Domain II(C): perform survey protocols & requirements

survey meter

gas detector measuring counts; used to survey pertinent areas (packages/surfaces) for radiation contamination

GM meter

- gas detector used for small amounts of contamination, checking-in packages

- operates in pulse mode

well counter

scintillation detector with a central well; sources & biological samples can be inserted & their radioactive emissions are counted

well counter

- converts CPM to DPM

- analyzes instrument efficiency

GM meter

- detects ionizing radiation by ionization produced in a gas-filled tube

- used to check for spills/contamination, monitoring exposure levels for personnel

- cannot distinguish between different types of radiation

GM meter

photon from radiation enters the gas-chamber, interacts with an electron, bounces around & finds other neighboring electrons to create an avalanche, & then gets detected as a pulse of radiation

NaI scintillation detectors

- determines amount &/or distribution of radionuclides in 1 or more organs of a patient for diagnostic purposes

- converts gamma radiation into light, which is then converted to an electrical signal by a PMT

NaI scintillation detectors

radiation detection device:

- good for imaging

- operates in pulse mode

- hygroscopic

- sensitive to temperature changes

gamma camera, well counter, uptake probe

3 types of NaI scintillation detectors

gamma camera

- NaI crystal doped with thallium, allows electrons to fall in the band gap that allows for scintillation (light) to be emitted

- has numerous PMTs

detector material, PMT, high voltage power supply, preamplifier, amplifier, PHA, display

7 components of scintillation detection system

NaI(Tl) crystal

scintillation detector material

photomultiplier tube

PMT

PMT (photomultiplier tube)

converts scintillation photons from the crystal into electrical energy, amplifies the resultant electrical pulse

high-voltage power supply

- supplies voltage to each dynode on PMTs to create "attraction"

- must be very stable & uniform to avoid drift (instability)

preamplifier

amplifies relatively small signals coming from PMT anode

amplifier

amplifies pulses from preamplifier

pulse height analyzer

PHA

PHA (pulse height analyzer)

- evaluates pulse size (# of scintillation photons detected)

- either accepts or rejects data

single channel analyzer, multichannel analyzer

2 types of pulse height analyzers

single channel analyzer

type of PHA: only events within the window are counted/displayed

multichannel analyzer

type of PHA: displays all events/energies as a spectrum

camera rooms, stress lab rooms, injection rooms, hot lab, restrooms

weekly survey areas

0.05 mR/hr

default trigger limit of surveys

optically stimulated luminescence

OSL

thermoluminescent dosimeter

TLD

5 rem

effective dose equivalent limit for whole body (TEDE(DDE))

50 rem

effective dose equivalent limit for extremity/skin (SDE)

15 rem

effective dose equivalent limit for lens of the eye (LDE)

5 rem

effective dose equivalent limit for organs (DDE)

0.5 rem / 9 months

effective dose equivalent limit for declared pregnant radiation workers

0.1 rem

effective dose equivalent limit for the general public