Tutorial stuff

Question 1

What is the absolute efficiency of a detector setup.

Answer 1

Fraction of radiation from the source that is detected.

Question 2

Why are scintillation detectors used for beta counting carbon-14 rather than semiconductor detector?

Answer 2

Scintillation detectors have a higher effiency but lower resolution compares to semiconductor detectors. Carbon-14 has a long half life so you need high effiency. We only need decay rate to determine age.

Question 3

Explain AMS

Answer 3

Negative ion source produces ions which are deflected based on m/z. Tandum accelerator towards positive terminal of CDG generator next to stripper. Positive ions are repelled from VDG, moves through second magnet separating out C14.

Question 4

List three effects that have casued a variation in the amount of atmospheric 14C.

Answer 4

Variation in cosmic ray flux, emission of old carbon from fossile fuels (suess effect), atmospheric nuclear weapons testing.

Question 5

How does Uranium-lead dating work

Answer 5

Uranium-235 and 238 both decay to Pb207 and Pb206 respectively. The ratio of the parent and daughter nuclear from two different points in the rock is used to determine the age

Question 6

Energy of head on collision

Answer 6

4Em/M &laquo_space;E

Question 7

Avogadros law

Answer 7

Atom density = (rho*N_A) / A. Multiply by Z for electron density.

Question 8

relationship between stopping power, charge and speed

Answer 8

S \propto z^2/v^2

Question 9

neutron collision parameter

Answer 9

min energy = E_0*alpa

Question 10

Photon attenuation

Answer 10

I = I_0exp(-mu x)

Question 11

Neutron attenuation

Answer 11

I = I_0exp(-Sigma x), Sigma = rhoN_Asigma/A

Question 12

Proportional counter electric field

Answer 12

E = rho/(2piE_0r)

Question 13

Absorbed dose

Answer 13

D = E/m

Question 14

Equivelant dose

Answer 14

H = wD

Question 15

Effective dose

Answer 15

Sum of all equivelant doses

Question 16

Dose rate approx

Answer 16

dD/dt approx= (A(Mbq)*E(MeV)/6r^2

Question 17

Neutron flux

Answer 17

phi = nv

Question 18

reactuin rate

Answer 18

r = Sigma nv

Question 19

4 factor formula

Answer 19

k (8) = eta E p f (infinite reactor)

Question 20

6 factor formula

Answer 20

k = eta E p f P_(fast nuetron leak) P_( (infinite reactor)

Question 21

reactor period

Answer 21

T_p = l / (k-1)

Question 22

Fusion reaction rate

Answer 22

n1n2 <sigma></sigma>

Question 23

Fusion gain factor

Answer 23

Q = Pfus/Pheat

Question 24

Breakeven

Answer 24

Q = 1

Question 25

Transient equilibrium

Answer 25

N2 = y1/(y2-y1)N1(0)(exp(-y1t)-exp(-y2t))

Question 26

Activity from measured gamma spectrum

Answer 26

alpha = n / (eps(abs)*Egamma T I)

Question 27

Secular equilibrium

Answer 27

A1 = A2, y2>>y1

Question 28

Distance for infinite thickness

Answer 28

d> 7/mu

Question 29

Difference between electron mass stopping power in Aluminium and lead.

Answer 29

Lead has a higher atomic number, so greater deflection and greater braking radiation.

Question 30

Give the definition of the absorbed dose

Answer 30

Energy deposited per unit mass (JKg-1) Gy

Question 31

How does the energy of the photon change the way it interacts with a detector

Answer 31

Higher energy is less likely to interact with the detector so it will have a lower efficiency. Higher energy are more likely to do compton scattering, not giving all of their energy compared to photoelectric effect

Question 32

List the radiation weighting factors

Answer 32

Photon: 1, electrons and muons: 1, Protons and charged pions: 2, alpha particles or fission fragments: 20

Question 33

What are the sum of weighting factors for different tissues, Bladder thyroid liver osophagus

Answer 33

Bone marrow + loads of shit: 0.72, Gonads 0.08, bladder + thyroid +liver +osopagus: 0.16, bone , saliver,brain skin: 0.04

Question 34

Name the acute radiation syndromes and the doses at which they occur

Answer 34

Haematopoeitic: 2Gy, Gasto-intestinal: 6 Gy, Nuerovascular: 12

Question 35

What is the UK dose limit for whole body

Answer 35

1 m Sv yr-1

Question 36

Why is zircon useful

Answer 36

zircon is a mineral that holds uranium but expels lead, any lead in zircon is produced by radioactive decay

Question 37

Name all parameters in k_infinite

Answer 37

eta - thermal reproduction factor = fast neutrons produced from thermal fission / thermal neutrons absorbed in fuel. epsilon - Fast fission factor = number of neutrons from all fission / number of fast neutrons from thermal fissions. p - resonance escape probability = neutrons that reach thermal energy / neutrons that slow down. f - thermal utilisation factor = number of thermal neutrons absorbed/number of thermal neutrons absorbed in fuel

Question 38

Name where energy of fission is deposited and the percent of energy.

Answer 38

PROMPT: FIssion fragments (80%) - Fuel rods. Fission neutrons (2.5%) - moderator/ sheilfing. gamma rays (3%) - sheilding / reactor core. DELAYED: B- electron (4%) fuel rod. B- antu neutrino (6%) - lost. gamma ray from B- (3%) reactor core/ sheilding. Radiative Capture (2.5%) reactor core/ sheild

Question 39

What is the purpose of the frisch grid

Answer 39

Same radiaiton causes the same signal in the detector independant of where the radiation interacts.

Question 40

How can a gas filled detector be adaptes to detect thermal neutrons.

Answer 40

If the gas is He-3, Bf-10 or has Uranium -235 lining.

Question 41

Describe how you could find the level of enrichment of a 10mm plate of uranium.

Answer 41

Gamma ray spectroscopy with HPGe detector. Calibrate for absolute efficiency against E (done with152 Eu) and background spectrum. Activity then determined and then N

Question 42

Intrinsic calibration method

Answer 42

Using a samples own emission as calibration. good for irregular shapes