SAMPLE OF THE 3/8
INCH
BOLTS THAT WERE REMOVED FROM THE CRD HCUs WILL BE TESTED TO
DETERMINE
WHETHER OR NOT THEY WOULD HAVE BEEN ABLE TO WITHSTAND A DESIGN
BASIS
EARTHQUAKE WHILE INSTALLED ON THE CRD HCUs.
THIS 10CFR21 REPORT ONLY APPLIES TO THE CLINTON POWER STATION.
THE LICENSEE ALSO HAS SUBMITTED LER #96-018 ON THIS EVENT TO THE NRC
AND
HAS INFORMED THE NRC RESIDENT INSPECTOR.
ATTACHMENT TO 9612270138 PAGE 2 OF 2
Illinois Power Company
Clinton Power Station
P. O. Box 678
Clinton, IL 61727
Tel 217 935-5623
Fax 217 935-4632
ILLINOIS
POWER
U-602673
2C.220
4F.140
WC-377-96
December 17, 1996
10CFR50.73
Docket No. 50-461 10CFR21
Document Control Desk
Nuclear Regulatory Commission
Washington, D.C. 20555
Subject: Clinton Power Station - Unit 1
Licensee Event Report No. 96-018-00
Dear Madam or Sir:
Enclosed is Licensee Event Report No. 96-018-00: Incorrect Torque
Value for Control Rod Drive Hydraulic Control Units Was Specified by
Supplier Causing Inoperability of the Control Rod Drive System. This
report is being submitted in accordance with the requirements of
10CFR50.73 and 10CFR21.
Sincerely yours,
Wilfred Connell
Vice President
MRS/csm
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
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