Presentation on theme: "Where should we put the nuclear power stations? The deciding factors."— Presentation transcript:
Where should we put the nuclear power stations? The deciding factors
2 How does nuclear power work?
3 Where were the first nuclear power stations sited and when? Issues: Issues: distance from urban centres access to national grid good water supply for cooling absence of natural hazards transport links proximity to both civil airports and military installations
We are now going to look in a bit more detail at the issues
5 Distance from urban centres and access to the national grid Early on, everyone knew that radiation was dangerous. Most of those alive could remember what happened to Japan when the H-bombs were dropped and the devastating after effects. So long as there were concerns about the safety of nuclear power plants, it was felt that it was essential that they were as remote as possible from the big cities. However, in terms of cost and efficiency this had a downside. Remote areas would not have the heavy duty transmission lines necessary to take all the electricity generated by the power station to the grid. The only feasible way to get it there was by carrying it in huge ugly pylons that stretch far over the country in a visually intrusive way. These remote areas were often near National Parks. The National parks did not appreciate their presence.
6 Distance from urban centres and access to the national grid But generally the overhead power transmission is very reliable, although overhead power lines are vulnerable to: lightning strikes; high winds; heavy snowfall. But the cost of burying and the difficulty in repairing underground cables if things did go wrong meant that this means of transmitting electricity almost impossible. Another problem is that electricity does loose power over distance. So the electricity from these remote sites did not provide as much energy to the public as electricity from a power station nearer to centres of population. So once a design was tested and deemed to be safe, the inclination was to build the ones that came after closer to centres of population. This cut down on the number and cost of transmission lines and was a more efficient use of the electricity. But when any new technology was developed, the tendency was again to go for the remoter sites.
7 Good water supply for cooling Because of the heat generated by the process, often more than by coal or gas fired stations, there was a need for vast quantities of water to carry out the cooling process. Cooling towers had been used for coal fired power stations. Bigger, tall more intrusive versions would have required for nuclear power, provide the site was near enough to a good water supply, like a large river for example. The other solution was to put the power station near the sea, where no cooler tower would be needed. The sea would always bring in more water to cool the steam down.
8 Transport links For both the building and maintenance of nuclear power stations, good transport links were a priority. All nuclear power stations have a rail link, often a side line from a main line not too far away and very often the roads have had to be reinforced to take the heavy loads that enter and leave the power station. These are massive structures to build, which need very heavy machinery and vast quantities of raw materials to build them. Once on-line, the fuel rods which are radioactive have to be changed regularly. This was the main use of the railway. It was not acceptable to take these in and out by road as there could accidents or even terrorism attacks were considered.
9 Proximity to both civil airports and military installations Whilst the buildings that house the nuclear power stations are extremely strong, aircraft crashing into them or stray shells falling nearby was not something the authorities wished to happen. So military training grounds nearby was a definite NO. As 75% of all accidents to planes happen close to take-off or landing, nuclear power plants could not be sited under the landing or take-off paths of major airports.
10 Absence of natural hazards Release of radio active materials was the main worry, so the buildings containing the process could not be allowed to be damaged by natural hazards, such as earthquakes, fault lines, floods. In addition places which liable to high winds, extremes of temperature or drought, all of which in excess cause land movements also had to be watched out for. However, now that sea levels are rising due to global warming, this could be problems for those power stations built near the sea.
11 For the first research nuclear power station they went for: prepared site with road access not far from London near to a major university good train link pleasant surroundings! They settled on Harwell: a WW2 airfield that was no longer used that was south of Oxford, which had roads, access and plenty of space with few houses very close to the site already.
12 Why did they build them in pairs? In the meantime …. ….. nuclear power stations were being built in the USA on a production (as against experimental) basis. They had developed their own thoughts – the danger of radiation leakage had become an issue, so their main criteria was to make their nuclear power plants remote which was defined as 5miles (8k) from any town with a population of 1,000 people, 25 miles (40km) from any town with 10,000 people and 50 miles (80km) from any town with 50,000 people. Once the UK decided on building enough to provide about 25% of our electricity in 1960s, we followed their lead. This was one of the rules for all our 22 MAGNOX power stations – 22 of them, built mostly in pairs, over 10 sites. Many were built on the coast and all the other considerations mentioned were taken into account.
13 By the time the second generation of power stations were being built, the Advance Gas cooled reactors (AGR), there were plenty of them around in Europe and there was more confidence in their safety. So the strict remote siting gave way to a acknowledgement of the importance of the other factors influencing the siting. So these gained in importance loss of power and expense of joining them to the national grid And this generation of power stations were place closer to population centres, e.g. Heysham and Hartlepool (which is only 5 miles from Middlesbrough on the mouth of the River Tees).
14 The last one constructed in the UK was a pressurised water reactor (PWR). This was considered to be more experimental and therefore a potential danger. Hence a precautionary approach was taken when deciding its site. And the final stage
15 Our first task of the morning Why was Sizewell chosen as a site for one of the first pair of MAGNOX power stations? Remember these are the issues: distance from urban centres access to national grid good water supply for cooling absence of natural hazards transport links proximity to both civil airports and military installations On the slides 16 & 17 is some information about Sizewell
16 Per sq km
17 Note: the Airport until 1967 was a RAF base. It was no longer used from then although the accommodation housed RAF personnel and Norwich University students. It did not open as a civil airport until Although called an International airport, it is not highly used, mostly in the Summer for package holidays. The 2 RAF airbases have shut – in 1992 and 1993 RAF Airport Main roads and also airfields
18 This is where we are now The squares are all the early MAGNOX stations – most of them are black because they are not operating – they are too old yellow The 2 yellow ones are still going at Oldbury and Wylfa * for those interested in Welsh pronunciation, the last one is oo-ul-va! orange The orange ones are AGRs and all still running – notice some were built alongside the MAGNOX but some were on new sites near towns. Red The only PWR is in Red at Sizewell (called Sizewell B)
19 This is where we are now This is where we are now Why do you think the UK government is having a bit of a panic? It says we need more nuclear power stations as soon as possible! NB 1MW supplies, very roughly, 1000 households. How many households are going to need replacement energy between now and 2016?
20 This is the diagram being used by the government to decide on a hierarchy of possible sites for the next group of nuclear power stations. What it does not show is that those existing power station with shutdown MAGNOX stations will be best of all! Why do you think this is?
21 So the second task is to … Decide whether Sizewell is one of the likely sites for the new generation of nuclear power stations Good reasons please! Do flick back through slides to collect evidence – or maybe even back as far as slides 16 and 17
22 Homework To write up the answers to the 2 questions we have tackled this morning, using full sentences, and justifying all the statements you make wherever possible. 1. Explain why was Sizewell chosen as a site for a MAGNOX nuclear power station. 2. Do you think that Sizewell is likely to be a site for a new nuclear power station in the next 15 years? Explain your reasoning.