Week 1 - Ch 16 Physics

Question 1

Q for x-ray, gamma, and electrons

Answer 1

1

Question 2

Q for Neutrons < 10 keV

Answer 2

5, “Thermal Neutrons”

Question 3

Q for Protons >2 Mev

Answer 3

2

Question 4

Q for alpha, fission fragments, heavy nuclei

Answer 4

20, “Fast Neutrons”

Question 5

Units for Dose Equivalent

Answer 5

***This assumes uniform dose

SI –> Sievert (SV)
1 SV = 1 J/kg = 100 rem

H=DQ–> in units Rem = Dose (rads)Q

Question 6

Effective Dose Equivalent

Answer 6

***This helps to normalize non uniform radiation

Influences Weighting factors (these are stochastic)

Question 7

Total effective background dose

Answer 7

3.0 mSv/yr

Question 8

What are the 3 types of background radiation?

Answer 8

Cosmic
Terrestrial (in soil), Radon is biggest in USA
Internal, from K40

Question 9

What are the effects of low-level radiation and what is the dose threshold?

Answer 9

<10cGy

a) Genetic Effects (mutations and Chrome breaks)
b) Increase Cancer/Tumors (thyroid, luekemia, skin)
c) Neg impact on growth and dev.
d) diminished life span
e) Lense cateracts/ opacification

Question 10

Stochastic

Answer 10

Probability of outcome, NO change in severity of outcome, No known thresholds

↑ Dose = ↑ Probability

Question 11

Non Stochastic

Answer 11

**Also called deterministic
↑ Dose = ↑ Severity of event

Lenses is non-stochastic, has threshold

Question 12

What the the annual dose limits set to achieve?

Answer 12

• Avoid nonstochastic (keep below thresholds)
• Lessen probability that stochastic occurs
• ALARA

***Discount background and medical procedures

Question 13

Annual Occupational Exposure Limit

Answer 13

50mSV / year

Question 14

General Public Limit (2 Types)

Answer 14

Infrequent → 5mSV / year

Frequent → 1mSV/ year (minors included)

Question 15

Embryo Fetus Exposure Limit

Answer 15

5mSV Total

0.5mSV/ Month

Question 16

Cumulative Occupational Exposure Limit

Answer 16

10mSV*Age

Question 17

Lens Occupational Exposure Limit

Answer 17

150 mSV /year

Question 18

Skin, Hands, Feet Occupational Exposure Limit

Answer 18

500 mSV/ year

Question 19

Shielding Max Permissible Dose (2 types)

Answer 19

Controlled 0.1 mSV/ wk or 5mSv/yr

Noncontrolled 0.02 mSV/wk or 1mSV/yr

Question 20

What are the 3 types of radiation we sheild for

Answer 20

Primary&raquo_space;»Leakage»>Scatter

Leakage and scatter are secondary barrier

Question 21

Primary Barrier Calc Equation

Answer 21

Transmission Factor=(Dosed^2)/(WU*O)

Workload (W) - Weekly dose 1m from source. # of pt *dose per pt at 1m

Use Factor (U) time beam is in that direction (Table 16.6)
0 degrees>180 degrees>90 and 270 degrees

Occupancy Factor (O)

Distance (d): in METERS ***ISL applies

Question 22

Occupancy Factors (6)

Answer 22

Full = 1
Adjacent  to room = 1/2
Corridors/Employee lounge/bathroom = 1/5
Valut doors = 1/8
Public unattended locations = 1/20
Outside = 1/40

Question 23

If there are 2 scatters before hitting vault door, how much lead is needed?

Answer 23

6mm

*Should have hydrogenous material for thermal neutrons added

Question 24

What instrument should be used after linac installation?

Answer 24

ion chamber

Question 25

Leakage is defined as

Answer 25

@ 1 m < 0.1% of useful beam dose

Question 26

Inverse square Law

Answer 26

Intensity 1/ intensity 2 = (distance 2/ distance 1)^2