1. Purpose and Background
Facility owners or operators may estimate radionuclide emissions to the atmosphere for dose calculations instead of measuring emissions. Particulate emissions from mill tailings piles should be estimated using the procedures listed in reference re #2. All other emissions may be estimated by using the “Procedures” listed below, or using the method described in reference #1.
2. Procedure
To estimate emissions to the atmosphere:
(a) Determine the amount (in curies) used at facilities for the period under consideration. Radioactive materials in sealed packages that remain unopened, and have not leaked during the assessment period should not be included in the calculation.
(b) Multiply the amount used by the following factors which depend on the physical state of the radionuclide. They are:
(i) 1 for gases;
(ii) 10−3 for liquids or particulate solids; and
(iii) 10−6 for solids.
If any nuclide is heated to a temperature of 100 degrees Celsius or more, boils at a temperature of 100 degrees Celsius or less, or is intentionally dispersed into the environment, it must be considered to be a gas.
(c) If a control device is installed between the place of use and the point of release, multiply emissions from (b) by an adjustment factor. These are presented in Table 1.
Table 1—Adjustment to Emission Factors for Effluent Controls
| Controls
| Types of radionuclides controlled
| Adjustment factor to emissions
| Comments and conditions
|
|---|
| HEPA filters | Particulates | 0.01 | Not applicable to gaseous radionuclides; periodic testing is prudent to ensure high removal efficiency.
|
| Fabric filter | Particulates | 0.1 | Monitoring would be prudent to guard against tears in filter.
|
| Sintered metal | Particulates | 1 | Insufficient data to make recommendation.
|
| Activated carbon filters | Iodine gas | 0.1 | Efficiency is time dependent; monitoring is necessary to ensure effectiveness.
|
| Douglas bags: Held one week or longer for decay | Xenon | 0.5/wk | Based on xenon half-life of 5.3 days;
|
| Douglas bags: Released within one week | Xenon | 1 | Provides no reduction of exposure to general public.
|
| Venturi scrubbers | Particulates
Gases | 0.05
1 | Although venturis may remove gases, variability in gaseous removal efficiency dictates adjustment factor for particulates only.
|
| Packed bed scrubbers | Gases | 0.1 | Not applicable to particulates.
|
| Electrostatic precipitators | Particulates | 0.05 | Not applicable for gaseous radionuclides
|
| Xenon traps | Xenon | 0.1 | Efficiency is time dependent; monitoring is necessary to ensure effectiveness.
|
| Fume hoods | All | 1 | Provides no reduction to general public exposures.
|
| Vent stacks | All | 1 | Generally provides no reduction of exposure to general public. |
(1) Environmental Protection Agency, “A Guide for Determining Compliance with the Clean Air Act Standards for Radionuclides Emissions from NRC-Licensed and Non-DOE Federal Facilities”, EPA 520/1-89-002, January 1989.
(2) Nuclear Regulatory Commission, “Methods for Estimating Radioactive and Toxic Airborne Source Terms for Uranium Milling Operations”, U.S. Nuclear Regulatory Commission Regulatory Guide 3.59, March 1987.
[54 FR 51711, Dec. 15, 1989]