United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 97-55: Calculation of Surface Activity for Contaminated Equipment and Materials

                                       UNITED STATES
                               NUCLEAR REGULATORY COMMISSION
                     OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
                                WASHINGTON, DC  20555-0001

                                       July 23, 1997


Information Notice No. 97-55:  CALCULATION OF SURFACE ACTIVITY FOR         
                                   CONTAMINATED EQUIPMENT AND MATERIALS


Addressees

All Uranium Recovery Licensees.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to the correct method for calculating surface
activity of contaminated materials.  Recipients should review the information
for applicability to their radiation protection programs and consider actions
as appropriate, to avoid similar problems.  However, suggestions contained in
this information notice are not requirements; therefore, no specific action or
written response is required.

Description of Circumstances

During recent inspections at uranium recovery sites, the staff noted that two
licensees had used the 2-pi efficiency factor (radioactive emissions from the
surface to the meter) when converting counts per minute to disintegrations per
minute (dpm) in the determination of surface activity levels.  The activity
values are compared with the guideline limits, in Regulatory Guide 1.86, for
the release of equipment and materials from a uranium recovery site.  The
appropriate efficiency factor to use in this situation is the 4-pi value
because activity is released in all directions and because the main health
risk from surface activity is subsequent inhalation or ingestion of the
radionuclides.  The 2-pi factor would be appropriate for use in the
determination of beta dose from exposure to a contaminated surface.  

The use of the incorrect efficiency factor in the determination of surface
activity results in a value almost half the correct value.  In other words,
material contaminated with approximately twice the recommended surface
activity limit could be released from sites, using the 2-pi value in the
calculation of surface activity.

Discussion

A significant health risk has not been created by the mistaken use of the 2-pi
efficiency factor for determining surface activity for release of material,
since all radiation protection programs include procedures to maintain
exposures as low as is reasonably achievable.  The staff has estimated
(Nuclear Material Safety and Safeguards Decommissioning Handbook, 


9707170217.                                                                     IN 97-55
                                                                     July 23, 1997
                                                                     Page 2 of 2


Appendix C, Table 1) that exposure to material with the total surface activity
limit for the uranium chain (5000 dpm/100 cm2) would produce a dose of 0.13
mSv/yr (13 mrem/yr).  Therefore, twice this dose would be significantly less
than the 1 mSv/yr (100 mrem/yr) limit for members of the public specified in
10 CFR Part 20.

Staff will address this issue during future inspections by reviewing licensee
procedures and records to ensure that the correct efficiency factor has been
used to determine surface activity levels.  This information notice requires
no specific action or written response.  If you have questions about the
information in this notice, please contact the technical contact listed below.


                                                       signed by

                                                 John T. Greeves, Director
                                                 Division of Waste Management
                                                 Office of Nuclear Material Safety 
                                                   and Safeguards

Technical contact:  Elaine Brummett, NMSS
                    (301) 415-6606
                    E-mail:  esb@nrc.gov
Page Last Reviewed/Updated Tuesday, December 03, 2013