Typical Decay scheme II

http://www.nucleide.org/DDEP_WG/Nuclides/Na-22_tables.pdf

•Nuclei can decrease their proton number by one in three ways, positron emission (the most common)Electron capture (much more rarely; see next slide), or proton emission (very rare).•Decay rates expressed in terms of Becquerrel (1/sec) or Curies (37 GBq)

Absorption length for gammas(in lead and aluminum)

From E. Segre,“Nuclei and Particles” 2nd ed. (1977)

Examples

1. The LENS neutron source at IU creates roughly 4e4 neutrons per

pC of proton charge (incident at 13MeV) through the reaction:

9Be(p,n)9B in a 1mm thick target. Estimate the cross section for this reaction

(Note: Fro Be =1.85 g/cm3 and W=9.01g/mole).

2. A foil of natural In that is 1.0 mm thick is placed in a thermal neutron beam (v=2200 m/s) of flux 107n/cm2.s. In has a molecular weight of 114.8 g/mole, and a density of 7.31 g/cm3. 116In is a beta emitter and we will assume that it is only produced in a state that decays with a 54 min half life.

a). What is the flux of neutrons on the back side of the foil? b). If the foil is in the beam for 1.0 min, what is the activity due to 116In?

c). What is the 116In activity if the foil is in the beam for 10 hours?

The information at the website on the following slide may be useful.

Cross Sections

http://www.ncnr.nist.gov/resources/n-lengths/

Alpha Decay

http://en.wikipedia.org/wiki/File:Alpha1spec.pngT&R Fig. 12.11

Lecture 23Potential Barrier: Alpha decay

The deeper the “bound” state is below the top of the barrier, the lower will be the kinetic energy of the alpha particle once it gets out, and the slower will be the rate of tunneling (and hence the longer the half-life). Figures from Rohlf “Modern Physics from to Zo”.

Radiation Shielding•Different types of radiation penetrate through matter with different ranges. Alpha particles are very easily stopped (doubly charged and relatively slow), beta particles are relatively easy to stop, gamma rays need very heavy shielding, and neutrons are the hardest to shield against.•https://reich-chemistry.wikispaces.com/b.sulser+and+k.nagle+powerpoint+presentation

neutron

Radiation Dose•Dose:

•1 Gray = 1 J/kg of whatever radiation (energy deposited per unit mass), supplants the RAD (Radiation absorbed dose)•Roentgen (older unit, radiation needed to produce a certain charge per unit mass (1 esu /cm3 of dry air). This corresponds to 0.258 mC/kg.

•Equivalent Dose•1 Sievert: absorbed dose multiplied by factors to account for relative biological effectiveness for particular radiation type (, n etc.; energy etc. ) and body part involved. NOTE units are the same as the Gray, but the meaning is quite different. •REM (Roentgen Equivalent Man): 1 REM = 10 mSv

Radiation Dose

http://www.ccohs.ca/oshanswers/phys_agents/ionizing.html

NOTES:•Prior to 1990 the weighting factor was referred to as the “Quality Factor and you will still see this term used.•There is some controversy over the appropriateness of the weighting factors (especially for alphas)

Effects of Radiation•“LD50/60” Dose that would result in death for 50% of the population so exposed within 60 days (Lethal Dose to 50% of the population)

•LD50/60 limit for gamma radiation is roughly 450 RAD (or 4.5Gray) for whole-body exposure•Threshold lethal Dose (2 Gy, whole body exposure)

•Beyond these acute dose issues, future development of cancer is also a concern

•Doses at ~10 cSv appear to produce no increased risk of cancer•Occupational limits for radiation workers are set at levels below this to be conservative (typically 50 mSv/yr for radiation workers). •Typical background exposure in the US is of the order of 3.5 mSv/yr (as high as 8 mSv/yr in Colorado mountains).

Sources of Background Radiation

•Cosmic Rays•Naturally occurring radioactive nuclei

•40K this is the most abundant radio-nuclide in your body•14C (e.g. about 50 times/sec one C atom in the DNA of one of your cells is converted to N by beta decay).•222R, a decay product from 238U, and a common concern in buildings

•Medical tests•Man-made nuclides (fallout, waste, release etc.).

Sources of Background Radiation

http://web.princeton.edu/sites/ehs/osradtraining/backgroundradiation/background.htm

Effects of Radiation

•Recall: 1 rem is roughly 10mGy for gammas•Typical background radiation is 350 mrem/yr, airline travel gives roughly 0.4-1 mrem/hr (4-10 Sv/hr) http://www.physics.isu.edu/radinf/risk.htmSee also: http://trshare.triumf.ca/~safety/EHS/rpt/rpt_4/node20.html

Radiation Dose•Different types of radiation at a given energy have different “Relative Biological Effectiveness”, and different parts of the body have different susceptibilities to radiation, so you have to be a bit careful about how you quote numbers. •Today medical physicists discuss dose in Gray to specific organs, rather than Sieverts etc..

Relative Biological Effectiveness

http://www.ccohs.ca/oshanswers/phys_agents/ionizing.html

NOTES:•Different parts of the body have different susceptibilities to radiation (in terms of their likelihood of developing cancer after a given exposure) •This is taken into account in planning radiation treatments for cancer.

Relative Biological Effectiveness

http://en.wikipedia.org/wiki/Relative_biological_effectiveness

Note that a 1.5 Gy dose of Carbon ions has the same biological effect as a 4.5Gy dose of photons (for this particular cell type).

Applications of Radiation•Radiation and radioactive materials are used in numerous applications today, we’ll touch on only a few of these:

•Nuclear Medicine•Diagnostics (x-rays, CAT scans, PET scans, etc.)•Cancer treatment (x-rays/gamma-rays, radio-nuclides, protons, heavy ions)

•The key here is that rapidly reproducing cells (such as CANCER, in children/fetuses) are more susceptible to radiation damage AND CANCER cells are less able to repair the damage radiation causes (at least that is the dogma, there is some conflicting information on this).

•Dating of artifacts (archeologic, organic, geologic etc.)•trace element analysis•Nuclear power

Proton Radiotherapy

http://en.wikipedia.org/wiki/Proton_therapy http://mpri.org/science/vstreatments.php

Nuclear Fission

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fission.html

KEY element (from CALM):•Large, unstable, nuclei (2)•Neutron activated dissociation (3)•These are both necessary but not sufficient:•“Chain reaction (8)” but what does that mean?•One neutron induces a reaction that produces MULTIPLE neutrons out (to sustain the reaction) (6) THIS IS THE KEY ingredient.

Fission products

http://www.euronuclear.org/info/encyclopedia/f/fissionproducts.htm

http://en.wikipedia.org/wiki/Fission_products

Nuclear Reactors (LWR’s)

http://reactor.engr.wisc.edu/power.html

Boiling water reactor (BWR) Pressurized water reactor (PWR)66% of US reactors are this type

Yucca Mountain

http://www.ocrwm.doe.gov/ymp/about/why.shtml

American Nuclear Plants

http://www.nrc.gov/info-finder/reactor/

Nuclear Waste depots

http://en.wikipedia.org/wiki/Radioactive_waste

Nuclear Decay Chains

Does not include the 4n+3 chain or Actinium series which terminates in 207Pb (Wikipedia does not have so nice a graphic for that chain; from: http://en.wikipedia.org/wiki/Decay_chain

4n chain: Thorium series 4n+1 chain

Neptunium series

4n+2 chain Radium series

•Dates have to be calibrated to account for historic variations in the production and distribution of 14C in the atmosphere (thank goodness for the Bristlecone pine tree). Figs from:•http://www.ndt-ed.org/EducationResources/CommunityCollege/Radiography/Physics/carbondating.htm

and http://en.wikipedia.org/wiki/Radiocarbon_dating

About 1 part per trillion of atmospheric carbon is 14C, thanks to this mechanism.

Various Dating schemesSee article at: http://physics.info/half-life/

Radiocarbon Dating of a Hypothetical Organic Sample

age (half-lives) age (years) 14C (atoms) 12C (atoms) 14C : 12C (ppt)*

0 0 128 128 × 1012 1

1 5,730 64 128 × 1012 0.5

2 11,460 32 128 × 1012 0.25

3 17,190 16 128 × 1012 0.125

4 22,920 8 128 × 1012 0.0625

5 28,650 4 128 × 1012 0.03125

6 34,380 2 128 × 1012 0.015625

7 40,110 1 128 × 1012 0.0078125

Note; this is really a toy example (1014 carbon atoms is only 2 ng of sample, typically you would need much more; estimate how much more)

Various Dating schemesSee article at: http://physics.info/half-life/

Potassium-Argon Dating of a Hypothetical Mineral Sample

age (half-lives) age (109 years) 40K (atoms) 40Ar (atoms) 40K : 40Ar

0 0 64 0 –

1 1.26 32 32 1 : 1

2 2.52 16 48 1 : 3

3 3.78 8 56 1 : 7

4 5.04 4 60 1 : 15

5 6.30 2 62 1 : 31

6 7.56 1 63 1 : 63

Potassium-Argon Dating of a Hypothetical Mineral Sample

Various Dating schemesSee article at: http://physics.info/half-life/

Radioisotopic Dating Techniques

technique range (years past) dateable items

lead 210 1 – 150 lake and ocean sediments, glacial ice

carbon 14 1 – 40,000 previously living things

uranium series 1 – 400,000 bone, teeth, coral, shells, eggs

potassium-argon 10,000 – 3 billion minerals, igneous rocks

uranium-lead 1 million – 4.5 billion minerals, igneous rocks

rubidium-strontium 60 million – 4.5 billion minerals, igneous rocks

Early Particle discovery: -

From E. Segre “Nuclei and Particles”, 2nd editionParticles appear as tracks (in bubble chambers in the early days, in electronic trackers of various sorts today) that are bent by a magnetic field. By measuring curvature, track length etc.things like half-life, momentum, charge etc. can be determined.

Early categorization of Particles

Early collider experiments started to reveal more and more particles, and people started to question whether they were truly “Fundamental”, but did allow for the prediction of “missing particles that were later found.Attempts to rationalize this “zoo” of particles led Gell-Mann (and independently Zweig) to suggest more fundamental building blocks (based largely on the observation of patterns [symmetries] in the properties of the particles; they appeared in families of 1, 8, 10, 27 etc. members]:

The Standard Model

http://newsimg.bbc.co.uk/media/images/41136000/gif/_41136526_standard_model2_416.gif