P1 Revision Booklet

Energy Resources

Medium (Grade C)

Q1.          The diagram shows the National Grid system.

(a)     The National Grid includes step-up transformers.
Explain why.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)

(b)     In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.
Over the next 10 years, more than 300 kilometres of new high voltage transmission cables are to be added to the National Grid. Most of the new cables will be suspended from pylons and run overhead while the rest will be buried underground.

Outline the advantages and disadvantages of both overhead transmission cables and underground transmission cables.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(6)

(c)     When an electric current flows through a transmission cable, a magnetic field is produced.
The graph shows how the strength of the magnetic field varies with distance from both overhead and underground transmission cables that carry the same current.

What conclusions may be drawn from this graph?
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)

(d)     Some people think that, because of the magnetic fields, living close to transmission cables is dangerous to health. Laboratory studies on mice and rats exposed to magnetic fields for two or more years found that the magnetic fields had no effect on the animals’ health.
Draw a ring around the correct answer in the box to complete the sentence.
 
 	economic	 	
Using animals in scientific research raises	environmental	issues.	
 	ethical	 	

(1)
(Total 11 marks)
 Q2.          Electricity may be produced from a number of different energy resources.
(i)      Complete the table below.
The first one has been done for you.
 
Device	Energy
resource	Useful energy transfer
from resource	
Coal-fired power station
	
Coal	
Chemical  electrical	
Hydroelectric power station
	
Stored
water	
....................  electrical	
Solar cell in calculator
	
Sun	
....................  electrical	
Wind turbine
	
Wind	
....................  electrical	
Gas-fired power station
	
Gas	
....................  electrical	

(4)

(ii)      Give one of the five energy resources opposite, which is not classified as renewable.
....................................................................................................................................
(1)

(iii)     State another non-renewable energy resource.
....................................................................................................................................
(1)
(Total 6 marks)

 

Q3.          The drawing shows a hydro-electric dam. Water from the top of the dam flows through pipes to the power station at the bottom of the dam.

(a)     Complete the following boxes to show the useful energy transfer which occurs as the water flows through the pipes to the power station.

(2)

(b)     The electricity generated by the power station is transmitted over long distances. Before this happens its voltage is increased by using a step-up transformer.
          State and explain one advantage and one disadvantage of transmitting electricity at high voltage.
Advantage .................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
Disadvantage ............................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
(2)
(Total 6 marks)
 Q4.          The bar chart shows how the UK’s electricity demands in 2007 were met.

          (a)     What proportion of electricity was generated using renewable energy sources?
          Show clearly how you work out your answer.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)

(b)     By 2020, most of the UK’s nuclear reactors and one-third of coal-fired power stations are due to close, yet the demand for electricity is expected to increase.
          Four students, A, B, C and D, were asked how a demand of 380 billion kilowatt-hours could be met. They made the suggestions given in the table.
 
Student 	Fossil fuels 	Nuclear 	Renewable 	Bought from other countries 	
A 	200 	100	40 	40 	
B	80 	240	40 	20 	
C 	160	80 	100 	40 	
D 	280	0 	100	0 	

(i)      Which student has made the suggestion most likely to result in the lowest carbon dioxide emissions?
...........................................................................................................................
         Give a reason for your answer.
...........................................................................................................................
...........................................................................................................................
(2)

(ii)     Suggest one realistic way in which a householder could help to reduce the annual electricity demand.
...........................................................................................................................
...........................................................................................................................
(1)

(c)     To increase the amount of electricity generated using renewable energy resources would probably involve erecting many new wind turbines.
          The graph shows the power curve of a wind turbine.

(i)      Describe, in detail, how the power output of the turbine varies with the wind speed.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)

(ii)     Give one disadvantage of using wind turbines to generate a high proportion of the electricity required in the UK.
...........................................................................................................................
...........................................................................................................................
(1)
(Total 9 marks)
 Q5.           (a)   Geothermal energy and the energy of falling water are two resources used to generate electricity.
(i)      What is geothermal energy?
...............................................................................................................
...............................................................................................................
(1)

(ii)      Hydroelectric systems generate electricity using the energy of falling water.
A pumped storage hydroelectric system can also be used as a way of storing energy for future use.
Explain how.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)

(b)     In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.
Read the following extract from a newspaper.

Discuss the advantages and disadvantages of the plan to build thousands of offshore wind turbines around Britain and the suggested electricity power link between Britain and Iceland.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(6)
(Total 9 marks)
 Q6.          (a)     Coal, gas, oil and wood are all examples of fuels.
(i)      What are fuels?
...........................................................................................................................
(1)

(ii)     Write the names of these fuels in the table below to show which are renewable and which are non-renewable.

(2)

(b)     The list below shows energy resources which are not fuels.
geothermal        nuclear         solar         tides           wind
          Write the names of the energy resources in the table below to show which are renewable and which are non-renewable.

(2)

(c)     Why is it better to use more renewable energy resources rather than
non-renewable resources?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 7 marks)
 Q7.          (a)     The pie-chart shows how energy is used in a home.
          Complete the table using the information on the pie-chart.

(2)

(b)     We get some of the energy we need in our homes from electricity.
          The graphs show how the amounts of coal and gas used to generate electricity changed between 1960 and 1990.

          Describe these changes.
          Coal ............................................................................................................................
.....................................................................................................................................
.....................................................................................................................................

          Gas ..............................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)

(c)     Read the information below.
•        More carbon dioxide in the air may change the weather. Farmers may then not be able to produce the food we need.
•        Burning coal produces sulphur dioxide. Burning gas does not do this.
•        It is cheaper to generate electricity from gas than from coal.

•        Sulphur dioxide causes acid rain which can kill fish and damage
buildings.
•        Two power stations generate the same amount of electricity. The
one which burns gas produces less carbon dioxide than the other
which burns coal.

          Many people say that the change from coal to gas is better for the environment.
          Why do you think they say this?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 9 marks)
 Q8.          (a)     (i)      A student wrote "Coal traps energy from the Sun". Explain what the student means.
..........................................................................................................................
..........................................................................................................................
..........................................................................................................................
(2)

(ii)     How is energy released from coal?
..........................................................................................................................
..........................................................................................................................
(1)

(b)     The diagram shows the waste products from a coal-fired power station.

(i)      In what form does the power station waste energy?
..........................................................................................................................
(1)

(ii)     Carbon dioxide released into the atmosphere will lead to a rise in the Earth’s temperature. Why?
..........................................................................................................................
..........................................................................................................................
(1)
(Total 5 marks)
 Q9.          A farmer has installed a biogas electricity generator on his farm. This device generates electricity by burning the methane gas produced from rotting animal waste. Methane is a greenhouse gas. When methane burns, carbon dioxide and water are produced.
The animal waste rots in an anaerobic digester. The digester and the generator are kept inside a farm building and cannot be seen from the outside.
(a)     The animal waste used in the anaerobic digester is a renewable energy source.
What is meant by an energy source being renewable?
........................................................................................................................
........................................................................................................................
(1)

(b)     Suggest one reason why farmers have been encouraged to install their own biogas generators.
........................................................................................................................
........................................................................................................................
(1)

(c)     The farmer’s monthly electricity bill using the mains electricity supply was £300.
The biogas generator cost the farmer £18 000 to buy and install.
Assuming the biogas generator provides all of the farmer’s electricity, what is the pay-back time for the generator?
........................................................................................................................
                       Pay-back time = ............................................................
(1)

(d)     It would have been cheaper for the farmer to have bought and installed a small wind turbine.
Give two advantages of using the biogas generator rather than a wind turbine, to generate the electricity used on the farm.
1 .....................................................................................................................
........................................................................................................................
2 .....................................................................................................................
........................................................................................................................
(2)
(Total 5 marks)
Q10.          The table shows the main sources of the energy used in Britain in 1990.
 
coal	35%	
oil	35%	
gas	24%	
nuclear	5%	
moving water
(hydro)	1%	

(a)     Finish the pie-chart, using the figures in the table.

(3)

(b)     How does the amount of energy obtained from nuclear sources in 1990 compare with the amount obtained from moving water?
.....................................................................................................................................
.....................................................................................................................................
(1)

(c)     Moving water (hydro) is a renewable energy source.
          Write down the name of one other renewable energy source.
.....................................................................................................................................
(1)

(d)     Explain why electricity is not included in the table of energy sources.
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 6 marks)
 Q11.          (a)     An electricity company claims to generate all of its electricity from environmentally friendly energy sources.
The energy sources used by the company are shown in the pie chart.

Do you think that the claim made by the company is correct?
Draw a ring around your answer.
 
Yes	No	Maybe	

Explain the reasons for your answer.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(2)

(b)     The government is committed to increasing the amount of electricity generated from renewable sources. A newspaper reported that:

Why is the statement made in the newspaper incorrect?
........................................................................................................................
........................................................................................................................
(1)
(Total 3 marks)
 Q12.          (a)     By 2023, nearly all of the existing nuclear power stations in the UK will be closed down.
(i)      Before a nuclear power station can be demolished, the remaining nuclear fuel, radioactive waste materials and reactor must be carefully removed.
What is this process called?
Put a tick () in the box next to your answer.
 
decommissioning		

decontaminating		

dismantling		

(1)

(ii)     The workers are exposed to radiation as they remove the reactor. One of the biggest risks is from the isotope cobalt-60, which has a half-life of 5.3 years.
Explain the advantage of waiting 11 years after a nuclear power station has closed down before starting to remove the reactor.
...............................................................................................................
...............................................................................................................
...............................................................................................................
...............................................................................................................
(2)

(b)     It is almost certain that new nuclear power stations will be built in the UK.
The table shows the results of surveys asking people in the UK whether they were in favour of, or against, the building of new nuclear power stations.
 
 	2001	2005	2007	
Percentage (%) in favour	20	41	65	
Percentage (%) against	60	28	20	
Percentage (%) not sure	20	31	15	

(i)      From these surveys, how did public opinion on the building of new nuclear power stations change between 2001 and 2007?
...............................................................................................................
...............................................................................................................
(1)

(ii)     Suggest a reason why some people may think that the results from these surveys are unreliable.
...............................................................................................................
...............................................................................................................
(1)

(iii)    Give one reason in favour of building new nuclear power stations.
...............................................................................................................
...............................................................................................................
(1)

(c)     The government of one Middle Eastern country has decided to build its first nuclear power station. The oil that would have been used to generate electricity can then be sold to other countries.
On what is this decision based?
Put a tick () in the box next to your answer.
 
economic issues		

ethical issues		

social issues		

(1)
(Total 7 marks)
 Energy Resources-Mark scheme

M1.          (a)     increases the voltage (across the cables)
or
decreases the current (through the cables)
1

reducing energy losses (in cables)
accept heat for energy
do not accept electricity for energy
do not accept no energy loss
accept wires do not get as hot
or
increases efficiency of (electricity / energy) transmission
ignore reference to travel faster
1

(b)     Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the Marking Guidance, and apply a ‘best-fit’ approach to the marking.
0 marks
No relevant content
Level 1 (1-2 marks)
There is a brief description of one advantage or disadvantage of using either overhead or underground cables.
Level 2 (3-4 marks)
There is a description of some of the advantages and / or disadvantagesfor both overhead and underground cables, with a minimum of three points made. There must be at least one point for each type of cable.
Level 3 (5-6 marks)
There is a clear and detailed description of the advantages and disadvantages of overhead and underground cables, with a minimum of five points made. At least one advantage and one disadvantage for each type of cable.
examples of the points made in the response
marks may be gained by linking an advantage for one type of cable with a disadvantage for the other type of cable
eg
overhead cables are easy to repair = 1 mark
overhead cables are easier to repair = 1 mark
overhead cables are easier to repair than underground cables = 2 marks
Overhead
Advantages
•        (relatively) quick / easy to repair / maintain / access
easy to install is insufficient
do not accept easy to spot / see a fault
•        less expensive to install / repair / maintain
less expensive is insufficient
•        cables cooled by the air
accept thermal energy / heat removed by the air
•        air acts as electrical insulator
accept there is no need for electrical insulation (around the cables)
•        can use thinner cables
difficult to reach is insufficient
land beneath cables can still be used is insufficient
Disadvantages
•        spoil the landscape
•        greater risk of (fatal) electric shock
•        damaged / affected by (severe) weather
accept specific examples eg high winds, ice
more maintenance is insufficient
•        hazard to low flying aircraft / helicopters
kites / fishing lines can touch them is insufficient 
hazard to aircraft is insufficient
Underground
Advantages
•        cannot be seen
•        no hazard to aircraft / helicopters
•        unlikely to be / not damaged / affected by (severe) weather
less maintenance is insufficient
(normally) no / reduced shock hazard
installed in urban areas is insufficient
Disadvantages
•        repairs take longer / are more expensive
accept harder to repair / maintain
have to dig up for repairs is insufficient
•        (more) difficult to access (cables)
hard to locate (cables) is insufficient
faults hard to find is insufficient
•        (very) expensive to install
•        thicker cables required
•        need cooling systems
•        need layers of electrical insulation
•        land disruption (to lay cables)
accept damage to environment / habitat(s)
or
cannot use land either side of cable path
accept restricted land use
6

(c)     examples of acceptable responses:
allow 1 mark for each correct point
•        closest to cables field from underground is stronger
•        field from overhead cables stronger after 5 metres
•        field from underground cables drops rapidly
•        field from overhead cables does not drop much until after 20 metres
accept values between 20 and 30 inclusive
•        overhead field drops to zero at / after 50 metres
•        underground field drops to zero at / after 30 metres
•        (strength of) field decreases with distance for both types of cable
if suitably amplified this may score both marks
2

(d)     ethical
1
[11]
 M2.          (i)      gravitational or potential
do not accept stored
1
          light
credit solar
1
          kinetic or movement
credit moving
1
chemical
1

(ii)      any one from
gas
coal
1

(iii)     any one from
          oil
do not accept petrol or paraffin
          peat or turf 
nuclear
credit coal or gas if not given as answer to part (ii)
do not accept wood or fossil fuel or chemical
1
[6]
 M3.          (a)     mark independently
(from) gravitational
accept potential
do not credit stored
1
(to) kinetic
accept movement
1

(b)     advantage
          * the current can be low (for the same power)
* less energy or heat loss or  power loss
accept the cables do not have to be (so) thick 
accept less cost to support higher (rather than heavier) cables
accept aluminium can be used and aluminium is cheaper than copper
do not credit efficient or cheaper
do not credit no loss of energy
do not credit electricity loss
2

disadvantage
          * it is difficult to insulate high voltage
* pylons have to be taller and so more expensive
...to give a good separation between them and the ground /people/high vehicles
or ... to prevent/reduce the danger of electric shock or lethal 
do not credit dangerous
do not credit get a shock
do not credit reference to step down transformers or electromagnetic field
2
[6]
 M4.          (a)     1/25 or 1:25 or 0.04
accept 4 % or  or 1 in 25 for both marks
 
allow 1 mark for total of 375
allow 1 mark for a clearly correct method using a clearly incorrect total
do not accept 1:26
2

(b)     (i)      B
do not credit reason if B is not chosen
1
         (only) burning fossil fuels produces carbon
dioxide / carbon (emissions)
or nuclear fuels don’t produce carbon dioxide
insufficient – smallest amount of fossil fuels
accept less carbon dioxide
1

(ii)     accept anything reasonable eg
         increased level of insulation
         use energy efficient light bulbs
         do not leave appliances on standby
         switch thermostats down (1°C)
         generate own electricity
         install solar panels
accept insulate
accept specific examples eg loft
1

(c)     (i)      any three from:
•        no power output until wind speed exceeds 4m/s
•        output rises rapidly after 4m/s
•        output begins to level out / rises less rapidly at /
after 13m/s
•        output peaks at 21 / 22m/s
•        output constant between 21 / 22 and 25 / 26 m/s
•        output falls (rapidly) after 25 / 26m/s
accept for 1 mark goes up then comes down
3

(ii)     any one from:
•        unreliable energy source
•        dilute energy source
•        take up too much land
accept wind does not always blow
accept need thousands / lots of turbines
ignore reference to visual / noise pollution
ignore reference to kill birds
1
[9]
 M5.          (a)     (i)     energy from hot rocks in the Earth
accept heat that occurs naturally in the Earth
accept steam / hot water rising to the Earth’s surface
accept an answer in terms of the energy released by radioactive decay in the Earth
heat energy is insufficient
1

(ii)     water is pumped / moved
1
up (to a higher reservoir)
this mark point only scores if first mark point is awarded
1

(b)     Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response.Examiners should also refer to the Marking Guidance and apply a ‘best-fit’ approach to the marking.
0 marks
No relevant content

Level 1 (1-2 marks)
There is a brief description of at least one advantage or disadvantage for either the planned wind turbines or the suggested electricity power link.
Level 2 (3-4 marks)
There is a description of advantages and disadvantages for either the planned wind turbines or the suggested electricity power link.
or
A description of the advantages or disadvantages for both the planned wind turbines and the suggested electricity power link.

Level 3 (5-6 marks)
There is a clear and detailed description of at least one advantage and one disadvantage for both the planned wind turbines and suggested electricity power link.
examples of the points made in the response

Offshore wind turbines
advantages
•        renewable (energy resource)
•        low running costs
•        energy is free
•        no gas emissions (when in use)
accept a named gas eg CO2
accept no fuel is burned
accept less dependent on fossil fuels
•        land is not used (up)

disadvantages
•        unreliable – accept wind does not always blow
ignore references to destroying or harming habitats
•        hazard to birds / bats
•        visual pollution – do not accept noise pollution
do not allow if clearly referring to onshore wind turbines
do not accept spoils landscape
•        difficulty of linking turbines to the National Grid
•        large initial cost
•        difficult to erect / maintain
accept a lot of maintenance needed
•        CO2 emissions in manufacture (of large number of turbines)

Suggested Link
advantages
•        income for Iceland
•        using Iceland’s (available) energy (resources)
accept using (Iceland’s) renewable energy (resources)
do not accept reduce the amount of Iceland’s wasted energy
•        provide electricity when wind does not blow / reliable
•        provide electricity at times of peak demand
•        even out fluctuations in supply
•        excess electricity from Britain (windy days) to Iceland and used to pump water up to store energy
•        Britain less dependent on fossil fuels
accept Britain needs fewer (new) power stations
accept conserves fossil fuels

disadvantages
•        large initial cost
accept expensive (to lay cables)
•        power loss along a long cable
•        (engineering) difficulties in laying / maintaining the cable
accept difficult to repair (if damaged)
6
[10]
 M6.          (a)     (i)      sources of energy
for 1 mark

(ii)     wood      coal
              oil 
              gas 
all correct gains 2 marks
3 correct gains 1 mark
3

(b)     geothermal      nuclear
tides
wind
solar
all correct gains 2 marks
4 correct gains 1 mark
2

(c)     non-renewable fuels cause pollution (or reverse)
conserve/limit use of coal/gas/oil;
so supplies last longer/renewable sources can be replaced 
any 2 from 4 for 1 mark each
2
[7]

##
          (a)     cooking and heating water 30
heating rooms 50
each for 1 mark
2

(b)     coal
idea that amount used fell/declined/line goes down
gains 1 mark
          but idea that fall/decline is steady/gradually/approx halved
gains 2 marks
          gas
ideas that
amount used rose/increased
in/from 1980/more used before 1980/ref to 1980
        as an important date/rapid increase in use
(credit idea that gas>coal from c.1990
in either part with 1 mark (to maximum 4)
each for 1 mark
max 4

(c)     •    less carbon dioxide produced
•        less change to weather/food production/gained
warming/water levels (no mark for “greenhouse gas” alone)
•        no/less sulphur dioxide produced/coal produces sulphur dioxide
•        less acid rain/damage to fish/buildings/trees/crops/animals/tumours etc
(do not credit reference to cost unless : cheaper so can spend more on environment)
(“It” used in an answer will refer to “gas”) any 3 for 1 mark each
3
[9]
M8.          (a)     (i)      photosynthesis for growth
accept plants require sunlight for growth
1
plants change into coal
any mention of animals negates second mark
1
(ii)     burning
do not accept heating
accept combustion
1
          (b)     (i)      heat
1
(ii)     less heat radiated into space
accept increased insulation round earth
accept reflects heat back to earth
accept greenhouse effect
accept traps heat or energy
1
[5]

 

M9.         (a)     can be replaced as fast / faster than it is used
accept will not run out
can be used again negates this mark
1

(b)     any one from:
•        reduce demand on power stations / National Grid (system)
•        to increase the amount of electricity generated (from renewable energy)
•        to conserve fossil fuels
accept use less fossil fuels
•        plenty of animal waste / fuel (available)
accept so animal waste can be used usefully
accept to save money / sell the electricity
produces less harmful gases / SO2 is insufficient
better for environment is insufficient
1

(c)     60 (months) / 5 (years)
ignore any unit given
1

(d)answers must be in terms of the biogas generator
any two from:
•        reliable energy source
or
does not depend on the weather
accept works all of the time
•        uses up waste products
accept animal waste readily available
•        not visually polluting
•        concentrated energy source
•        quieter
ignore it is renewable
do not accept generates more electricity (than wind turbine)
2
[5]

M10.          (a)     sectors closer to correct value than ± 1% nuclear (5%)
gas 24% moving water 1%
each for 1 mark 
maximum of 2 marks
3
          sectors labelled correctly w.r.t. rank order of size
for 1 mark
          But deduct 1 mark if not all sectors used

(b)     5 × as much     (do not credit simply more/4% more)
4 × as much
1
(c)     wind/waves/solar/tides
(allow geothermal/wood/biomass)
any one for 1 mark
1

(d)     idea that
electricity is a secondary/man made source/needs another
source to produce it
for 1 mark
1
[6]
 
M11.          (a)marks are awarded only for the reason but must match the 
ringed answer
for both marks a MAYBE answer should include a YES and NO response answers in terms of the sources being renewable ornon-renewable are insufficient
any two from:
YES answers may include:
•        wind produces no pollutant gases
accept wind burns no fuel
accept CO2 / SO2 / oxides of nitrogen / greenhouse gas for pollutant gases
•        nuclear produces no pollutant gases
accept nuclear burns no fuel
•        (burning) gas does not produce SO2
accept gas does not cause acid rain
do not accept they don’t / none produce pollutant gases
NO answers may include:
•        nuclear produces radioactive waste
•        (burning) gas produces CO2 / pollutant gases / air pollution
accept contributes to global warming / greenhouse effect
2

(b)     nuclear power stations use a non-renewable fuel
accept uranium / plutonium is non-renewable
do not accept some are unrenewable
1
[3]
 M12.         (a)      (i)     decommissioning
1

(ii)     level of radiation or radiation dose (to workers) decreased
accept the isotope / cobalt(-60) has decayed (a lot)
accept the isotope / cobalt(-60) has decayed in 2 half lives
accept exposed to less radiation
do not accept no radiation left
1

less hazardous / dangerous (to workers' health)
accept safer
do not accept there is no hazard
accept allows reactor to cool (down)
an answer of radiation levels decrease by 75 % or drops to 25 % gains 2 marks
1

(b)     (i)      more in favour
or
fewer against
quoting figures alone is insufficient
do not accept it increases
ignore any reasons given
1

(ii)     any one from:
•    sample too small
•    do not know how many (people) were asked
•    different people asked (in different years)
•    sample not representative (of population)
•    people did not understand the questions
•    do not know who carried out the surveys
do not accept they are biased unless acceptable reason for bias given
•    do not know if surveys asked same questions
1

(iii)    any one from:
•    no / less pollutant gases produced
accept a named gas
accept does not contribute to global warming
•    reliable source (of energy / electricity)
•    running out of fossil fuels
accept a named fossil fuel
•    conserve fossil fuels
accept fossil fuels won’t have to be used
•    meet increasing demand
•    less reliance on imported fossil fuels / electricity
accept named fossil fuel
•    concentrated energy source(s)
•    lower transportation costs for fuel
•    to replace old nuclear power stations
ignore references to efficiency / job creation / local economy / selling electricity
1

(c)     economic issues
1
[7]