pn junction diode experiment connections

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V-I Characteristics of p-n-Junction Diode

V-I characteristics of p-n-Junction Diode

Objectives:

• To understand the basic concepts of semiconductors.
• To study p type and n type semiconductor and potential barrier.
• To understand forward and reverse biasing.
• Perform the experiment on bread board and the trainer kit and plot the graph of V-I characteristics of PN junction diode.

Components and equipments required: single strand cable, diode, resistors, bread board, multimeter, connecting wires, CRO, voltage source.

General Instructions: You will plan for Experiment after self study of Theory given below, before entering in the Lab.

PN Junction Diode The effect described in the previous tutorial is achieved without any external voltage being applied to the actual PN junction resulting in the junction being in a state of equilibrium. However, if we were to make electrical connections at the ends of both the N-type and the P-type materials and then connect them to a battery source, an additional energy source now exists to overcome the barrier resulting in free charges being able to cross the depletion region from one side to the other. The behavior of the PN junction with regards to the potential barrier width produces an asymmetrical conducting two terminal device, better known as the Junction Diode.

A diode is one of the simplest semiconductor devices, which has the characteristic of passing current in one direction only. However, unlike a resistor, a diode does not behave linearly with respect to the applied voltage as the diode has an exponential I-V relationship and therefore we cannot described its operation by simply using an equation such as Ohm's law. If a suitable positive voltage (forward bias) is applied between the two ends of the PN junction, it can supply free electrons and holes with the extra energy they require to cross the junction as the width of the depletion layer around the PN junction is decreased. By applying a negative voltage (reverse bias) results in the free charges being pulled away from the junction resulting in the depletion layer width being increased. This has the effect of increasing or decreasing the effective resistance of the junction itself allowing or blocking current flow through the diode.

Then the depletion layer widens with an increase in the application of a reverse voltage and narrows with an increase in the application of a forward voltage. This is due to the differences in the electrical properties on the two sides of the PN junction resulting in physical changes taking place. One of the results produces rectification as seen in the PN junction diodes static I-V (current-voltage) characteristics. Rectification is shown by an asymmetrical current flow when the polarity of bias voltage is altered as shown below.

But before we can use the PN junction as a practical device or as a rectifying device we need to firstly bias the junction, ie connect a voltage potential across it. On the voltage axis above, "Reverse Bias" refers to an external voltage potential which increases the potential barrier. An external voltage which decreases the potential barrier is said to act in the "Forward Bias" direction.

There are two operating regions and three possible "biasing" conditions for the standard Junction Diode and these are:

• Reverse Bias - The voltage potential is connected negative, (-ve) to the P-type material and positive, (+ve) to the N-type material across the diode which has the effect of Increasing the PN-junction width.
• Forward Bias - The voltage potential is connected positive, (+ve) to the P-type material and negative, (-ve) to the N-type material across the diode which has the effect of Decreasing the PN-junction width.

Forward Biased Junction Diode When a diode is connected in a Forward Bias condition, a negative voltage is applied to the N-type material and a positive voltage is applied to the P-type material. If this external voltage becomes greater than the value of the potential barrier, approx. 0.7 volts for silicon and 0.3 volts for germanium, the potential barriers opposition will be overcome and current will start to flow. This is because the negative voltage pushes or repels electrons towards the junction giving them the energy to cross over and combine with the holes being pushed in the opposite direction towards the junction by the positive voltage. This results in a characteristics curve of zero current flowing up to this voltage point, called the "knee" on the static curves and then a high current flow through the diode with little increase in the external voltage as shown below.

The application of a forward biasing voltage on the junction diode results in the depletion layer becoming very thin and narrow which represents a low impedance path through the junction thereby allowing high currents to flow. The point at which this sudden increase in current takes place is represented on the static I-V characteristics curve above as the "knee" point.

This condition represents the low resistance path through the PN junction allowing very large currents to flow through the diode with only a small increase in bias voltage. The actual potential difference across the junction or diode is kept constant by the action of the depletion layer at approximately 0.3v for germanium and approximately 0.7v for silicon junction diodes. Since the diode can conduct "infinite" current above this knee point as it effectively becomes a short circuit, therefore resistors are used in series with the diode to limit its current flow. Exceeding its maximum forward current specification causes the device to dissipate more power in the form of heat than it was designed for resulting in a very quick failure of the device.

Reverse Biased Junction Diode When a diode is connected in a Reverse Bias condition, a positive voltage is applied to the N-type material and a negative voltage is applied to the P-type material. The positive voltage applied to the N-type material attracts electrons towards the positive electrode and away from the junction, while the holes in the P-type end are also attracted away from the junction towards the negative electrode. The net result is that the depletion layer grows wider due to a lack of electrons and holes and presents a high impedance path, almost an insulator. The result is that a high potential barrier is created thus preventing current from flowing through the semiconductor material.

Procedure:-

• Make the connections as shown in fig.:
• Switch on the power supply.
• Now vary in small step the forward bias voltage and current readings on multimeter. Draw the graph between current and voltage.
• Make the connection as shown in fig:

Observation:

Forward biasing

Observation Table

Reverse biasing

Do and Don’ts to be strictly observed during experiment:

Do (also go through the General Instructions):

• Before making the connection, identify the components leads, terminal or pins before making the connections.
• Before connecting the power supply to the circuit, measure voltage by voltmeter/multimeter.
• Use sufficiently long connecting wires, rather than joining two or three small ones.
• The circuit should be switched off before changing any connection.
• Avoid loose connections and short circuits on the bread board.
• Do not exceed the voltage while taking the readings.
• Any live terminal shouldn't be touched while supply is on.

Outputs: Submit the graph as per observation table.

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PN Junction Diode Characteristics – Explained in Detail with Graphs

In this article, we learn about PN junction diode characteristics in detail – like how to bias a PN junction (Forward & Reverse bias methods), behavior of PN junction during forward & reverse bias setups, how to plot the VI characteristics, what is reverse breakdown and many other essential concepts regarding a PN junction diode. So let’s begin.

In chapter 1 – Understanding the PN junction , we have seen how a PN junction is formed from a p-type and n-type semiconductor. We have also learned about diffusion current, depletion region, drift current and barrier potential. If you find these terms foreign, just read the chapter about “ understanding the pn junction ” once more. Lets just make some questions. What is the use of a PN junction? Why have scientists created a pn junction device? What kind of problem it solves ? Learning anything is really fun when we question it. So these are our questions. Why there exists a pn junction in this world! ?;)

To get an answer to all these questions, lets first try to understand the characteristics of a PN junction. We know a pn junction has a “barrier potential”. Only if we overcome this “barrier potential” by applying an external voltage to the pn junction, we would be able to make it conducting. This simply means, current will pass through the pn junction only if we apply an external voltage higher than the “barrier potential” of pn junction. In chapter 1, we have seen that  net current inside a pn junction is zero. Inorder to understand the behavior of a pn junction we need to make it conducting by applying an external voltage over a range (say from 0 volts 5 or 10 volts ), and then we study how the current passed through the pn junction varies with increasing voltage levels. To apply an external voltage, we usually connect 2 metallic contacts at the two ends of the pn junction ( known as terminals ); one on the p-side and other on the n-side. A PN junction with two metallic contacts is known as a pn junction diode or a semiconductor diode. 

Note:- I have written an interesting article which tells the story behind invention & discovery of PN Junction diode. If you like to read the story, follow here:- Story behind Invention & Discovery of PN Junction

PN junction diode is symbolically represented as shown in picture. The direction of arrow is the direction of conventional current flow (under forward bias). Now lets try applying an external voltage to the pn junction diode. The process of applying an external voltage is called as “biasing” . There are two ways in which we can bias a pn junction diode.

1) Forward bias and 2) Reverse bias  

The basic difference between a forward bias and reverse bias is in the direction of applying external voltage. The direction of external voltage applied in reverse bias is opposite to that of  external voltage applied in forward bias.

Forward biasing a PN Junction diode

Forward biasing a pn junction diode is very simple. You just need to take a battery whose values can be varied from (o to V volts), connect its positive terminal to the p-side of pn junction diode and then connect the negative terminal of battery to the n-side of the pn junction diode. If you have done upto this, the forward bias circuit of pn junction diode is complete. Now all we need to do is understand how the pn junction diode behaves when we increase the voltage levels from 0 to say 10 volts or 100 volts. We have learned that if we apply an external voltage higher than the barrier potential of pn junction diode, it will start conducting, which means it will start passing current through it. So how we are going to study the behavior of pn junction diode under forward biased condition? Lets get a voltmeter and ammeter and connect it to the forward biased circuit of pn junction diode.A simple circuit diagram is shown below, which has a pn junction diode, a battery (in picture it is not shown as variable. keep in mind we are talking about a variable power source), an ammeter (in milli ampere range) and a voltmeter.

Note:- Assume that the pn junction diode is made from Silicon. The reason is difference in barrier potential for a diode made from Germanium and Silicon. (For a silicon diode – barrier potential is 0.7 volts where as for a Germanium diode barrier potential is low ~ 0.3 volts)

How to plot the characteristics of a pn junction ?

What we are going to do is, vary the voltage across diode by adjusting the battery. We start from o volts, then slowly move 0.1 volts, 0.2 volts and so on till 10 volts. Lets just note the readings  of voltmeter and ammeter each time we adjust the battery (in steps of 0.1 volts). Finally after taking the readings, just plot a graph with voltmeter readings on X-axis and corresponding Ammeter readings on Y axis. Join all the dots in graph paper and you will see a graphical representation as shown below. Now this is what we call “characteristics of a pn junction diode” or the “behavior of diode under forward bias” 

How to analyse the characteristics of a pn junction diode ?

Its from the “characteristics graph ” we have just drawn, we are going to make conclusions about the behavior of pn junction diode. The first thing that we shall be interested in is about “barrier potential” . We talked a lot about barrier potential but did we ever mention its value ? From the graph, we observe that the diode does not conduct at all in the initial stages. From 0 volts to 0.7 volts, we are seeing the ammeter reading as zero! This means the diode has not started conducting current through it. From 0.7 volts and up, the diode start conducting and the current through diode increases linearly with increase in voltage of battery. From this data what you can infer ? The barrier potential of silicon diode is 0.7 volts 😉  What else ? The diode starts conducting at 0.7 volts and current through the diode increases linearly with increase in voltage. So that’s the forward bias characteristics of a pn junction diode. It conducts current linearly with increase in voltage applied across the 2 terminals (provided the applied voltage crosses barrier potential).

What happens inside the pn junction diode when we apply forward bias ?

We have seen the characteristics of pn junction diode through its graph. What really happens inside the diode during the forward bias ? We know a diode has a depletion region with a fixed barrier potential. This depletion region has a predefined width, say W . This width will vary for a Silicon diode and a Germanium diode. The width highly depends on the type of semiconductor used to make pn junction, the level of doping etc. When we apply voltage to the terminals of diode, the width of depletion region slowly starts decreasing. The reason for this is, in forward bias we apply voltage in a direction opposite to that of barrier potential. We know the p-side of diode is connected to positive terminal and n-side of diode is connected to negative terminal of battery. So the electrons in n-side gets pushed towards the junction (by force of repulsion) and the holes in p-side gets pushed towards the junction. As the applied voltage increases from 0 volts to 0.7 volts, the depletion region width reduces from ‘ W’ to zero. This means depletion region vanishes at 0.7 volts of applied voltage.  This results in increased diffusion of electrons from n-side to p-side region and the increased diffusion of holes from p-side to n-side region. In other words, “ minority carrier ” injection happens on both p-side (in a normal diode (without bias) electrons are a minority on p-side) and n-side (holes are a minority on n-side) of the diode.

How current flow takes place in a pn junction diode ?

This is another interesting factor, to explain. As the voltage level increases, the electrons from n-side gets pushed towards the p-side junction. Similarly holes from p-side gets pushed towards the n-side junction. Now there arises a concentration gradient between the number of electrons at the p-side junction region and the number of electrons at the region towards the p-side terminal. A similar concentration gradient develops between the number of holes at the n-side junction region and the number of holes at region near the n-side terminal. This results in movement of charge carriers (electrons and holes) from region of higher concentration to region of lower concentration. This movement of charge carriers inside pn junction gives rise to current through the circuit.

Reverse biasing a PN junction diode

Why should we reverse bias a pn diode ? The reason is, we want to learn its characteristics under different circumstances. By reverse biasing, we mean, applying an external voltage which is opposite in direction to forward bias. So here we connect positive terminal of battery to n-side of the diode and negative terminal of the battery to p-side of the diode. This completes the reverse bias circuit for pn junction diode. Now to study its characteristics (change in current with applied voltage), we need to repeat all those steps again. Connect voltmeter, ammeter, vary the battery voltage, note the readings etc etc. Finally we will get a graph as shown.

Analysing the revere bias characteristics

Here the interesting thing to note is that, diode does not conduct with change in applied voltage. The current remains constant at a negligibly small value (in the range of micro amps) for a long range of change in applied voltage. When the voltage is raised above a particular point, say 80 volts, the current suddenly shoots (increases suddenly). This is called as “ reverse current ” and this particular value of applied voltage, where reverse current through diode increases suddenly is known as “ break down voltage “.

What happens inside the diode ?

We connected p-side of diode to negative terminal of battery and n-side of diode to positive terminal of battery. So one thing is clear, we are applying external voltage in the same direction of barrier potential. If applied external voltage is V and barrier potential is Vx , then total voltage across the pn junction will be V+Vx . The electrons at n-side will get pulled from junction region to the terminal region of n-side and similarly the holes at p-side junction will get pulled towards the terminal region of p-side.  This results in increasing the depletion region width from its initial length, say ‘W’ to some ‘W+x’. As width of depletion region increases, it results in increasing the electric field strength.

How reverse saturation current occurs and why it exists ?

The reverse saturation current is the negligibly small current (in the range of micro amperes) shown in graph, from 0 volts to break down voltage. It remains almost constant (negligible increase do exist) in the range of 0 volts to reverse breakdown voltage. How it occurs ? We know, as electrons and holes are pulled away from junction, they dont get diffused each other across the junction. So the net “ diffusion current ” is zero! What remains is the drift due to electric field. This reverse saturation current is the result of drifting of charge carriers from the junction region to terminal region. This drift is caused by the electric field generated by depletion region.

What happens at reverse breakdown ?

At breakdown voltage, the current through diode shoots rapidly. Even for a small change in applied voltage, there is a high increase in net current through the diode. For each pn junction diode, there will be a maximum net current that it can withstand. If the reverse current exceeds this maximum rating, the diode will get damaged.

Conclusion about PN junction characteristics

To conclude about pn junction characteristics, we need to get an answer to the first question we have raised – What is the use of pn junction? From the analysis of both forward bias and reverse bias, we can arrive at one fact – a pn junction diode conducts current only in one direction – i.e during forward bias. During forward bias, the diode conducts current with increase in voltage. During reverse bias, the diode does not conduct with increase in voltage (break down usually results in damage of diode). Where can we put this characteristics of diode into use ? Hope you got the answer! Its in conversion of alternating current to direct current (AC to DC). So the practical application of pn junction diode is rectification!

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Hey! That’s so helpful

Thickness of diplition layer depend on which factor?

DESC: Diode forward biased 24VDC QTY: 20pcs

DESC: Diode Reverse biased 24VDC QTY: 20pcs

Faith N. Dolorito Procurement Specialist MANILA OVERSEAS INC. TEL:6328004227 FAX:6328004172

thank you so very much…. I am clearly understood to read it……. ……..

As width of depletion region increases, it results in increasing the electric field strength.Why?

What is zener effect and avalanche effect.?

Utmost/extremly thanks ….. For this crystal clear explanation….. I really got something from it…. But sir what is Zener effect.and avalenche effect.?

Why internal electric field generate after diffusion process in pn junction

i hve a question. why the arrow in pn junction thicker????

explain the working of PN junction diode in forward and reverse biasing configuration please ?

why the battery in reverse bias is greater than in forward bias

I think I missed something. You say that the PN junction only starts to conduct current after the voltage aplied on the diode (Vd) reaches 0.7V, the barrier potential as you call it, but all the graphics and equations shows us that there is current through the diode for values of Vd smaller than 0,7V. I mean, even considering the current for Vd near zero negligible, with Vd~0.60V there is current.

As I see it, we just consider 0.7V as a practival value for a conducting diode, where any variation of the current will cause a small variation on Vd, keeping it around the same 0.7V. It would me consistent with the diode current equation Id=Is(exp(Vd/nVt)-1), cause in 0.7V for a regular diode, de slope in the curve is too large to see any change in Vd as the current varies.

I don’t know if I made myself clear, but thats a point that is not really clear in many books about semiconductors physics and it’s annoying me. If you could clarify that for me I would be glad.

Why the forward voltage values are almost constant for source voltage from 5V to 1V during forward-biased?

what is the difference between the connections of forwardbias and reverse bias in pn junction…?

in forward biasis -VE terminal of battery is connected to pentavelent group N and +ve is connected to trivalent group P but in reverse biasis the connection is opposite …

can I get a pdf of this chapter??

very clear presantation if you were around i would offer you a cup of tea or coffee good work

why is the voltmeter connected across the ammeter and reverse biased diode..?

Can a diode work on ac voltage or not

@Anuj – A diode is basically a PN Junction. It is used to convert AC to DC.

diode worked on ac voltage but it will give output is DC why because ac has two half cycles in that case,it will conduct only positive half cycle….do not allow -ve cycles…

it’s working on ac voltage

The junction information is clearly understand so nice of it thanx

for eachelectron hole combination that take place near the junction a covalent bond breaks in the p section near the +ve pole of the battery how it is formed?

it is so helpful and it clears all the confusion…….plz answer meone question thatis why in CB mode the emitter current increases with increase of V(CB)

this is a exellent article……….sir plz letme know about base width modulation

It is very short notes It is very useful i am very happy after read that notes thank u very much

thanks 4 the good explanation. will you please show the one connected image source circuit of both forward and reverse biased a pn-junction

Please see Fig.10

wow it is very much helpful to me. Thanks the author

yes, its very great answer that i want. Thanks.

I really appreciate. Got a clearer explanation that i did in class… Kudos. Thanks Admin

a great work with full clearification. thanx !

Really interesting and clear clarification of every aspect of a junction diode characteristics.Very nice

Brilliant! Very helpful article. It’s clearly explaind and easy to understand. Bravo for the person who has put so much work to make it!!

Thanq So Much 🙂 this helped me a lot 🙂 Is there explanation for Transistor as a Switch and Amplifier?

explanation is little bit invalid

thaks very much for the good explanation.can you describe the current voltage characteristics of a photodiode when light is incident on it?

veryyyy goood explanation, i got it perfectly, please tell me about bridge wave rectifier, we connect 4 diodes in bridge but when the d1 and d2 are forward biased then haw the d3 and d4 are reversr biased

@Nayan – Read this article:- https://www.circuitstoday.com/full-wave-bridge-rectifier

It will help you understand bridge rectifier perfectly.

when we talk about reverse bias ,thn the width of depletion layer increases thn after more reverse voltage(greater than reverse breakdown voltage) how current flow through dide?

At break down, what happens really is that the diode gets damaged. It loses its junction & characteristics associated with the junction. The “diode” almost behaves like a shorted wire & hence current flows through it easily. Theoretically, internal resistance of a diode at breakdown is zero. But in practice, there exists a small internal resistance and hence the current increases with a deviation factor (and not a perpendicular graph).

Hope this helps!

Really helpfull , Thanks sir..

good explanation with neat a diagrams

its very simple to understand ……i like to read a lot in webpage…thank u to author who wrote this.

well explained. really enyoyed.

sir please add the curve charcterstic found when we use ge semiconductor as pn junction diode due to the this experiment

it was very useful and was written in a readble mannar

I like this and I enjoy

its a rely nuc explanation abt pn junctoin m a net qualified scientist

Thank you Pintu 🙂 It was very nice words 🙂

the difference between depletion barrier’s height and width . i mean why they are different and what they indicate?

If depletion region’s width indicates the area covered by defused electrons/holes then read further.

In forward bias condition external electric field ( produced by battery) will be opposite to the internal electric field ( produced depletion barrier ). in this case the external electric field will cancel the internal electric field and more electron will flow from n type to p type material(assumed external voltage is greater than depletion barrier) which increases the depletion region but in real, in forward bias condition the depletion region’s width decreases. And in reverse bias condition the depletion region increases instead of decreasing. (I am familiar with the increase/decrease of potential of depletion barrier and agree with the books)

I am very confused with this question. so please help me. Thank you

What really matters is the “barrier potential” of a diode. In a Silicon diode, the “barrier width” is higher than a Germanium diode. So “barrier potential” of a Silicon diode is higher than Germanium diode. I hope you understood.

cool great approach. hoping that 2 give more information about electronics

Please help me out.. In forward bias if battery voltage is 2v , drop across si diode cant be more than 1v i.e. Vd<1v… So now my qusetion is where this remaining 1v of battery is if no resistor is in series with diode?

In that case, 1 volt will be dropped across the wires with the help of a very large current.

Awesome explanation.thank you

Crystal Clear approach, awesome!!

it’s very useful thank you

Really amazing! I have never seen a website this successful in explanation! You can’t imagine how much this helped me! Thanks

Keep adding more and more info….

owsam… PERFECT …!!

Thanks so much. That was a comprehensive expose. Keep keeping

oh thank u..i am very confused to read my text book but now every thing is clear….thank you very much ..

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VI Characteristics of a Diode            

Aim of the experiment.

At the end of the experiment, the student should be able to

• Explain the structure of a P-N junction diode
• Explain the function of a P-N junction diode
• Explain forward and reverse biased characteristics of a Silicon diode
• Explain forward and reverse biased characteristics of a Germanium diode

PN Junctions

• First Online: 14 September 2024

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• Badih El-Kareh 3 &
• Lou N. Hutter 4  

The PN junction is the fundamental building block of most semiconductor devices. The junction shape, profile, and characteristics have a direct impact on device and circuit parameters. Thus, a thorough discussion of the PN junction is essential to understand the operation of silicon devices and integrated circuits.

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El-Kareh, B., Hutter, L.N. (2024). PN Junctions. In: Silicon Components and Processes Self Study. Springer, Cham. https://doi.org/10.1007/978-3-031-59185-3_2

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Tomsk-7/Seversk, Russia

The explosion of a nuclear reprocessing facility in Tomsk-7 dispersed large amounts of radioactivity over an area of 120 km² , exposing tens of thousands of people to increased levels of radiation and contaminating air, water and soils for many generations to come. It is considered the most serious Russian nuclear accident after Chernobyl and the Kyshtym accident at Mayak.

Photo: Until the 1990s, the town of Tomsk-7, now known as Seversk, produced military plutonium and nuclear fuel and was home to about 100,000 workers and their families. © GlobalSecurity.org

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Health and environmental effects

Most acutely affected by nuclear fallout were the villages of Georgievka and Nadezhda. Radioactive snowfall in the days after the disaster created hot-spots with radiation levels of up to 30 µGy/h – approximately 100 times normal background radiation. Soils in the areas affected by radioactive fallout showed significantly increased levels of long-lived radioisotopes such as cesium-137 or strontium-90. Cesium-137 can cause solid tumors and genetic defects in offspring when inhaled or ingested through food or water, while strontium-90 is a known cause for leukemia.

With the help of foreign specialists, initial clean-up operations were able to collect and remove about 577 g of plutonium from the area around Tomsk-7. Interestingly enough, only about 450 g of plutonium had been present in the basin before to the explosion, suggesting unreported prior plutonium leaks from the facility. Even months after the explosion, snow samples continued to show increased levels of radioactive isotopes such as plutonium, uranium, zirconium, ruthenium, cerium, niobium and antimony, continually exposing the population to radioactivity. According to the Bellona Foundation, a Norwegian environmental NGO, about 30 major accidents occurred at the Tomsk-7 nuclear facility, releasing about 10 g of plutonium into the atmosphere each year. The NGO also documents large quantities of nuclear waste from 50 years of plutonium production, which have accumulated on the confines of the nuclear facility. Dumped into underground depots or pumped into uncovered holding pools, they pose a continued threat to health. In 2008, a study found increased levels of plutonium and cesium-137 in soils and water samples, suggesting further leaks.

Some reactors at Tomsk-7 were shut down in June 2008, following the 2003 agreement between Russia and the U.S. concerning the elimination of weapons-grade plutonium production. The reprocessing of spent fuel and the dumping of nuclear waste on the premises of what is now called the Siberian Chemical Combine continue to this day, however. Despite the findings of increased levels of plutonium, strontium, cesium and other radioactive particles in soil and water, no meaningful medical studies were performed on the local population. In 2001, a county court in Tomsk ruled on a lawsuit by contaminated inhabitants of the village of Georgievka against the Siberian Chemical Combine, deciding that the company was to pay each claimant a compensation sum equivalent of 860 US-Dollars. During the hearings, 14 of the 26 claimants passed away, according to the Bellona Foundation. Their health was compromised for the production of nuclear fuel and nuclear warheads. They, and everyone else in the area whose health was affected by the catastrophe at Tomsk-7, are also Hibakusha.

• “The radiological accident at the reprocessing plant at Tomsk.” International Atomic Energy Agency (IAEA), October 1998. www-pub.iaea.org/mtcd/publications/pdf/p060_scr.pdf
• Alimov R. “People vs. Siberian Chemical Combine.” Website of the Bellona Foundation, February 10, 2001. http://bellona.ru/bellona.org/english_import_area/international/russia/nuke_industry/siberia/seversk/22031
• Gauthier-Lafaye F. “Radioisotope contaminations from releases of the Tomsk-Seversk nuclear facility.” Journal of Environmental Radioactivity 2008 Apr;99(4):680-93. www.ncbi.nlm.nih.gov/pubmed/17996340
• Goulet M. “Siberia Nuclear Waste – Case 393.” American University Washington. www1.american.edu/ted/sibnuke.htm

In Ekker , Algeria

At its algerian nuclear test site, in ekker, france performed 13 underground nuclear detonations, causing vast radioactive contamination of soil, air.

Reggane , Algeria

The french army conducted four atmospheric nuclear tests near reggane, algeria in 1960 and 1961, contaminating the sahara desert with plutonium,.

Ezeiza , Argentina

The ezeiza atomic center is located in a suburb of argentina’s capital city buenos aires. in recent years, it has been the cause of much concern, as.

Radium Hill , Australia

Radium hill, australia’s first uranium mine, was operational between 1906 and 1961. due to their exposure to uranium dust and radon gas, many miners.

Olympic Dam , Australia

The uranium mine at olympic dam poses a threat to the ecosystem of the region and a health hazard to the workers and the surrounding populations..

Ranger , Australia

Ranger is an open-pit uranium mine in the middle of the world heritage kakadu national park. numerous radioactive leaks and spills have contaminated.

Emu Field , Australia

After testing its first nuclear weapons off the west coast of australia in 1952, the uk sought to test its newer models on land. in 1953, the british.

Maralinga , Australia

Between 1952 and 1957, the united kingdom conducted seven major and hundreds of minor nuclear tests at the maralinga test site in southern australia..

Goiânia , Brazil

The accident in september 1987 in goiânia was one of the most serious radiation accidents in history. the opening of a radiotherapy machine containing.

Elliot Lake , Canada

As a lasting legacy of the “golden age” of uranium mining, the radioactive tailings of elliot lake pose a threat to the environment of the great lakes.

Saskatchewan , Canada

Saskatchewan mines roughly 25 % of the world’s uranium. the radioactive tailings produced by the mining process contaminate native land, pose a health.

Lop Nor , China

Between 1964 and 1996, the people’s republic of china conducted 45 nuclear tests in lop nor, a lake region in the western province of xinjiang. for.

Têwo/Diébù , China

“uranium mine 792” at diébù has been producing uranium for the chinese nuclear industry and nuclear weapons program since 1967. reports about.

Jáchymov , Czechia

Having grown rich by the discovery of uranium in its mines, the town of joachimsthal/jáchymov soon became one of the soviet union’s suppliers of.

La Hague , France

The reprocessing facility la hague produces plutonium and uranium from spent nuclear fuel. large amounts of plutonium and nuclear waste are stockpiled.

Fangataufa and Moruroa , French Polynesia

Nearly 200 nuclear tests were conducted on fangataufa and moruroa atolls, severely contaminating the environment of the archipelago and exposing its.

Mounana , Gabon

During decades of uranium mining in the jungle of gabon, the french nuclear company comuf neglected environmental safety standards, exposed mine.

Wismut region , Germany

Between 1946 and 1990, the joint soviet-east german stock company wismut turned the erzgebirge mountain range in saxony and the adjacent vogtland in.

Thule , Greenland

The crash of a u.s. air force b-52 bomber with nuclear weapons on board contaminated a large areas of land and the surrounding waters with radioactive.

Jadugoda , India

Uranium mining in the region around jadugoda has not only contributed to india’s nuclear weapons program, but has caused grave environmental damage as.

Basra , Iraq

The use of depleted uranium (du) ammunition during the gulf war of 1991 caused the local population to be exposed to radioactive uranium dust. this.

Fallujah , Iraq

The use of depleted uranium in the war on iraq in 2003 has led to expo­sure of the local population to radioactive uranium dust. this could.

Fukushima , Japan

The three reactor meltdowns at the fukushima dai-ichi nuclear power plant in march 2011 caused the greatest radioactive contamination of the world’s.

Tōkai-mura , Japan

The accident at the tokai-mura nuclear facility in 1999 irradiated a total of 667 people, two of whom died from acute radiation poisoning. tokai-mura.

Nagasaki , Japan

On august 9, 1945, the u.s. detonated the nuclear bomb “fat man” over the japanese city of nagasaki, with a population of more than 240,000. the.

Hiroshima , Japan

On august 6, 1945, the u.s. detonated the atomic bomb “little boy” over the city of hiroshima. of the 350,000 citizens, about 140,000 had died by the.

Semipalatinsk , Kazakhstan

The story of soviet nuclear testing at semipalatinsk is a cautionary tale of how “national security” can be used to justify willful deception that.

Kiritimati and Malden , Kiribati

A total of 33 nuclear detonations were conducted on two atolls of the Republic of Kiribati by the UK and the U.S. in the 1950s and 1960s. Thousands of

Mailuu-Suu , Kyrgyzstan

The former uranium mining town of mailuu-suu is notorious for its insecure radioactive waste rock heaps and tailings dumps in tectonically unstable.

Bikini and Eniwetok , Marshall Islands

Nuclear testing on the bikini and enewetak atolls left entire islands uninhabitable, exposed thousands to high levels of radioactivity and contributed.

Rössing , Namibia

The rössing uranium mine has been a cause for concern for more than 30 years. unsafe and inhumane working conditions, occupational exposure to.

Arlit and Akokan , Niger

Niger, a country with one of the world’s lowest ranks on the human development index, is also the world’s third largest producer of uranium. uranium.

Mayak/Kyschtym , Russia

Through a series of accidents and spills, the Russian nuclear facility at Mayak contaminated more than 15,000 km² with highly radioactive waste. In

Novaya Zemlya , Russia

From 1954 to 1990, the islands of novaya zemlya were used by the soviets to conduct atmospheric and underground nuclear tests. decommissioned nuclear, tomsk-7/seversk , russia.

The explosion of a nuclear reprocessing facility in Tomsk-7 dispersed large amounts of radioactivity over an area of 120 km² , exposing tens of

Chazhma Bay , Russia

In august 1985, an explosion on a soviet nuclear-powered submarine caused a massive release of radioactivity in chazhma bay. more than 290 people.

Witwatersrand , South Africa

Inadequate controls and safety standards in the uranium mining industry in the witwatersrand basin have resulted in an environmental catastrophe..

Palomares , Spain

In 1966, four hydrogen bombs were dropped near the spanish city of palomares, when a u.s. b-52 bomber crashed into another plane in mid-air. the non.

Chernobyl , Ukraine

The chernobyl nuclear meltdown in april 1986 was the most devastating nuclear catastrophe in history. huge stretches of land were radioactively.

Sellafield/Windscale , United Kingdom

Europe’s largest civil and military nuclear complex is located in sellafield. it used to produce plutonium for the british nuclear weapons program and.

Black Hills/Paha Sapa , United States

The black hills are considered a sacred place by the lakota people and are representative of the entire four-state region of south dakota, wyoming,.

Hanford , United States

At the hanford site, the u.s. produced most of its weap­ons-grade plutonium during the cold war. although the compound was decommissioned in 1988, it.

Sequoyah and Watts Bar , United States

The twin nuclear power plants of sequoyah and watts bar were included in this exhibition in order to represent nuclear reactors around the world, all.

Shiprock/Tsé Bit’ A’í , United States

The uranium mine at shiprock left a legacy of health and environmental damage that affects indigenous navajo communities to this day. moreover,.

Amchitka , United States

Three underground nuclear tests were carried out on the island of amchitka in the north pacific. the most controversial of these, code-named “cannikin.

Three Mile Island , United States

The most infamous nuclear reactor accident in u.s. history occurred at the three mile island nuclear plant in march 1979. equipment malfunction,.

Alamogordo , United States

The world’s first nuclear explosion took place near alamogordo on july 16, 1945. this detonation marked the beginning of the “nuclear age,” epitomized.

Spokane Reservation , United States

Over several decades, the spokane reservation was contaminated by open-pit uranium mining and its inhabitants exposed to increased levels of.

Nevada , United States

More than 1,000 nuclear detonations at the nevada test site between 1951 and 1992 dispersed massive amounts of radioactive particles across the earth,.

Church Rock/Kinłitsosinil , United States

In july 1979, a dam breach at the united nuclear corporation’s uranium mill in church rock, new mexico released massive amounts of radioactive waste, satellite map.

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Tomsk-7/Seversk, Russia

Nuclear facility

The explosion of a nuclear reprocessing facility in Tomsk-7 dispersed large amounts of radioactivity over an area of 120 km² , exposing tens of thousands of people to increased levels of radiation and contaminating air, water and soils for many generations to come. It is considered the most serious Russian nuclear accident after Chernobyl and the Kyshtym accident at Mayak.

Tomsk-7 was a “secret city” in Siberia until 1992, when it reverted to its historical name of Seversk. It housed several nuclear facilities for large-scale production of plutonium and uranium for nuclear fuel and weapons, including reprocessing of spent fuel. The closed city was home to about 100,000 workers and their families. One of the worst accidents in the history of the Russian nuclear industry occurred at the Tomsk-7 reprocessing facility on April 6, 1993. That day, workers were pouring nitric acid into a tank in order to separate plutonium from spent nuclear fuel. It is not clear whether the accident was caused by human or technical error, but it is believed that a lack of compressed air caused the mixture of nitric acid, uranium and plutonium to overheat and reach critical temperatures within a few minutes. The ensuing explosion knocked down walls on two floors of the complex, started a fire and released about 250 m³ of radioactive gas, 8.7 kg of uranium and 500 g of plutonium to the environment. This amounted to about 30 Tera-Becquerel (Tera = trillion) of beta- and gamma-emitters and about 6 Giga-Becquerel (Giga = billion) of plutonium-239. An area of 1,500 m² around the plant was severely contaminated, while the radioactive plume covered a total area of 120 km², where increased levels of radioactivity could be detected. The explosion at Tomsk-7 was ranked level 4 of the International Nuclear and Radiological Event Scale (INES), comparable to the Tokai-mura nuclear accident in Japan in 1999.

Health and environmental effects

Most acutely affected by nuclear fallout were the villages of Georgievka and Nadezhda. Radioactive snowfall in the days after the disaster created hot-spots with radiation levels of up to 30 µGy/h – approximately 100 times normal background radiation. Soils in the areas affected by radioactive fallout showed significantly increased levels of long-lived radioisotopes such as cesium-137 or strontium-90. Cesium-137 can cause solid tumors and genetic defects in offspring when inhaled or ingested through food or water, while strontium-90 is a known cause for leukemia.

With the help of foreign specialists, initial clean-up operations were able to collect and remove about 577 g of plutonium from the area around Tomsk-7. Interestingly enough, only about 450 g of plutonium had been present in the basin before to the explosion, suggesting unreported prior plutonium leaks from the facility. Even months after the explosion, snow samples continued to show increased levels of radioactive isotopes such as plutonium, uranium, zirconium, ruthenium, cerium, niobium and antimony, continually exposing the population to radioactivity. According to the Bellona Foundation, a Norwegian environmental NGO, about 30 major accidents occurred at the Tomsk-7 nuclear facility, releasing about 10 g of plutonium into the atmosphere each year. The NGO also documents large quantities of nuclear waste from 50 years of plutonium production, which have accumulated on the confines of the nuclear facility. Dumped into underground depots or pumped into uncovered holding pools, they pose a continued threat to health. In 2008, a study found increased levels of plutonium and cesium-137 in soils and water samples, suggesting further leaks.

Some reactors at Tomsk-7 were shut down in June 2008, following the 2003 agreement between Russia and the U.S. concerning the elimination of weapons-grade plutonium production. The reprocessing of spent fuel and the dumping of nuclear waste on the premises of what is now called the Siberian Chemical Combine continue to this day, however. Despite the findings of increased levels of plutonium, strontium, cesium and other radioactive particles in soil and water, no meaningful medical studies were performed on the local population. In 2001, a county court in Tomsk ruled on a lawsuit by contaminated inhabitants of the village of Georgievka against the Siberian Chemical Combine, deciding that the company was to pay each claimant a compensation sum equivalent of 860 US-Dollars. During the hearings, 14 of the 26 claimants passed away, according to the Bellona Foundation. Their health was compromised for the production of nuclear fuel and nuclear warheads. They, and everyone else in the area whose health was affected by the catastrophe at Tomsk-7, are also Hibakusha.

• “The radiological accident at the reprocessing plant at Tomsk.” International Atomic Energy Agency (IAEA), October 1998. www-pub.iaea.org/mtcd/publications/pdf/p060_scr.pdf
• Alimov R. “People vs. Siberian Chemical Combine.” Website of the Bellona Foundation, February 10, 2001. http://bellona.ru/bellona.org/english_import_area/international/russia/nuke_industry/siberia/seversk/22031
• Gauthier-Lafaye F. “Radioisotope contaminations from releases of the Tomsk-Seversk nuclear facility.” Journal of Environmental Radioactivity 2008 Apr;99(4):680-93. www.ncbi.nlm.nih.gov/pubmed/17996340
• Goulet M. “Siberia Nuclear Waste – Case 393.” American University Washington. www1.american.edu/ted/sibnuke.htm

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Alamogordo (USA) Amchitka (USA) Arlit & Akokan (Niger) Basra (Iraq) Bikini and Enewetak Atolls (Marshall Islands) Black Hills/Paha Sapa (USA) Chazhma Bay (Russia) Chernobyl (Ukraine) Church Rock/Kinłitsosinil (USA) Elliot Lake (Canada) Emu Field (Australia) Ezeiza (Argentina) Fallujah (Iraq) Fangataufa and Moruroa (French Polynesia) Fukushima (Japan) Goiânia (Brazil) Hanford (USA) Hiroshima (Japan) In Ekker (Algeria) Jáchymov (Czech Republic) Jadugoda (India ) Kiritimati and Malden (Kiribati) La Hague (France) Lop Nor (China) Mailuu-Suu (Kyrgyzstan) Mayak (Russland) Maralinga (Australia ) Mounana (Gabon) Nagasaki (Japan) Nevada Test Site (USA) Novaya Zemlya (Russia) Olympic Dam (Australia) Palomares (Spain) Radium Hill (Australia) Ranger (Australia) Reggane (Algeria) Rössing (Namibia) Saskatchewan (Canada) Sellafield/Windscale (UK) Semipalatinsk (Kazakhstan) Sequoyah and Watts Bar (USA) Shiprock/Tsé Bit’ Aí (USA) Spokane Reservation (USA) Têwo/Diébù (China) Three Mile Island (USA) Thule (Greenland) Tokai-mura (Japan) Tomsk-7/Seversk (Russia) Wismut region (Germany) Witwatersrand (South Africa)