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9.Usage and Disposal of Radioactive materials

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9.Usage and Disposal of Radioactive materials

The President's Green Column

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9.Usage and Disposal of Radioactive materials

In the past 3 entries, I wrote about the 'Insufficiency of Energy Resources, Water and Food'. I would like to move on to write about the 'Usage and Disposal of Radioactive materials'.

The 2 main usages of radioactive materials are generation of nuclear power and nuclear weapon.

I would not comment too much with regards to use of nuclear weapons. However, I think that it is absolutely important that nuclear weapons within countries that have the proper management system.

I intend to focus on the generation of nuclear power and bring up problems of using and disposing radioactive materials.

Generation of nuclear power in the limelight

Inflation of Oil Prices and the aftermaths of CO2 to global warming have led to the global attention towards generation of nuclear power as an alternative to cater to growing demand for energy resources. As of now, plans to build 127 nuclear plants in 21 countries have already been materialized. The eventual goal is to have 222 nuclear plants in 29 countries. (Reference made from data of World Nuclear Association in Dec, 2007)
I would like to analyze how nuclear power contributes to the reduction of CO2 emission and how it might adversely affects our environment upon disposing it.

How nuclear power contributes to the reduction of CO2 emission?

I would first like to look into how efficient is nuclear in reducing the emission of CO2. The amount of CO2 emitted varies with methods of power generation. The varying conditions and methods affect the figures. The below is the latest analysis from the Central Research Institute of Electric Power Industry showing data of 10th July 2001.

From http://criepi.denken.or.jp/research/news/pdf/den338.pdf

As stated above, generation of nuclear power emits less CO2 than when using solar and wind energy.

However so, it is difficult to stop and start generation of nuclear power as and when according to demand for electricity. In addition, need for electricity in one day also differs greatly. Generally speaking, electricity consumption at night is less than that of during the day. In order to supply energy accordingly, it is necessary to allow changes in generation of power. Nuclear power alone is not able to accommodate such changes. For example, nuclear power will have to be paired with thermal power that can be adjusted readily. At such, on top of CO2 emission from nuclear power, emission from usage of thermal power would also be incurred.

Despite this, generation of nuclear power is indeed efficient in reducing CO2 emission as proven by the graph above.

How nuclear power eases the problem of insufficiency of energy resources?

Firstly, let's take a look at the Ratio of Reserves to Production for Uranium in 2007. From 'Uranium 2007'.


(Yearly production falls below yearly demand due to the presence of Uranium stock)

Although the Ratio of Reserves to Production, 82 years might seem long, judging by the fact that only 6% of total energy produced is generation from uranium, it is in fact a very limited energy resource.

Recycling of nuclear fuel to increase the Ratio of Reserves to Production of Uranium

The reason for the low ratio of reserves to production for uranium is due to the limited (0.7%) presence of uranium 235 amongst uranium. The remaining 99.3% of uranium is made of uranium 238 for which nuclear fission practically does not occur and thus, cannot be used to generate electricity.
Nevertheless, the ratio of reserves to production for uranium may be greatly increased if incombustible uranium 238 can be used as fuel.
For that, the 2 technologies below may be considered.

1) Plutonium Thermal Use
Natural uranium is being combusted in the nuclear reactor (for about 3 year) and some of its remains, uranium 238, absorb neutrons to become plutonium 239 of which nuclear fission occurs easily. Extracts this easily combustible plutonium and mixed it with uranium. This mixed nuclear fuel (MOX fuel) consist of 4~9% plutonium and can be used as a fuel in normal nuclear reactor. At such, the efficiency of use of uranium is being enhanced by 25%.
This method has been relatively successful in France and Germany. In Japan itself, agreements have been made to work towards the introduction of Plutonium Thermal Use in 4 nuclear plants.
Nonetheless, this method can only increase the ratio of reserves to production for uranium from 80 to about 100 years. Moreover, due to the risk its implementation can have on people living near the plant, it ought to be carefully thought after.
2) Fast Breeder Reactor
Fast Breeder Reactor is a special nuclear reactor, in which fast neutrons from combustible uranium 235 and plutonium 239 is being absorbed by incombustible uranium 238 to become plutonium 239 of which nuclear fission easily occurs. At such, the combustibility of uranium can theoretically be increased from 0.7% to 60%.
This method, if put into practical use, can increase ratio of reserves to production for uranium to thousands of years.
However, this technology is still at experimental stage and several nuclear plants have already been closed or stopped. The tremendous sum that comes with the experiments of such a technology is also a reason for many countries to stop its developments. The fire caused by sodium leakage in 1995 has also cause the halt of operation of Fast Breeder Reactor Monju in Japan.

Both of the above recycles combusted nuclear fuel to increase the ratio of reserves to production for uranium. However so, neither of which has progressed to a stage whereby both safety aspect and general understanding have been achieved.

How dangerous are nuclear waste?

It take more than 10,000 years for High level Radioactive wastes to reach a stage whereby it will have no effects on human. (Refer to graph below) Judging by the long duration of aftermaths it might bring, it makes one wonder if it is right to carry on such a usage. In addition, in the recycling of nuclear fuel (Plutonium Thermal Use and Fast Breeder Reactor), plutonium is being used as fuel. Plutonium is highly dangerous and one is advised (by the International Commission on Radiological Protection) not to deal with more than 3g of it. Moreover, it can also be used as raw materials of nuclear weapons. The fact that such a fuel is to be widely used suggests a possibility of growth of risk level.

Depletion of radioactive effects of High Level Radioactive Wastes

From http://www.fepc.or.jp/present/haikibutsu/high_level/shobun/sw_index_01/index.html

Conclusion of Generation of Nuclear Power

  • It is effective for the reduction of CO2 emission.
  • It is only of a limited amount as an energy resource unless fast breeder reactor is being realized.
    It is estimated to reach extinction in about 80 years under current demand. The increase in demand would accelerate its extinction.
  • Plutonium Thermal Use and Fast Breeder Reactors are being considered as options to increase amount of energy resources. However, upon considering the safety aspect and dealing of nuclear waste, it is essential to be extremely careful with its implementation.
    Furthermore, despite the high risk of Plutonium Thermal Use, it only increases the amount of energy resource by 25%.

In my opinion, generation of nuclear power is indeed effective in bringing down CO2 emission. Nevertheless, it should be our last option as much as possible. However, I do think that it should be used as energy resource for a limited and short period of time. Instead of Plutonium Thermal Use and Fast Breeder Reactors, I think it would be better to use nuclear energy as a short-term alternative to sustain current energy usage. In terms of reducing CO2 emission in the long run, I think that we should consider methods other than generation of nuclear power.

Despite so, due to the insufficiency and inflation of energy resources, I think that it is necessary to broaden its usage while taking extra care in terms of safety for the next 20 to 30 years. After which, we should move to other energy resources that can be regenerated as soon as possible.

In my next entry, I would like to write about 'Rapid Global Warming', the most talked about problem amongst the 3 major environmental problems.

15 Nov 2008 Hironobu Matsui

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