NRRPT Detection and Measurement 5

Question 1

In a proportional counter, the gas multiplication factor (M) represents:

Accepted Answer

The factor by which primary ionization is amplified through avalanche multiplication

Answer

In the proportional region, primary electrons accelerate and create additional ionization; the gas multiplication factor M is the ratio of total collected charge to initial ionization charge.

Question 2

A fission chamber detector is primarily used to measure:

Accepted Answer

Neutron flux in reactor environments where high gamma fields are present

Answer

Fission chambers use U-235 or Pu-239 coatings where neutron-induced fission produces heavy, highly ionizing fragments detectable above the gamma background through pulse height discrimination.

Question 3

The 'air-equivalence' of a detector material is important because:

Accepted Answer

The detector's energy response should mimic the ionization characteristics of air or tissue

Answer

Air-equivalent or tissue-equivalent detector materials have similar atomic composition (effective Z) to air or tissue, ensuring the detector's energy response matches the quantity being measured.

Question 4

What does the 'W-value' represent in radiation detection?

Accepted Answer

The average energy required to produce one ion pair in a detector fill gas

Answer

The W-value (approximately 35 eV for air) is the mean energy deposited per ion pair formed, used to convert ionization measurements to absorbed dose.

Question 5

An area radiation monitor continuously displaying dose rate near a hot cell would most likely use which detector type?

Accepted Answer

High-pressure ionization chamber or Geiger-Mueller tube with remote readout

Answer

Area radiation monitors typically use robust ionization chambers or GM tubes with remote readout capability, providing continuous real-time dose rate data to a central monitoring system.

(NRRPT) National Registry of Radiation Protection Technicians Practice Test

(NRRPT) National Registry of Radiation Protection Technicians Practice Test

NRRPT Detection and Measurement 5