Due to the tendency of iodine to concentrate in the thyroid gland, researchers using I-125 or I-131 must take precautions to insure that radioiodine is not inhaled or ingested. Persons performing radioiodinations must receive additional training regarding the properties of radioiodine, observe several iodinations, complete dry runs of the procedure, and obtain a necessary thyroid bioassay before completing iodination activities.

1. Use of radioiodine in a fume hood or approved facility Procedures involving 100 µCi or more of unbound radioiodine or 1.0 mCi or more of non-volatile iodine must be performed in a fume hood or other facility that has been approved by the Radiation Safety Program. Because iodine effluent limits are based on the maximum volume of air exhausted from a hood, these approved radioiodination hoods should run continuously and not be turned off. Notify Radiation Safety if the hood you use needs to be shut down or if you notice the hood is not running.
2. Thyroid counts

   A background thyroid count must be taken within 6 months preceding an individual's use of 100 µCi or more of volatile or dispersible radioactive iodine or 1.0 mCi or more of radioactive iodine bound to a nonvolatile agent. Persons using these quantities and chemical forms of radioiodine must also have a thyroid count taken within ten days (but not less than 24 hours) of the date on which the iodination was performed. An extension for I-125 bioassays may be granted upon request, but can not exceed 14 days from the date the material was used. Thyroid scans are performed in the radiation safety laboratory (Lapham 218) without charge. Call 229-4275 to schedule an appointment.

3. Evaluation of radioiodine concentrations in air

   Air monitoring of a radiation worker's breathing zone is required during each procedure involving 100 µCi or more of volatile radioiodine or 1.0 mCi or more of nonvolatile radioiodine. The steps involved in breathing zone monitoring are as follows:

   • An activated charcoal filter will be distributed with the radioiodine order.
   • Additional filters are available upon request.
   • Before beginning the procedure, connect the filter to the vacuum line of the calibrated personal exposure level (PEL) pump.
   • Turn on the PEL pump and note the time. The pump must run continuously while the iodine procedure is being performed.
   • Record the flow rate indicated by the flow meter on the pump.
   • After the radioiodine procedure is complete, turn the pump off, note the time elapsed, put the filter in the plastic bag provided and fill in the required information on the label.
   • Return the filter to Radiation Safety for analysis.

   Monitoring of iodine effluent levels at the rooftop fume hood exhaust point is performed by the Radiation Safety Program.

1. Effluent Releases

   Procedures which may produce airborne tritium must be conducted in a fume hood or other approved facility. Some uses may require the Authorized User to provide an adequate system of breathing zone and/or effluent monitoring to assure regulatory levels are not exceeded. Potential releases of volatile H-3 must be assessed. This includes estimation of the concentrations which may be released from the rooftop fume hood vents. The Radiation Safety Program will assist in calculating potential release rates and airborne concentrations.

2. Monitoring Equipment

   All personnel using H-3 must have access to a liquid scintillation counter or gas flow counter in order to assess wipe tests for contamination. Because of its low-energy, H-3 contamination is undetectable with GM or other survey instruments.

Authorized Users having procedures and/or materials which may produce airborne radioactivity (gases, aerosols, or dusts) must perform their operations in a hood or other approved facility. Any radioactive material exhausted or vented to the atmosphere (e.g., ¹⁴CO₂) must be preapproved and reported to the Radiation Safety Program on at least a monthly basis. Contact the Radiation Safety Officer for further information.

A sealed source is any radioactive material that is permanently encapsulated in a sturdy medium which prevents leakage or escape of radioactivity. The NRC requires the Radiation Safety Program to keep an inventory of and to perform leak tests on all sealed sources in UWM facilities. If you receive a sealed or plated source or a piece of equipment containing a sealed source (i.e. gas chromatograph, EC foils, or vacuum gauges), notify us at once so that the source can be inventoried and included in the leak test schedule.