How dangerous is a 'dirty bomb'? Top nuclear scientist explains

Mumbai: More than a Hiroshima or Nagasaki- type atom bomb today, security agencies worry about the use of a 'dirty bomb', especially by terrorists. So how dangerous is a 'dirty bomb' or an explosive-laced with radioactive material?

View of the radioactive plume from the bomb dropped on Nagasaki City, as seen from 9.6 km away, in Koyagi-jima, Japan, August 9, 1945. Getty images

View of the radioactive plume from the bomb dropped on Nagasaki City, as seen from 9.6 km away, in Koyagi-jima, Japan, August 9, 1945. Getty images

On the eve of the anniversary of the Pokhran explosions, KS Pradeepkumar, head of emergency preparedness for India's main nuclear laboratory Bhabha Atomic Research Center, busts some of the commonly held myths about dirty bombs and says India is well prepared to detect such devices, thanks to a countrywide network.

Excerpts from an interview.

These days there is a lot of fear of something called a 'dirty-bomb'. What is a dirty bomb?

Dirty means it is dirty, that is it will not really harm you but it makes you uncomfortable. See it is like getting dirt on your dress that does not mean you are going to die or that your health is in trouble but definitely, you have to go and change your dress. Same way, a dirty bomb, which normally like any other  explosive has some effect, but since it is integrated with radioactive material and after an explosion that radioactivity could spread out.

Therefore, there is a chance of contamination on your body, even contamination on your dress,
so definitely it calls for a decontamination of the people who are nearby. It also calls for a decontamination of the area.

Therefore, it is not in terms of a casualty or a serious  injury we are worried about a dirty bomb, or what is called a radiological dispersal device. The concern is about the fear it may inject into the people because very large number of people will believe that they are all affected because they are all contaminated. It causes disruption.

But what are the materials, which can be used to make a dirty bomb?
First of all a dirty bomb has never been used anywhere in the world. Nevertheless, it is mentioned that there were attempts made where people have tried to make one using radioactive Cesium-137 and explosives like RDX. It has never been used in India.

What is feared is that since the use of radioactive sources and radioisotopes is increasing in a very significant way world over. Moreover, in some places the security of sources is not fully ensured. Hence, there are cases of lost sources, misplaced sources etc.

These orphan sources can get into the hands of the bad-boys. It is believed that they can integrate these with explosives, and they can use it. However, it has never been used.

But is it not dangerous to handle radioactive sources?
It is indeed so it is also a big challenge for those bad people who could try to assemble such devices, that is one of the reasons why assembling them has not been successful. Compared to the conventional explosives, whoever tries to integrate radioactive sources like Cesium-137 or Cobalt-60, they are all high-energy gamma emitters.

Therefore, during the assembly itself, even if one spends more than few minutes, the bad boys will get very high radiation exposure and will fall sick.

So you are saying that if a terrorist has to use it, then the likelihood of the terrorist himself being exposed to such serious doses of radiation is high. Is that what you are saying?
Yes, unless, until they manage it with many remote controlled mechanisms, and if it is not shielded, they themselves would be subjected to high radiation field. Not only will they get affected, the pain will be extremely severe, so keeping it a secret will be very difficult from the

Unlike conventional explosives transporting dirty bombs is very difficult. Escaping detection is almost impossible since transport of radioactive material is very difficult.

Either it requires extremely large quantity of shielding like say by using hundreds of kilograms of lead. In that case, the person will be moving about in a suspicious way, since it is hard to carry so much weight, or it will be a group of people. If enough shielding is not there, even the vehicle he is using, co-passengers, driver, they will all start getting a radiation exposure syndrome or acute radiation syndrome.

Therefore, world over it is considered very difficult to assemble it, as the terrorists are likely to be harmed more. However, much more challenges are on people like security agencies who would have to respond and take care of the public.

In India, do we have the capability to detect hidden dirty bombs?
BARC has developed many systems. We have developed many systems like aerial gamma spectrometry systems, which can be used for searching such types of sources. It can be detected easily by BARC's equipment, even if it is shielded or kept hidden inside some building.

There are some stories going around which say that if an explosive device like a dirty bomb is exploded let's say, in the heart of Delhi then all of Connaught Place will be obliterated and radiation will spread up to the Parliament Building, and all around several kilometers would get affected. In your assessment in the worst-case scenario what would be the situation?

Let me explain, the word 'affected' has to be used very carefully. See, we have highly sensitive radiation monitors. With this, even extremely small quantity of radioactivity can be detected. See for example, let me take the Fukushima accident, people detected extremely small doses
of radioactivity as far away as in Europe and USA, and people started predicting everybody will be affected and there will be cancer.

It was wrong, okay, so what I want to tell is the radioactivity in the environment was extremely small, nevertheless, the scientists could detect it. Same way, if there is an explosion of a dirty bomb, what you have called it; there can be presence of radioactivity slightly above the natural background, even in 3-4 kilometers because it can be transported by the wind.

Nevertheless, if you ask me the question, even that radiation level will not be even one thousandth of the radiation level of what you are having in the high background dose area of Kerala where people are living for many-many generations.

So I will not like to use the word, people will be 'affected', but definitely nearby area may be around 30-50 meters from where a dirty bomb is exploded it can have high level of contamination, beyond that there can be a cigar shaped area where spread of contamination will take place.

That also may be 80 meters or slightly more than that, but it all depends upon what is the source you are using. I can tell you, more than 1.5 kilometer one need not bother at all. Again, I am telling, it may be possible to detect even up to 3 kilometer etc but that is not a concern.

So, in case of a dirty bomb, what I understand is that the possibility of people dying is because of the thermal part of the bomb, and not because of the radiation. Is that what you are suggesting?
Yes, I think I have to make it very specific, when you talk of a 'dirty bomb'; we are talking about an explosive mixed with a radioactive material. When we use the word radiological dispersal device, it is of two types. One is a dirty bomb, where there is an explosive involved. Another is just a dispersal of the radioactive powder in the public domain. However, in any case, if we are talking about a dirty bomb, it will have the same effect like any other explosive, blast effect, thermal effect, etc and added to it there will be a radioactive fallout.

What I want to tell is, any death or serious injury to the people will be limited due to the blast and thermal effect because of the explosive power. Radioactive fallout and radiation exposure is not going to cause serious health effects.

So the people dying of radiation exposure are unlikely.
It is unlikely. Today, there are many myths around a dirty bomb. Not only about dirty bomb, you talk about radiation, there are myths. 30-40 years back, even to take an X-ray people were scared, but today the awareness has come to the level that people are asking for an X-ray.

Incidentally, in India no one has ever died due to a high radiation dose at any of the facilities run by the Department of Atomic Energy.

Do you suspect that a dirty bomb would ever be used in India; people have an anxiety about it?
The threat does exist since radioactive sources do get lost and misplaced but assembling a pile with a gigantic radiation dose is very very difficult. Moreover, at the same time, I would like to underline the fact that making a dirty bomb and using it is a big challenge. Since first, it will harm those who try to assemble such a device.

Published Date: May 10, 2016 04:30 pm | Updated Date: May 10, 2016 04:30 pm

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