05000382/LER-1990-014-01, :on 900922,control Room Outside Air Isolation Due to Procedural Inadequacy
| ML20058A842 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 10/22/1990 |
| From: | Mcgaha J, Tanya Smith ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-90-014-01, LER-90-14-1, W3A90-0429, W3A90-429, NUDOCS 9010290235 | |
| Download: ML20058A842 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation |
| 3821990014R01 - NRC Website | |
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4 W3A90-0429 A4.05 QA October 22, 1990 U.S. Nuclear Regulatory Commission ATTENTION:
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Subject:
Waterford 3 SES i
Docket No. 50-?0e License No. ifPF-38 Reportina of Lice'nsee Event Report Gentlemen Attached is Licensee Event Report Number LER-90-014-00 for Waterford Steam Electric Station Unit 3.
This Licensee Event 4
Report is submitted pursuant to 10CFR50.73 (a) (2) (iv).
Very truly yours, 7
J.R. McGaha General Manager - Plant Operations JRM/DDW/rk Attachment cc:
Messrs. R.D. Martin J.T. Wheelock - INPO Records Center E.L.
Blake W.M. Stevenson l
D.L. Wigginton NRC Resident Inspectors Office l
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l On September 22, 1990, Waterford Steam Electric Station Unit 3 experienced an l
l unplanned actuation of the Engineered Safety Feature (ESF) portion of the l
Control Room Ventilation System. The actuation was initiated by a high alarm from one of the four normal Control Room Outside Air Intake (CROAI) radiation monitors, resulting in a control room isolation and an automatic start of the associated Control Room Emergency Filtration Unit. All other CROAI radiation monitors were indicating normal radiation levels and air sampics taken in the area of the alarming radiation monitor showed no detectable activity. This event is reportable as an unplanned ESF actuation.
l The root cause of this actuation was an inadequate procedure which caused the l
CROA1 high alarm setpoint to be inadvertently set at a low value. Normal l
background radiation fluctuation exceeded the alarm setpoint and caused this l
actuation. The Control Room Emergency Filtration System functioned as designed and there was no actual release of radioactive material; therefore, this event did not result in an increased risk to the health ar.d safety of the public or plant personnel. The alarm setpoint has been corrected and the alarm setpoint procedure will be revised.
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"'1*32 Electric Station Unit 3 0 l6 l0 l0 l0 l3 l8 l2 9l0 0l1[4 0l0 0 l2 0F 0l3 ff ET (3 more apoco e reewed. asse esseenW NAC perm J.hCat HM At 0155 hours0.00179 days <br />0.0431 hours <br />2.562831e-4 weeks <br />5.89775e-5 months <br /> on September 22, 1990, Waterford Steam Electric Station Unit 3 was operating at 100% power when an unplanned actuation of the Engineered Safety Feature (EST) portion of the Control Room Ventilation System (EIIS Identifier VI) occurred. The actuation was initiated by a high alarm from
. 'M-IRE-0200.lS one of the four normal Control Room Outside Air Intake (CROAI) radiation monitors (EIIS Identifier IL-MON). This alarm caused an automatic control room isolation and a start of the 'A' Control Room Emergency Filtration Unit (EIIS Identifier VI-AllU). The high alarm cleared approximately two minutes later and air sampics taken in the vicinity of the radiation monitor indicated no detectable activity. All other Ch0A1 radiation monitors were indicating normal radiation levels. This event is reportable under 10CFR50.73(a)(2)(iv) as an unplanned operation of an ESF, since the Control Room Emergency Filtration Units are considered part of the ESF System.
The CROAI high alarm setpoint was set much lower than required, due to an inadequate procedure which did not provide guidance regarding background count subtraction. The CROAI high alarm setpoint, as established by Technical Specification 3.3.3.3, is less than 2.0 timen background.
"The Calculation and Adjustment of Radiation Monitoring Serpoints procedure," Hp-001-235, specifies a more conservative setpoint of 1.8 times background. The CROAI system has a software feature which permits the removal of background counts from the detector output.
Since the high alam setpcint is background dependent, any background count subtraction will effect the high alarm setpoint.
l A background count subtraction of 156 counts lowered the CROAI detector output.
The average of the detector output is used to determine the high alarm setpoint.
l Consequently, the alarm setpoint which should have heen set at approximately 1.0E-6 microcuries per cubic centimeter was set at 6.3E-8 microcuries per cubic centimeter. The three other CROAI radiation monitors, ARM-IRE-0200.2S, ARM-IRE-0200.5S and ARM-IRE-0200.6S, had background subtract values set lower than the ARM-IRE-0200.lS value.
NRC Form 3 A (649)
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~ w,- nn The root cause of the alarm actuation on CROAI radiation monitor ARM-IRE-0200.lS was inadequate procedures which allowed the alarm setpoint to be reduced to a level so low that a background fluctuation induced actuation could occur. The background count subtract values on all four CROAI radiation monitors have been set to zero so that no background counts are removed. The high alarm setpoints are now based on the entire measured background as intended. The lip-001-235 procedure and the CROA1 monitor calibration procedure, M1-003-374, sill be revised by January 1, 1991 to ensure background count subtraction values equal zero. Additionally, changing the alarm setpoints to a set value, which is not dependent on background radiation levels, is being investigated. This investigation will be completed by September 1, 1991.
The Control Room Emergency Filtration System functioned as designed during'the event. Air samples taken in the vicinity of the alarming radiation monitor revealed no detectable activity, indicating that there was no actual release of radioactive material; therefore, this event did not result in an increased risk to the health and safety of the public or plant personnel.
SIMILAR EVENTS
Spurious Control Room Emergency Filtration Unit Actuations were reported in LER 90-11,88-003, 87-022,87-015, 86-029,86-022, 86-020,86-003, 85-048,85-045, 85-043,85-039, 85-036,85-030, 85-005,85-002 and 84-001. Design changes to prevent spurious actuations caused by electrical spiking and CROA1 aluminum beta window perforations have been implemented.
PLANT CONTACT T.ll. Smith, Plant Engineering Superintendent, (504)-464-3127 NRC Penn astA (6491 A