Radiation Measurement and Instrumentation Flashcards
7 cards from real CHP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Radiation Measurement and Instrumentation flashcards as text
The 'shelf effect' in portable survey meter calibration refers to:
Answer: Increased reading when the meter is placed on a reflective surface during calibration
Placing an instrument on a table or floor during calibration causes backscatter from the surface, artificially elevating the reading; calibrations should be performed with the meter in free air.
A pocket dosimeter (direct-reading, air-filled ionization type) displays dose by:
Answer: Measuring displacement of a charged quartz fiber against an internal scale
Direct-reading pocket dosimeters use a gold-plated quartz fiber that deflects when the internal charge bleeds away due to ionization, and the deflection is read through an eyepiece.
When using a liquid scintillation counter for tritium measurement, the figure of merit E²/B is maximized to:
Answer: Identify the counting window that gives the best detection limit
The figure of merit E²/B (efficiency squared divided by background) identifies the pulse-height window that minimizes the minimum detectable activity for low-energy beta emitters like tritium.
Nuclear track etching in CR-39 detectors records alpha particles because:
Answer: Alphas cause latent damage trails in the polymer that etch faster than the bulk material
Alpha particles create dense ionization damage trails (latent tracks) in CR-39 polymer; chemical etching enlarges these tracks into visible pits whose density is proportional to fluence.
The intrinsic detection efficiency of a detector is defined as the ratio of:
Answer: Pulses recorded to number of radiation quanta striking the detector
Intrinsic efficiency describes how well the detector responds to radiation that actually enters it, independent of source-detector geometry.
Activation foil analysis for neutron fluence measurement relies on which nuclear reaction product?
Answer: Radioactive product isotope whose decay activity is measured post-irradiation
After neutron irradiation, the foil is removed and its induced radioactivity is measured; the saturation activity and decay data back-calculate the neutron fluence or flux.
In high-dose dosimetry (e.g., radiation processing), the Fricke (ferrous sulfate) dosimeter measures absorbed dose by:
Answer: Colorimetric measurement of Fe²⁺ oxidized to Fe³⁺ in aqueous solution
The Fricke dosimeter quantifies dose by measuring the increase in Fe³⁺ concentration (via UV spectrophotometry at 304 nm) resulting from radiation-induced oxidation of Fe²⁺.