Information Notice No. 85-31: Buildup of Enriched Uranium in Ventilation Ducts and Associated Effluent Treatment Systems
SSINS No.: 6835
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
April 19, 1985
Information Notice No. 85-31: BUILDUP OF ENRICHED URANIUM IN VENTILATION
DUCTS AND ASSOCIATED EFFLUENT TREATMENT
All uranium fuel fabrication licensees.
This information notice is provided to alert recipients of a potentially
significant problem pertaining to criticality safety at enriched uranium
fuel fabrication plants. It is expected that recipients will review the
information for applicability to their facilities and consider actions, if
appropriate, to preclude a similar problem occurring at their facilities.
However, suggestions contained in this information notice do not constitute
NRC requirements; therefore, no specific action or written response is
Description of Circumstances:
This notice provides information regarding a potential for the buildup of
uranium in ventilation ducts and associated effluent treatment systems of
enriched uranium fuel fabrication plants. For nuclear criticality safety
purposes, licensees establish controls to prevent a buildup of enriched
uranium in unsafe or unfavorable geometry ventilation equipment and other
effluent treatment systems.
On two occasions recently, significant quantities of highly enriched uranium
were found in unfavorable geometry effluent ducts and treatment systems as a
result of settling or deposition of uranium-bearing solids.
In one event, uranium-bearing solids or vapors were picked up in the ventil-
ation system and deposited on the inside of the ventilation ducts and scrub-
ber walls above the water line. The deposition appears to have increased as
the air stream cooled and when air changed direction in elbows. The accumul-
ation above the water line appears to have resulted from splashing and sub-
sequent drying of scrubber liquid on the scrubber walls. To control this
situation the licensee initiated a surveillance program to identify accumu-
lations of uranium in the effluent system and to take appropriate corrective
actions when uranium buildup
April 19, 1985
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exceeded predetermined limits. Also, a program was initiated to identify the
uranium source and to take remedial actions to prevent the uranium from
entering the system.
In another event, uranium solids were deposited in unfavorable geometry
ducts as a result of changes in the speed or direction of air flows.
Periodic cleaning of the ducts prevented a significantly large accumulation
of uranium. As a control measure, the licensee initiated a visual inspection
and a radiation detection surveillance program to identify significant
accumulation of uranium in unfavorable geometry ventilation and effluent
These incidents are significant to nuclear criticality safety because
enriched uranium accumulated in excess of acceptable quantities in
ventilation and effluent treatment s stems of unfavorable geometry. The lack
of an adequate licensee program for detecting, locating, and estimating the
quantity of the depositions was the major contributing factor.
No specific action or written response is required by this information
notice. If you have any questions about this matter, please contact the Reg-
ional Administrator of the appropriate NRC regional office or this office.
James G. Partlow, Director
Division of Inspection Programs
Office of Inspection and Enforcement
Technical Contact: Douglas Sly
Attachment: List of Recently Issued IE Information Notices
Page Last Reviewed/Updated Friday, May 22, 2015