Online edition of India's National Newspaper
Thursday, Feb 03, 2011
Finland far ahead in nuclear waste management

— PHOTO:AFP

 

The solution: A general view of the Olkiluoto 3 European Pressurised Reactor (EPR) being built in Finland. Finland demonstrates that it has in place a popularly accepted technological solution.

Finland consumes nearly 17,000 units of electric power per capita annually; its share of nuclear electricity is about 28 per cent. Though its nuclear power programme is very modest compared to that of U.S. or U.K. it is far ahead in its universally applauded plans for nuclear waste management.
The general refrain of lay public (often reinforced by antinuclear rhetoric) is that there is no ultimate solution for managing high level nuclear waste. Finland demonstrates that it has in place a popularly accepted technological solution.
Finnish programme
Currently, Finland operates four nuclear power reactors with a total installed capacity of 2716 MWe. It produces about 70 tonnes of spent fuel annually. Finland has no plans to reprocess the spent fuel.
Finland started its preliminary preparations for its nuclear waste management shortly before the first reactors started operation 1n 1977-1978. In 1978, the first lot of spent fuel entered the facility for interim storage at Loviisa.
The Nuclear Energy Act 990/1987 passed by its parliament stated that nuclear waste generated in connection with or as a result of the use of nuclear energy in Finland shall be handled, stored and permanently disposed of in Finland.
In 1983, Finland started screening of potential sites for spent fuel disposal. Within the next four years, Finnish scientists started field research in five municipalities for selecting the final disposal site.
Final repository
In 2000, they chose Olkiluoto. They plan to dispose of spent fuel in an underground geological repository. Posiva, a Finnish company which is entrusted with the job has drilled a 6.5 metre –high, 5 m- wide and 5000m long Okalo tunnel. It has removed over 100,000 cubic metre of rock.
The company successfully located the place where no one would ever be likely to dig a deep hole later for exploiting minerals because the place is not mineral-rich. The idea is to abandon forever, the mostly natural, and partly engineered underground repository after filling it.
Canister design
After a few decades of interim storage, the levels radioactivity and heat of spent fuel reduce to about 0.1 per cent of the original values.
It is then encapsulated in a cast iron insert which in turn is covered by a 5 cm thick copper canister. Each insert may carry up to 12 fuel bundles.
They will be placed in neatly bored holes a few metre apart in the underground repository. The gaps between each canister and the hole will be filled with bentonite clay, which swells by absorbing water.
This clay provides cushioning to the canister in case of geological movements and ensures that there are no voids through which water can enter and corrode the container.
Finland hopes to start filling the repository by 2012 and completing it by 2120. They can cover the mouth of the tunnel and forget about it.
Canister integrity
Most of the radioactivity in the spent fuel is due to fission products.
They have a half life of about 30y. In 100,000 years, the radioactivity remaining in the fuel will be negligible. Finnish scientists proved that 1.5 cm of copper cladding would last over 100,000 years. Evidently, 5 cm of copper cladding will be more than adequate.
During the period, an ice age may come and cover the area under 2-3 km of ice. The pressure on the canister due to ice, tightly gripping bentonite clay and ground water may equal that experienced by it at an ocean depth of 4.5 km. Finns proved that their copper cylinders will withstand a pressure three times that before failing.
Waste management cost is manageable. Finland collects a few percentage of the electricity cost per unit of power to manage the waste and deposits it in an independent National Nuclear Waste Management Fund, controlled and administered by the Ministry of Trade and Industry.
The agency estimates and assesses the liability annually.
Finland's nuclear waste management programme was accepted by people because the Government took them into confidence at every stage.
Finland demonstrates that nuclear waste can be managed safely. This issue need not come in the way of harnessing nuclear power.
K.S.PARTHASARATHY
Raja Ramannna Fellow, Department of Atomic Energy
( ksparth@yahoo.co.uk)

Are the units 1 & 2 of Tarapur safe?

The article titled "Are the units 1 & 2  of Tarapur safe? in The Economic Times (28 May 2011) summarizes the safety upgrades carried out by the Nuclear Power Corporation of India limited (NPCIL) at Units 1 & 2 of TAPS. In view of Fukushima accident NPCIL plans to carry out further steps to enhance safety.

Background radiation and radioactivity in India

                                                                      May 5, 2011

Background radiation and radioactivity in India

We live in a sea of radiation. In any city, an unsuspecting owner of a 0.1 acre backyard garden may not know that the top one metre of soil from his garden contains 11,200 kg of potassium, 1.28 kg which is of potassium- 40 (K-40, a radioactive isotope of potassium), 3.6 kg of thorium and one kg of uranium.

These values may be higher or lower depending on the soil. Uranium and thorium decay through several radio-nuclides to lead, a stable element. The presence of radioactive nuclides does not pose any significant risk.

Total dose

The total annual external dose from sources in soil and cosmic rays in Mumbai, Kolkata, Chennai, Delhi and Bengaluru is 0.484, 0.81, 0.79, 0.70 and 0.825 milligray respectively. Gray is a unit for absorbed dose; when the radiation energy imparted to a kg of material is one joule, it is called a gray. Since gray is very large, milligray (one thousandth of a gray), and microgray (one millionth of a gray), are commonly used.

Cosmic rays come from outer space. Their intensity at a place depends on the altitude. Cosmic rays alone contribute 0.28 milligray at the first three cities as they are at sea level; the column of air helps to reduce their intensity. At high altitudes, the protection from the column of air is less.

The cosmic ray contributions are higher at 0.31 milligray and 0.44 milligray respectively at Delhi and Bengaluru as these cities are at altitudes of 216 metre and 921 metre. Air passengers receive 5 microgray per hour from cosmic rays.

Parts of Kerala and Tamil Nadu are high background radiation areas (HBRA) because of the presence of large quantities of monazite in the soil. Thorium content in monazite ranges from 8-10.5 per cent. Researchers found that the radiation levels in 12 Panchayats in Karunagappally varied between 0.32 to 76 milligrays per year; the levels in 90 per cent of over 71,000 houses were more than one milligray per year.

The average value of population dose in HBRA is 3.8 milligray per year. One milligray is the average value for areas of normal background radiation. The units milligray and millisievert are the same in these instances. Study at the HBRA during 1990-99 by the researchers from the Regional Cancer Centre and Bhabha Atomic Research Centre did not show any health effect attributable to radiation.

Radon, which occurs in uranium series present in soil seeps into homes. In temperate areas radon decay products build up in air due to poor ventilation and deliver high doses to the lungs of millions of people. In tropics ventilation is adequate to disperse radon .In the United Kingdom persons in 5 per cent of the homes are exposed to doses above 23.7 mSv/year. One per cent of the population receives doses above 55.8 mSv/year. The highest estimated dose was 320 mSv/year in Cornwall.

All foodstuffs contain potassium-40 (K-40). We need potassium for sustenance. K-40 is 0.012 per cent of potassium. Once ingested, most of the potassium enters the blood stream directly and gets distributed to all tissues and organs.

Homeostatic control

The potassium content in the human body is strictly under homeostatic control. The body retains only the amounts in the normal range essential for its functioning; it is independent of the variations in the environmental levels.

The body excretes excess amounts with a biological half life of 30 days. K-40 delivers a constant annual radiation dose of 0.18 mSv to soft tissue. This dose is unavoidable as potassium is an essential element. Every time we eat a banana, we are introducing 14 Bq of K-40 in to our body. Trucks containing bananas have triggered radiation alarms at border posts in the U.S.

Brazil nut

Brazil nut is probably the most radioactive food. Scientists have measured 700Bq of radium per kg of Brazil nut.

The roots of the Brazil nut tree pass through acres of land; They have a tendency to concentrate barium; along with barium, the roots collect radium as well. Radium appears in the nuts. Many vegetables like brinjal, carrot etc. also contain the radioactive isotope.

Indian researchers have measured polonium-210 in fish and other marine organisms. Our whole body is hit by particles coming from all sides. Radiation is a part of our life. We cannot avoid eating food just because it contains radioactivity

(Raja Ramanna fellow, Department of Atomic Energy)

ksparth@yahoo.co.uk

Keywords: radio activity, potassium, radiation in food