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2 RCRS provides: Pick-up and delivery of meters Required 9-month calibration Preventive maintenance and repairs Shipping for extensive repairs RCRS Contact: John Parker Nuclear Science Center

 Direct measurements o Portable survey instruments  Indirect measurements o Swipes and use of counters (Liquid Scintillation and Gamma) 3

4 Read the instrument’s operating manual Check the batteries before each use

5 Use a check source to determine operability of detector Determine efficiency of detector Determine the instruments response time Determine the operating background

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7 GM are tubes filled with a mixture of Q-gas Used for radioactive contamination monitoring Detects high energy beta radiation GM measures each individual interaction inside the detector Do NOT identify the radioisotope or specific energy

8 Probe has a NaI crystal and a photomultiplier tube Detection is based on emission of photons Used for radioactive contamination monitoring Detects low energy x-rays Does NOT identify the radioisotope

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11 Ion Chambers are filled with air Used for measuring radiation field intensity (exposure rate) Detect x-rays and gamma radiation Measure average current produced over many interactions Do NOT identify the radioisotope or specific energy

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13 A.K.A. - Dose Rate Meter Roentgen (R): a unit of exposure to x-rays or gamma rays. One roentgen is the amount of gamma or x-rays needed to produce ions carrying 1 electrostatic unit of electrical charge in 1 cubic centimeter of dry air under standard conditions.x-rays gamma raysions

14 Detection is based on emission of visible or near visible light (photon) Sample vial must contain scintillation cocktail Interaction between radiation and cocktail causes photons to be emitted Photomultiplier tubes are used to detect and amplify the photons It can identify the activity and energy of a beta emitter in a sample vial It is much more efficient than a portable survey meter

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16 Radioactive molecule Solvent molecule Fluor molecule Photomultiplier tube  Beta particles are emitted, which cause solvent molecules to become excited.  The energy of the solvent molecule is transferred to the fluor molecule, which in turn emits light.

17 Detection is based on emission of visible or near visible light (photons) Uses solid scintillation (no scintillation cocktail required) Interaction between radiation and a solid scintillator causes photons to be emitted Photomultiplier tubes detect and amplify photons Used to determine the activity of a x-ray or gamma emitter in a sample vial Gamma counters can identify activity and energy of gamma emitters

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19 Radiation Field / Dose Rate (mR/hr) Ion chamber Activity / Contamination amounts Beta emitters Low and Mid energy LSC only High energy GM Detector LSC (for documentation purposes) Gamma emitters Sodium Iodide Gamma counter (for documentation purposes)

20 Hmm…a conversion might help here!  1 µCi = 2.22 x 10 6 dpm  net cpm = gross cpm – background  efficiency = (net cpm) / (dpm)  dpm = (net cpm) / (efficiency)  cpm = (dpm) x (efficiency)

21 GM Tube Ion ChamberNaI ProbeGCLSC P-32 x-ray I-125 Tritium Cr-51 Radiation Field

22 Hint: 5800 counts / 5 minutes = 1160 gross cpm You have a swipe that was counted for 5 minutes that yields 5800 counts. If the background is 125 cpm and the counter efficiency is 80%, what is the dpm of the swipe? Hint: 1160 gcpm – 125 background cpm = 1035 net cpm Big Hint: 1035 net cpm / 0.80 efficiency = 1294 dpm

23 Hint: 120,000 counts / 2 minutes = 60,000 gross cpm You have a standard that has an activity of 105,000 dpm. After 2 minutes of counting in a gamma counter you get 120,000 counts. If the background is 350 cpm, what is the efficiency of the gamma counter? Hint: 60,000 gcpm – 350 background cpm = 59,650 net cpm Big Hint: 59,650 ncpm / 105,000 dpm = 57% efficiency

24 You are using P-32 as a tracer and determine that 20% of fed material ends up in your final sample. If you need a count rate of 2,000 cpm in a sample, determine how many microcuries you must use given the fact that your LSC has an efficiency of 50% for P-32. Hint: 2,000 cpm / 0.20 = 10,000 cpm Hint: 10,000 cpm / 0.50 efficiency = 20,000 dpm Big Hint: 20,000 dpm / 2.22 x 10 6 dpm/µCi = µCi

25 Life is not measured by the number of breaths we take, but by the moments that take our breath away…