As with radiation exposure, contamination is undetectable by human senses alone. Laboratory workers must make a deliberate effort to detect contamination by routinely surveying work areas. All users of radioactive materials are responsible for ensuring that adequate area monitoring surveys for radioactive contamination are performed within the laboratory at the end of each day's work with unsealed sources of radioactive materials. If radioactive materials are in storage (i.e. refrigerator, waste, source bottle, etc.) and are not used on a particular day or series of days, a survey is not required. All surveys must be documented and a copy of the current month's survey sheet (or a notice detailing where the survey sheet is kept) must be posted in each laboratory.

The area should be surveyed with counting equipment appropriate for the type and energy of radioactive materials being used. If H-3 and/or low levels of C-14 are used, wipe tests must be taken and counted on a gas flow proportional counting system or a liquid scintillation counter. If higher level beta and gamma emitters are used, a survey with a portable GM meter or sodium iodide probe would be adequate. The proper operation of the counting system or meter must be verified with a reference standard or check source prior to counting the survey samples or performing a meter survey.

Any area which has count rates or exposure levels in excess of five times (5X) the background rate is considered contaminated and corrective actions, including decontamination, must be performed. After decontamination is completed the area must be re-surveyed to verify the count rates or exposure levels are below 5X background. Documentation of this result must be provided on the survey sheet.

To be considered adequate, all lab survey documentation must include:

• Location and date of survey
• Diagram of the area surveyed (map)
• Identification of person conducting survey
• Type of survey equipment used (LSC, GM)
• Unit of measure (cpm, dpm, mR/hr)
• Check source or reference source reading
• Background reading
• Measured reading of areas surveyed keyed to locations indicated on survey diagram.
• If contamination is found, documentation as to corrective action taken and results of re-survey of area following corrective action.

Examples of proper survey documentation are provided in Appendix N. A copy of the most recent survey or a posting that notes where the current surveys are maintained must be posted in each laboratory. This must be readily visible upon entering the laboratory. Copies of the survey documentation should be retained by the laboratory for a minimum of 3 years and be available for review by radiation safety staff and regulatory inspectors.

Laboratories or other facilities containing radioactive material will be monitored by the Radiation Safety Program as a spot check to confirm that the contamination control program established by the Authorized User and conducted on a day to day basis by his/her laboratory staff is effective. In laboratories or other areas where >100 mCi of radioactive material in unsealed sources is used surveys will be conducted weekly. In areas containing < 100 mCi but > 200 µCi of radioactive material surveys will be conducted monthly. In areas where < 200 µCi is used or where radioactive materials are in storage only monitoring will be conducted semiannually.

Wipe tests will be taken to determine the presence of removable contamination from low energy beta emitters. For high energy betas and gammas, Geiger counter surveys will be taken in addition to the wipe tests. The wipe tests will be counted on appropriate counting equipment and the results, along with the results of the Geiger surveys, will be tabulated.

Survey records will be kept in the Radiation Safety Program files for at least three years. If contamination is found during a radiation safety monitoring survey, the Authorized User will be contacted and informed as to where the activity is and how to clean it up, or what steps must be taken in order to rectify the situation. In the event of gross contamination, the room will be closed until such time as complete decontamination procedures can be carried out. In such an instance, access to the room will be controlled by radiation safety personnel.

If an Authorized User wants to remove a room or area from their authorization or to return a radionuclide laboratory to unrestricted status, RS Form 150 (Appendix E) should be submitted. Arrangements for a final survey of the area can be made by contacting us at 229-4275. Once a final survey is completed and the area shows no residual contamination the laboratory can be declared an unrestricted area and the radiation warning signs removed.