CHP Radiation Shielding Design and Analysis 2

Question 1

NCRP Report No. 151 provides shielding guidance for medical X-ray facilities. The concept of 'workload' (W) is defined as:

Accepted Answer

The weekly time-integrated tube current expressed in mA·min/week

Answer

Workload (W) in NCRP 151 is the time-integrated tube current per week (mA·min/week), representing the total use of the X-ray machine and the radiation output generated.

Question 2

In NCRP 151 shielding calculations for diagnostic X-ray rooms, the 'use factor' (U) accounts for:

Accepted Answer

The fraction of the workload during which the primary beam is directed at a given wall

Answer

The use factor (U) is the fraction of the total workload for which the primary beam is directed toward a particular barrier, reflecting that not all exposures target every wall.

Question 3

For a point isotropic gamma source in air, if the distance from the source doubles, the dose rate changes by a factor of:

Accepted Answer

Decreases by factor of 4

Answer

By the inverse square law, dose rate is proportional to 1/r²; doubling the distance (r×2) reduces dose rate by a factor of 4.

Question 4

Concrete is commonly used for gamma and neutron shielding in nuclear facilities primarily because:

Accepted Answer

It provides both gamma attenuation (high density) and neutron moderation (hydrogen content) in a structural material

Answer

Concrete combines structural integrity, gamma attenuation from its density, and neutron moderation from its hydrogen content (water of hydration), making it versatile for mixed-field shielding.

Question 5

The linear attenuation coefficient (μ) for photons in a material has units of:

Accepted Answer

cm⁻¹

Answer

The linear attenuation coefficient μ has units of inverse length (cm⁻¹), as it describes the fraction of photons removed per unit thickness of material.

(CHP) Certified Health Physicist Practice Test

(CHP) Certified Health Physicist Practice Test

CHP Radiation Shielding Design and Analysis 2