ML20197A545

Ro:On 860501,high Alarm Indications Discovered on Effluent Process Monitors RM054A,RM054B & RM062.Caused by Increased Background Radiation Due to Presence of Noble Gases in Auxiliary Bldg.Ventilation Discharge Sys Shut

ML20197A545
Person / Time
Site:	Fort Calhoun
Issue date:	05/02/1986
From:	Andrews R OMAHA PUBLIC POWER DISTRICT
To:	Martin R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
EP-86-148, LIC-86-213, NUDOCS 8605120342
Download: ML20197A545 (3)

Text

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Omaha Public Power District 1623 Hameu omaha. wbrawa 68102 2247 l 402 s36 4000 j

l May 2, 1986 EP-86-148 cm .

LIC-86-213 I]IM@[5I)h/[

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i MAY - S sm l Mr. Robert D. Martin Regional Administrator "

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h U. S. Nuclear Regulatory Commission .

Region IV 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011

Reference:

Docket No. 50-285

Dear Mr. Martin:

Written Summary - Notification of Unusual Event The Omaha Public Power District's Fort Calhoun Station declared a "Notifi-cation of Unusual Event" at 9:05 p.m. on May 1, 1986. The initiating condi-tion was indication of high alarms on effluent process monitors RM054A, RM054B and RM062. RM054A and RM054B monitor the liquid blowdown discharge of "A" Steam Generator and "B" Steam Generator. It was later determined that the increased values for RM0054A and B were due to increased background radi-ation in the general area of the detectors due to the presence of noble gases in the Auxiliary Building and did not result from any malfunction of the Steam Generators. RM062 monitors the gaseous portion of airborne effluents from Fort Calhoun Station. RM061, which monitors the particulate portion of airborne effluents, followed RM062 into alarm, but it was determined to be due to increased radioactive noble gas concentrations and not attributable to

! particulate presence in the effluent.

The unplanned release of radioactive gas through the plant ventilation stack occurred during the weekly gas sampling of the waste piping in the Auxiliary Building of Fort Calhoun Station. Due to malfunctioning solenoid valves, a flow path to the area floor drain allowed the radioactive gas to become present in the Auxiliary Building. The ventilation discharge system was shut within several minutes of the high alarms, thus stopping quickly the short release which was occurring. The total duration of the unplanned radioactive noble gas release has been confirmed as two minutes. Notification to governmental agencies with periodic updates and recommendations were made during the evening.

At 2:30 a.m., May 2, 1986, the " Notification of Unusual Event" emergency classification was officially terminated with verbal summary to and concur 8605120342 860502 t PDR ADOCK 05000285 1

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e e Mr. R. D. Martin May 2, 1986 Page Two rence with (1) The State of Iowa, Office of Disaster Services, (2) The State of Nebraska, State Civil Defense, and (3) the U. S. Nuclear Regulatory Commission, Region IV. A conference call was also completed to the counties of Washington (Nebraska), Pottawattamie (Iowa), and Harrison (Iowa) informing them of the emergency classification termination.

A sequence of significant events and evaluations in chronological order was as follows:

1. High alarm in control room was signaled for monitor RM054A, RM054B (steam generator blowdown).

2. High alarm in control room was signaled for monitor RM062 (stack ven-tilation monitor).

3. Auxiliary Building ventilation secured.

4. Notification of Unusual Event emergency condition declared.

5. Radiological Emergency Response Plan initiated with Emergency Organization activated.

6. The States of Nebraska and Iowa and their respective Counties of Washington, Pottawattamie and Harrison notified of emergency classi-fication.

7. U. S. Nuclear Regulatory Commission notified of emergency classifica-tion.

8. In plant radiological surveys indicate maximum radioactive noble gas concentration of 1.73E-03 microcurie / cubic centimeters on the Auxil-iary Building. General radiation levels were below 10 mrem / hour.

9. Offsite dose assessment performed with the following results:

a. The instantaneous release rate of noble gases was 7.39E+03 micro-curie per second. The quantity of noble gas released was 8.87E-05 curie. The maximum concentration at the site boundary was 6.87E-07 microcurie per cubic centimeter or 2.29 times the applicable Technical Specification.

b. The maximum dose rate at the site boundary was 0.28 mrem / hour.

c. The total whole body exposure for a person at the site boundary for this event would have been less than 1.13 mrem.

d. The total whole body exposure for a person at the two mile radius from the site for this event would have been 0.14 mrem.

10. Perimeter surveys of airborne activity showed all sample media at nor-mal background levels.

11. The Site Director, Emergency Recovery Manager, and Emergency Coordin-ator agreed to terminate the emergency classification and with State concurrences declare operations return to normal.

. v' Mr. R. D. Martin May 2, 1986 Page Three

12. Appropriate governmental agencies notified of verbal summary of closeout.

The Omaha Public Power District is continuing to review the events leading to the emergency condition. The actions taken in response to this emergency ap-pear correct, timely and in accordance to the Fort Calhoun Station Radiolog-ical Emergency Response Plan.

Sincerely, R. L. Andrews M Division Manaaer Nuclear Production RLA/FFF/rh cc: LeBoeuf, Lamb, Leiby & MacRae 1333 New Hampshire Avenue, N.W.

Washington, DC 20036 Mr. D. E. Sells, NRC Project Manager Mr. P. H. Harrell, NRC Senior Resident Inspector