 So good morning hope you had a good dose of radioactivity of course without causing harm because I am only talking about radioactivity but be assured it is not that bad to worry about. I will continue this radiation we talked about the exposure the doses and we also had a look at the natural radiation which we get from the cosmic rays from the soil and how we are getting lot of amount of exposure due to medical diagnostic tools so we need to minimize wherever we can. Now we also talked about how the damage can happen on the cells but how do we know about all these biological effects how do we how are we knowing that in the last 3, 2 or 4, 5 decades after the Hiroshima Nagasaki as I mentioned to you follow up of the survivors has been going on even the scientists working on radiation they have also been from time to time given the results of what are the observations and all these has been collocated and also uranium mine workers that on the uranium mine workers we have got from the therapy radiation therapy diagnostic radiology everywhere. So one important point here to note is because of the fact that we felt that radiation could be damaging after the Hiroshima and Nagasaki bombings we really took care to document and also today with growing science we have got very good instruments which can measure accurately the radiation doses that is also one more point which has grown in the last 3, 2, 4 decades it is a very, very important contribution in knowing that earlier we could not detect but today I can detect even millionth of radiation that is harmful. So all this information on the health effects are available from these data the effects the biological effects we say we are not talking about any material we will talk about the biological effects depends as we saw how much of exposure how much is the rate of exposure how much rate of exposure do I get then which portion of my body is getting the exposure what is the type of radiation is it a neutron is it alpha it is beta or gamma what it is all these factors finally are to be considered in assessing the biological effect of radiation. Now if you look up short term biological effects are there and if it is a genetic we call it as a long term biological effect and we correlate it or we measure the dose in terms of seawards. Now it is noticed that these cells are more sensitive to radiation when they are in the process of dividing now the most sensitive or radio sensitive tissues are the blood forming organs the intestinal walls the skin and the fetus they are highly sensitive to radiation. Then what are the non radio resistance or less radio the radio resistant not less most radio resistant or I should say the muscles the nerves and the brain where cell reproduction is minimal many of you may be aware in the brain if the cells died they do not get produced in fact with age also with cells dying the dementia also starts the forgetfulness starts but luckily God has given us such a shielding on our body that our brain does not get affected by radiation. So these are all some of the things which we need to keep in mind. Now if few cells are damaged you may not come to know but if quite a significant number of cells are damaged then you get the clinical symptoms. In fact in most cases only by the clinical symptoms you come to know that some effect has taken place. Now so these symptoms and effect we refer to the mass deterministic that is yes he is exposed to radiation this is a clinical symptom which is happening. So that is a deterministic effect but again if you are looking at a definition it can be told it is one deterministic effect is one in which the severity of the effect is a function of the dose that is all. And of course there is a threshold below which there is no effect above that there is an effect and that effect is proportional to the dose as the dose is increased the effects gets worse and maybe after some time it saturates there is a maximum effect. Now what is this disease or what we call there is one term called as radiation sickness that is any sickness caused due to radiation is not a single one it consists of lot of things called it could be diarrhea it could be vomiting it could be nausea could be some sort of a hemorrhage or could be infection and maybe if the dose is very high could be death also. So all these things happening due to radiation is we call as radiation sickness does not mean that you get a nausea or you are affected by radiation not at all. So one of the causes of nausea could be radiation. Let us look at at what dose levels some changes or health effects take place. The blood count changes you know the blood we take that white corpuscles and red corpuscles and the total counts also we take beyond 0.5 grade there is a change of the blood counts. And if it is beyond 1 vomiting is there in the patient then beyond 1.5 could be a death then there are some terminologies which is called as lethal dose lethal dose means practically you know personal die there is a terminology called LD 50 by 60 which is used to refer to death dose where without treatment 50% of the people will die in 60 days. So that is the thing LD 50 by 60 if such sort of a population you take you give some supportive care maybe they may be still able to survive 3.2 to 3.6 is the threshold if it is beyond 4.5.4 they really need to have a real supportive and this higher thing needs bone marrow transplant which is quite a severe sort of treatment but in many cases where basically after the Hiroshima and Nagasaki some of the bone marrow transplants have helped and of late this stem cell transplantation is started that gives you the resistance of the body of the stem cells taken from the family persons and stored and you know safely stored it can be helpful. Then what are the long-term biological effects the major long-term biological effects basically when I mean very large doses but short term of doses or smaller doses again as I mentioned one has to look at integral energy deposited in the tissue in an integral manner. So dose into the exposure into the time this is most important and some of the things could be cancer and could be hereditary or what you call as the genetic effects. Now cancer let us take cancer is a stochastic effect what we really mean it is not that a particular amount of radiation we give cancer in all persons it may give it is a probability that with this a probability some probability that a person may get cancer. You may get cancer due to different things not that cancer came after we started the nuclear reactors or the nuclear diagnostics etc in medical diagnostics etc it has existed but today we know okay cancer is there cancer is cause cancer is causing death that we know very well. Now so what is this effect is the probability that a person will get this disease above a certain threshold. So this is just graph the figure shows it is a function it is not really a very linear function that is told but probably you know sigmoid but we just assume it to be linear because when we do not know things we take that it is proportional to the thing. So whenever you do any estimation we take a proportional but actually it is not. Now again comes some organs are more sensitive to cancer induction than the other organs. Now what are the organs which are sensitive the tumors in the female breast is one of the thing which is sensitive tumors basically tissue tumors in the breast the lungs the thyroid and the skin and the order is same tissues for the female breast the lungs the bone thyroid and skin in that order. Now this radiation induced cancers is not sudden they have got a long latent period before they have detected that means you get the clinical symptoms much later not immediate. For example if you are to get leukemia the latent period must be something like 10 years and some of the solid tumors in other parts of the body this could be as well as 20 to 30 years and the best estimate risk currently for fatality from radiation induced cancer is something like 5 per 100 percent seawats that is 100 percent seawats you get about 5 fatal deaths. In other words if 10,000 people are given 1 milli seawats then 0.5 of them may die in 20 to 30 years due to cancer. Now anyway if you just take a general deaths in 10,000 people among 10,000 people about 1,600 would have anyway died due to normal cancers. So where is the question of 0.5 and 1,600 how you can really it is a very, very, very small. Let me tell you one thing you get cancer after such a long time how do you know it cause due to what is such a latent high latent period. Cancer is caused due to so many things even our diet smoking is one of the causes of cancer. Why smoking? You take many of the beautification agents that is contains chemicals they are all called chemical carcinogens and they can cause you cancer. In fact one of the reasons for cancer increase has been attributed to indiscriminate use of chemical fertilizers and today we get organic vegetables which are produced without you know using chemical fertilizers. So you cannot pinpoint that radiation cancer has been caused. Let me tell you very simple way I have a sore throat I go to the doctor is my sore throat because of talking too much in the class giving lectures or was it the ice cream that I took one or two days back or my drinking very cold water or it is due to some sort of an infection which I have inhaling something from the outside or some pollen. How does the doctor tell you which is a causative factor we just do not know the causative factor but we know this much that cancer can be caused by radiation but remember cancer or radiation is only one of the causes of cancer not the only this I think has to be imprinted in your mind. Now as I mentioned in the beginning after the Hiroshima and Nagasaki bombings and why even after the Fukushima immediately the fear is that many people will get cancers many people will get genetic defects. Now if you really take up the data based on the Hiroshima Nagasaki bombings it is found probably maximum 2 individuals with genetic mutations are found among more than 27000 children born to parents who are exposed in the Hiroshima Nagasaki bombings that is they are the survivors so their genetic that is genetic progenies if you take maybe some two people what is this compared to the other things which are existing even otherwise. So it is very wrong to say that okay radiation means only why then why that people get that fear simple it cannot be smelt it cannot be heard it cannot be tasted so I am not able to see. See for example we are able to withstand a chemical being diluted or from the factory getting into the thing we are seeing OVCO it is color we are ready to accept it but radiation so it is a fear of the unknown nothing else there is nothing to fear then considering the whole population as a whole the current best estimate of the risk of quantifiable hereditary things could be something like 0.65 per 100% seabirds effective dose this could be what is a reasonable estimate but again if you see the risk is not high so what I want to convey that risk there is not much risk which you are taking by radiation through say worrying about genetic effects then the dose limits as I mentioned to you the international council or sorry international commission on radiological protection ICRP is the body which makes the recommendations as regards the matters of radiation protection it tells the dose limits basically the major role is to tell the dose limits now how what is the basis now they should keep the dose below the threshold level for deterministic effects that is above which above that threshold you get effect so it should be below that threshold first and below that threshold with some margin not that just exactly below that threshold now what is the limit for occupationally exposed persons means people who work in the establishments which involve usage of radiation or medical diagnostics or anything though they are called the occupational workers or the occupational exposed persons the limit is 20 millisieverts per year averaged over 5 years that means he can get on an average in a 5 year period on an average 20 millisieverts then there is a further provision that in a particular year okay suppose you say okay 20 millisieverts per year for 5 years 100 millisieverts so okay one year itself let me we get 100 millisieverts no in a particular year it should not cross 50 millisieverts now the 5 year period which is to be defined has to be very clearly defined by the regulatory agency as 5 calendar periods or what it is so it has to be very clearly monitored that is where we have the health physics people and they who are maintaining the dose a dose exposure levels at in different areas of any nuclear establishment. Now there is also a need that we should optimize the working conditions in such a way that to the best extent you should not cross 20 millisieverts per year that should be our effort I mentioned to you that the human fetus basically fetus means when the woman is pregnant the fetus is there in the womb that is quite sensitive to radiation related to the other parts. So for the occupational worker if she is a woman and pregnant it is not the same because we need to consider that the fetus should not be affected by radiation. So once we know that a lady is pregnant we should apply a additional factor so that the woman is safe here again it is a matter of safety more safety relatively more safety we have put a limit for the abdomen portion about 2 millisieverts because maybe some x-rays may need to be taken so 2 millisieverts. But the inhalation or intake that is the inhaled radionuclides should be only 1 by 20th of the annual limit because when you are living or working in a condition where some of the radioactive polishes are there some of them may be inhaled also so that inhalation limit is there out in the case of such ladies it should be only 120th. So all these having very carefully what you call standardized so that it does not mean that just above this because there is enough safety margins which have been kept in the thresholds. Now how does this ICRP set this dose as I mentioned there is a risk due to radiation. So the normal publicly accepted radiation that is what a what a public can accept is from accidents in the public transport that is a which a common thing which happens which we have come to accept and this data over many years in the different countries have been taken and it is seen that a risk in the range of 10 raised to of minus 6 to minus 5 per year instead of minus 5 per year is an acceptable risk to a member of the public. So we look at that radiation which will have a similar amount of risk so that it is acceptable. For example the dose lifetime dose of a individual if it is 1 millisieverts per year then this is has a risk of 10 raised to of minus 5 to 10 raised to of minus 6 to minus 5 per year is a risk. Now if you look at the natural radiation which is already present you are getting about 1 millisieverts so and in some cases double of this. So looking at this ICRP has put annual limit of effective dose of 1 millisieverts. This then gives a tabulation value. We saw effective dose occupational workers of the people who are working in the plants 20 millisieverts per year averaged over 5 years for public 1 millisievert per year. But our occupancy records maximum should be received which will be 50 millisieverts. Then they have also looked at different parts of the body. Length of the eye 150 millisieverts for the occupational workers 15 millisieverts for the public skin 500 millisieverts and 50 millisieverts hands and feet. So this sort of so if you look at this then what do this mean to us what does this mean okay 20 millisieverts per year 50 millisieverts per year in a year what does it mean. Suppose we find a person has received one year let us say 2013-14 he worked we took the exposure he had he was he got 50 millisieverts or more than 50 millisieverts we will take him off work in a radiation area and we will observe his health not that it is something to be very much get worried about it. It only shows that okay whatever thresholds we had set he has crossed that does not mean that he is going to immediately get fall sick or something now we will try to remove him from there and so that he does not get any further radiation and observe his health that is all. So we have put this limits to ourselves as a discipline and again I always repeat that statement thanks to the fact that Hiroshima and Nagasaki came first before the reactors we are aware that radiation cast cause damage and we want to limit the radiation to as low a dose as possible. Then how to protect it is a very simple suppose I have a radiation source at a point I treat to keep away from the source my exposure will be less because exposure will come down as I move away it is the inverse square law any radiation. So I keep myself away I will get less then if I am in the area where radiation is there for a longer time I get more exposure I get a more dose I more energy is deposited on my tissues then what is the third one okay I may have to work very close then I need to provide a shielding so that the shielding will protect me put me in a lesser radiation zone and I would be able to work. So these are the three things by which we can protect lesser the time he spends lesser the dose further he is away lesser the dose and you provide shielding between the source and the human being he gets lesser source. So these are the three ways by which we implement the radiation protection. So shielding of sources is one by which we are able to implement. Then physical barriers now where we know that a radiation of a particular strength is there and we know it can cause we try to cordon off that area we have got some color codes by which different area red area means person should not enter that area without any clearance from the top people. So they are called then physical barriers by which you cannot go then in all cases you may not be able to put a permanent shielding you can use a mobile shielding and again the shielding which you use should be suitable for the type of radiation as a alpha beta gamma. For example a single sheet of paper the thin paper can stop your alpha radiation if you want to stop the effect of stop I would not say stop it practically brings it to a very low level 1 centimeter of plexiglass would reduce the effect of the beta radiation and for gamma etc it is possible by if you use high nuclei atomic number nuclei as a shield like lead or concrete even water itself is a very good shield we talked about the exposures coming externally that is from the different sources. But as I mentioned there is something within us how do you reduce that suppose you have some radioactive particles in the atmosphere in the environment where you are working and they go you inhale how do you do that now in the case of inhalation basically first thing is you have to confine the source you must have ventilation of the areas ventilation means there should be a change of air so that the radioactive particles do not get accumulate there should be change of the air so air changes ventilation is very important then you must have filters in this path of the air circulation so that the radiative particles are filled I am sorry filtered then another thing is you have air locks you might wonder what is an air lock see it is nothing let us take you take our reactor building inside which is concerned the reactor then what we do we do not want the air inside to come out because that air could contain radioactivity so we do not want it to come out but we need to go inside the reactor building to do some operation or some surveillance or survey what is happening we want to do we have to go we cannot say no so what we do we have two doors so that at a time only one door is open suppose let us say a person is coming from outside he opens the first door when you open the first door the air inside is not in communication with the air between the two doors so he comes in then he closes the door now he opens the inner door then he can enter the containment now only the air within the space between the two doors gets a bit of contamination but this again this air is taken filtered and so this is called as air lock in reactors we have air locks we called as personal air lock where humans move and where materials are being taken like fuel bundles fresh fuel bundles or the reprocessed fuel bundles which are burnt and taken for reprocessing they go to a material air lock so they are called air locks so this is one way of confining the activity to a particular area now what are the ways by which we can reduce the ingestion or contamination one very important rule for any person who is working in a radioactive area is that never use your bare fingers you always use a gloves and when you are using a gloves at that time don't touch any other part of the face or the body if you are working only work you do and when you are coming out these gloves you throw off you dispose it when you come out and then only come out so there is an area in the plant when you come out in fact we not only wear gloves for the hands we do have for the shoes we have a shoe cover again it's a cotton shoe cover we put the shoe cover and then go while coming out we remove the shoe cover put it in a bin which consists of all the radiation people coming from in radiation area to the outside area they put that and this contamination gloves are taken separately laundered and washed and specifically in a particular manner in our waste management facilities this is a very very common practice which we follow in all nuclear establishments so here what I want to tell you safety safety safety at every stage has been the what you call line behind our nuclear activities then other thing is called as the legislative means or also another terminology called as administrative means is okay you put rules for radioactive sources for example you have a radioactive solution then you are handling it in a laboratory you are analyzing you must not use some pipes like a pipette or burette for so that it doesn't get into your system this one this you must have a person must know and most of us know that whatever is harmful we don't do then other one let us say your worker is there normally there is a practice many of us take our lunch packets to our place of work and we eat there in normal cases it's okay but if he's a worker working in a radiation area will never allow him to take the food inside in fact in all our nuclear reactor establishments where intense activity is going on or the reprocessing and all we are not allowed to take any of our carriers we are our lunch boxes are kept outside and lunch boxes are not allowed inside and this is checked by administrative means we have the security personnel who checked not only us whether we are authorized to go inside they also do this checking that we don't carry anything like lunch boxes etc. So this is a way of trying to minimize the contamination so this also requires for example individual has to follow these rules without any of these things so that he is safe now we looked at the internal contamination and what protection we can do then the external body contamination what we can do we talked about the shoes gloves hand gloves there is also protective clothing for the work workers and as I mentioned disposable gloves and for all this we are giving training before itself and how to do that so that you don't spread contamination these are all training which are given to the people then the other one is how do you have the layout the layout of the plant should be such that any radiation worker should come out into a non-radiative thing he should not get into a non-radiative again get into a radioactive zone so in order to avoid spreading and we have to limit the movement of basically the people and even the movement of the sources of radiation so if we do that then contamination will not take place last but not the least we have to do continuous checks and we need to see whether any contamination is happening and in case it has happened we should see how to isolate the what you call person or the clothing and take proper action now coming to the reactors we looked at external and inhalation etc but what are the sources of radiation in a reactor now in a reactor your coolant flows to the core the coolant also contains impurities if we say water water does contain impurities the coolant itself will get activated and these impurities also get activated then there are fission products which can come in case there is a damage to the fuel clad and they can get activated and these activated products because of the coolant flow can get into the whole coolant system so that could be an activation of the coolant system now okay it is in the coolant system what is there to worry the activities within the coolant system the particles are contaminated within the coolant system but in case there is a leak it can come to outside environment it could be in a pipe or it could be let us say in a heat exchanger failure the element might come down and if you take a boiling water reactor we saw that the reactor steam produces a steam and that steam goes to the turbine so it is an active so that way also it can go to the turbine and then the turbine then let us say it is to go to the condenser and if there is a leak in the condenser it can get into the environment in a similar way if you have a gas cool reactor also if the leaks gas leaks it can come out active thing can come out so this sort of activity can come to the atmosphere in case of any leak just to keep track what sort of activation products which we can look for and the fission products in the reactor they are krypton strontium iodine these are very important but you see their half-lives 10 years 28 years 8 days for iodine 131 then you have got cesium 30 years carbon 14 5770 years in fact carbon 14 is this one thing I forgot to tell you we use in dating the life based on the carbon 14 content because it would have been there for 5770 years so anything within this period based on the analysis radioactive carbon analysis we can do so this has been used even for old sculptures and things we can find out dating of archaeological products zinc cobalt then tritium so these are all the important fission and activation products from the reactors then what else then the discharges as I said we have ventilation we have filters and then finally some of the air needs to go out that should not that also might contain but there is that limit should be maintained so it could be a gaseous pathway or if you are using a reprocessing plant or it could be a liquid pathway and solids in case there are solids which are activated now the total cumulative experience throughout the world has been showing that if we follow we should not only follow the limits set by the ICRP but we should be achieve as low as reasonably achievable this is called as the Alara concept the idea is don't stick to the threshold you bring it as low as possible and you do every effort to see that the exposures are minimal in fact when we look we call for every plant we look at the man rem exposure or man seabird exposure we try to audit that and we put limits in such a way that if any plant is having minimal man seabirds then we do compliment them and give them some added benefits so at least to know that it is it is not that okay anything above that is with everything is within threshold but within the threshold keep minimum as low as possible and this is being implemented with the licensing authorities and the regulatory authorities shielding just as I mentioned alpha and beta particles are stopped easily but for gamma you require a heavier material like a hydrogen containing material so you could go for lead or boron steel basically for neutrons this is just a figurative picture for alpha being stopped by a piece of paper thin sheet of paper B by a thicker metal gamma by a solid and neutrons by any other absorption in any other material now there are one is what we call talked about was a radiation shield then there is also called a thermal shield because we do not want the heat of the reactor the temperature reactor to be felt outside in the environment so we have got thermal shields so around the reactor we have steel followed by concrete to shield against the different radiation and the water basically in the concrete slows down the first fast neutrons and you put barium iron etc. so to attenuate the effect of the gamma rays and they also absorb these neutrons so that way concrete mixed with iron elements or boron or they are all used as very good biological shield of course stainless steel or it is like a biological as well as a thermal shield and the density of concrete is something like 700 kg per meter cube but beware concrete is one thing it cannot stand temperature beyond 80 degree centigrade 60 is normally the limit beyond that we might lose the water which is the concrete and it might lose its shielding property so always wherever we use concrete we try to keep the temperature below 60 and if it is getting heated you try to provide cooling in the so even in the shielding you need to provide cooling for the shield to maintain its temperature below in case it is concrete. So let me just summarize what we have learned in these two lectures last two lectures you are introduced to the concept of radiation dose exposure then we looked at the effect of the type of radiation the effect of the type of tissue then what are the naturally occurring radiation effects how much we get from the cosmic how much we get we saw we then looked at in this lecture on the biological effects of radiation and how we put conservatism in deciding these limits and not only that even though limits are prescribed we still have to achieve as low as we want to limit limit as low as possible and this we have detailed some of the ideas of how shielding can be done whether it is a thermal shield or a radiation shield. So with these two lectures I am sure you had a would get a good idea I am sure that would be some questions please do go through and the next class we will try to resolve the questions. Thank you bibliography as in my earlier talks I have given you some bibliography the you can see the reference Phi by Ramachandran gives the background radiation and people and in India is a very important paper for basically for India wherein you get a total picture of what is there in India these are some of the assignments which I think you must take to have a complete understanding thank you.