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Types of Nuclear Accidents
Easy to handle: Accidents which are easy to handle and immediately recognized
Difficult to handle: Accidents with delayed recognition and difficult to handle
Catastrophic: Catastrophic Accidents with immediate recognition like accident at Unit 4 of Chernobyl nuclear power station on April 26, 1986;
Terrorist Attacks or Dirty Bombs:

Through use of 'Radiological Dispersion Device' (RDD), an expedient weapon, wherein radioactive material is disseminated by using conventional explosives and debris is subsequently scattered across the targeted area. Also through other modes like attack of the nuclear power plant or facility using or processing radioactive material via air craft strike or bombardment with heavy munitions or sabotage. This kind of attack would be similar to radiological bomb and could cause far greater casualties.

Theft of nuclear material can enable the creation of crude bombs commonly known as 'dirty bombs' which can be fused by anti-social elements or terrorists. A dirty bomb is a radioactive dispersal device (RDD). The radioactive material is dispersed in conjunction with conventional explosives. The explosion of a bomb in a thickly populated area, may lead to number of causalities on account of the explosive material itself. The people in the surrounding area will also get a dose of radiation (both external dose and internal dose). As a consequence of this, a limited area may also get contaminated. Unlike a nuclear bomb, a dirty bomb is not a weapon of mass destruction. However, it may lead to disruption of normal civil life because the mere possibility of imminent exposure to radiation causes a sense of panic among people.

Nuclear/Radio active materials /Agents

The radionuclides, which could be used, are isotopes of Cesium, Cobalt, Iridium, Iodine, Strontium, Uranium, Plutonium etc.

Radiological/Nuclear disaster scenario

The catastrophic scenario that can emerge after nuclear bombing can be tentatively worked out looking into what has happened in the past instances as described in the previous paragraphs and other literature. The estimates in the prediction of results of the atomic weapon effects bear an uncertainty of about 30%. Also offensive and defensive calculations are done through different sets. However, the later is preferred for working out preparedness/combating strategies. When the yield is in the low KT ranges, the cloud remains in the lower atmosphere and. its effects will be entirely restricted local area. But when the yield exceeds 30 KT, part of the cloud will punch into the stratosphere, which begins about 7 miles up. Accordingly, for inflicting grave maximum effects 20 KT weapons are considered to be the preferable devices.

The degree of damage shall depend upon the protection available at the time of detonation of damage. The above table gives a schematic picture with reference to unprotected objects and individuals. The blast winds, the last effect to follow may extinguish fire. Though there are several uncertainties and possible combination of the damages, the preparedness has to take the maximum possible damage in consideration.

Another phase of detrimental effect that will follow is due to fallout. The radioactivity deposition on the ground and its effect on human beings will depend upon several factors, like out put, height of burst, environment conditions including wind velocity and scavenging of the cloud by rains, etc as a conservative estimate shows that due to the immediate and direct effect 20 KT nuclear weapon detonation would affect:

  • About 65 square km of area
  • About 32 lakh inhabitants (population density 0.5 lakh /km2
  • About 3.2 lakh deaths in the first few months (- 50 % on 151 day)
  • About 7.5 lakh will be injured affected due to INR
  • Fallout zone approximately 4,000 km2 may change on wind direction and velocity. In case of Chernobyl it was more than 200,000 km2
  • About 40 lakh will be affected due to fall out
The fallout may persist for years and would need special consideration.
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