Radiation ShieldingA Practical Approach to an Engineering

Physics Problem in Engineer 1P03.

Introduction• Geoff Gudgeon

• Tony Machado

• Aliraza Murji

• Evie Sararas

Outline• Problem & Constraints

• Background

• Lab Results

• Material Selection

• Proposed Design

• Recommendations

• Conclusion

Problem & Constraints• Design an object that will shield the gamma

rays given off by a radioactive source.

• Maximum radiation emitted after shield limited to 50 mSv per year.

• Design must be economically and practically feasible.

Background• Types of Radiation

Alpha (α)

Beta (β)

Gamma (γ)

Neutron

Background• Nuclear Decay

– Atoms with greater than 83 Protons are unstable and will break down (known as Radioactivity).

• Gamma Ray Absorption– Photoelectric Absorption– Compton Scattering– Pair Production

• Absorbing Powers of Materials– Gamma radiation is attenuated exponentially when passing

through a shielding material.

Lab ResultsLab #1• Verify 1/r2 law

experimentally using Cesium source.

• Determine background radiation (0.2 µSv).

A graph of radius against activity

0

2

4

6

8

10

12

14

16

0 10 20 30 40 50 60

Radius (mm)

Act

ivit

y N

(u

Sv)

Lab ResultsLab #2• Experimentally

calculate Gamma Attenuation of Plastic, Lead, Aluminum, and Copper.

Plastic 0.00697 mm-1

Aluminum 0.0115 mm-1

Copper 0.0386 mm-1

Lead 0.119 mm-1

Attenuation Coefficients

Material Selection (CES)

Proposed Design

Three Assumptions:– Source emits 1mSv/s.– Density of lead is

11,340 kg/m3. – Price of lead is $1.50/kg.

Proposed Design

Three Unknowns– Thickness of lead.– Volume of lead.– Price of lead.

Solution ???

– Create C++ Program!

Why ???– Allows us to vary

parameters to maximize design attenuation and minimize cost!

Proposed Design

• Final Design:– Distance from source to inner wall of lead is 5cm.– Thickness of lead is 13.7cm.– Amount of lead used would total 111.055 kg.– Total cost of lead would be $172.58

Recommendation

• Design can be easily altered using the C++ program to accommodate changes in input variables.

• If not used on bottom floor, a lead plate with equal thickness to radius of dome should be implemented to protect people below.

• Cover lead with plastic to prevent handling of toxic lead.

Conclusion

• Our design offers the best choice of material to provide highest attenuation.

• Low-cost due to small volume of design.

• By using a dome, our design becomes geometrically efficient by absorbing radiation evenly.

• Health and Safety regulation limiting 50mSv/year of radiation is met.

Conclusion

• Thank you for your attention.

• At this time, we would invite questions from the audience.