Measuring Radiation and Equipment - West Virginia Division of ...

MEASURING RADIATIONAND EQUIPMENTWV Division of Homeland Security and EmergencyManagement

Common Measurements Radioactivity – Curie (Ci) or Becquerel (Bq) Exposure – Roentgen (R) or Coulomb/kilogram (C/kg) Absorbed Dose – Rad (rad) or Gray (Gy) Dose Equivalent – Rem (rem) or Sievert (Sv) For practical purposes: 1R = 1 rad = 1rem

Radioactivity Measurements Measure of the amount of radioactivity present Curie (Ci) or Becquerel (Bq) Measurement is independent of mass (a gram ofCobalt-60 has the same amount of radioactivity as1800 tons of natural uranium) Radioactive material with long half-lives has verylow specific activity

Exposure Measurements Measure of charge in air from ionization Roentgen (R) or Coulombs/kilogram (C/kg) Most common form of measurement by surveyinstruments

Absorbed Dose Measurements Measure of energy deposited by ionizing radiationin a unit mass of material Rad or Gray (Gy) Can be used to describe absorbed dose to personor object

Dose Equivalent Measurements Measure that equates relative hazard for radiationin terms of risk Roentgen Equivalent Man/Mammal (rem) or Seivert(Sv) Also called effective dose About the same as the absorbed dose for beta andgamma radiation Higher than the absorbed dose for alpha andneutron radiation since these types of radiation aremore damaging to the human body

CDV-700 Survey Meter Commonly used,normally outfitted withexposure probe 0-50 mR/hr 0-30,000 cpm Will detect beta andgamma radiation withwindow open Only detects gammawith window closed

Other Survey Meters* Ludlum 3 Ludlum 14C Ludlum 2241 Canberra UltraRadiac Normally outfittedwith different probes*List is not all inclusive

Survey Meter ProbesLudlum 44-38 “Hotdog” Exposure 0-500 mR/hr Saturates to Zero Beta/GammaLudlum 44-9 “Pancake” Contamination 0-999,000 cpm Saturates to Zero Alpha, Beta, Gamma

Detection Ranges for Common SurveyMeters and ProbesGamma Exposure Rate 1µR/hr 10µR/hr 100µR/hr 1mR/hr 10mR/hr 100mR/hr 1R/hr 10R/hr 100R/hr 1kR/hrLudlum 44-2(Scintillator) 1µR/hr 25mR/hrLudlum 44-38(GM) "Hot Dog" 250µR/hr 500mR/hrLudlum 133-8(GM) "Peanut" 150mR/hr 1kR/hrCanberra UltraRadiac(GM) 1µr/hr 500R/hrLudlum 9-3(Ion Chamber) 200µR/hr 50R/hrLudlum 14C(Internal GM) 100mR/hr 2R/hrContamination 0cpm 10cpm 100cpm 1kcpm 10kcpm 100kcpm 1McpmLudlum 44-9(GM) "Pancake" 0cpm 999kcpmGamma Exposure 1µR 10µR 100µR 1mR 10mR 100mR 1R 10R 100R 1kRCanberra UltraRadiac(GM) 1µR 1kR

DosimetersDirect-Read Dosimeters – Canbe read in field. Variousranges and fragile todroppingElectronic Personal Dosimeters- Can be read in field and setup to alarm at certainreading or dose rate Indirect-Read Dosimeters –Track long term exposure andmust be read in lab. Anexample is thermoluminescentdosimeter

Equipment Concerns Must be calibrated at least annually Batteries should be stored separately Compatibility of probes and meters may be issue