Radiation, nuclear stability and detection (1,2,3) Flashcards
uk net zero by
2050
fission supplies how much of baseline electricity in uk
16-20% (but lots of these reactors are going to be decomitioned by 2036)
fusion
controlled use of nuclear fusion to release energy for work -haven’t harness this process yet
nuclear process
heat chain reaction, which boils water and stream push turbine
baseline energy (consistent, doesn’t turn on and off quickly)
Fission power
controlled use of nuclear fission (atomic splitting) to release energy for work
nuclear limiting issues
health risks, security (terrorism), cost, radioactive waste disposal, reactor saftey
chernobyl disaster year
1986
Fukushima disaster year
2011
lecture 2 electrons (wieght &charge)
light
negative charge
protons (wieght &charge)
positive
mass similar to neutrons
neutrons (wieght &charge)
same mass as proton
no charge, no electrostatic repulsion
is radioactive decay influenced by environment?
no
radioactive decay nucleus
nucleus configuration not stable so rearranges by kicking out a particle
random for individual atom
do Nuclei with>83 protons tend to be stable or unstable?
unstable and have many isotopes
needs more neutrons than protons to be stable
nucleus stability balance between
the Coulombic repulsions and short-range attractions that exist
between component neutrons and protons
the nucleus will be stable if…
the attractive forces within the nucleus balance or outweigh
repulsive forces
the nucleus will be unstable if…
the repulsive forces outweigh the attractive forces,
then the nucleus loses stability and will spontaneously disintegrate,
emitting particles and/or electromagnetic radiation.
This is the phenomenon of
radioactivity.
ionising radiation process
interact with matter, ionise the particle by generating a free radical
UV x-ray gamma ray
alpha
greatest mass
easily stopped (sheet of paper)
only bad if inside you
minus 4 mass no
minus 2 atomic no (bottom)
beta
high speed electron
6mm of aluminium stops it
plus 1 atomic no (bottom)
co-product of beta decay-neutrino
gamma rays
short wavelength, hard to stop,
by product of a lot of radioactive decay
only stopped by dense metals
positron emission
minus 1 from atomic no
oposite of beta
electron capture
nucleus captures an electron
converts proton to neutron
release of gamma
no of protons decreases and neutrons increases by one
Rutherford-Soddy rule
sum of the mass numbers and charges before and after the radioactive decay are the same
nucleus plus something else
sources of radiation
1/4 of daily is you
banana
mostly-rocks, soil, gas, cosmic rad
Ur (decay chain)
first decay has really long half life, then the rest of the decay chain is faster
uranium is a big mineral
doesn’t move via diffusion
if the daughters diffuse out of the rock it can tell you about an environmental event as the atomic clock has been reset
lead Pb
end of Ur decay series, stable, can help date rocks
Fission track analysis
done for large minerals
atom of U-238 disintegrates emitting an alpha particle, a Helium nucleus (He-4). This massive atomic particle causes massive structural damage in the crystal that can be revealed by chemical etching.
The number of tracks in a given area is proportional to the age of the mineral.
Dating metamorphic events
redistribute daughter atom and isotopically reset the date of that rock
can tell you when granite protruded
difference between nuclear reactions and radioactive decay
nuclear reactions are instigated but radioactive decay is natural and random
fusion
joining of two nuclei at extremely high temperature and pressure,
and is the process responsible for the energy of the sun and other stars
fission
splitting of a large nucleus into smaller pieces
carbon 14 is created in the
upper atmosphere
through interactions w cosmic particles and CO2 or nitrogen
plants will use it and become radioactive
fertile
won’t fission but will take a neutron and then will potentially fission later
can fissile fission?
yes
most of U found in ground is
238 U
which is fertile
neutron capture instigates…
fission of the nucleus
causing it to split into 2 fission nuclei, 2-3 free neutrons and release energy
neutrons fly out too fast to cause another fission reaction so we slow them down -chain reaction
speed of neutron
*A slow neutron may induce fission in one type of nucleus (U-235) and not
others (U-238).
*Too fast and it spends too little time near a nucleus for capture to be likely
*Fast neutrons can disrupt U-238 causing ‘transmutation’ into U-239
moderation of chain reactions
free neutrons slowed by inelastic collisions w particles of similar mass
hydrogen nuclei- efficient moderators so h2o often used
D2o -heavy water
When fully moderated, neutrons have energies corresponding to the
temperature of their surroundings, and are referred to as ‘thermal’ neutrons
lifetime supply of fuel (oil and U)
1000 Olympic swimming pools worth of oil
a thimble of uranium
what makes fusion viable
Tritium to fuel the process
not enough and short half life
can take lithium and make tritium but supply from unstable countries
does fusion or fission have less issues
fusion (could be safer)
fusion in stars
hot and dense
For elements lighter than iron (Fe), the fusion process liberates energy.
The fusion of elements heavier than iron consumes energy rather than liberates it
Blocking temperatures in minerals
the processes that result in a “resetting” of the atomic clocks in a rock.
it is possible to heat igneous and metamorphic rocks to high enough temperatures that they no longer
behave as “closed systems”.
daughter products can “leak” out of the primary mineral (diffusional
migration), giving an erroneous parent/daughter ratio and
hence a wrong age
