Atomic and Nuclear m - 1. D [1] 2. A [1] 3. C [1] 4. None...

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1. D [1] 2. A [1] 3. C [1] 4. None [1] 5. B [1] 6. (a) Deduct [1] for each error or omission, stop at zero 2 max Property Effect on rate of decay increase decrease stays the same temperature of sample pressure on sample amount of sample (b) (i) α / He 4 2 4 2 ; Rn 222 86 ; 2 (ii) mass defect = 5.2 × 10 -3 u ; energy = mc 2 = 5.2 × 10 –3 × 1.661 × 10 –27 × 9.00 × 10 16 / 1 u = 930 MeV; = 7.77 × 10 –13 J / 4.86 MeV; 3 max (c) (i) (linear) momentum must be conserved; momentum before reaction is zero; so equal and opposite after (to maintain zero total); 3 1
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(ii) 0 = m α v + m Rn v Rn ; - = α m m v v Rn Rn = – 4 222 = –55.5; 3 Ignore absence of minus sign. (iii) kinetic energy of α -particle = ½ m v 2 ; kinetic energy of radon nucleus = 2 2 1 5 . 55 m 4 222 V α ; this is 1 / 55.5 of kinetic energy of the α-particle; 3 max Accept alternative approaches up to [3 max] . (d) eg ( γ -ray) photon energy or radiation; 1 (e) (i) two (light) nuclei; combine to form a more massive nucleus; with the release of energy / with greater total binding energy; 3 (ii) high temperature means high kinetic energy for nuclei; so can overcome (electrostatic) repulsion (between nuclei); to come close together / collide; high pressure so that there are many nuclei (per unit volume); so that chance of two nuclei coming close together is greater; 5 [25] 7. (a) (i) fission 1 max (ii) kinetic energy 1 max (b) the two neutrons can cause fission in two more uranium nuclei producing four neutrons so producing eight etc ; OWTTE ; 1 max 2
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(c) (i) the fuel rods contain a lot more U-238 than U-235; neutron capture is more likely in U-238 than U-235 with high energy neutrons; but if the neutrons are slowed they are more likely to produce fission in U-235 than neutron capture in U-238; 3 max The argument is a little tricky so be generous. The candidate needs to know about there being two isotopes present in the fuel and something about the dependence of the fission and capture in the two isotopes on neutron energy. (ii) control the rate at which the reactions take place; by absorbing neutrons; 2 max (d) Look for four of the following main points and award [1] each. energy lost by the slowing of the neutrons and fission elements heats the pile; this heat extracted by the molten sodium / pressurized water / other suitable substance; which is pumped to a heat exchanger; water is pumped through the heat exchanger and turned to steam; the steam drives a turbine; which is used to rotate coils (or magnets) placed in a magnetic field (or close to coils) which produces electrical energy; 4 max Alternatively, award [4] for a good answer, [2] for a fair answer and [1] for a weak answer. [12] 8. (a) Deduct [1] for each error or omission, stop at zero 2 max Property Effect on rate of decay increase decrease stays the same temperature of sample pressure on sample amount of sample (b) (i) the probability of decay (of a nucleus); is 4.3 × 10 –4 (1 in 2326) in each year; 2 (ii) mass defect = 5.2 × 10 –3 u ; energy = mc 2 = 5.2 × 10 –3 × 1.661 × 10 –27 × 9.00 × 10 16 / 1 u = 930 MeV; = 7.77 × 10 –13 J / 4.86 MeV; 3 max 3
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(c) (i) (linear) momentum must be conserved; momentum before reaction is zero;
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This note was uploaded on 09/21/2009 for the course PHYSICS 2211 taught by Professor Uzer during the Fall '08 term at Georgia Institute of Technology.

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Atomic and Nuclear m - 1. D [1] 2. A [1] 3. C [1] 4. None...

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