05000285/LER-1993-001, :on 930108,discovered That Bast Level Surveillance Not Performed Properly.Caused by Inadequate Surveillance Test to Monitor Bast Levels.Mod Initiated to Provide Individual Annunciator Windows
:on 930108,discovered That Bast Level Surveillance Not Performed Properly.Caused by Inadequate Surveillance Test to Monitor Bast Levels.Mod Initiated to Provide Individual Annunciator Windows
05000285/LER-1999-002, :on 980910,inadvertent Ventilation Isolation Actuation Signal Occurred While Maint Was Being Performed. Caused by Switch Failure.Key Switch for RM-062 Has Been Replaced.With
05000285/LER-1999-002, :on 980910,inadvertent Ventilation Isolation Actuation Signal Occurred While Maint Was Being Performed. Caused by Switch Failure.Key Switch for RM-062 Has Been Replaced.With
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LIC-99-0084, Monthly Operating Rept for Aug 1999 for Fort Calhoun Station.With
ML20211J932
LIC-99-0096, Monthly Operating Rept for Sept 1999 for Fcs,Unit 1.With
J. L. Milhoan, NRC Regional Administrator, Region IV S. D. Bloom, NRC Project Manager R. P. Mullikin, NRC Senior Resident Inspector INP0 Records Center I
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LER NUMBER (0)
REPORT NUMDER (r) 01HER FACillilES INVOLVED (8)
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ABSTRACT (umtt to 1400 spaces. I.e., approximately 15 single spaced typewritten lines) (15) on "B" Boric Acid Storage Tank (BAST)pervisor was reviewing maintenance to be performed On January 8, 1993, the Operations Su levelindication(floatswitchLAS-253)withthe Reactor Engineer. A potential 3roblem was discussed regarding the surveillance requirements for a channel checc. On review, it was identified that the BAST level surveillance was not being properly performed in that the existing surveillance test involved comparing two level indications (local and remote) from the same sensor (level bubbler), rather than comparing two independent sensors as required by Technical Specification (TS) 3.1, Table 3-2, Item IS.a.
The root cause of the event was determined to be an inadecuate surveillance test to monitor the BAST levels. A review of plant records showec that the original 1973 surveillance test incorrectly identified the local and remote indications from the level bubblers as meeting the intent of comparing independent indications.
Tem)orary " sight glasses" have been installed to provide independent level indication at eati tank.
Additional actions will include a modification to control room alarm indication for low BAST level to provide individual annunciator windows for float switches t.AS-260 and t.AS-253 for coigarison to level bubbler indications, we tem m paa,
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.mm % en BACKGROUND The Fort Calhoun Station (FCS) Chemical and Volume Control System (CVCS) includes two concentrated Boric Acid Storage Tanks (BASTS)._ The BAST 1cvels are monitored to ensure that a minimum Technical Specification required volume of boric acid is maintained in theavailabletank(s)toachieveacoldshutdownconditionatanytimeduringcorelife.
Permanent level indication on the BASTS is provided by two independent methods. The first is a level bubbler and transmitter that )rovides both a local indication and a remote (control room) level indication for eaci BAST. The local indicator provides a high level alarm in the control room at 94.2% level. The remote indicator provides alarms in the control room for low level at 80.0% level and low low level at 6.0% level.
L1T/LIA-261 provides indication for the "A" BAST and LIT /LIA-254 provides indication-for the "B" BAST.
The second level indication is an independent float switch for cach BAST that is activated at a level of 82.4%. Annunciator A2, Window C-4U in the control room alarms when a coincident low level is indicated by the float switches on both' BASTS. The float-switches for the "A" and "B" BASTS are LAS-260 and LAS-253 respectively.
FCSTechnicalSpecification(TS)3.1, Table 3-2,"MinimumfrequenciesforChecks, Calibrations and Testing:of Engineered Safety Features,-Instrumentation and Controls",
item 15.a. requires a daily check of " Boric Acid Tank Level".
The surveillance method-
- specified is to " Compare two independent sensors." This check is addressed by FCS SurveillanceTest(ST)OP-ST-SHIFT-0001,"OperationsTechnicalSpecificationRequired Shift Surveillance".
EVENT DESCRIPTION
On January 7, 1993, while operating in Mode 1 at 100% power, the Operations-Supervisor
'was involved in discussions to determine if on-line maintenance could be performed on the "B" BAST level switch (LAS-253), or if the maintenance should be scheduled during an-
.. outage. The maintenance was required in order to correct a " false" low level signal
--being provided by LAS-253 to the coincident alarm circuitry.
The' TS requirements for BAST level indications were reviewed by the-Operations l Supervisor and a Shift Supervisor.
The level indication at that time concisted of one channel, LIT /LIA-254 (local / remote), on_"B" BAST and two channels, LIT /LIA-261 (local / remote)andLAS-260,on"A" BAST.
This was considered an allowable configuration,-however, it was noted that the loss of one level channel on "A" BAST would put the plant in: a 24-hour Limiting Condition for Operation (LC0).
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.ac, we emn On January 8, 1993, the Operations Supervisor reviewed the issue and its implications with the Reactor Engineer.
The Reactor Engineer expressed concern that a problem could exist with the Surveillance Requirements for a channel check.
On review it was identified that the BAST level surveillance specified that LIT-254 be compared to-LIA-254, and that LIT-261 be compared to LIA-261.
The surveillance method specified in TS 3.1, Table 3-2, Item 15.a is to " Compare two independent sensors".
The ST, therefore,didnotcompare"lndependentsensors",butrathercomparedtwodifferent indicators from the same sensor.
On January 9, 1993, administrative controls were established to maintain "A" BAST at a minimum icvel above the alarm setpoint of LAS-260.
This would allow the level surveillance to be performed on "A" by comparing the indication from LIT /LIA-261 to the.
. alarm condition on Window C-4U, which, due to the continuous low level signal from LAS-253, would now annunciate on a low level-signal from LAS-260.
On January 12, 1993 a temporary modification was installed that would allow monitoring ofbothBASTs'levelslocally. This: modification installed a tem orary " sight glass" on each BAST.- The Auxiliary Building Operator began logging the "si ht glass" level indication every two hours in addition to the local level indicat on.
Surveillance Test OP-ST-SHIFT-000h was then revised to address comparing " sight glass" and bubbler readings.
.This event resulted in the identification of a failure to meet the IS 3.1 requirement
.for a daily comparison of independent sensors of boric acid tank level.
This report is beingsubmittedpursuantto10CFR50.73(a)(2)(1)(B).
SAFETY ASSESSM NT The event did not impact nuclear safety. BAST levels are logged every two hours-and-unexplained trends in level would have been identified by'the. operators..
Similar logs have been taken since before 1977.). An increasing level would provide ind cation ofsa.
1 plugged. bubbler or unexplained BAST in-leakage.
Corrective action would.then be taken to identify and correct the problem.. Historically, the LAS float switches are generally =
a highly reliable method for monitoring a minimum tank level. /. condition resulting in an actual low level, below that needed to reach cold shutdown, would-have been identified by the available instrumentation, a
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The root cause of the event has been determined to be an inadequate surveillance test to monitor the BAST levels. A review of plant records showed that the original 1973 surveillance test incorrectly identified the local and remote indications from the level bubblers (originally designated LIA-254 X & Y and LIA-261 X & Y) as meeting the intent of comparing independent indications.
A 3rinciple contributing factor in this event was found to be that incomplete action was tacen in responding to one corrective action identified in LER 91-008. The LER indicated that each surveillance procedure would be reviewed to ensure they met the intent of TS surveillance requirements.
Individuals were assigned-to review each i
surveillance procedure except OP-ST-SHIFT-0001, which, because of its multiple parts, was to be divided among several reviewers. However, due to an administrative oversight, the intended multi-reviewer review of OP-ST-SHIFT-0001 was not assigned, and therefore was not completed.
CORRECTIVE ACTIONS
The following corrective actions-have been or will be completed:
1.
Temporary Modification 93-005 installed a temporary " sight glass" level indication on each BAST, and OP-ST-SHIFT-0001 was revised to address comparing.
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" sight glass" and bubbler readings, in order to meet TS 3.1, Table 3-2, Item 15.a.
2.
Surveillance Test OP-ST-SHIFT-0001 has been reviewed and determined to adequately meet _the intent of associated TS surveillance requirements.
3.
Modification MR-FC-93-001 has been initiated to split the current single:
annunciator associated with LAS-260 and LAS-253. The modification will provide each BAST with an individual annunciator window.. Necessary procedure changes, including a-change to OP-ST-SHIFT-0001 to specify LAS-260 and LAS-253 as the independent sensors for comparison to LIT /LIA-261 and LIT /LIA-254-respectively, will be completed when the modification is accepted for operation.
This modification will be installed at the first outage of sufficient duration to support the work, but not later than the~1993 Refueling Outage.
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PREVIOUS SIMILAR EVENTS
.LERs91-008, 91-001,89-002, 88-008,87-037 and 87-010 discuss other events involving surveillance tests that did not meet TS surveillance requirements.
on 930108,discovered That Bast Level Surveillance Not Performed Properly.Caused by Inadequate Surveillance Test to Monitor Bast Levels.Mod Initiated to Provide Individual Annunciator Windows
on 930122,determined That Current SG LP Signal Block Reset Values Greater than Allowed Ts.Caused by Improper Design.Test Procedures Will Be Revised by 930917 to Specify Desired Value for Block Function
on 930126,discovered That IST Requirement for Raw Water Pump Not Satisfied.Caused by Inadequate Administrative Controls.Station Engineering Instruction on Surveillance Testing Changed
on 930301,confirmed That Channel D Axial Shape Index (Asi) Being Calculated in Reverse Since 921031-930301 Due to Drawing Discrepancies Associated W/Control Channel B. Temporary Mod 92-078 & Standing Order 0-25 Revised
on 930422,determined That Incident Reportable in That SIRWT Recirculation Piping Associated w/MR-FC-83-046 Used Between Dec 1986 & 1992 Refueling Outage in Unacceptable Configuration
on 930118,Halon Fire Suppression Sys for Switchgear Rooms Disabled to Allow Repair/Replacement of Halon Sys Piping.On 930427,individual Responsible for Fire Watch Not Present.Individual Relieved of Responsibilities
on 930430,unplanned Emergency Generator Start & RT Signal Occurred.Caused by Inadequate Attention to Detail,Labeling of Fuse Drawers,Caution Signs & Training. Labeling & Caution Signs Upgraded
on 930520,determined That TS SR Not Satisfied for Stack Flow Indicator,Per Amend 137 Issued on 910307. Caused by Lack of Attention to Detail.Calibr & Functional Test Procedures Developed
Retracts LER 93-009 Re Automatic Start of Both Backup Charging Pumps Due to Spurious Signal & Subsequent Automatic Isolation of Letdown.Event Did Not Involve Train Level ESF Actuation & Not Reportable
on 930611,1 of 14 Halon Cylinders Did Not Meet Min Pressure Acceptance Criteria Listed in Semiannual Switchgear Rooms Surveillance Test.Caused by Failure of Test to Include Necessary Steps.Cylinder Recharged
on 930624,experienced Reactor Trip Due to Loss of Load.Caused by Lack of Proper Job Planning,Lack of Formal Decision Making Process & Incomplete Communications.Training Will Be Provided to Operations Personnel
on 930923,identified Condition Involving Five MOVs Having Cables That Were Inadequately Sized Due to Lack of Attention to Detail in Design Package Preparation for 1990 Mod.Thermal Overloads Enabled
on 931002,discovered That as-found Lift Setting Pressure of Pressurizer Safety Valve (Psv) RC-141 Outside Specified Lift Setting Acceptance Criterion.Caused by Normal Setpoint Drift.Psv RC-141 Adjusted
on 931113,CEA Withdrew from Reactor Core & Rod 31 Became Fully Withdrawn.Caused by Lack of Ground Detection Sys for Associated Power Supplies.Ground Detection for CRD Power Supply Installed
on 931116,time Delay Relays for Offsite Power Low Signal (Opls) Found Out of Tolerence Due to Inadequate Technical Review of Calibr Procedures for Opls Circuitry. Opls Calibr Procedures Revised
on 931206,reactor Trip Occurred Due to Turbine Trip on Low Hydraulic Fluid Pressure.Caused by Inadequate Design of ECN 93-162.Configuration of EHC Sys Tubing Corrected
on 931229,toxic Gas Monitor (Tgm) Rendered Inoperable When Tgm Ran Out of Chemically Impregnated Paper Tape Due to Failure to Complete Procedural Requirements. Briefings Held W/Operating Crews