Extremity Dose Reduction By Aggie Barlow, CHP, MS, MBA
Over or unnecessary exposure There have been incidents at other institutions where workers have received radiation exposures to their hands which were over regulatory limits. In almost every case, these exposures were preventable.
ALARA As Low As Reasonably Achievable - working every day, during every procedure involving radioactive material [RAM] in such a manner as to keep exposure doses low. Regulatory agencies expect ALARA practices.
Extremity Exposure Limits 50 Rem per year limit for extremities [ex. hands or wrists]
Sources of Exposure Stock vials Tubes Columns Gels Experiments in progress Sealed sources Waste containers
Sources of Exposure Continued One does not have to be working with large activities to receive large radiation exposures. Even microcurie amounts can result in high extremity doses when performing repetitive operations.
Causes of high exposures • Direct holding of unshielded RAM/source • Inadequate use of shielding • Inadequate use of remote handling devices • Lack of awareness of exposure levels in close proximity to radiation sources • Operational pressures to meet deadlines • Working too slowly; not being prepared • Inadequate attention to As Low As Reasonably Achievable Philosophy
Time Constraints Work pressures and workloads must not be allowed to interfere with appropriate radiation safety practices.
What Can YOU do? Do not pick up stock vials of high energy beta emitters or gamma emitters directly with the hand. Use tongs whenever feasible. Rubber coating on tongs ensures grip.
Stock vials Stock vials contain concentrated solutions. Store and carry them in the [lead] pig or other shipping container. Place stock vials in secondary containers for transport between rooms. Increased distance from the vial reduces your exposure.
Proper Use of Container Design The bottom of the container is generally designed to securely hold the vial in position for removal of an aliquot without the need for the worker to hold the stock vial itself. The top of many containers can also be used for hands-free opening of the stock vial.
Correct Use of of vial container Containers are designed to hold vials in place
Take aliquots from stock vials without removing the vial from the container whenever feasible. This keeps your fingers farther away from the RAM.
Handling vials directly increases exposure to your fingers. Avoid this whenever possible. Use the container, rubber coated tongs or other remote handling means. Techniques to avoid
Proper Container Holding If you must pick up a stock vial or tube of RAM, keep your fingers as far away from the contents as possible. That is, pick it up from the top, so that your thumb is not under the container near the contents at the bottom. Gently tap liquid solutions to the bottom of the container.
Hold vials so that your fingers are away from the radioactive material Poor Technique vs Good Technique
Remote Handling Carry tubes containing RAM in a tube rack or other container so that your fingers are at an increased distance from the RAM.
Remote handling devices • Use ring stands or other holding devices.
Exposure vs distance The radiation dose rate varies inversely as the square of the distance from the source for electromagnetic radiation. Therefore, keep your hands as far from the radioactive material as feasible.
Dose rates from stock vials One millicurie of I-125 has a dose rate of > 500 mRem/hr on contact, but < 2 mRem/hr at 6 inches [such as when handled with rubber coated tongs]
Proper Glove Technique- preventing contamination Use of double gloves is strongly advised when handling radioactive material. Check your hands for contamination frequently while you work. If contamination is found, change to a new pair of gloves. Be sure to survey hands.
Skin Contamination Surveys When done using RAM, survey your hands using a portable survey meter. Perform a slow, careful survey of both sides of the hand. But sure to include both sides of your thumb, your wrists and lab coat sleeves.
Contamination of hands or skin Contact Tufts Police at 6-6911 for emergencies Also have someone call Health Physics Group- Boston [6-6168]. In Grafton or Medford call RS/EHS at 6-3615 for assistance. After hours call 636-6911 and Campus Police will help you get assistance. Begin hand washing procedure using soap and warm water. Wash, dry and resurvey the skin. Continue washing if contamination is still present. Seek Health Physics advice before using abrasive cleansers.
Emergencies Call 6-6911 for all Emergencies 24/7, Call Radiation Safety Officer at 6-3615 or 617 308-3781 [cell], Tufts EHS/Rad Safety Main Office number is 6-3615. After hours, Campus Police will summon the personnel to assist you.
For More Information – non emergencies Contact Health Physics Group or Tufts RS/EHS at 636-3615 or 636-3450