folio fizik the uses of radioisotopes

7/27/2019 Folio Fizik the Uses of Radioisotopes

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Name: Muhammad Zakwan Bin Md Daud

Class: 5 Al-Battani

I.C. No :940216-10-6585


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Content

No Title Pages1 The folios title 12 Content 23 The introduction:

1. What is a radioactivity?2. What is a radioisotopes?

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4 Radioisotopes in medicine:1. Introduction2. Nuclear Medicine3. Diagnostic techniques in nuclear medicine

4. Radionuclide therapy (RNT)5. Biochemical Analysis6. Diagnostic Radiopharmaceuticals7. Therapeutic Radiopharmaceuticals8. Radioisotope Poisons9. Supplies of radioisotopes10. Nuclear Medicine Wastes11. Isotopes used in Medicine

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5 Radioisotopes in Industry:1. Intrdoduction2. Neutron Techniques for Analysis

3. Gamma & X-ray Techniques in Analysis4. Gamma Radiography5. Gauging6. Gamma Sterilisation7. Scientific Uses8. Tracing/Mixing Uses9. Wastes10. Industrial Radioisotopes

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6 Radioisotopes in agriculture:1. Agricultural Tracers2. Insect Control

3. Food Treatment and Preservation4. Quarantine and Exportation

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7 Radioisotopes in archaology:1. Radioactive Dating2. Geology and Element Identification

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8 Negative effects of radioactive substances 329 Referrence 33


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Introduction

What is a radioactivity?

Atoms with unstable nuclei are constantly changing as a result of the imbalanceof energy within the nucleus. When the nucleus loses a neutron, it gives off energy andis said to be radioactive. Radioactivity is the release of energy and matter that resultsfrom changes in the nucleus of an atom.

What is a radioisotope?

Isotopes are atoms of the same element that have a different number ofneutrons. In other words, the atoms have the same number of protons but a differentnumber of neutrons in the nucleus. Because the like charges of the protons repel each

other,there are always forces trying to push the atom nucleus apart. The nucleus is heldtogether by something called the binding energy.

In most cases, elements like to have an equal number of protons and neutronsbecause this makes them the most stable. Stable atoms have a binding energy that isstrong enough to hold the protons and neutrons together. Even if an atom has anadditional neutron or two it may remain stable. However, an additional neutron or twomay upset the binding energy and cause the atom to become unstable. In an unstableatom, the nucleus changes by giving off a neutron to get back to a balanced state. Asthe unstable nucleus changes, it gives off radiation and is said to be radioactive.Radioactive isotopes are often called radioisotopes.

All elements with atomic numbers greater than 83 are radioisotopes meaning thatthese elements have unstable nuclei and are radioactive. Elements with atomicnumbers of 83 and less, have isotopes (stable nucleus) and most have at least oneradioisotope (unstable nucleus). As a radioisotope tries to stabilize, it may transform intoa new element in a process called transmutation. We will talk about transmutation inmore detail a little later.


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Radioisotopes in Medicine

Introduction

Nuclear medicine uses radiation to provide diagnostic information about thefunctioning of a person's specific organs, or to treat them. Diagnostic procedures arenow routine.

Radiotherapy can be used to treat some medical conditions, especially cancer,using radiation to weaken or destroy particular targeted cells.

Tens of millions of nuclear medicine procedures are performed each year, anddemand for radioisotopes is increasing rapidly.

Nuclear Medicine

This is a branch of medicine that uses radiation to provide information about thefunctioning of a person's specific organs or to treat disease. In most cases, theinformation is used by physicians to make a quick, accurate diagnosis of the patient'sillness. The thyroid, bones, heart, liver and many other organs can be easily imaged,and disorders in their function revealed. In some cases radiation can be used to treatdiseased organs, or tumours. Five Nobel Laureates have been intimately involved withthe use of radioactive tracers in medicine.

Over 10,000 hospitals worldwide use radioisotopes in medicine, and about 90%

of the procedures are for diagnosis. The most common radioisotope used in diagnosisis technetium-99, with some 30 million procedures per year, accounting for 80% of allnuclear medicine procedures worldwide.

In developed countries (26% of world population) the frequency of diagnosticnuclear medicine is 1.9% per year, and the frequency of therapy with radioisotopes isabout one tenth of this. In the USA there are some 18 million nuclear medicineprocedures per year among 305 million people, and in Europe about 10 million among500 million people. In Australia there are about 560,000 per year among 21 millionpeople, 470,000 of these using reactor isotopes. The use of radiopharmaceuticals indiagnosis is growing at over 10% per year.

Nuclear medicine was developed in the 1950s by physicians with an endocrineemphasis, initially using iodine-131 to diagnose and then treat thyroid disease. In recentyears specialists have also come from radiology, as dual CT/PET procedures havebecome established.

Computed X-ray tomography (CT) scans and nuclear medicine contribute 36% ofthe total radiation exposure and 75% of the medical exposure to the US population,
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according to a US National Council on Radiation Protection & Measurements report in2009. The report showed that Americans average total yearly radiation exposure hadincreased from 3.6 millisievert to 6.2 mSv per year since the early 1980s, due tomedical-related procedures. (Industrial radiation exposure, including that from nuclearpower plants, is less than 0.1% of overall public radiation exposure.)

Diagnostic techniques in nuclear medicine

Diagnostic techniques in nuclear medicine use radioactive tracers which emitgamma rays from within the body. These tracers are generally short-lived isotopeslinked to chemical compounds which permit specific physiological processes to bescrutinised. They can be given by injection, inhalation or orally. The first type are wheresingle photons are detected by a gamma camera which can view organs from manydifferent angles. The camera builds up an image from the points from which radiation isemitted; this image is enhanced by a computer and viewed by a physician on a monitorfor indications of abnormal conditions.

A more recent development is Positron Emission Tomography (PET) which is amore precise and sophisticated technique using isotopes produced in a cyclotron. Apositron-emitting radionuclide is introduced, usually by injection, and accumulates in thetarget tissue. As it decays it emits a positron, which promptly combines with a nearbyelectron resulting in the simultaneous emission of two identifiable gamma rays inopposite directions. These are detected by a PET camera and give very preciseindication of their origin. PET's most important clinical role is in oncology, with fluorine-18 as the tracer, since it has proven to be the most accurate non-invasive method ofdetecting and evaluating most cancers. It is also well used in cardiac and brain imaging.

New procedures combine PET with computed X-ray tomography (CT) scans togive co-registration of the two images(PETCT), enabling 30% better diagnosis than withtraditional gamma camera alone. It is a very powerful and significant tool which providesunique information on a wide variety of diseases from dementia to cardiovasculardisease and cancer (oncology).

Positioning of the radiation source within the body makes the fundamentaldifference between nuclear medicine imaging and other imaging techniques such as x-rays. Gamma imaging by either method described provides a view of the position andconcentration of the radioisotope within the body. Organ malfunction can be indicated ifthe isotope is either partially taken up in the organ (cold spot), or taken up in excess(hot spot). If a series of images is taken over a period of time, an unusual pattern or rateof isotope movement could indicate malfunction in the organ.

A distinct advantage of nuclear imaging over x-ray techniques is that both boneand soft tissue can be imaged very successfully. This has led to its common use indeveloped countries where the probability of anyone having such a test is about one intwo and rising.


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The mean effective dose is 4.6 mSv per diagnostic procedure.

Radionuclide therapy (RNT)

Rapidly dividing cells are particularly sensitive to damage by radiation. For thisreason, some cancerous growths can be controlled or eliminated by irradiating the areacontaining the growth.

External irradiation (sometimes called teletherapy) can be carried out using agamma beam from a radioactive cobalt-60 source, though in developed countries themuch more versatile linear accelerators are now being utilised as a high-energy x-raysource (gamma and x-rays are much the same). An external radiation procedure isknown as the gamma knife radiosurgery, and involves focusing gamma radiation from201 sources of cobalt-60 sources on a precise area of the brain with a cancerous

tumour. Worldwide, over 30,000 patients are treated annually, generally as outpatients.

Internal radionuclide therapy is by administering or planting a small radiationsource, usually a gamma or beta emitter, in the target area. Short-range radiotherapy isknown as brachytherapy, and this is becoming the main means of treatment. Iodine-131is commonly used to treat thyroid cancer, probably the most successful kind of cancertreatment. It is also used to treat non-malignant thyroid disorders. Iridium-192 implantsare used especially in the head and breast. They are produced in wire form and areintroduced through a catheter to the target area. After administering the correct dose,the implant wire is removed to shielded storage. This brachytherapy (short-range)procedure gives less overall radiation to the body, is more localised to the target tumour

and is cost effective.

Treating leukaemia may involve a bone marrow transplant, in which case thedefective bone marrow will first be killed off with a massive (and otherwise lethal) doseof radiation before being replaced with healthy bone marrow from a donor.

Many therapeutic procedures are palliative, usually to relieve pain. For instance,strontium-89 and (increasingly) samarium 153 are used for the relief of cancer-inducedbone pain. Rhenium-186 is a newer product for this.

A new field is Targeted Alpha Therapy (TAT) or alpha radioimmunotherapy,

especially for the control of dispersed cancers. The short range of very energetic alphaemissions in tissue means that a large fraction of that radiative energy goes into thetargeted cancer cells, once a carrier such as a monoclonal antibody has taken thealpha-emitting radionuclide to exactly the right place. Laboratory studies areencouraging and clinical trials for leukaemia, cystic glioma and melanoma are underway. TAT using lead-212 is said to show promise for treating pancreatic, ovarian andmelanoma cancers.


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An experimental development of this is Boron Neutron Capture Therapy usingboron-10 which concentrates in malignant brain tumours. The patient is then irradiatedwith thermal neutrons which are strongly absorbed by the boron, producing high-energyalpha particles which kill the cancer. This requires the patient to be brought to a nuclearreactor, rather than the radioisotopes being taken to the patient.

Radionuclide therapy has progressively become successful in treating persistentdisease and doing so with low toxic side-effects. With any therapeutic procedure theaim is to confine the radiation to well-defined target volumes of the patient. The dosesper therapeutic procedure are typically 20-60 Gy.

Biochemical Analysis

It is very easy to detect the presence or absence of some radioactive materialseven when they exist in very low concentrations. Radioisotopes can therefore be usedto label molecules of biological samples in vitro (out of the body). Pathologists have

devised hundreds of tests to determine the constituents of blood, serum, urine,hormones, antigens and many drugs by means of associated radioisotopes. Theseprocedures are known as radioimmuno-assays and, although the biochemistry iscomplex, kits manufactured for laboratory use are very easy to use and give accurateresults. In Europe some 15 million of these in vitro analyses are undertaken each year.

Diagnostic Radiopharmaceuticals

Every organ in our bodies acts differently from a chemical point of view. Doctorsand chemists have identified a number of chemicals which are absorbed by specificorgans. The thyroid, for example, takes up iodine, the brain consumes quantities of

glucose, and so on. With this knowledge, radiopharmacists are able to attach variousradioisotopes to biologically active substances. Once a radioactive form of one of thesesubstances enters the body, it is incorporated into the normal biological processes andexcreted in the usual ways.

Diagnostic radiopharmaceuticals can be used to examine blood flow to the brain,functioning of the liver, lungs, heart or kidneys, to assess bone growth, and to confirmother diagnostic procedures. Another important use is to predict the effects of surgeryand assess changes since treatment.

The amount of the radiopharmaceutical given to a patient is just sufficient to

obtain the required information before its decay. The radiation dose received ismedically insignificant. The patient experiences no discomfort during the test and after ashort time there is no trace that the test was ever done. The non-invasive nature of thistechnology, together with the ability to observe an organ functioning from outside thebody, makes this technique a powerful diagnostic tool.


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A radioisotope used for diagnosis must emit gamma rays of sufficient energy toescape from the body and it must have a half-life short enough for it to decay awaysoon after imaging is completed.

The radioisotope most widely used in medicine is technetium-99m, employed in

some 80% of all nuclear medicine procedures - almost 30 million per year (2008), ofwhich 6-7 million are in Europe, 12-15 million in North America, 6-8 million inAsia/Pacific (particularly Japan), and 0.5 million in other regions. It is an isotope of theartificially-produced element technetium and it has almost ideal characteristics for anuclear medicine scan.

These are:

It has a half-life of six hours which is long enough to examine metabolicprocesses yet short enough to minimise the radiation dose to the patient.

Technetium-99m decays by a process called "isomeric"; which emits gamma

rays and low energy electrons. Since there is no high energy beta emission theradiation dose to the patient is low.

The low energy gamma rays it emits easily escape the human body and areaccurately detected by a gamma camera. Once again the radiation dose to the patientis minimised.

The chemistry of technetium is so versatile it can form tracers by beingincorporated into a range of biologically-active substances to ensure that itconcentrates in the tissue or organ of interest.

Its logistics also favour its use. Technetium generators, a lead pot enclosing aglass tube containing the radioisotope, are supplied to hospitals from the nuclear

reactor where the isotopes are made. They contain molybdenum-99, with a half-life of66 hours, which progressively decays to technetium-99. The Tc-99 is washed out of thelead pot by saline solution when it is required. After two weeks or less the generator isreturned for recharging.

A similar generator system is used to produce rubidium-82 for PET imaging fromstrontium-82 - which has a half-life of 25 days.

Myocardial Perfusion Imaging (MPI) uses thallium-201 chloride or technetium-99m and is important for detection and prognosis of coronary artery disease.

Canadian 2006 data shows that 56% of Tc-99 use there is in myocardialischemia perfusion, 17% in bone scans, 7% in liver/hepatobiliary, 4% respiratory, 3%renal, 3% thyroid.

For PET imaging, the main radiopharmaceutical is Fluoro-deoxy glucose (FDG)incorporating F-18 - with a half-life of just under two hours, as a tracer. The FDG isreadily incorporated into the cell without being broken down, and is a good indicator ofcell metabolism.


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In diagnostic medicine, there is a strong trend to using more cyclotron-producedisotopes such as F-18 as PET and CT/PET become more widely available. However,the procedure needs to be undertaken within two hours reach of a cyclotron, whichlimits their utility compared with Mo/Tc-99.

Therapeutic Radiopharmaceuticals

For some medical conditions, it is useful to destroy or weaken malfunctioningcells using radiation. The radioisotope that generates the radiation can be localised inthe required organ in the same way it is used for diagnosis - through a radioactiveelement following its usual biological path, or through the element being attached to asuitable biological compound. In most cases, it is beta radiation which causes thedestruction of the damaged cells. This is radionuclide therapy (RNT) or radiotherapy.Short-range radiotherapy is known as brachytherapy, and this is becoming the mainmeans of treatment.

Although radiotherapy is less common than diagnostic use of radioactive materialin medicine, it is nevertheless widespread, important and growing. An ideal therapeuticradioisotope is a strong beta emitter with just enough gamma to enable imaging,eg lutetium-177. This is prepared from ytterbium-176 which is irradiated to become Yb-177 which decays rapidly to Lu-177.Yttrium-90 is used for treatment of cancer,particularly non-Hodgkin's lymphoma, and its more widespread use is envisaged,including for arthritis treatment. Lu-177 and Y-90 are becoming the main RNT agents.

Iodine-131 and phosphorus-32 are also used for therapy. Iodine-131 is used totreat the thyroid for cancers and other abnormal conditions such as hyperthyroidism(over-active thyroid). In a disease called Polycythemia vera, an excess of red blood

cells is produced in the bone marrow. Phosphorus-32 is used to control this excess.

A new and still experimental procedure uses boron-10, which concentrates in thetumour. The patient is then irradiated with neutrons which are strongly absorbed by theboron, to produce high-energy alpha particles which kill the cancer.

For targeted alpha therapy (TAT), actinium-225 is readily available, from whichthe daughter bismuth-213 can be obtained (via 3 alpha decays) to label targetingmolecules. The bismuth is obtained by elution from an Ac-225/Bi-213 generator similarto the Mo-99/Tc-99 one. Bi-213 has a 46-minute half-life. The actinium-225 (half-life 10days) is formed from radioactive decay of radium-225, the decay product of long-livedthorium-229, which is obtained from decay of uranium-233, which is formed from Th-232 by neutron capture in a nuclear reactor.

Another radionuclide recovered from used nuclear fuel is lead-212, with half-lifeof 10.6 hours, which can be attached to monoclonal antibodies for cancer treatment. Itsdecay chain includes the short-lived isotopes bismuth-212 by beta decay, polonium-212by beta decay and thallium-208 by alpha decay of the bismuth, with further alpha andbeta decays respectively to Pb-208, all over about an hour.


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Considerable medical research is being conducted worldwide into the use ofradionuclides attached to highly specific biological chemicals such as immunoglobulinmolecules (monoclonal antibodies). The eventual tagging of these cells with atherapeutic dose of radiation may lead to the regression - or even cure - of somediseases.

Radioisotope Poisons

In 2006 Britain witnessed the apparent murder of one of its newer citizens, aformer Russian intelligence official, by poisoning with radioactive polonium. His deathwas slow and excruciating.

Polonium has about 26 isotopes, all of which are radioactive. Webelementsperiodic table says that it is 250 billion times more toxic than hydrocyanic acid. It isreadily soluble in weak acid. (It was the first element discovered by Marie Curie, in1898, and named after her native Poland. Her daughter Irene was contaminated with

polonium in a laboratory accident and died of leukemia at the age of 59.)

Polonium-210 is the penultimate decay product of U-238, before it alpha decaysto become stable lead. It results from the beta decay of Pb-210 (in the U-238 decayseries) to Bi-210 which rapidly beta decays to Po-210. This gives rise to its occurrencein nature, where uranium is ubiquitous. However, because of its short (138 day) half life,very little Po-210 would be found in uranium ore or mill tailings (Webelements suggests0.1 mg/tonne). Po-210 levels in soil would be even less, but it is concentrated intobacco and traces of it can be found in smokers' urine.

Po-210 can also be made by neutron irradiation of Bi-209, and that is most likely

source of any significant quantity. Russia has used Po-210 as a heat source in short-lifespacecraft and lunar rovers. It also operates reactors using lead-bismuth cooling, whichbecomes contaminated with Po-210 due to neutron bombardment.

Because its half-life is so short, a gram of Po-210 is about 5000 times asradioactive as a gram of radium - which sets the standard of activity. But at 138 days itshalf life is long enough for it to be manufactured, transported and administered beforeits loses its potency. It would not put the carrier at much risk, since alpha radiation isonly really a hazard inside the body - a layer of skin is protection. About 10 micrograms(2 GBq) was said to have been used, administered in a cup of tea (it would be warmdue to the decay).

However, simply dosing someone with polonium might not have much effect if itsimply went in one end and out the other in a day or two without being absorbed fromthe gut. It would probably need to be complexed on to an organic carrier which wouldenter the bloodstream and take it to vital organs where it would stay. (This is whathappens with targeted alpha therapy (TAT) using very low levels of alpha-activeradioisotopes: the carriers take them to dispersed cancerous tissues where they areneeded.)


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In Mr Litvinenko's case the intense alpha radiation was reportedly in vital organsand sufficient to destroy them over three weeks. It was apparently over one hundredtimes the dose used in TAT for cancer treatment and the Po-210 is much longer-livedthan isotopes used for TAT. It could have been attached to something as simple as asugar.

Supplies of radioisotopes

Most medical radioisotopes made in nuclear reactors are sourced from relativelyfew research reactors, including:

- NRU at Chalk River in Canada (supplied via MDS Nordion)

- HFR at Petten in Netherlands (supplied via IRE and Covidien)

- BR-2 at Mol in Belgium (supplied via IRE and Covidien)

- Maria in Poland (supplied via Covidien)

- Osiris & Orphee at Saclay in France (supplied via IRE)

- FRJ-2/ FRM-2 at Julich in Germany (supplied via IRE)

- LWR-15 at Rez in Czech Republic

- HFETR at Chengdu in China

- Safari in South Africa (supplied from NTP)

- Opal in Australia (supplied from ANSTO to domestic market)

- ETRR-2 in Egypt (forthcoming: supplied to domestic market)

- Dimitrovgrad in Russia (Isotop-NIIAR)

Of fission radioisotopes, 40% of Mo-99 (for Tc-99m) comes from MDS Nordion,25% from Covidien (formerly Tyco), 17% from IRE and 10% from NTP. For I-131, 75%

is from IRE, 25% from NTP. Over 90% of the Mo-99 is made in five reactors: NRU inCanada (40%), HFR in Netherlands (30%), BR-2 in Belgium (9%), Osiris in France(5%), and Safari-1 in South Africa (10%). Canadian 2008 data gives 31% for NRU.

World demand for Mo-99 is 23,000 six-day TBq/yr.* It is mostly prepared byfission of U-235 targets in a nuclear research reactor. Most is produced using high-enriched uranium targets which are then processed to separate the Mo-99 and also to
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recover I-131. Opal, Safari, and increasingly other reactors, are moving to low-enricheduranium targets, which adds about 20% to production costs.

* 23,000 TBq is on basis of activity at 6 days from production reference point, ie22% of nearly 100,000 TBq required in production processing (given 66 hour half-life).

This is still about two days from the end of irradiation, so some 167,000 TBq/yr must bemade in the actual reactors to allow for cooling, processing and decay en route to theusers.

A number of incidents in 2008 pointed up shortcomings and unreliability in thesupply of medical isotopes, particular technetium. As indicated above, most of theworld's supply of Mo-99 for this comes from only five reactors, all of them 43 to 52 yearsold (in mid 2010). The Canadian and Netherlands reactors required major repairs over2009-10 and were out of action for some time. Osiris is due to shut down in 2015. Amajor and increasing supply shortfall of Tc-99 is forecast from 2010, and the IAEA isencouraging new producers in Egypt, East Europe and central Asia. During the 2009-

10 supply crisis, South Africa's (NECSA) Safari was able to supply 25% of the supply ofMo-99.

Australia's Opal reactorhas the capacity to produce half the world supply of it,but a much larger Mo production facility would be required. Also the processing anddistribution of isotopes is complex and constrained, which can be critical when theisotopes concerned are short-lived. A need for increased production capacity and morereliable distribution is evident. The Mo-99 market is about $5 billion per year, accordingto NECSA.

The US Congress has called for all Mo-99 to be supplied by reactors running on

low-enriched uranium (LEU), instead of high-enriched uranium (HEU). Also it has calledfor proposals for an LEU-based supply of Mo-99 for the US market. This supply shouldreach 111 six-day TBq per week by mid-2013, a quarter of world demand. Tenders forthis closed in June 2010.

In January 2009 Babcock & Wilcox (B&W) announced an agreement withinternational isotope supplier Covidien to produce Mo-99 sufficient for half of USdemand, if a new process involving an innovative reactor and separation technology issuccessful. They plan to use Aqueous Homogeneous Reactor (AHR) technology withlow-enriched uranium in small 100-200 kW units units where the fuel is mixed with themoderator and the U-235 forms both the fuel and the irradiation target. A singleproduction facility could have four such reactors. B&W and Covidien expect a five-yearlead time to first production. (LEU is dissolved in acid then brought to criticality in a200-litre vessel. A

s fission proceeds the solution is circulated through an extraction facility toremove the fission products with Mo-99 and then back into the reactor vessel, which isat low temperature and pressure.) At Russia's Kurchatov Institute the 20 kW ARGUS

AHR has operated since 1981, and R&D on producing Mo-99 from it is ongoing.
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Also in the USA, the University of Missouri is reported to be planning a licenceapplication to NRC in 2010 to produce half of US requirements of Mo-99 at its researchreactor using low-enriched uranium targets by 2012.

In Russia, the Research Institute of Atomic Reactors (NIIAR or RIAR, with 3

reactors) and Trans-regional Izotop Association (VA Izotop) have established a jointventure, Isotop-NIIAR to produce Mo-99 at Dimitrovgrad from 2010. Phase 1 of the Mo-99 production line with capacity of 1700 TBq/yr was commissioned in December 2010,and Phase 2 will take capacity to 52,000 TBq/yr according to Rosatom, without sayingwhen the activity is measured. (VA Izotop is authorized since 2009 by Rosatom tocontrol all isotope production and radiological devices in Russia).

This JV is aiming to capture 26% of the world market for Mo-99 by 2012. InSeptember 2010 JSC Izotop signed a framework agreement with MDS Nordion toexplore commercial opportunities outside Russia on the basis of this Isotop-NIIAR JV,initially over ten years.

Cobalt-60 has mostly come from Candu power reactors by irradiation of Co-59 inspecial rods, and production is being expanded. Production sites include: Bruce B,Pickering and Gentilly in Canada; Embalse in Argentina; Qinshan Phase III units 1 and2 in China; Wolsong 1 and 2 in South Korea (all Candu); and Leningrad 1 in Russia(RBMK). These will be joined by the Clinton and Hope Creek BWRs in USA from 2012.

Nuclear Medicine Wastes

The use of radioisotopes for medical diagnosis and treatments results in thegeneration of mainly Low-Level Waste (LLW). This waste includes paper, rags, tools,

clothing and filters, which contain small amounts of mostly short-lived radioactivity.These types of waste often undergo decay storage for periods of months to a few yearsbefore being disposed of at urban land-fill sites.

When radiography sources have decayed to a point where they are no longeremitting enough penetrating radiation for use in treatments, they are considered asradioactive waste. Sources such as Co-60 are treated as short-lived Intermediate-Levelwastes (ILW). Other sources such as Radium-226, used in cancer therapy, will howeverrequire long-term storage and geological disposal as ILW, as a result of their higherlevel of long-lived radioactivity.

Isotopes used in Medicine

Many radioisotopes are made in nuclear reactors, some in cyclotrons. Generallyneutron-rich ones and those resulting from nuclear fission need to be made in reactors,neutron-depleted ones are made in cyclotrons. There are about 40 activation productradioisotopes and five fission product ones made in reactors.


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1. Reactor Radioiso topes (half- l i fe ind icated)

Below is the table of type reactor radioisotopes and their uses:

No. Type of radioisotopes Their uses

1 Bismuth 213 (46 min) targeted alpha therapy (TAT), especially cancers,as it has a high energy (8.4 MeV).2 Chromium 51 (28 d) label red blood cells and quantify gastro3 Cobalt 60 (5.27 yr) formerly used for external beam radiotherapy, now

used more for sterilising4 Dysprosium 165 (2 h) aggregated hydroxide for synovectomy treatment of

arthritis.5 Iodine 131 (8 d)* Widely used in treating thyroid cancer and in

imaging the thyroid; also in diagnosis of abnormalliver function, renal (kidney) blood flow and urinarytract obstruction. A strong gamma emitter, but used

for beta therapy.6 Lead-212 (10.6 h) used in TAT for cancers, with decay products Bi-

212, Po-212, Tl-208.7 Rhenium-188 (17 h) beta irradiate coronary arteries from an angioplasty

balloon.8 Samarium-153 (47 h) Sm-153 is very effective in relieving the pain of

secondary cancers lodged in the bone, sold asQuadramet. Also very effective for prostate andbreast cancer. Beta emitter.

9 Sodium-24 (15 h) for studies of electrolytes within the body.10 Strontium-89 (50 d)* very effective in reducing the pain of prostate and

bone cancer. Beta emitter.11 Technetium-99m (6 h) image the skeleton and heart muscle in particular,

but also for brain, thyroid, lungs (perfusion andventilation), liver, spleen, kidney (structure andfiltration rate), gall bladder, bone marrow, salivaryand lacrimal glands, heart blood pool, infection andnumerous specialised medical studies. Producedfrom Mo-99 in a generator.

13 Xenon-133 (5 d)* pulmonary (lung) ventilation studies.14 Ytterbium-169 (32 d) cerebrospinal fluid studies in the brain.15 Ytterbium-177 (1.9 h) progenitor of Lu-177.

16 Yttrium-90 (64 h)* cancer brachytherapy and as silicate colloid for therelieving the pain of arthritis in larger synovial joints.Pure beta emitter and of growing significance intherapy.

17 Radioisotopes of caesium,gold and ruthenium

used in brachytherapy.

18 Erbium 169 (9.4 d) relieving arthritis pain in synovial joints.19 Rhenium-186 (3.8 d) pain relief in bone cancer. Beta emitter with weak


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gamma for imaging.20 Potassium-42 (12 h) determination of exchangeable potassium in

coronary blood flow.21 Phosphorus-32 (14 d) the treatment of polycythemia vera (excess red

blood cells). Beta emitter.

22 Palladium-103 (17 d) make brachytherapy permanent implant seeds forearly stage prostate cancer.23 Molybdenum-99 (66 h)* as the 'parent' in a generator to produce

technetium-99m.24 Lutetium-177 (6.7 d) Lu-177 is increasingly important as it emits just

enough gamma for imaging while the beta radiationdoes the therapy on small (eg endocrine) tumours.Its half-life is long enough to allow sophisticatedpreparation for use. It is usually produced byneutron activation of natural or enriched lutetium-176 targets.

25 Iron 59 (46 d) studies of iron metabolism in the spleen.26 Iridium 192 (74 d) supplied in wire form for use as an internal

radiotherapy source for cancer treatment (used thenremoved).

27 Holmium 166 (26 h) being developed for diagnosis and treatment of livertumours.

28 Iodine 125 (60 d) cancer brachytherapy (prostate and brain), alsodiagnostically to evaluate the filtration rate ofkidneys and to diagnose deep vein thrombosis inthe leg. It is also widely used in radioimmuno.

29 Selenium-75 (120 d) form of seleno-methionine to study the production of

digestive enzymes.* fission product

2. Cyclotron Radioisotopes


1 Carbon-11, Nitrogen-13,Oxygen-15, Fluorine-18

these are positron emitters used in PET forstudying brain physiology and pathology, inparticular for localising epileptic focus, and indementia, psychiatry and neuropharmacologystudies. They also have a significant role in

cardiology. F-18 in FDG (fluorodeoxyglucose) hasbecome very important in detection of cancers andthe monitoring of progress in their treatment, usingPET.

2 Cobalt-57 (272 d): as a marker to estimate organ size and for in-vitrodiagnostic kits.

3 Copper-64 (13 h) study genetic diseases affecting coppermetabolism, such as Wilson's and Menke's


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diseases, and for PET imaging of tumours, andtherapy.

4 Copper-67 (2.6 d) beta emitter, used in therapy.5 Fluorine-18 as FLT

(fluorothymidine), F-miso

(fluoromisonidazole), 18F-choline

tracer.

6 Gallium-67 (78 h) for tumour imaging and localisation of inflammatorylesions (infections).

7 Gallium-68 (68 min) positron emitter used in PET and PET-CT units.Derived from germanium-68 in a generator.

8 Thallium-201 (73 h) diagnosis of coronary artery disease other heartconditions such as heart muscle death and forlocation of low-grade lymphomas.

9 Germanium-68 (271 d) as the 'parent' in a generator to produce Ga-68.10 Indium-111 (2.8 d) specialist diagnostic studies, eg brain studies,

infection and colon transit studies.11 Iodine-123 (13 h) increasingly used for diagnosis of thyroid function,

it is a gamma emitter without the beta radiation of I-131.

12 Iodine-124 tracer.13 Strontium-82 (25 d) the 'parent' in a generator to produce Rb-82.


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Radioisotopes in Industry

Intrdoduction

Modern industry uses radioisotopes in a variety of ways to improve productivityand, in some cases, to gain information that cannot be obtained in any other way.

Sealed radioactive sources are used in industrial radiography, gaugingapplications and mineral analysis.

Short-lived radioactive material is used in flow tracing and mixingmeasurements.

Gamma sterilisation is used for medical supplies, some bulk commodities and,increasingly, for food preservation.

Nuclear techniques are increasingly used in industry and environmental management.

The continuous analysis and rapid response of nuclear techniques, many involvingradioisotopes, mean that reliable flow and analytic data can be constantly available.This results in reduced costs with increased product quality.

Neutron Techniques for Analysis

Neutrons can interact with atoms in a sample causing the emission of gammarays which, when analysed for characteristic energies and intensity, will identify thetypes and quantities of elements present. The two main techniques are ThermalNeutron Capture (TNC) and Neutron Inelastic Scattering (NIS). TNC occurs immediatelyafter a low-energy neutron is absorbed by a nucleus, NIS takes place instantly when a

fast neutron collides with a nucleus.

Most commercial analysers use californium-252 neutron sources together withsodium iodide detectors and are mainly sensitive to TNC reactions. Other use Am-Be-241 sources and bismuth germanate detectors, which register both TNC and NIS. NISreactions are particularly useful for elements such as C, O, Al & Si which have a lowneutron capture cross section. Such equipment is used for a variety on on-line and on-belt analysis in the cement, mineral and coal industries.

A particular application of NIS is where a probe containing a neutron source canbe lowered into a bore hole where the radiation is scattered by collisions with

surrounding soil. Since hydrogen (the major component of water) is by far the bestscattering atom, the number of neutrons returning to a detector in the probe is a functionof the density of the water in the soil.

To measure soil density and water content, a portable device with an americium-241-beryllium combination generates gamma rays and neutrons which pass through asample of soil to a detector. (The neutrons arise from alpha particles interacting with Be-9.) A more sophisticated application of this is in borehole logging.


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Gamma & X-ray Techniques in Analysis

Gamma ray transmission or scattering can be used to determine the ash contentof coal on line on a conveyor belt. The gamma ray interactions are atomic numberdependant, and the ash is higher in atomic number than the coal combustible matter.

Also the energy spectrum of gamma rays which have been inelastically scattered fromthe coal can be measured (Compton Profile Analysis) to indicate the ash content.

X-rays from a radioactive element can induce fluorescent x-rays from other non-radioactive materials. The energies of the fluorescent x-rays emitted can identify theelements present in the material, and their intensity can indicate the quantity of eachelement present.

This technique is used to determine element concentrations in process streamsof mineral concentrators. Probes containing radioisotopes and a detector are immerseddirectly into slurry streams. Signals from the probe are processed to give the

concentration of the elements being monitored, and can give a measure of the slurrydensity. Elements detected this way include iron, nickel, copper, zinc, tin and lead.

X-ray Diffraction (XRD) is a further technique for on-line analysis but does notuse radioisotopes.

Gamma Radiography

Gamma Radiography works in much the same way as x-rays screen luggage atairports. Instead of the bulky machine needed to produce x-rays, all that is needed toproduce effective gamma rays is a small pellet of radioactive material in a sealed

titanium capsule.

The capsule is placed on one side of the object being screened, and somephotographic film is placed on the other side. The gamma rays, like x-rays, passthrough the object and create an image on the film. Just as x-rays show a break in abone, gamma rays show flaws in metal castings or welded joints. The technique allowscritical components to be inspected for internal defects without damage.

Gamma sources are normally more portable than x-ray equipment so have aclear advantage in certain applications, such as in remote areas. Also while x-raysources emit a broad band of radiation, gamma sources emit at most a few discrete

wavelengths. Gamma sources may also be much higher energy than all but the mostexpensive x-ray equipment, and hence have an advantage for much radiography.Where a weld has been made in an oil or gas pipeline, special film is taped over theweld around the outside of the pipe.

A machine called a "pipe crawler" carries a shielded radioactive source down theinside of the pipe to the position of the weld. There, the radioactive source is remotely


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exposed and a radiographic image of the weld is produced on the film. This film is laterdeveloped and examined for signs of flaws in the weld.

X-ray sets can be used when electric power is available and the object to be x-rayed can be taken to the x-ray source and radiographed. Radioisotopes have the

supreme advantage in that they can be taken to the site when an examination isrequired - and no power is needed. However, they cannot be simply turned off, and somust be properly shielded both when in use and at other times.

Non-destructive testing is an extension of gamma radiography, used on a varietyof products and materials. For instance, ytterbium-169 tests steel up to 15 mm thick andlight alloys to 45 mm, while iridium-192 is used on steel 12 to 60 mm thick and lightalloys to 190 mm.

Gauging

The radiation that comes from a radioisotope has its intensity reduced by matterbetween the radioactive source and a detector. Detectors are used to measure thisreduction. This principle can be used to gauge the presence or the absence, or even tomeasure the quantity or density, of material between the source and the detector. Theadvantage in using this form of gauging or measurement is that there is no contact withthe material being gauged.

Many process industries utilise fixed gauges to monitor and control the flow ofmaterials in pipes, distillation columns, etc, usually with gamma rays.

The height of the coal in a hopper can be determined by placing high energy

gamma sources at various heights along one side with focusing collimators directingbeams across the load. Detectors placed opposite the sources register the breaking ofthe beam and hence the level of coal in the hopper. Such level gauges are among themost common industrial uses of radioisotopes.

Some machines which manufacture plastic film use radioisotope gauging withbeta particles to measure the thickness of the plastic film. The film runs at high speedbetween a radioactive source and a detector. The detector signal strength is used tocontrol the plastic film thickness.

In paper manufacturing, beta gauges are used to monitor the thickness of the

paper at speeds of up to 400 m/s.

When the intensity of radiation from a radioisotope is being reduced by matter inthe beam, some radiation is scattered back towards the radiation source. The amount of'backscattered' radiation is related to the amount of material in the beam, and this canbe used to measure characteristics of the material. This principle is used to measuredifferent types of coating thicknesses.


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Gamma Sterilisation

Gamma irradiation is widely used for sterilising medical products, for otherproducts such as wool, and for food. Cobalt-60 is the main isotope used, since it is anenergetic gamma emitter. It is produced in nuclear reactors, sometimes as a by-product

of power generation.

Large-scale irradiation facilities for gamma sterilisation are used for disposablemedical supplies such as syringes, gloves, clothing and instruments, many of whichwould be damaged by heat sterilisation. Such facilities also process bulk products suchas raw wool for export from Australia, archival documents and even wood, to killparasites. Currently ANSTO in Australia sterilises up to 25 million Queensland fruit flypupae per week for NSW Agriculture by gamma irradiation.

Smaller gamma irradiators are used for treating blood for transfusions and forother medical applications.

Food preservation is an increasingly important application, and has been usedsince the 1960s. In 1997 the irradiation of red meat was approved in USA. Some 41countries have approved irradiation of more than 220 different foods, to extend shelf lifeand to reduce the risk of food-borne diseases.

Scientific Uses

Radioisotopes are used as tracers in many research areas. Most physical,chemical and biological systems treat radioactive and non-radioactive forms of anelement in exactly the same way, so a system can be investigated with the assurance

that the method used for investigation does not itself affect the system. An extensiverange of organic chemicals can be produced with a particular atom or atoms in theirstructure replaced with an appropriate radioactive equivalent.

Using tracing techniques, research is conducted with various radioisotopes whichoccur broadly in the environment, to examine the impact of human activities. The age ofwater obtained from underground bores can be estimated from the level of naturallyoccurring radioisotopes in the water. This information can indicate if groundwater isbeing used faster than the rate of replenishment. Trace levels of radioactive fallout fromnuclear weapons testing in the 1950s and 60s is now being used to measure soilmovement and degradation. This is assuming greater importance in environmental

studies of the impact of agriculture.

Tracing/Mixing Uses

Even very small quantities of radioactive material can be detected easily. Thisproperty can be used to trace the progress of some radioactive material through acomplex path, or through events which greatly dilute the original material. In all thesetracing investigations, the half-life of the tracer radioisotope is chosen to be just long


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enough to obtain the information required. No long-term residual radioactivity remainsafter the process.

Sewage from ocean outfalls can be traced in order to study its dispersion. Smallleaks can be detected in complex systems such as power station heat exchangers.

Flow rates of liquids and gasses in pipelines can be measured accurately, as can theflow rates of large rivers.

Mixing efficiency of industrial blenders can be measured and the internal flow ofmaterials in a blast furnace examined. The extent of termite infestation in a structurecan be found by feeding the insects radioactive wood substitute, then measuring theextent of the radioactivity spread by the insects. This measurement can be madewithout damaging any structure as the radiation is easily detected through buildingmaterials.

Wastes

Industries utilise radioactive sources for a wide range of applications. When theradioactive sources used by industry no longer emit enough penetrating radiation forthem to be of use, they are treated as radioactive waste. Sources used in industry aregenerally short-lived and any waste generated can be disposed of in near-surfacefacilities.

Some industrial activities involve the handling of raw materials such as rocks,soils and minerals that contain naturally occurring radioactive materials. Thesematerials are known by the acronym "NORM". Industrial activity can sometimesconcentrate these materials and therefore enhance their natural radioactivity (hence the

further acronym: TENORM - technically-enhanced NORM).

This may result in:

A risk of radiation exposure to workers or the public

Unacceptable radioactive contamination of the environment

The need to comply with regulatory waste disposal requirements

The main industries that result in NORM contamination are:

1. Oil and gas o perat ions

Oil and gas exploration and production generates large volumes of water containingdissolved minerals. These minerals may be deposited as scale in piping and oil fieldequipment or left as residues in evaporation lagoons. Occasionally the radiation dosefrom equipment contaminated with mineral deposits may present a hazard. Moresignificantly contaminated equipment and the scale removed from it may be classified


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as radioactive waste. Oil and gas operations are the main sources of radioactivereleases to waters north of Europe for instance.

2. Coal burn ing

Most coal contains uranium and thorium, as well as other radionuclides. The totalradiation levels are generally about the same as in other rocks of the earth's crust. Mostemerge from a power station in the light flyash. Some 99% of flyash is typically retainedin a modern power station (90% in some older ones) and this is buried in an ash dam.

Around 280 million tonnes of coal ash is produced globally each year.

3. Phos phate Ferti l isers

The processing of phosphate rock to produce phosphate fertilizers (one end product ofthe phosphate industry) results in enhanced levels of uranium, thorium and potassium.

4. Process and Waste Water Treatment

Radionuclides are leached into water when it comes into contact with uranium andthorium bearing rocks and sediments. Water treatment often uses filters to removeimpurities. Hence, radioactive wastes from filter sludges, ion-exchange resins,granulated activated carbon and water from filter backwash are part of NORM.

5. Scrap metal indu stry

Scrap metal from various process industries can also contain scales with enhancedlevels of natural radionuclides. The exact nature and concentration of theseradionuclides is dependent on the process from which the scrap originated.

6. Metal smel t ing sludg es

Metal smelting slags, especially from tin smelting, may contain enhanced levels ofuranium and thorium series radionuclides.

7. Research

Following the operation of a particle accelerator, the facility will generally bedecommissioned. As radioactive materials will be present in the facility, these must betreated as radioactive wastes and handled accordingly. Following a 40 year operation ofone of the new generation of particle accelerators, the volume of decommissioningwaste and activity is expected to be within the same order of magnitude as for a 1GW(e) nuclear power plant which has operated over 40 years. However, it should benoted that the concentration of radioactivity is more evenly distributed in the case ofsuch an accelerator facility.


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Radiation sources utilised within universities and research institutions alsorequire appropriate management and disposal. Many sources are of low activity and/orshort half-life. However some exceptions include high-level long-lived sources such asRadium-226 and Americium-241 used in biological and or agricultural research. Theserequire long-term management and disposal as Intermediate-Level Wastes (ILW).

Industrial Radioisotopes

1. Below is table about naturally-occurring radioisotopes:


1 Carbon 14 measure the age of water (up to 50,000 years)2 Chlorine 36 measure sources of chloride and the age of water

(up to 2 million years)3 Lead 210 date layers of sand and soil up to 80 years4 Tritium (H3) measure 'young' groundwater (up to 30 years)

2. Below is the table about artificially-produced radioisotopes:


1 Americium-241: backscatter gauges, smoke detectors, fill heightdetectors and in measuring ash content of coal.

2 Caesium-137: radiotracer technique for identification of sources ofsoil erosion and deposition, in density and fill heightlevel switches.

3 Chromium 57: label sand to study coastal erosion.4 Gold-198 & Technetium-

99m

study sewage and liquid waste movements, as well

as tracing factory waste causing ocean pollution,and to trace sand movement in river beds andocean floors

5 Gold-198: label sand to study coastal erosion.6 Hydrogen-3 tracer to study sewage and liquid wastes7 Iridium-192 gamma radiography to locate flaws in metal

components.8 Nickel-63 light sensors in cameras and plasma display, also

electronic discharge prevention and in electroncapture detectors for thickness gauges.

9 Selenium-75 gamma radiography and non-destructive testing.

10 Strontium-90 industrial gauging.11 Thallium-204 industrial gauging.12 Ytterbium-169 gamma radiography and non-destructive testing.13 Zinc-65 predict the behaviour of heavy metal components in

effluents from mining waste water.14 Manganese-54 predict the behaviour of heavy metal components in

effluents from mining waste water.15 Krypton-85 industrial gauging.


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16 Cobalt-60, Lanthanum-140,Scandium-46, Silver-110m,Gold-198

used together in blast furnaces to determineresident times and to quantify yields to measure thefurnace performance.

17 Cobalt-60 gamma sterilisation, industrial radiography, densityand fill height switches.


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Radioisotopes in agriculture

Agricultural Tracers

Tracers like those used in medicine are also used in agriculture to study plantsand their intake of fertilisers. The usage of tracers allows scientists and farmers tooptimise the use of fertilising and weedkilling chemicals. Optimisation of thesechemicals is desirable because it saves money, and reduces chemical pollution. Whenfertilisers are used in overly excessive amounts, the excess will run off and pollute riversnearby, as well as possibly seeping through to the water table underground andpolluting the water supply.

To prevent this, studies are conducted to find out the optimal amount of chemicalrequired, with fertilisers and weedkillers often tagged by nitrogen-15 or phosphorus-32

radioisotopes. These radioisotopes are analysed in the crops to see how much of theoriginal chemical was actually consumed by the plants, compared to how much wasgiven.

The ionising radiation from radioisotopes is also used to produce crops that aremore drought and disease resistant, as well as crops with increased yield or shortergrowing time. This practice has been in place for several decades, and has helped feedsome third-world countries. The collection of crops that have been modified withradiation include wheat, sorghum, bananas and beans

Insect Control

About 10% of the world's crops are destroyed by insects. In efforts to control insectplagues, authorities often release sterile laboratory-raised insects into the wild. Theseinsects are made sterile using ionising radiation - they are irradiated with this radiationbefore they hatch. Female insects that mate with sterile male insects do not reproduce,and the population of the insect pests can be quickly curbed as a consequence. Thistechnique of releasing sterile insects into the wild, called the sterile insect technique(SIT), is commonly used in protecting agricultural industries in many countries aroundthe world.

The technique is considered to be safer and better than conventional chemicalinsecticides. Insects can develop resistance against these chemicals, and there arehealth concerns about crops treated with them.

The largest application of this technique so far was conducted in Mexico againstMediterranean fruit-fly and screwworm in 1981. It was highly successful, and over thenext 10 years the eradication program yielded about US$3 billion in economic benefitsto the country.


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SIT is in use in several countries, with support from the UN Food and AgricultureOrganisation (FAO) and the International Atomic Energy Agency (IAEA). Australia is alarge producer of many fruits and sterilises up to 25 million fruit fly pupae per week.

Food Treatment and Preservation

Ionising radiation is used as an alternative to chemicals in the treatment andpreservation of foods. A French scientist first discovered that radiation could be used toprolong food shelf life in the 1920s and it became more widely used in World War II.Today, astronauts often eat radiation-preserved food while on space missions.

In meats and other foods of animal origin, irradiation destroys the bacteria thatcauses spoilage as well as diseases and illneses such as salmonella poisoning. Thisallows for a more safer food supply, and meats that can be stored for longer beforespoilage. Additionally, irradiation also inhibit tubers that cause fruits and vegetables toripen. The result is fresh fruits and vegetables that can be stored for longer before

ripening.

The irradiation technique is particularly important when exporting to countrieswith tropical climates, where foods can be spoiled easily due to the warm temperatures.

Irradiation of food is carried out using accelerated electrons (beta radiation), andionising radiation from sources such as the radioisotopes cobalt-60 and cesium-137. X-rays are also sometimes used. None of these sources of radiation used have enoughenergy to make the exposed foods radioactive.

The above table shows the typical doses of radiation used for food treatment:

Radiation dose(kilograys, kGy)

Purpose

"low" up to 1 kGyinhibits fruit and vegetable ripening controls some bacteria inmeats controls insects in grains

"medium" 1-10destroys bacteria in meat including salmonella, shigella,campylobacter and yersinia inhibits mold growth on fruit

"high" more than 10kGy

destroys insects and bacteria in spices sterilises food to the sameextent achieved by high heat

Inside the food treatment plant there is a conveyor belt or similar system thattransports the food to the radiation source, so that workers do not have to move close tothe radiation. The source is packaged in a pencil like device, about 1cm in diametre.The room where irradiation takes place is shielded by concrete walls to preventradiation from escaping into the environment, although the radiation risk is considerablymuch less than that from a nuclear reactor. Where gamma radiation is used from a


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radioisotope source, the radioisotope is stored in a pool of water while not in use, toalso help prevent radiation from escaping. However, the plant is in many ways similar toany other - refrigeration is still important. No process can make food completely spoil-proof.

Food treatment plants of this kind are monitored closely by government healthand occupational safety authorities to ensure safe working conditions for employees, aswell as safety to any nearby residents.

Food irradiation is a well-tested process. Scientists have performed numerousdecades of research, and it has been shown that irradiation will not cause significantchemical changes in foods that may affect human health, nor will it cause losses thatmay affect the nutritional content of food. (Chemical residues left behind by irradiationare in concentrations equivilant to about 3 drops in a swimming pool. Chemical-basedpreservatives and treatments usually leave more residues.) Taste is usually unaffected.The World Health Organisation and food safety authorities in many countries have

approved irradiation as a safe method of food treatment and preservation.

Radiation-treated food is still not very widely used today. Despite the scientificevidence and approvals, many activist organisations claim that irradiation is unsafe andexploit the lack of public awareness and concerns about food safety and nuclear issues.Some even say that irradiation is a way that governments can utilise nuclear wastes leftover from weapons testing or power generation. (However, the wastes left cannot beused in food processing because they do not provide the right type of ionising radiation.)Consequently, these scare tactics deter the public and some food producers arereluctant to use irradiation for fear of consumer boycotts.

However, a recent survey conducted in mid-1998 by the Food Marketing Institute(a United States organisation) revealed that less than one percent of all those surveyedidentified irradiation as a concern. Most said that spoilage and microbial hazards wereof great concern - they very problem that irradiation addresses. Another study by anacademic revealed that about 99% of consumers were willing to buy irradiated foodafter they were shown scientific data and irradiated food samples. This compared to50% before shown this data.

Irradiation poses less of a risk to human health than many chemical treatmentsthat are used today, which include the addition of chemical preservatives. The use ofradiation is sometimes favoured to using chemical preservatives, because no allergicside-effect results. It is also better than heat-sterilisation because irradiation does notdestroy nutrients and vitamins, whereas heat treatment does.

Irradiation is inexpensive - typical costs are about 1-20 cents per kilogram of foodirradiated.

About 40 countries worldwide allow irradiation of foods. Depending on thecountry, irradiated foods may need to be labelled.


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Quarantine and Exportation

Ionising radiation is used to rid goods of parasites and bugs before they areexported out of a country. The radiation kills these parasites that may be quarantinehazards in other countries.

The technique is used in Australia to clear primary produce materials such asraw wool and wood for export. It is also used worldwide in transporting archival andhistorical documents. This is beneficial in that any microorganisms existing in the paperthat cause paper deterioration are destroyed.


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Radioisotopes in archaology

Radioactive Dating

The principals of radioactive decay are applied in the technique of radioactivedating, a process widely used by geologists and archaeologists to determine the age ofmaterials and artifacts.

Radioactive carbon-14 atoms exist naturally. They are everywhere around us: inour clothes, in the food we eat, even in the air we breathe. However, there are not manyof these - only 1.3 10-12 percent of all carbon atoms are the carbon-14 isotope. This iswhy they do not pose danger to us - there are so few of them.

The ratio of radioactive carbon-14 atoms to stable carbon-12 atoms in theatmosphere has remained constant over thousands of years. Although carbon-14

naturally decays, it is also continually being formed. Carbon-14 atoms are formed whenneutrons from the sun's cosmic radiation collide with nitrogen-14 atoms in theatmosphere:

Thus the decay of carbon-14 is reasonably balanced with its production, resultingin a constant ratio of carbon-14 to carbon-12.

Carbon dioxide (CO2) molecules in the air can contain either isotope of carbon.This CO2 is continually used by plants to grow. Because the ratio of carbon-14 tocarbon-12 in atmospheric CO2 is constant, the intake of CO2 by a plant results in aconstant ratio of the two isotopes in the plant's body while it is alive. However, when the

plant dies it will no longer take in CO2. As a result, the carbon-14 decaying in the deadplant will not be replenished by a "fresh supply" of more CO2, resulting in the ratio ofcarbon-14 to carbon-12 decreasing over time.

Because animals eat plants, the ratio of carbon-14 to carbon-12 in them alsodecreases once they die, since the carbon-14 cannot be replenished.

This process of dating using carbon-14 is used by paleontologists.Paleontologists burn a small sample of a fossil to react the carbon in it with oxygen, toform CO2. The CO2 that contains carbon-14 will be radioactive, and the amount can beeasily measured using a radiation counter. Burning is done to facilitate measuring the

level of carbon-14.

Carbon-14 has a half life of about 5730 years. This means that in a given sampleof a carbon-containing substance, (without the carbon-14 being replenished) the ratio ofcarbon-14 to carbon-12 will decrease by half every 5730 years. Suppose for example,some archaeologists uncovered ancient manuscripts and found that the ratio of carbon-14 to carbon-12 in the paper was half of that found in living trees. This would mean thatthe manuscripts would be about 5730 years old.


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The use of radioactive carbon-14 for dating was first done by William Libby, anacademic at the University of Chigaco, USA, in 1947.

The relatively short half-life of carbon-14 (5730 years) means that the amount ofcarbon-14 remaining in materials and objects older than about 80,000 years is too small

to be measured with today's equipment. Thus carbon dating is limited to objects whichare not older than this. However, the abundance of other atoms with longer half-lives,such as uranium-238 (half-life 4.5 109 years) can be measured in place of carbon-14.Geologists measure the amounts of other radioactive metal isotopes such as uranium-238, rubidium-84 and potassium-40 (see below) found in rocks to determine their age.Measurements show that the oldest rocks on Earth are about 4.6 billion years old -which is a reasonably accurate estimate of the Earth's age. Similarly, analysis offossilised plants shows that they first occurred on Earth about 3 billion years ago.

The major problem using radiocarbon dating is the chance of getting carbon fromthe samples mixed up with "fresh" carbon.

As well as using carbon-14 to carbon-12 decay, geologists also measure thedecay of potassium-40 to argon in dating rocks. However, this method is not accuratefor rocks that have been heated above 120c (250f) because the argon diffuses outfrom the rock at these temperatures. The decay of rubidium-87 to strontium-87 is usedto check potassium-argon dates, and is much more accurate because neither isotope isdiffused by heat. This rubidium technique was used by scientists to determine the ageof the moon. Measurements using uranium-238 were used to determine the age of theEarth.

Geology and Element Identification

Radioactivity is used to identify the location of deposits of uranium and otherradioactive minerals. This is useful in mining exploration. The intensity of detectedradiation also is an indication of the amount of uranium that may be located there.

The mining industry employs radioactivity in its routines. One example isidentification of rocks and minerals. X-rays from a radioactive material can induce othermaterials to emit fluorescent X-rays. These subsequent X-rays can have their energiesmeasured, and then this gives an indication of the elements present in the originalmaterial. The intensity of these X-rays also is an indicator of the amount of the elementpresent.

This technique is done by placing probes into the slurry - water that containssediments of minerals, etc. The probes contain a radioisotope and a detector. Theradiation from the isotope causes metals in the slurry to emit fluorescent X-rays - theseare identified by the detector also located on the probe. The probe's input is thenanalysed to give an indication of the types and amount of metals present in the slurry.Metals that are detected this way include lead, copper, tin, zinc, nickel and iron.


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Elements that can absorb neutrons will release gamma rays. These gamma rays can beanalysed for their energies. Specific energies correspond to specific elements - thus thisis another way of identifying the metals and minerals that may be present.


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Negative effects of radioactive substances

Radiation, even in small doses, can cause cancer in humans and other livingthings. Fast moving photons (gamma rays), electrons (beta rays) and helium nuclei

(alpha particles) can crash into other molecules and change their structure. If thishappens to a DNA molecule, it can damage the genetic information, and sometimesturn a cell cancerous. Radiation also causes burns, much like sunburn, in large dosesover short amounts of time.

Usually you can walk away from radioactive substances, lowering your risk. But ifyou ingest radioactive elements, they stay with you. Particulrly nasty radioactiveelements include radon and radioactive iodine. Radon is a chemically inert gas with ashort half-life (and therefore decays rapidly, emitting radiation faster than otherelements). It is produced naturally as a decay product of longer-lived radioactiveelements in rock and soil. It may diffuse through basement walls and into people's

homes.

It increases the rate of lung cancer when people breathe it in. It is a good idea toventilate basements and have them checked, particularly in areas of the country whereradon is common. Radioactive iodine is also readily absorbed by the body and becomesincorporated in bones, and is therefore difficult to eliminate from the body. The radiationit emits can cause bone cancer over long periods of time.

The radium on watch dials was incorporated in paint. Workers used to paint thewatch dials by hand, and some would even lick their paint brushes to make a sharpertip. They ingested radon paint, and some became ill with cancer.

Naturally ocurring uranium also was used to make bright yellow paint, but Ibelieve this too has been stopped.

Some people complain about radiation emitted by those depleted-uranium bulletsand shells left over in wars. Residents of areas where such munitions have been usedare concerned about the long-term health effects of the radioactivity. There is someconcern that the main dangers from the leftover uranium dust may be due to chemicalpoisoning rather than radiation.

Plutonium, while radioactive, also happens to be just plain poisonous. Humanbodies do not deal well with heavy metals: lead, mercury, and arsenic come to mind asthings not to ingest because they are poisonous. Plutonium may well be the mostpoisonous of the lot.


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Referrence

http://library.thinkquest.org/C004606/applications/radioactivedating.shtml

http://www.ndt-ed.org/EducationResources/HighSchool/Radiography/radioactivity.htm

http://www.world-nuclear.org/info/inf55.html

http://www.world-nuclear.org/info/inf56.html

http://library.thinkquest.org/C004606/applications/foodagriculture.shtml
http://library.thinkquest.org/C004606/applications/radioactivedating.shtmlhttp://www.ndt-ed.org/EducationResources/HighSchool/Radiography/radioactivity.htmhttp://www.world-nuclear.org/info/inf55.htmlhttp://www.world-nuclear.org/info/inf56.htmlhttp://library.thinkquest.org/C004606/applications/foodagriculture.shtmlhttp://library.thinkquest.org/C004606/applications/foodagriculture.shtmlhttp://www.world-nuclear.org/info/inf56.htmlhttp://www.world-nuclear.org/info/inf55.htmlhttp://www.ndt-ed.org/EducationResources/HighSchool/Radiography/radioactivity.htmhttp://library.thinkquest.org/C004606/applications/radioactivedating.shtml

folio fizik the uses of radioisotopes

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