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3 H Module

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  1. 3H Module Objectives • To understand the physical nature of 3H. • To understand that 3H is both an internal and external radiation hazard. • To understand the need to utilize shielding. • To recognize that special procedures and protective measures are required when using activities greater than 100 mCi.

  2. IsotopesTritium (3H) • The Maximum beta energy is 0.018 MeV. • It is a pure beta emitter (100 of the radiation emitted is beta particles) • The number of betas emitted per second = number of decays per second (for 1 mCi, 3.7 x 107 betas emitted)

  3. IsotopesTritium (3H) • The half-life is 12.28 years • The Average beta energy is 0.006 Mev or 6 keV. • The range of the most energetic tritium beta particles is only about 5 mm in air or 5 mm in water or soft tissue. • 3HCannot be detected with a Geiger Counter • 3H Cannot be detected by a dosimeter badge

  4. IsotopesTritium (3H) • The Annual limit of intake via ingestion is 80 mCi. (this means that a total burden in the body of 80 mCi from ingestion alone will give a 5 Rem dose). • Annual limit of intake via inhalation is 80 mCi. (this means that a total burden in the body from the lungs alone of 80 mCi will give a 5 Rem dose).

  5. IsotopesTritium (3H) • Three to four hours after intake, ingested, inhaled or absorbed tritiated water is uniformly distributed in all body water(1). • On average, tritiated water is eliminated with a 10-day biological half-life(1). This can be shortened with an increase of liquid intake (up to 20 liters), or in severe cases, by using dialysis machines. • ICRP Publication 30, Part 1, Limits for Intakes of Radionuclides by Workers, Pergamon Press, Oxford, 1979. • ICRP Publication 10, Recommendations of the International Commission on Radiological Protection, Pergamon Press, London, 1968.

  6. IsotopesTritium (3H) • The biological incorporation (uptake) of airborne HTO (tritiated water) can be extremely efficient: • up to 99% of inhaled HTO is taken into the body by the circulating blood. • Ingested liquid HTO is also almost completely absorbed by the gastrointestinal tract and quickly appears in the blood stream. Within minutes, it can be found in varying concentrations in the organs, fluids, and tissues of the body. • Skin absorption of airborne HTO is also important, especially during hot weather, because of the normal movement of water through the skin. For skin temperatures between 30 and 40EC, the absorption of HTO is about 50% of that for HTO by inhalation (assuming an average breathing rate associated with light work, 20 L/min). No matter how it is absorbed, the HTO will be uniformly distributed in all biological fluids within one to two hours..

  7. IsotopesTritium (3H) • Contamination is controlled and surveyed by wipe test/liquid scintillation counting. • For tritium, the liquid scintillation counter has a maximum efficiency of ~ 50% (meaning, at best, only ~1/2 of the betas are counted)

  8. IsotopesTritium (3H)Wipe Tests Standard industry practice 100 cm2 100 cm2 12” to 14” 4” x 4”

  9. IsotopesTritium (3H)Liquid Scintillation Counters Photomultiplier Tubes Electronic Noise 3H 14C 32P log Scale

  10. IsotopesTritium (3H) Blank: Prepare blank exactly as samples without activity • Radionuclide standard: • Amount of spike = expected activity in sample • Prepare exactly as all samples are prepared • Count exactly as samples are counted • CPM from spiked sample/DPM of spike = Efficiency in CPM/DPM

  11. IsotopesTritium (3H) Dark adapt samples for a minimum of 30 minutes: (Light interacts with sample usually causing the first sample to appear hot) Chemical interaction can cause spurious pulses (chemoluminescense) in the Tritium Window (first 3 or 4 channels) How do I know if I have contamination? Is my sample greater than my background upper control limit? If yes, then I am 99% confident that I have levels above background.

  12. IsotopesTritium (3H) • Suggestions: • Have the first carrier be anything that is counted for 30 minutes to dark adapt all of the samples. • Shake samples to reduce chemoluminescence and wipe off vials to reduce refraction of the light from oil on the vials from your fingers. • Have the second carrier contain a blank and a standard to use for the QA/QC. • If possible, have the LSC program subtract the background upper control limit and divide by the calculated efficiency.

  13. IsotopesTritium (3H) • Suggestions: • Be sure your scintillation fluid is made to work with the sample that is to be counted (high pH/low pH, high aqueous load, high color, etc.) • Never count solid samples. Always digest them first. • Use teflon vials for high precision/low level counting. Tritium atoms can be absorbed into the plastic of plastic vials. Borosilicate vials will not absorb tritium either but they have a higher background.

  14. QUESTIONS(Select the best answer below using the mouse) What is the Annual limit of Intake (the activity that will yield a 5 Rem dose over the period of 1 year)? A. 80 mCi B. 800 mCi C. 8.0 mCi D. 80 mCi

  15. CORRECT The Annual limit of intake via ingestion or inhalation is 80 mCi. (this means that a total burden in the body from the stomach or lungs alone of 80 mCi will give a 5 Rem dose).

  16. QUESTIONS(Select the best answer below using the mouse) Which Protective equipment is NOT required? A Lab Coat B Properly selected glove C Protective Eyewear D Shielding

  17. CORRECT Due to the low energy of the 3H beta particles, shielding is NOT required

  18. QUESTIONS(Select the best answer below using the mouse) The Following is prohibited in isotope laboratories A. Eating B. Drinking C. Smoking D. All of the above

  19. CORRECT This should be obvious!!!!!

  20. QUESTIONS(Select the best answer below using the mouse) What instrument do you employ to when checking for tritium contamination ? A. Liquid Scintillation Counter B. Geiger Counter C. Gamma Counter D. HPLC

  21. CORRECT The Geiger Counter and gamma counter will not detect the low energy tritium betas or any bremstrahlung radiation.

  22. DOCUMENTING TRAINING Please sign and date the training form and click on the letter that indicates the first letter of your last name (ie. Farina is A) A. A - F B. G - L C. M - R D. S - Z

  23. Questions ??? If you have any questions while reading the Radiation Safety Procedures Please Feel Free to Contact: The Radiation Safety Office University Research Support and Administration Office of Research Integrity Georgia State University Ground Floor Alumni Hall Atlanta, Georgia 30303 413-3540

  24. INCORRECT PLEASE TRY AGAIN Return to question

  25. INCORRECT PLEASE TRY AGAIN Return to question

  26. CORRECT BUT PLEASE TRY AGAIN There is a better answer! Return to question

  27. Place the letter A in the last column after your signature & Date Finish Training

  28. Place the letter B in the last column after your signature & Date Finish Training

  29. Place the letter C in the last column after your signature & Date Finish Training

  30. Place the letter D in the last column after your signature & Date Finish Training

  31. INCORRECT PLEASE TRY AGAIN Return to question