United States Nuclear Regulatory Commission - Protecting People and the Environment


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



*** END OF DOCUMENT ***





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