topic test - nuclear physics Flashcards
nuclide
atom with a particular number of protons and a particular number of neutrons
nuclear stability
the result of SNF overcoming the electrostatic repulsion between protons in the nucleus, thus “holding” the atom together
characteristic feature of all unstable nuclei that commence decaying?
radioactive nuclei that undergo spontaneous decay have an imbalance between strong nuclear force and electrostatic force, due to either excess or lack of neutrons, resulting in instability
radiation
energy released as electromagnetic radiation and/or high-speed particles from the nucleus of an unstable isotope in an attempt to attain more stability
radioactive decay
(spontaneous transmutation)
emission of radiation energy and/or particles from nucleus to achieve a more stable state (giving up energy for stability)
radiopharmaceuticals
compound formed by chemically attaching a radioisotope to it
binding energy
energy required to hold the constituent parts together as a nucleus
absorbed dose
physical dose quantity absorbed by a target material when irradiated with some form of nuclear radiation, measured in Grays (Gy)
dose equivalent
equivalent dose that accounts for type of radiation using a weighted factor to quantify biological effects, measured in Seiverts (Sv)
nuclear fusion
reaction in which two or more lighter nuclei combine to form a heavier, more stable nuclide, with the release of energy
applications of nuclear fusion
- potential alternative, cleaner source of energy:
- no high-level radioactive waste
- does not require mining and refining processes
- reduced likelihood of catastrophic accidents
- releases significantly large amounts of energy per reactants
- development of thermonuclear fusion weapons (hydrogen bombs)
nuclear fission
splitting of heavy nucleus into lighter, more stable nuclei (roughly equal)
fissile materials
composed of atoms that can be split by neutrons in a self-sustaining chain reaction (i.e. net release of neutrons) to release enormous amounts of energy
fission chain reaction
self-sustaining process where fast-moving neutrons ejected from one fission reaction result in neutron captures that trigger more reactiosn
controlled nuclear fission
production of thermal energy
uncontrolled accelerating chain reaction
can release energy explosively
critical mass
minimum amount of given fissionable material necessary to achieve a self-sustaining nuclear chain reaction under special conditions
dependant on: kind of fissionable materials, concentration/purity, geometry of surrounding reaction system (surface area, space, shape e.g. pellets)
conditions for a self-sustaining chain reaction
- must be fissile material e.g. uranium-235
- must be at, or greater than, critical mass level (material, purity, geometry)
ways to protect from radiation
- limit TIME of exposure
(reduces total absorbed dose) - maximise DISTANCE from radiation sources
(reduces concentration of radiation by the inverse square law) - wear protective clothing and use protective SHIELDING devices
(blocks radiation from penetrating to living tissue)
harms of radon gas when ingested
inhaled as a gas => easily taken into lungs
(internal dose more dangerous, as it doesn’t need to penetrate)
decays to solid, radioactive polonium which remains in lungs
alpha emitter, which is ionising to body cells (cell death, preventing reproduction, permanent mutations etc)
advantages and disadvantages of nuclear fission power
✅ no CO2 or air pollution
✅ produces more energy/kg than coal
❌ radioactive waste needs to be stored
❌ harmful radiation if reactor meltdown (escapes)
❌ expensive (time, money)
❌ need to mine uranium
advantages and disadvantages of fusion as power source
✅ produces more energy than fission with no waste
❌ requires very high temperatures
currently not a feasible alternative but scientists are still working on it
symptoms of radiation sickness begin to appear in people who receive doses greater than ________________ over a short time period
~ 0.5 Sv
(usually single exposure)
