PSC 4010

PSC 4010Nuclear Technology: A matter of Energy

PSC 4010: Chapter 5Goals:

_ SWBAT compare the A-bomb and the H-bomb (components, power, nuclear reaction, effects)

_SWBAT compare nuclear power stations with thermal and hydroelectric ones

_SWBAT describe the operation of a CANDU nuclear reactor

_SWBAT compare the technology used in CANDU reactors with that used in other countries

_SWBAT describe the use of radioactivity in medicine, food irradiation and C-14 dating

_ SWBAT compare advantages and disadvantages (and difficulties) of using nuclear fission or fusion to produce electricity

PSC 4010: Chapter 5Introduction (p. 5.3):

Uses for nuclear energyMedicineElectrical generationMilitary (bombs, submarines, spaceships)

PSC 4010: Chapter 5Atomic bomb (A-bomb)(p. 5.4 5.8):

First tested, and then used (Hiroshima & Nagasaki) in 1945Uses nuclear fissionEasily fissionable isotopes (U-235 or Pu-239) as fuel for chain reaction

Critical mass: minimum amount of radioactive matter which produces stable number of fissions over timeAmount of fissionable material can be calculated (more than critical mass, uncontrollable chain reaction; less, chain reaction does not sustain itself in time)

PSC 4010: Chapter 5Atomic bomb (A-bomb)(p. 5.4 5.8):

Fissionable material is separated into two blocks, each with mass < critical mass.These block are propelled against each other with the detonation of an explosive (dynamite).The mass of both blocks exceeds critical mass, so chain reaction is uncontrolledPower of A-bomb is equivalent to 20 000 tons of TNT

PSC 4010: Chapter 5Atomic bomb (A-bomb)(p. 5.4 5.8):

Four aspects (consequences) of A-bomb explosion:Direct radiation (billion of small bullets shot at you, made of all 3 types, alpha, beta, gamma)Extremely high temperaturesBlast of air (can destroy buildings or dismember animals and human beings)Contamination of dust

PSC 4010: Chapter 5Nuclear changes:

Practice ExercisePage 5.6, Ex. 5.1 & 5.2Page 5.8, Ex 5.4

PSC 4010: Chapter 5Hydrogen bomb (H-bomb)(p. 5.9 5.13):

First tested in 1952Uses nuclear fusionTemperature at center of explosion is 5 times that of center of Sun! (Fig. 5.3, p. 5.9)Thermonuclear bomb (high temperatures needed : millions of degrees)Using Deuterium and Tritium (H isotopes) can lower T neededNeeds an atomic bomb (nuclear fission) to provide energy for detonation!

PSC 4010: Chapter 5Hydrogen bomb (H-bomb)(p. 5.9 5.13):

Use dynamite to trigger nuclear fission (A-bomb)Then use temperature and energy from A-bomb to detonate H-bomb (Figure 5.4, p. 5.11)Fusion of uranium in A-bomb releases neutrons that collide with lithium, and transform it to tritiumTritium then fuses with deuterium to form helium, releasing SPECTACULARLY LARGE amounts of energy (and neutrons)No critical mass, therefore no limits of explosive power of H-bombEnergy produced (fusion) is 3 to 3.5 times that of A-bomb (fission)

PSC 4010: Chapter 5Nuclear changes:

Practice ExercisePage 5.13, Ex. 5.8 & 5.9

PSC 4010: Chapter 5Use of Nuclear Fission to produce electricity:(p. 5.13 5.17):

History1945 Atomic Energy of Canada Limited (Ontario)1955 Canada Energy Program selected principles for CANDU (nuclear reactor)1962 first experimental reactor started producing electricity (Ontario)1972 first Canadian nuclear station (Pickering One)

PSC 4010: Chapter 5Use of Nuclear Fission to produce electricity:(p. 5.13 5.17):

ProductionElectrical generator (force into electricity)Turbine moved by pressurized steamFigs. 5.5 & 5.6 (pp. 5.14, 5.15) Diagrams of power stationsFig 5.8, p. 5.16:0.5 kg coal, 1.5 kW/h0.5 kg gas, 2.0 kW/h0.5 kg uranium, 30 000 kW/h

PSC 4010: Chapter 5Use of Nuclear Fission to produce electricity:(p. 5.13 5.17):

Operation

Nuclear fissionUranium (natural or enriched) arranged in rods or bundles (mass below critical to avoid chain reaction)Cadmium rods are inserted in core of reactor (control rods: absorb neutrons produced which will slow down chain reaction)Coolant: heats water and turns it into steam (at boiler), which is latter used to move turbine

PSC 4010: Chapter 5Use of Nuclear Fission to produce electricity:(p. 5.13 5.17):

Operation

In Canada, coolant is heavy water (D2O, made of Deuterium instead of Hydrogen). It also has the ability to act as moderator, slowing neutrons ejected by core of reactorIn other countries, coolant is ordinary water or gasHeat after being absorbed by coolant is transported to Boiler (big water reservoir)Boiler, produces pressurized steam (large T and P) that is sent to rotate the turbine, which is connected to a generator, thus producing the electricity

PSC 4010: Chapter 5Use of Nuclear Fission to produce electricity:(p. 5.13 5.17):

Operation

Steam is then cooled down back to water in a condenser, using cold water pumped from outside source

Water is sent to reactor afterwards for new cycle (closed circuit, minimum environment contact)

Fuel bundles are changed during operation, in order to work continuously

PSC 4010: Chapter 5Power plants comparison:

HydroelectricThermalNuclearCondenserNAYesYesE producedPotential Energy (Water)Chemical Change*operates with coal*contributes to acid rainNuclear ChangePollution / WasteNAYesYesTurbineYesYesYesBoilerNAYesYesCoolantNANAYesSteam to move turbineNAYesYesPSC 4010: Chapter 5CANDU Reactor (p. 5.18 5.20):

CANada, Deuterium, UraniumUse Cadmium control rods (slow chain reaction)Use Heavy Water (coolant and moderator / to slow neutrons)Use natural uranium (nuclear waste, as old ones are replaced by new ones) (*States use enriched uranium)Work continuously (no interruptions)

PSC 4010: Chapter 5*Enriched uranium due to higher capacity of ordinary water to absorb neutrons. Thus, higher proportion of U-235 improves fission probability

*No containment shell (Cherbnobyl, Ukraine), Containment shell (Three Mile Islan, PA, USA)

Reactor ComponentCanadaUSAUK (England)RussiaFuelNatural UraniumEnriched Uranium*Enriched Uranium*Enriched Uranium*ModeratorHeavy WaterOrdinary WaterGraphiteGraphiteCoolantHeavy WaterOrdinary WaterPressurized GasOrdinary WaterPSC 4010: Chapter 5Nuclear changes:

Practice ExercisePage 5.20, Ex. 5.14 - 5.16Page 5.24, Ex 5.17 & 5.19

PSC 4010: Chapter 5Slowpoke reactor (p. 5.21):

Miniature nuclear reactor (12 m high)Household of water with reactor insideProduces up to 12 MW and 9 liters of waste per year of use

PSC 4010: Chapter 5Medical applications (p. 5.25 5.28):

Destruction of cancerous cellsCo-60 destroys tumors ( rays), breaks down genetic material _rotate to minimize affectation _many treatments to minimize overdose

PSC 4010: Chapter 5Medical applications (p. 5.25 5.28):

TracersDetecting rate of absorption of radioactive tracers by an organ, can show proper functioning of said organ (Figure 5.11, p. 5.26)Must have short half-life to minimize body exposure

PSC 4010: Chapter 5Food irradiation(p. 5.29 5.30):

Co-60 radiations kills microorganisms that can cause food decayFood does NOT become radioactive (advantageChanges chemical composition of food, therefore changes it nutritional value (disadvantage)

PSC 4010: Chapter 5Nuclear changes:

Practice ExercisePage 5.30, Ex 5.24 & 5.25

PSC 4010: Chapter 5Other uses of Nuclear Energy(p. 5.30 5.32):

Carbon-14 dating

_While alive, beings absorb C-12 & C-14 in same ratio

_Once dead, C-12 stays, C-14 decays (half life = 5730 years)

_C-12/C-14 ratio tells us age of dead tissues

PSC 4010: Chapter 5Nuclear changes:

Practice ExercisePage 5.31, Ex 5.27

PSC 4010: Chapter 5Other uses of Nuclear Energy(p. 5.30 5.32):

Submarines

_To produce electricity and move propels of submarines

_To produce water (electrolysis)

PSC 4010: Chapter 5Other uses of Nuclear Energy(p. 5.30 5.32):

Spaceships, cargo planes, boats

_To power cargo planes and boats

_To power spaceships

PSC 4010: Chapter 5Use of Nuclear Fusion to produce electricity(p. 5.33 5.38):

Sun

_Natural fusion reactor (hydrogen atoms fuse to deuterium, which fuses with hydrogen to turn into tritium, which fuses with deuterium to form helium)

_Earths uses very little of suns energy produced, still enough for our needs

_Nuclear fusion brings about Plasma (4th state of matter)

PSC 4010: Chapter 5Use of Nuclear Fusion to produce electricity(p. 5.33 5.38):

Energy associated with fusion (Advantages)

_Fusion produces 3 times the energy of Fission for same amount of initial material

_No risk of uncontrolled reaction for fusion requires constant heat

_Cheap and abundant fuel (deuterium is easily found in sea water)

_Process releases very little radiation

Energy associated with fusion (Disadvantages)

_Temperatures needed are too high (millions of degrees). No material can withstand heat without melting (use of magnetic fields to contained lab-generated nuclear fusion material)

PSC 4010: Chapter 5The Tokamak fusion reactor:

Very strong electric currents (heat up plasma in middle of contained magnetic field)Fusion is forced as T and P rise inside reactorEnergy produced boils water into steam and this moves turbines to generate electricity

*UK (1991) first ever experimental fusion reactor (two minutes, 1 million Watts worth of energy!)PSC 4010: Chapter 5Practice Exercises for Chapter 5:

Page 5.41 5.43 Ex 5.34 5.45