Information Notice No. 83-73: Radiation Exposure from Gloves Contaminated with Uranium Daughter Products

                                                             SSINS NO. 6835 
                                                             IN 83-73      

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C. 20555
                                     
                              OCTOBER 31, 1983

Information Notice No. 83-73:   RADIATION EXPOSURE FROM GLOVES 
                                   CONTAMINATED WITH URANIUM DAUGHTER 
                                   PRODUCTS 

Addressees: 

All licensees authorized to process uranium as source material and metal 
producers of alloys containing uranium as source material except uranium 
mills, UF-6 facilities, uranium fuel fabrication plants, and nuclear power 
plants. 

Purpose: 

The purpose of this Notice is to bring to the attention of all persons 
involved in the administration and operation of uranium processing 
facilities a recent incident that resulted in multiple exposures to workers' 
hands in excess of regulatory limits, and to discuss its generic 
implications for other, similar operations. 

Description of Incident: 

Nuclear Metals, Inc., Concord, Massachusetts, receives depleted uranium 
derbies that are sent to their foundry for melting, alloying, and casting. 
The melting is done in graphite crucibles in a vacuum furnace. Foundry 
workers load the crucibles into the furnace and, once a liquid state is 
reached, the metal is poured into castings from the bottom of the crucible. 
The foundry workers, wearing leather gloves, remove the brick top from the 
furnace, remove the crucible from the furnace, and subsequently clean the 
crucible before it is reused. 

One of the licensee's health physics technicians found that the leather 
gloves worn by the foundry workers were routinely contaminated during 
handling of the bricks and crucible upon completion of a melt. Measurements 
made with a Junotype survey meter, with the gloves turned inside out, showed
radiation levels inside the gloves between 270 and 1000 millirems per hour. 
While foundry workers had been provided with wrist badges, these wrist 
badges did not adequately measure the exposure to workers' hands. The badges 
were located too far from the hands that were receiving most of the 
radiation exposure. 

Subsequently, dosimeters were placed on the fingers of foundry workers. Four
workers were removed from work because their measured exposure exceeded the 
licensee's administrative limit of 12.5 rems per quarter for the first 
quarter of 1983. An investigation was conducted to determine the workers' 
hand exposures during the fourth quarter of 1982 and the first quarter of 
1983. It was estimated from TLD measurements and interviews with foundry 
workers that beta 
.

                                                           IN 83-73        
                                                           October 31, 1983 
                                                           Page 2 of 2     

radiation dose rates of about 1 rem per hour existed inside the contaminated
gloves. Based on those estimated dose rates, from 10 to 15 foundry workers 
received hand exposures of up to 125 rems per.quarter during both quarters. 
Similar doses may have been received in previous quarters. The licensee's 
investigation is continuing. 

Discussion: 

The beta radiation dose rate at the surface of uranium metal is typically 
230 millirems per hour or less. However, when uranium is melted, less dense 
daughter products of uranium-238, primarily thorium-234 and 
protactinium-234m, float to the surface of the molten metal. When the 
uranium is poured, significant quantities of these daughter products remain 
behind, coating the crucible, fire brick, and inside of the furnace. The 
beta radiation dose rate from these residual daughter products is much 
higher than that of the original uranium. In addition, these daughter 
products are loose or transferable. Exposure to these daughter products, or 
transfer to clothing, tools, or other items is likely to result in 
unanticipated beta radiation doses. Protactinium-234m emits a beta particle 
with a maximum energy of 2.28 MeV, that contributes to the majority of the 
beta dose from the uranium-238 daughter products remaining in the crucible 
and found on contaminated clothing or equipment. 

All uranium manufacturing and processing licensees that melt uranium should 
review their operations to ensure that workers are not receiving excessive 
radiation exposures from unsuspected high levels of beta contamination on 
protective clothing or equipment. It should be kept in mind that available 
ring or finger dosimetry may not adequately assess the whole-body exposure 
from beta radiation fields. To assess whole-body radiation doses from fields
of radiation, whole-body dosimeters should be worn. 

No written response to this Information Notice is necessary. If you need 
additional information regarding this matter, contact the Administrator of 
the appropriate NRC regional office or this office. 


                              James G. Partlow, Acting Director 
                              Division of Quality Assurance, Safeguards, 
                                and Inspection Programs 
                              Office of Inspection and Enforcement 
 
Technical Contact:  J. R. Metzger, IE
                    (301) 492-4947

Attachment:
List of Recently Issued Information Notices
.