2001 - Q16 – whenever discussing an isotope you MUST say what sort of radiation it emits AND preferably give a decay equation (remember that you are trying to demonstrate how much Chemistry you know in your answers).
2002 - Q19 – you have to say too say unstable n/p ratio AND Z>82 (ie >82 protons - the atomic number is the # protons NOT the number of protons + neutrons). In addition when it says to use examples from the graph USE SPECIFIC EXAMPLES WITH EQUATIONS
2003 - Q18 – You need to revisit this video. The key idea is that a nuclear reactor is a source of neutrons (from fission*) and that a particle accelerator is a source of high velocity charged particles (NB you cannot accelerate neutrons in a PA as they are uncharged – hence the need for nuclear reactors to obtain neutrons). Radioisotopes can be made in TWO ways in a nuclear accelerator (from n-bombardment to make high n/p beta minus emitters AND as a direct result of fission as some fission daughter atoms are radioisotopes). Transuranics up to Z=95 can be made by n-bombardment of U, Np, Pu in a nuclear reactor which makes them beta-minus emitters which transmutate into Np, Pu, Am respectively.
Particle accelerators can be used to bombard protons into nuclei to decrease the n/p ratio and make beta plus emitters (eg O-18 + proton => F-18 + neutron), or can collide small ions into heavy nuclei to make heavy transuranics.
*in the reactor the fuel is a fissionable isotope - usually U-235. When U-235 absorbs neurons it undergoes fission = splits into two smaller nuclei and releases neutrons and gamma rays. Other (non-fissionable) isotopes do not undergo fission. They just absorb neutrons, eg U-238 + n => U-239.
Particle accelerators can be used to bombard protons into nuclei to decrease the n/p ratio and make beta plus emitters (eg O-18 + proton => F-18 + neutron), or can collide small ions into heavy nuclei to make heavy transuranics.
*in the reactor the fuel is a fissionable isotope - usually U-235. When U-235 absorbs neurons it undergoes fission = splits into two smaller nuclei and releases neutrons and gamma rays. Other (non-fissionable) isotopes do not undergo fission. They just absorb neutrons, eg U-238 + n => U-239.
2004 - Q26 -Benefits – must mention NDT for industry = increased productivity, safety, product control etc (NB that testing can be done ‘in situ’ ie while products are being made without stopping the process).
Must mention minimisation of invasive surgery for medical isotopes (lowering surgery risks eg infection) and diagnosing and treating cancer = healthier society
Risks – many – BUT make it clear that it is the RADIATION that the radioisotopes emit that is the danger. Risks include exposure to healthy people and healthy tissue = cellular DNA damage and cancer, terrorism risks, danger of radioactive waste to the environment, problems with long term storage etc
2006 – Q16 - see 2003 Q18 above. But make sure you DEFINE transuranic as Z > 92 (ie beyond uranium)
2007 - Q19 – You have to refer to all the things in 2004 Q26 AND detail how a medical and industrial isotope are used. You must give the decay equation, radiation emitted, you should give the half life and most importantly you have to specify what this isotope does that could not be done in other ways (or could not be done as efficiently/safely etc). ALWAYS say why the radiation it emits is useful - ie gamma is highly penetrating so it can penetrate thick steel AND it can exit the body to be detected with a gamma camera so diagnosis can be made.
But if you read the question carefully you will see that you have to specify CHEMICAL properties. You need to know that that half life and radiation emitted are nuclear properties so you have to also include things like reactivity, state etc. Eg Co-60 being a relatively inert solid metal can be easily regathered if spilled and is unlikely to contaminate the environment. Tc-99m can be tagged to many bioactive molecules so their path through the body can be traced AND our body had no chemical need for Tc so it is readily excreted. The judgement should evaluate their impact on society ie what can be achieved with these radioisotopes that could not otherwise be achieved and why that is good for society (ie health, economy, industry etc).
But if you read the question carefully you will see that you have to specify CHEMICAL properties. You need to know that that half life and radiation emitted are nuclear properties so you have to also include things like reactivity, state etc. Eg Co-60 being a relatively inert solid metal can be easily regathered if spilled and is unlikely to contaminate the environment. Tc-99m can be tagged to many bioactive molecules so their path through the body can be traced AND our body had no chemical need for Tc so it is readily excreted. The judgement should evaluate their impact on society ie what can be achieved with these radioisotopes that could not otherwise be achieved and why that is good for society (ie health, economy, industry etc).
KEY misconception to avoid: It is VERY important that there is no doubt in the examiners mind that you understand that the diagnosis, detection, treatment, sterilisation is done BY THE RADIATION NOT THE RADIOISOTOPE. The radioisotope emits the radiation that is detected so don’t fall into the trap of saying ‘the isotope is detected by the gamma camera’ or the isotope kills the cancer cells’ because that is literally what some people think and if you write that it will be assumed that you are one of ‘those’ people.
2011 - Q23b – as for 2006 Q16
2012 - Q27a – it is vital that you emphasise the need for gamma rays to pass through he body for diagnosis (high penetration and low ionising power means they can be detected outside the body and are less likely to cause damage to healthy tissue on their way out). Beta because it is highly ionising can cause local damage to tissues - ie tumours. But again make sure you emphasis that this radiation is EMITTED by the radioisotopes – the radioisotopes themselves are not the radiation.
Misconception - many seemed to think that the 'ability to pass through biological tissue' referred to the time it took for the radiation/radioisotope to pass through the body - NO!. Beta is ionising so it cannot penetrate very far (ie low ability to pass through biological tissue) once emitted as it collides with molecules, ionises them and loses its energy (good for killing tumours of the isotope is placed in the body at the site of the tumour). Gamma is highly penetrating so it can pass through tissue and exit the body once emitted and CAN be detected outside the body with a gamma camera so diagnosis can be done.
Misconception - many seemed to think that the 'ability to pass through biological tissue' referred to the time it took for the radiation/radioisotope to pass through the body - NO!. Beta is ionising so it cannot penetrate very far (ie low ability to pass through biological tissue) once emitted as it collides with molecules, ionises them and loses its energy (good for killing tumours of the isotope is placed in the body at the site of the tumour). Gamma is highly penetrating so it can pass through tissue and exit the body once emitted and CAN be detected outside the body with a gamma camera so diagnosis can be done.
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