Physics 100

Lecture 14

Energy from Nuclear

Fission

March 12, 2018

1

Radioactive decay

Random process leads to

exponential decay curves

applet 1

applet 2

The half-life &

radioactive clocks

0

1 2

0

ln 2 0.693

1

2

t

x

N N e

N

N

2

If you start with 2 kg of a radioactive

substance, how much will you have after

4 half-lives?

3

A. 125 g

B. 500 g

C. 2.0 kg

D. 8.0 kg

If you start with 2 kg of a radioactive

substance, how much will you have

after 4 half-lives?

A. 125 g

B. 500 g

C. 2.0 kg

D. 8.0 kg

4

0

0

1 1 1=

2 2 16

1 12.0 kg

16 16

0.125 kg 125 g

xN

N

N N

4

If the ratio of 14

C to 12

C in a piece of bone

is only 1/8 of the atmospheric ratio, how

old is the bone? The half-life of 14

C is

5700 years.

5

A. 713 y

B. 1900 y

C. 17,100 y

D. 45,600 y

If the ratio of 14

C to 12

C in a piece of bone

is only 1/8 of the atmospheric ratio, how

old is the bone? The half-life of 14

C is

5700 years.

A. 713 y

B. 1900 y

C. 17,100 y

D. 45,600 y

0

1 1 3

2 8

3 5700 y 17,100 y

xN

xN

6

Einstein and mass-energy

In 1905 Albert Einstein proposed his special theory of relativity

His theory predicted that the total energy of a particle is the sum of its kinetic energy and its rest energy.

E = rest energy (J), m = mass (kg), c2 = 9.0×1016 m2/s2

2E mc

7

A paper clip has a mass of 1.0 gram. If all of its

mass were converted to electrical energy, how

many kWh could be produced?

8

A. 2.5×107 kWh

B. 9.0×104 kWh

C. 2.5×1013 kWh

D. 9.0×1016 kWh

A paper clip has a mass of 1.0 gram. If all of its

mass were converted to electrical energy, how

many kWh could be produced?

2

16 2 2

13

6

7

0.0010 kg 9.0 10 m /s

1 kWh9.0 10 J

3.6 10 J

2.5 10 kWh

E mc

E

9

The binding energy per nucleon

10

How would nuclear energy be best

derived from polonium-209?

11

A. Nuclear fusion

B. Nuclear fission

C. Spontaneous

radioactive decay

D. It would be

impossible

A nuclear fission reaction

A colliding neutron can split or fission a 235U nucleus

The mass of the products is less than

the mass of the reactants

The remaining mass is converted to

energy

235 142 91

92 56 36n U Ba Kr 3n

12

A chain reaction

Each neutron produced can set off

another fission event

A chain reaction is initiated

Animation applet

13

How to build a nuclear reactor

University of Notre Dame

Engineering Magazine

Technical Review

14

Animated Nuclear Power Plant

15

The reactor

core

http://www.eia.doe.gov/cneaf/nuclear/page/nuc_reactors/pwr.html

16

US nuclear power plants

Map: Nuclear Energy Institute

17

Right here in Wisconsin

Map from radiological emergency preparedness site: http://emergencymanagement.wi.gov/REP-GIS/

18

Point Beach Nuclear Power

Plant – Two Rivers, WI

19

A 30% efficient nuclear power plant produces

2.0 GWe = 2.0×109

W of electricity. How much fuel

mass does it convert to energy in one day?

20

A. 6670 kg

B. 84 kg

C. 2.0 kg

D. 6.4 grams

A 30% efficient nuclear power plant produces

2.0 GWe = 2.0×109

W of electricity. How much fuel

mass does it convert to energy in one day?

99

98

2 16 2 2

8

2.0 10 J/s 6.67 10 J/s

0.30

6.67 10 J/s7.41 10 kg/s

9.0 10 m /s

7.41 10 kg/s 86,400 s/d 0.0064 kg 6.4 g

H

H

W We Q

Q e

Em

c

21

Class Quiz Chs. 13-14: What is the

daughter isotope for the beta

minus decay of ?

22

185

74W

181

72

185

73

185

75

189

76

Hf

Ta

Re

Os

A.

B.

C.

D.

Nuclear safety and consquences

Core must be run relatively cool – lower

efficiency (32% vs. 38% for coal plant)

Power plants have a limited life span

Environmental safety concerns and cost

overruns have halted new construction

23

Nuclear Waste

Spent fuel from a nuclear reactor is a high-level radioactive waste

We need a place to safely deposit these wastes for 10,000+ years• Long-term thermal management needed

• No water exposure

Waste is currently stored on site in large pools of water next to the reactor.

24

Disposal of nuclear waste

The government has chosen deep burial at

Yucca Mountain, Nevada

Other options include burial in salt beds, burial

under Antarctic ice sheets, seabed disposal,

launching into space, and fuel reprocessing,

but most countries choose burial in rock or salt.

Yucca Mountain, Nevada

25

Table 14-6, p. 496

26