transmutation, nuclear fission and fusion

Transmutation, Nuclear Fission and Fusion

Nuclear TransformationsNuclear Transformations: Changing one element into another by particle bombardmentNOH

Nuclear TransformationsRutherford: 1919 First to discover nuclear transformation

How is this different from radioactivity?Not a natural occurrenceCan be controlled stopped or startedTwo reactants instead of oneUses bombardment by a lighter particle

Nuclear TransformationIrene Curie and Frederick JoliotWere the 1st to create an artificial radioactive isotope14 years after Rutherford

Nuclear TransformationHow was it done?Both sets of scientists used alpha particlesThey bombarded a larger nucleus with a smaller particle.Both the nucleus and alpha particle were positive so they repelled each other. Very high energies needed to accomplish transformation. A particle accelerator was used to accelerate the particles to the required speeds.

Accomplishing Nuclear TransformationNeutrons also used. Why would they be easier? They are neutral and not repelled so they are absorbed easier.This is the method used to extend the periodic table.

Creating Synthetic IsotopesSynthetic isotopes are made by using particle accelerators Prior to 1940, the heaviest known element was UraniumSince 1940, many transuranium elements have been produced from nuclear transformations.Get to name them after anything you want Countries or scientists are common

Writing EquationsWrite equations showing the neutron formation of AmericiumBombard (react) Pu-240 with a neutron.Take the product from a and have it undergo beta decay.Show the gamma decay of Am-243.Show the alpha decay of Am-243.

NUCLEAR FISSION AND FUSION

Nuclear EnergyTwo types of nuclear processes that release energy:Fusion: combining two light nuclei to form a heavier nucleusFission: splitting a heavy nucleus into two nuclei with smaller mass numbers

Nuclear FissionWas discovered in the late 1930sA Uranium-235 nucleus was spilt into two lighter elements during neutron bombardment:

The fission of 1 mole of U-235 releases 26 million times as much energy as the combustion as 1 mol of methane

Nuclear FissionBesides the product nuclides, neutrons are also produced

Nuclear FissionEach fission event will produce neutrons that can collide with even more U-235 nucleiBecause each fission event produces neutrons, we call it a chain reaction

Nuclear FissionFor the fission to be self-sustaining at least ONE neutron from each fission event must go on to split another nucleusIf less than one neutron causes a fission event,

If exactly one neutron from each fission event causes ANOTHER fission event, the process sustains itself and is said to beIf more than one neutron from each fission event causes another fission event, the process escalates and the heat build-up causes an explosion(AKA: Ka-Boom)

criticalthe process dies out

Nuclear FissionDuring WWII, the US carried out a research effort called the Manhattan ProjectThe goal was to build a bomb based on the principles of nuclear fissionThis project produced the first fission bombUsed on Hiroshima and Nagasaki in 1945The bomb operates by rapidly escalating fission events that produce an explosion!Oak Ridge, Tennessee. 60,000 workers worked for three years to separate 2 kilograms of uranium-235 from uranium-238 for the Manhattan Project

The other Energy Source: Nuclear FusionCombining two light nuclei to create one heavier nucleusProduces even more energy than fissionOccurs in stars - including our sunFusion of protons to form helium

FusionEfforts are underway to develop a feasible fusion processThere is a ready availability of light nuclidesDeuterium( ) is in seawaterCan serve as fuel for fusion reactionsInitiating fusion is much more intensive than initiating fission

FusionForces binding nucleons together only work at very small distancesGetting protons close requires lots of energyMust be shot at each otherThis is because the protons repel each other, so the repelling forces must be overcome with spee

FusionNeed temperatures of 40 million KelvinProduct of fusion is plasma, which is hard to containScientists are studying two types of systems to produce the extremely high temperatures required:High powered lasersHeating by electric currents (magnets)

*1st artificial nucleus not radioactive needed more E*14 years laterBoth sets of scientists used ___ type of particle?They bombarded a larger nucleus with a smaller particle.Both were positive so repelled each other. Very high energies needed. Used a particle accelerator to accelerate the particles to the required speeds.Neutrons also used. Why would they be easier? They are neutral and not repelled so are absorbed easier.This is the method used to extend the periodic table.