ML19332C178

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LER 89-053-00:on 891022,control Room Personnel Manually Initiated Ventilation Sys Chlorine Isolation,Esf.Caused by High Vinyl Chloride Concentration in Outside Air Intake Plenum.Special Event Procedure implemented.W/891117 Ltr
ML19332C178
Person / Time
Site: Limerick Constellation icon.png
Issue date: 11/17/1989
From: Endriss C, Mccormick M
PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-053, LER-89-53, NUDOCS 8911220397
Download: ML19332C178 (6)
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! 10 CFR 50.73 i i

t PHILADELPHIA ELECTRIC COMPANY  :

LINCRICK GENER ATING ST ATION P. O. BOX A SAN ATOG A, PElih tY LV ANI A 19464 ,

I (116) 3271400 amt. 2000

m. November 17, 1989 ,

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g 50-353 License Nos. NPF-39 NPF-85  ;

U.S. Nuclear Regulatory Commission Attn Document Control Desk Washington, DC 20555

SUBJECT:

Licensee Event Report Limeri Q Generating Station - Units 1 and 2 ,

This LER concerns the n.anual isolation of Main Control Room

  • Ventilation System and the acteation of the Control Room Emerger.cy Presh Air Supply (CREFAS) system, Engineered Safety Features, due to ,

a high toxic chemical concentration signal.

Reference:

Docket Nos. 50-357; 50-353  ;

Report Number: 1-89-053 i

. Revision Number: 00 t Event Date: October 22, 1989 Report'Date: !bvmber 17, 1989 Facility: Limerick Generating Station P.O. Box A, Sanatoga, PA 19464 This LER is being submitted pursuant to the requirements of 10 CFR 50.73(a)(2)(iv).

8 Very truly yours, JKPich

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cc: W. T. Russell, Administrator, Region I, USNRC T. J. Kenny, USNRC Senior Resident Inspector, LGS I

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On October 22, 1989, Main Control Room (MCR) personnel manually initiated a MCR ventilation system chlorine isolation, an Engineered Safety Feature (ESP), as a result of a high vinyl chloride concentration in the MCR outside air intake plenum as detected by the 'A' and 'B' Toxic Gas Analyzers. In conjunction with the MCR ventilation system isolation, the Control Room Emergency Fresh Air Supply System (CREFAS), also an ESF, initiated as designed and provided total recirculation of the MCR air without any intake from the outside atmosphert,. The toxic gas analyzers detected a vinyl chloride concentration of approximately 15 ppm, initiating a high toxic chemical concentration annunciator alarm. MCR personnel immediately implemented Special Event Procedure, SE-2, by donning self-contained breathing apparatus and initiating a manual MCR ventilation system chlorine isolation. The 'A' train of CREFAS I started and the redundant 'B' train of CREFAS remained in standby.

[ All systems operated as designed. The indicated vinyl chloride j concentration was well below the hazardous concentration limit. Air h samples were obtained from the MCR and no vinyl chloride was L detected. This event was caused by the presence of vinyl chloride in the MCR outside air intake plenum from an atmospheric release of the toxic chemical from the Occidental Chemical Corporation (OCC)

I which is' located in the vicinity of Limerick Generating Station.

OCC is taking the necessary measures to prevent recurrence.

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Limerick cenerating Stat. ion, Unit 1 e is to lo lo l3 l5 12 8 l9 0 l Sj 3 0 l0 012 or 0 15 l

. Unit Conditions P'rior to the Event: '

Unit 1 Operating Condition: 1(Power Operation) '

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Unit 2 Operating Condition: 1(Power Operation)

Unit 1 Reactor Power: 99%

Unit 2 Reactor Power: 71%

Description of the Event:

On' October 22, 1989, at 2039 hours0.0236 days <br />0.566 hours <br />0.00337 weeks <br />7.758395e-4 months <br />, Main Control Room (MCR) personnel manually initiated a MCR ventilation system chlorine isolation, an Engineered Safety Feature (ESP), as a result of a high ,

vinyl chloride concentration in the MCR outsido air intake plenum as  ;

detected by the 'A' and 'B' Toxic Gas Analyzers (EIIE VI). In

' conjunction with the mar.ual MCR ventilation system isolation the

& Control Room Emergency fresh Air Supply System (CREFAS), also an '

ESP, initiated as designed and provided total recirculation of the MCR air without any intake from the outside atmosphere.

The toxic gas analyzers function to provide indication of high toxic gas concentrations in the MCR outside air intake plenum. A manual isolation of the MCR ventilation system is required in the event toxic chemicals are detected by these toxic gas analyzers.

The manual MCR isolation occurred following receipt of a MCR high toxic chemical concentration annunciator alarm at 2039 hours0.0236 days <br />0.566 hours <br />0.00337 weeks <br />7.758395e-4 months <br /> on '

October 22, 1989. The 'A' and 'B' MCR Toxic Gas Analyzers indicated the presence of vinyl chloride in concentrations of approximately 15 l

ppm (5 ppm above the alarm setpoint of 10 ppm) in the MCR outside l air intake plenum. Immediately following the receipt of the alarm,

  • MCR' personnel implemented Special Event Procedure SE-2, " Toxic Gas,"  !

and donned self-contained breathing apparatus (SCBA). The operators then manually initiated a MCR ventilatian system chlorine isolation, in accordance with system procedures, as directed by SE-2. The 'A' train of CREFAS started as designed, and the 'B' train of CREFAS remained in the automatic standby mode. Chemistry personnel then g donned SCBA, entered the MCR, and obtained air samples in the MCR.

L The results indicated that there was no vinyl chloride present in L the MCR. MCR pers>nnel then "A" and "B" Toxic Gas Analyzers indicated normal le,vels, verified and that the their SCBA at 2100 removed '

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Li.merick Generating Station, Unit 1 o p;olotol3l5l2 9l9 0l5l3 -- 00 n13 er oI5 m w - . ... - c ~ ,,nn At 0218 hours0.00252 days <br />0.0606 hours <br />3.604497e-4 weeks <br />8.2949e-5 months <br /> on' October 23, 1989, an MCR operator contacted

  • Occidental Chemical Corporation (OCC), a chemical plant located approximately two miles from Limerick Generating Station (LGS),;by telephone in reference to any atmospheric releases of toxic chemicals that may have occurred at their plant. The individual on the phone from OCC did state that they were currently experiencing difficulties with their incinerators, and to call again later. Upon

' contacting the company again at 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />, an OCC official verified there was an earlier release of vinyl chloride and that the incident was over. 'He also stated that the duration of the vinyl chloride release lasted for approximately fifteen (15) minutes and thereafter the plant had returned to a stabilized condition. The MCR isolation was reset at.1225 hours0.0142 days <br />0.34 hours <br />0.00203 weeks <br />4.661125e-4 months <br /> on October 23, 1989, and normal MCR ventilation was restored. A four (4) hour notification to the NRC .

was made in accordance with 10CFRSO.72(a)(2)(ii) at 2326 hours0.0269 days <br />0.646 hours <br />0.00385 weeks <br />8.85043e-4 months <br /> on October 22, 1989, since this event resulted in a manu'al actuation of

Consequences of the Event:

The consequences of this event were minimal. There was no release of radioactive material to the environment as a result of this event.

Both the 'A' and 'B' Toxic Gas Analyzers functioned as designed and alarmed on the presence of vinyl chloride. The MCR ventilation system isolated, and the 'A' train of CREFAS started and operated as designed. The redundant 'B' train of CREFAS was in the automatic standby mode and was available for operation in the event the 'A'

' train failed to properly function.

In the event these systems had failed to properly function, the consequences would have been minimal in 4 hat the vinyl chloride concentrations detected by the toxic gas analyzers were well below specified hazardous limits. NRC Regulatory Guide'l.78, " Assumptions for Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release," as referenced L in the LGS Final' Safety Analysis Report (Section 6.4.1), defines the l toxic limit of vinyl chloride,at 1000 ppm. The maximum limit t

observed during this event was 15 ppm which is well below this toxic limit. In addition, MCR personnel donned SCBA which provided .

protection against the inhalation of any toxic chemicals. ,'

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The cause of this event was the presence of vinyl chloride in the MCR outside air intake plenum as detected by the 'A' and 'B' Toxic Gas Analyzers. The source of the vinyl chloride originated from an atmospheric release of the toxic chemical from the OCC which is ,

located in the. vicinity of the station. The operators manually initiated a MCR isolation and CREFAS initiated as designed providing the release.designed protection for the operators from the toxic gas Corrective Actions:

MCR personnel immediately implemented Special Event Procedure SE-2,  !

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" Toxic the Gas," and donned SCBA within two (2) minutes as required by procedure. Operations personnel then manually initiated a MCR ventilation system chlorine isolation, on all four chlorine isolation channels ("A", "B", "C", and "D"), in accordance with system procedures, as directed by SE-2. Chemistry personnel don'ned SCBA and obtained air samples from the MCR. The results indicated i

that there was no vinyl chloride present in the MCR. All systems

( and equipment responded as designed and performed their intended functions. Following confirmation of the source of the vinyl chloride and that the release was terminated, MCR personnel restored #

MCR ventilation to normal operation and shutdown the CREFAS. The duration of MCR ventilation system isolation and CREFAS operation was approximately 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />.

Actions Taken to Prevent Recurrence:

This chloride.event re's'ulted from an actual release and detection of vinyl At LGS, all systems responded as designed and therefore no further corrective actions to prevent recurrence are planned.

OCC is taking the necessary action to prevent recurrence of the release of vinyl chloride.

These actions are documented in a.

National Emission Standard for flazardous Air Pollutants (NESHAP) report submitted by OCC to the US Environmental Protection Agency and Pennsylvania Department of Environmental Resources. A follow up meeting between OCC and LGS management will be arranged to review .

the twoOCC plants actions in theand event to establish of futuredirect events. communications between the N hh5 .

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Previous similar' Occurrences:

  • I LER's 85-90, 06-22, 86-28, 88-43 and 89-029 reported manual -

isolations of MCR ventilation due to high toxic chemical l concentration signals.

  • Tracking C6de C99 (Other External Cause) s P

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