05000285/LER-1985-001, :on 850303,ventilation Isolation Actuation Signal by Radiation Monitor RM-060 Occurred.Caused by Gases Released from Liquid Sample Drawn Through Ventilation Hood Into Auxiliary Bldg Ventilation Sys

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:on 850303,ventilation Isolation Actuation Signal by Radiation Monitor RM-060 Occurred.Caused by Gases Released from Liquid Sample Drawn Through Ventilation Hood Into Auxiliary Bldg Ventilation Sys
ML20113B735
Person / Time
Site: Fort Calhoun Omaha Public Power District icon.png
Issue date: 04/02/1985
From: Andrews R, Gregory Roach
OMAHA PUBLIC POWER DISTRICT
To:
NRC OFFICE OF ADMINISTRATION (ADM)
References
LER-85-001, LER-85-1, LIC-85-126, NUDOCS 8504110368
Download: ML20113B735 (4)


LER-1985-001, on 850303,ventilation Isolation Actuation Signal by Radiation Monitor RM-060 Occurred.Caused by Gases Released from Liquid Sample Drawn Through Ventilation Hood Into Auxiliary Bldg Ventilation Sys
Event date:
Report date:
2851985001R00 - NRC Website

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NRC Perni ses U.S. NUCLEAA REGULATORY COnesculON Wi APNIOVED Oest Iso.3150 4104

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LICENSEE EVENT REPORT (LER)

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DOCKET # SURGER (21 PAGE(3 Fort Calhoun Station, Unit No.1 ogslogolol2 al5 i lor l 0 :3 i

TITLE tel VIAS Actuation EVERIT DATE (El LER NURADER f8)

REPORT DATE 17)

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OO,734aH2 Hell) 30.73IeH2Hal LICENGEE CONTACT POR TM18 LER lith NAME TELEPHONE NUMSER Gary L. Roach, Supervisor-Chemical and Radiation Protection aata coot Fort Calhoun Station, Unit No.1 40,2 4, 2,6,, 4,0,1,1 i

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On March 3,1985, at 0112 hours0.0013 days <br />0.0311 hours <br />1.851852e-4 weeks <br />4.2616e-5 months <br />, an actuation of the entilation Isolation Actua-tion Signal (VIAS) by radiation monitor R:1-060 occurred. The actuation occurred coincident with nonnal purging of the reactor coolant sampl* line in a ventilation hood in preparation for drawing a depressurized reactor coolaf,t sample. The gases released from the liquid sample were drawn, as designed, through the ventilation hood int, the Auxiliary Building vontilation system and into the ventilation dis -

charge stack. DM-060 operates to analyze I-131 in gaseous effluents. The monitor responde1 to radionuclides other than 1-131 and initiated the VIAS. Sampling of reactor coolant was immediately suspended. The activity indicated by RM-060 rapidly decreased after sampling was stopped.

RM-060 was reset at 0115 hours0.00133 days <br />0.0319 hours <br />1.901455e-4 weeks <br />4.37575e-5 months <br /> on March 3,1985, three minutes after VIAS was initiated. There were no operator errors or violations of procedures. Reactor coolant sampling procedures including sample purge times were reviewed for adequacy and found to be appropriate.

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i LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AreaovEo oue No useato.

ExetRES 8/31/85 P ACILITV NAhti til DOCKET NUMBEM (U ggg gyggggggy pagg (33 VIA" t'n we Fort Calhoun S ation, Unit No.1 o ls lo lo lo [2 ; 8l 5 8; 5' 0l0l1 0l0 0l2 0l3 or On March 3,1985, at 0112 hours0.0013 days <br />0.0311 hours <br />1.851852e-4 weeks <br />4.2616e-5 months <br />, an actuation of the Ventilation Isolation Actua-tion Signal (VIAS) by radiation monitor RM-060 occurred with the plant in Mode 1, l

power operition at a nominal 100% of rated power.

A containment pressure reduction j

was in progress with the containment radiation monitors P.M-050 and RM-051 reading in the nomal range prior to the VIAS actuation.

The VIAS performs the following functions:

1.

Closus the containment purge valves.

2.

Closes the containment relief valves.

3.

Stops the containment purge fans.

4.

Closes the containment air sampling valves.

5.

Opens the inlet and outlet vent to the safety injection pump rooms and the spent regenerant tank room.

6.

Starts both control room air conditioning units and places this system in the filtered air makeup mode.

7.

Closes the waste gas header release valve to the stack.

The type of event des:ribed in the USAR that VIAS was designed to mitigate is a release of significant radiofodine or radioactive gas from the containment to the atmosphere from such sources as reactor coclant leaks. A VIAS is initiated by a Safety Injection Actuation Signal (SIAS) or a Containment Spray Actuation Signal (CSAS) or a Containment Radiation High Signal (CRHS). The CRHS feature employs five radiation monitors taking samples from the containment and/or ventilation stack. These monitors supply a 1-out-of-5 logic network to trip the VIAS lockout relays.

The five ventilation radiation monitors that actuat! VIAS are also used for an iso-lation function similar to that performed by other process radiation monitor sys-tems (e.g., waste evaporator condensate return line manitor and the waste liquid release to the overboard discharge header monitor). The ventilation monitors are used as process monitors in order to satisfy the Technical Specification 2.9 objec-tive of controlling the release of radioactive t ffluelts to the environs to as low as practicable.

Radiation monitor RM-060 monitors the ventilation stack for I-131 using a NaI (T1) detector with detection window centered around the 164 kev I-131 peak. The monitor is also sensitive to radionuclides with energies falling within the detection win-dow and increased Compton due to the presence of radionuclides with gamma energies greater than 364 kev. A number of gaseous fission products are, as a result, cap-able of causing an increase in the indicated RM-060 countrate.

At approximately 0105 hours0.00122 days <br />0.0292 hours <br />1.736111e-4 weeks <br />3.99525e-5 months <br />, a chemistry technician began purging the reactor cool-ant sample line within the primary sample sink prior to drawing a depressurized sam-ple for analysis. The liquid passes from the sample sink into the station liquid waste disposal system. A portion of the entrained gases in the coolant escapes from the liquid and is drawn through the sample sink hood exhaust into station ven-tilation exhaust and through the ventilation stack where it is monitored.

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NRc ree. sesA u s. NUCLEAR LEGULATOQY COMMi$$10N LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AreaovEo ous No. 2 iso cio.

E MPIRES. 8/31/85 F ACILITY NAME (11 DOCKET NUMEER (2)

LER NUMSER 163 PAGE (3)

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viAa Fort Calhoun S'tation, Unit No.1 o ls [o [o jo l 2[8l5 8]5 0l 0[ 1 0[ 0 0l 3 OF 0 l3 TEXT M more eseco e escurest use selsluenst 4AC Form JOECsJ (1M The gases released during the sampling caused an increase at 0112 hours0.0013 days <br />0.0311 hours <br />1.851852e-4 weeks <br />4.2616e-5 months <br /> in the RM-060 countrate and in the countrate of RM-061, the stack particulate monitor.

Operations personnel immediately notified the chemistry technician to cease sample purging.

Simultaneously, RM-060 went into alarm, initiating VIAS. RM-061 also went into alann, however, VIAS was already actuated. Sample purging was immediately terminated causing a rapid drop in the indicated countrate for RM-060 and RM-061. VIAS was reset at 0115 hours0.00133 days <br />0.0319 hours <br />1.901455e-4 weeks <br />4.37575e-5 months <br />.

During the event the containment monitors RM-050 and RM-051 remained constant.

Gases released from reactor coolant are predominantly noble gases, such as Xe-133, that are known to cause a response on RM-060 and RM-061. The sample that was drawn was analyzed and found to contain 12.00 uCi/gm of xenon and krypton gas. RM-062, the stack noble gas monitor, indicated a slight increase in countrate during the incident and returned to normal at the same time that RM-060 and RM-061 returned to normal. No releases above Technical Specification or 10CFR20 limits were made.

The chemistry technician complied with station procedures. Operations personnel took prompt and proper action.

The nature of the incident was reviewed with the involved chemistry technician and the chemistry staff. The importance of assuring purge times do not significantly exceed minimum purge times was emphasized to the chemistry staff.

Other LERs written as a result of VIAS actuations are as follows: 84-005,84-006, 84-007,84-010, 84-014,84-017, 84-018,84-019, 84-023,84-024 and 84-025.

How-ever, since January 1,1984, no other VIAS actuations have been caused by radio-nuclides released to the Auxiliary Building Ventilation System during reactor cool-ant sampling activities.

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6 Omaha Public Power District 1623 Harney Omaha. Nebraska 68102 402/536-4000 April 2,1985 LIC-85-126 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Reference: Docket No. 50-285 Gentlemen:

Licensee Event Report No.85-001 Please find attached Licensee Event Report 85-001 dated April 2,1985.

This report is being submitted per requirements of 10 CFR 50.73.

Sincerely, b

b R. L. Andrews Division Manager Nuclear Production RLA/CWN/dao cc: Mr. Dorwin R. Hunter, Chief Reactor Project Branch 2 U. S. Nuclear Regulatory Conmission Region IV 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 Mr. E. G. Tourigny, NRC Project Manager Mr. L. A. Yandell, NRC Senior Resident Inspector SARC Chairman PRC Chairman INP0 Records Center Fort Calhoun File (2) f5 I

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