Geiger Counter Gammascout

gammascout +heavy metal (Cd) in pelicase for underwater Gammascout without Cd underwater in pelicase, with a lead ball open Gammascout, rear side view


The Gammascout Geiger Counter is a calibrated measurement instrument for alpha, beta and gamma rays.
In a PELI Case 1040 (+heavy metal for taring, Cd for neutron detection) it can be used for underwater measurements down to 5 m water depth.
For greater depths i use a cheap water filter case (+lead metal for taring and two plugs for the input and output and some silicia gel) for underwater measurements down to 100 m water depth:

Gammascout in a water filter case (+lead metal for taring and two plugs for the input and output and some silicia gel) for underwater measurements down to 100 m water depth, front view Gammascout in a water filter case (+lead metal for taring and two plugs for the input and output and some silicia gel) for underwater measurements down to 100 m water depth, rear view


The central processor of the Gammascout is a MSP430.
The USB version uses a FT232BM for the conversion USB to UART for the MSP430.
The hardware is good, but the MS-Windows software not: With the GammaTool, which does not run under MS-Windows 8, for a plot of the measured and read values (dose rate/count) you first have to use the Calculate-button and than you find a button for show; the Display-Button shows only a log. The program does not store the parameters, e. g. 2d plot of the dose with no numerics, it can't be terminated via Alt-F4 and sometimes the mouse pointer is invisible in the program window. For clearing the gammascount memory you have to read out the memory, even if you have done so one minute ago, and the program can use only one of the first (virtual) ten serial ports which are often already used by a bluetooth driver.
Under MS-Widows 8 you can use the Gamma Scout Toolbox, but installing the drivers ist not easy ant the Gamma Scout Toolbox can't plot the data.
Under Linux there are two alternatives in Python: A script for reading the raw data and a script for plotting the data into a PDF file, under https://wiki.internet-village.be/display/safecast/Gamma-Scout. To get them working it's necessary to add some lines, e. g. to break the endless loop in the first script.
The second alternative is the Gamma Scout Utility for reading and conversion of the data, setting the date/time, clearing the memory etc.: http://johannes-bauer.com/linux/gammascout/. There are also the Gamma Scout Tools at http://www.teodori.org/software-development/gamma-scout-tools-on-opensuse-12-3.html but they are made only for OpenSuSE and even after conversion with Alien to a DEB package (and installation) they do not run under Ubuntu.

The data capacity of the Gammascout is 2 years with 1 day log interval, 4 weeks with 1 hour interval, 4 days with 10 min. interval and 10 hours with 1 min. interval.

The battery is a AA size Li battery (14,65 x 50,3 mm, 2.6 Ah) with soldering tags.
The data sheet of the geiger tube LND 712, aka ZP1401, says that with a shielding consisting of 50 mm Pb and 3 mm Al the maximum CPM rate is 10 CPM. Because with 20 CPM the dose rate shown by the Gammascout is about 0.2 µSv/h, this means the dose rate caused by the hard cosmic rays, which can pass the 50 mm Pb + 3 mm Al shielding, is about 0.1 µSv/h.
The gamma sensitivity shows that the saturation dose rate is about 10 mSv/h, at a pulse rate of 10 kHz. So you can't measure much less than 0.1 µSv/h and not more then 10 mSv/h with the Gammascout. It's the same with replacement types like the ZP1401.
Another restriction are that a geiger tube commonly detects only about 5 % of all incoming rays and that the Gammascout shows the dose rate for "common" radiation (gamma from 60Co), with the radiation weighting factor of 1, but the radiation can have a higher factor and the Gammasout can be less sensitive. Examples are low-energy alpha and beta rays which can't get into the tube and therefore can not be detected, but they have a high radiation weighting factor.
The LND 712 data sheet says nothing about the lifetime, but a typical geiger tube lifetime is 10 billion pulses, which is, at the usual activity of 20 pulses per minute, 951.3 years. Because of the flash memory of the MSP430 the effective life time limit is about 30 years (minimum), when you change the battery every 10 years.
The lifetime of the MSP430 can be extended by re-flashing the firmware via the JTAG interface connector (close to the left side of the MSP430).
Another restriction is the size of the internal flash memory: If the logging interval is set to one hour, it is full after four weeks.

The size is 163 x 71 x 30 mm, the 2011 price of the LN 712 is at june 2011 around 88 Euro, but is not availible before 2012, because it is sould out after the Fukushima Daiichi nuclear disaster: http://www.meggys-shop.de/Geiger-Mueller-Zaehlrohr-LND-712 and the price of the simple Gammacout is about 300 Euro: http://www.heise.de/preisvergleich/a622518.html.


Some measurement results

Indoor dose rate in Germany, Nuremberg (300 m AMSL) and also in Aalen: 185 ± 50 nSv/h
Outdoor Dose rate in Germany, Nuremberg, 4.5 m underwater ( Freibad Stadion and PELI case 1040): about 90 nSv/h
Indoor Dose rate in Germany, Nuremberg, 30 cm underwater: 160 ± 50 nSv/h
Indoor dose rate in Germany, Mülheim (100 m AMSL): 230 ± 50 nSv/h
Indoor dose rate in Germany, Bremervörde (4 m AMSL): 170 ± 50 nSv/h
Indoor dose rate in Hongkong (10 m AMSL): 400 ± 50 nSv/h
Indoor dose rate in Taipei (100 m AMSL): 195 ± 50 nSv/h
Indoor dose rate in Tanzania, Dar es Salaam (10 m AMSL): 130 ± 50 nSv/h
Indoor dose rate in Tanzania, Moshi (900 m AMSL): 280 ± 50 nSv/h
Dose rate from 15 g potash directly under the gammascout and 200 g salt with about 50 g K above: 25 ± 50 nSv/h (total dose rate: 210 ± 50 nSv/h) K rich salt
Dose rate from 200 g potash directly under and above the gammascout : 100 ± 50 nSv/h (total dose rate: 285 ± 50 nSv/h) potash
Dose rate from 1 kg potash directly around the gammascout : 220 ± 50 nSv/h (total dose rate: 405 ± 50 nSv/h)
Dose rate from radioluminescent keychains (Glow Rings) with Tritium Illumination or from 100 ml heavy water: 0 ± 50 nSv/h (the soft beta radiation can't get out of the housing and maybe not into the geiger tube) glow rings
heavy water
Dose rate from about 2 g RbCl (0,283 MeV β emission from 87Rb), placed on the window of the tube: 200 ± 50 nSv/h (total dose rate: 385 ± 50 nSv/h) TbCl
Dose rate in an art deco uranium glass vase from about 1925, with a weight of 807 g, 21.7 cm height, 14 cm diameter and 3 mm wall thickness about 0.7 µSv/h uranium glass vase from about 1925
Dose rate close to an opened alarm clock with radium paint from the middle of the 20th century: about 7 µSv/h Radium Paint
Dose rate close to three gas mantles with ThO2: about 12 µSv/h 3 Glühstrümpfe
Dose rate close to 90 g UO2(NO3)2.6H2O: about 25 µSv/h uranium
Dose rate from a 49 kdpm 14C standard capsule, placed on the window of the counting tube: about 26 µSv/h 14C
Dose rate close to 50 g ThO2: about 120 µSv/h thorium
Thoriumdioxide Merck

Comments:
If not commented with about, the value is an average of minimum two 24 hour averages, measured 2006 or later.
From a Cammenga Tritium Kompass i took a small luminescent piece on the window of the tube and could measure the beta radiation of the tritium. So even the soft beta ray from Tritium can be detected with the Gamma-Scout.
The 50 g ThO2 are a good source of gamma rays which can be used e. g. for testing Photomultiplier tubes (photomultipliers or PMTs for short) without light and for testing geiger counters and similar devices, but should be stored and transported with a little shielding and, more important, distance.
The comic ray intensity is anti-correlated with the sunspot activity and has therefore a period of 11 years, with a variation of 12 % around the average value (Physik Journal, March 2007, p. 60). Because of Solar flares, there are also short-time fluctuations of the comic ray intensity.
Measurements of the cosmic ray variations can be found here:
http://www.durangobill.com/SwindlePics/SwindleCosmicRays.gif
http://www.brighton73.freeserve.co.uk/gw/solar/cosmic_rays.gif
http://science.nasa.gov/headlines/y2005/images/afraid/doserates.jpg
and in the cosmic ray variations sites chapter at
http://helios.izmiran.rssi.ru/cosray/main.htm#links
The common dose limit for an employee, which is considered as a harmless dose rate, is 20 mSv/a, which is rounded 2.3 µSv/h and this is only about ten times more than the common natural background at low altitudes and about one hundred times more than the activity of the natural potassium content of the human body or common food.
With a natural potassium content of about 1 % a food (not a medium as drinking water) or stone has a natural activity of about 312 Bq/kg. Because potassium is only one of dozens natural radioactive elements, common food has a natural activity of about 500 Bq/kg. Because water has a low natural activity, dried food has a natural activity of several kBq/kg. So food with with a too low radioactivity is not good, because this food causes inadequate potassium intake and this causes Hypokalemia.


Trip from Nuremberg to the highest summit of the Mount Kilimanjaro and back in 2007

gammascout on the kibo summit


Uhuru peak at 2008-07-14 (winter), at sunrise (6 am), Dose rate: 0.7 µSv/h, Wind speed: 8 m/s, Air pressure: 495 hPa, Temperature: -7.4°C (wind chill temperature: -24°C, but because the wind chill temperature does not take into account the low air pressure, the effective wind chill temperature is about -10°C).
The common death rate at Kibo is about 0.02 % and about 60 % of the about 40.000 tourists per year do get a certificate for successfully climbing Uhuru Peak (5895 m), which means they climbed to Stella Point (5756 m) or higher.
The good trip organizing company was Afromaxx. The trip did cost about 1000 US-Dollar, including one week (one star) hotel.

dose rate on kibo


Short description
Data file
Raw data
Machame route profile

Trip from Nuremberg to the summit of the Aconcagua and back in 2009

dose rate on aconcagua


Due to a snowstorm with a sight distance of only 10 m, the summit was closed right before the canaletta at approx. 6600 m height, but the 4 days at Plaza de Mulas (PDM, 4365 m) and Nido de Condores (NDC, 5560 m) on the Normal Route can clearly be seen in the middle of the picture. You can also see the trip to Placa Francia before and the trip to (nearly) the summit, from NDC. At the leap of half a day at PDM the Gammascout had a blackout; it seems a "HOLD" key, which is blocking all (other) key pressures, is missing.
You can also see the flights Munich-Madrid, Madrid-Santiago, Santiago-Mendoza and back.
The dose rate was (0.1 ± 0.015) µSv/h per kilometer height at Aconcagua and higher above, during the flights. So it's possible to measure the height via the dose rate, without problems like a blocked or locked pitot tube. This also means that a good flight simulation chamber is incomplete without X-raying of 0.1 µSv/hkm, but it seems no flight simulation chamber has it.
At the Kibo trip the dose rate was a little higher during the flights and at the same altitude. The reasons were: The flights to/from Aconcagua where lower (10.5 km instead of 12.0 km maximum height, as shown on the monitors inside the plane) and the ground at the Kibo must have more radioactivity, not much less then the activity of the cosmic rays. This is consistent with the fact that volcanoes, and Kibo is a vulcano while Aconcagua is not, usually have more radioactivity, because of their higher Potassium content: http://www.kreis-ahrweiler.de/kvar/VT/hjb2001/hjb2001.48.htm. The reason may be that the heat of a higher concentration of radioactive material deep inside the earth can produce a Hotspot, which produces volcanoes.

temperature, pressure, humidity, acceleration


Temperature, air pressure, air humidity, and acceleration at the aconcagua trip.

During that time at Aconcagua 10 people died, one survived seriously wounded and one was lost:
lost on aconcagua

The common death rate at Aconcagua is about 0.5 % and there a about 4000 climbers per year. Some deaths can be found on youtube, e. g. http://www.youtube.com/watch?v=j6WxFqu5jIE&feature=player_embedded.
Because the death rate at the highest mountains with an elevation above 8 km is about 10 % (http://en.wikipedia.org/wiki/Eight-thousander), Aconcagua is relative harmless. One reason for the low death rate at aconcagua is that you have to get a medical check at the first camp (Confluencia) and the base camp (Place de Mulas), and if your pulse rate, blood pressure or oxygen saturation is not ok you get send back.
About 30 % of the tourists make it to the summit.
The rate of severe nonlethal injuries at aconcagua is about 1 %, which is about two times the death rate and also relative low.

The good trip organizing company was the austrian Verkehrsbüro. The trip did cost a little more than 2000 Euro, including all flights (with a baggage limit of 60 kg) and hotels.
The increase of the radiation dose with the altitude does not mean that the life expectancy is shorter; in facts it is longer: http://circ.ahajournals.org/cgi/content/abstract/CIRCULATIONAHA.108.819250v1?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=swiss&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT, german abstract: http://www.dradio.de/dlf/meldungen/forschak/1006678/.
One reason is that such low radiation doses are biopositive; they are more stimulating than destroying.




Journey from Nuremberg to Chernobyl and Prypiat and back in 2009

gammascout at chernobyl nuclear power plant


Memorial at the chernobyl nuclear power plant. Dose rate: About 15 µSv/h.
I took a regular one-day journey from http://chernobylzone.com for only 122 US-Dollar (depends on the number of people which pay for the english speaking guide; it's 162 for one), including supper and an english speaking guide.
Individual and longer journeys are also available, with helicopter and a visit inside the nuclear power plant, but significant more expensive.
Other also journey to Chernobyl organising companies are www.tourchernobyl.com , www.newlogic.ua , and www.panorama-tour.info .
You can find an overview for Chernobyl journeys at http://wikitravel.org/en/Chernobyl.

dose rate at chernobyl


In the diagram you can also see the flights Kologne-Kiev and back. The diagram starts with steps of 10 minutes (violet) and after that it's with one hour steps.
The results are nearly the same as described e. g. at http://forum.pripyat.com and http://www.berger.ma/gallery_trip.php: The radiation which you measure is about 90 % gamma, 9 % beta and 0.1 % alpha. Most of the radiation is caused by Cesium-137, a little from Strontium-90 and very little from Plutonium, Americinum and some other elements/nuclides. More than about 90 % of the radiation is caused by Cesium-137 and Strontium-90.
The dose rate i measured was:

0.20 ± 0.02 µSv/h at the hotel and in the center of Kiev

about 0.1 µSv/h in the Metro of Kiev

about 0.4 µSv/h in the central railway station of Kiev, maybe because of the granite floor

about 0.25 µSv/h in the center of Chernobyl

about 15 µSv/h at the memorial close to the nuclear power plant, because the memorial and the street around it was build with material from outside the chernobyl zone, after the Chernobyl disaster

about 0.2 µSv/h at the railway bridge close to the nuclear power plant, where you can feed the famous big fishes

dose rate at dnieper bridge at chernobyl


about 0.1 µSv/h on a bridge over the Prypiat river near Chernobyl

typical dose rate on the streets of pripyat


usually 1, at some places 2 µSv/h on the streets of Prypiat

typical dose rate in the forest in pripyat


usually 2, at some places about 4 µSv/h in the forest in Prypiat

dose rate at red forest at pripyat


about 11 µSv/h in the bus, while passing the Red Forest

about 0.2 µSv/h in the buildings in Prypiat

about 15 µSv/h at the first hotspot in Prypiat

nearly 35 µSv/h at the second hotsport in Prypiyat

nearly 900 µSv/h at the third hotspot in Prypiat.

Inside the bus the dose rate was about the half of the dose rate on the street.
More about the hotspots in Prypiat (also called Pripyat) can be found here.

In 1986 the dose rate after the disaster was about up to 1,000,000 µSv/h in Prypiat and about 10 times higher at the burning reactor, due to the Chernobyl Museum in Kiev and other sources, but now there is nothing dangerous, except close to the destroyed reactor or if you stay a long time at the hotspots or high activity areas like the red forest or eat animals or plants or drink water from there.
Another point is that a lot of the fallout is now deep in the earth and that's the reason why in Chernobyl e. g. the teleheating tubes are above ground.

The dose rate at Prypiat has decresed by a factor of about one million since the disaster.
Close to Prypiat the Red Forest has a dose rate up to 60 µSv/h, which is dangerous if you stay longer than a week, because commonly a dose limit of 20 mSv/a (twenty milliSievert per year), which is at average during a whole year rounded 2.3 µSv/h, is considered harmless.
A dose of 20 mSv, which is the dose caused by a typical Neonatal abdominal CT scan is harmless.
The most common long-term effect is cancer. When 100 adult people get a dose of 100 mSv in a short period of time, then at average one will get cancer, caused by the dose, during the rest of his life: http://www.dradio.de/dlf/sendungen/forschak/1445604/. So the harmless dose of 20 mSv, caused by a typical Neonatal abdominal CT scan, means that it causes at "only" one of 500 people cancer, which is a relative low risk.

Radiation sickness symptoms do begin at 0.5 Sv and severe radiation poisoning with 50% fatality after 30 days (LD 50/30) is at a dose of 3-4 Sv: http://en.wikipedia.org/wiki/Radiation_poisoning. And it takes about 2.5 times that dosage for the LD 50/30 of a chicken and over 100 times that for the LD 50/30 of a cockroach.
At CT Brain Perfusion Scans the common dose is 0.5 S, and 3 to 4 S at radiation overexposures, but only at one part of the body (the head), so some CT scans do cause radiation sickness: http://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm185898.htm (with 1 Sv = 1 G for X-rays). Another point is that beside the radiation sickness symptoms there are other damages like a higher cancer and mutation rate. So if a radiation exposure causes no radiation sickness symptoms it does not always mean that it's harmless. Therefore a lower dose is better when the dose is higher than 20 mSv/a. Because of the long-term effects, underage children should get a lower dose. They should get less then one half of this dose, and because embryos are additionally more sensitive, they should get less than one quarter of this dose.

High dose rates at the chernobyl area of alienation can be found only close to the destroyed reactor. It has been reported that on the roof of the sarcophag the dose rate is about 20,000 µSv/h (in 2006): http://www.fen-net.de/dr.helmut.pfister/20%20Jahre%20nach%20Tschernobyl.pdf.

Beside the radiation effects another problem is the liability for such desasters: Many insurances do not pay for radiation caused damages and in many countries the liability of the nuclear power plant owner is limited very low, e. g. in Bulgaraia to 17 million Euro, Denmark 60 MEuro, France 84 MEuro, Slovakia 83 MEuro, Italy and Lithuania 5 MEuro, source http://dip21.bundestag.de/dip21/btd/16/099/1609979.pdf.
So in case of a maximum credible accident like at chernobyl in most countries the victims will get no or only very few compensation, even in rich countries.

The other data, temperature, air pressure, humidity and acceleration, are not notably:

temperature, pressure, humidity, acceleration 2



You can see the journey to Chernobyl in these data because the air pressure in Chernobyl was a little higher than in Kiev.
You can also see that the three hours in ICE trains (in germany) at the start were 3°C warmer than at the end, where they were really cool and i could feel the difference. In the cooler ICE trains i also felt a stronger air ventilation, but the data logger does not log the wind speed.
Because the data logger was in the carry-on luggage on the flight to Kiev and in the cargo on the flight back there is no great difference to the first flight. This is necessary for living cargo.



Trip from Nuremberg to the summit of the Damavand and back in 2010

dose rate on damavand


temperature, pressure, humidity


Temperature, air pressure and air humidity at the damavand trip, with a short acclimatisation at Alam-Kuh, a pause at the Caspian Sea, a flight from Tehran to Shiraz and drive back to Tehran.
Due to a snowstorm, a too short acclimatisation and other problems, the maximum height was only 4900 m. The reason of the too short acclimatisation is that the trip organizing company, the austrian Verkehrsbüro, did not follow the the first two of the following recommendations for acclimatisation from the Altitude Tutorial from the International Society for Mountain Medicine:

Often the first recommendation can not be implemented, because the sleeping elevation can not be chosen arbitrary, but by spending more nights at the same elevation it's always possible to increase with an average of 300-500 meter per day. And it's always possible to follow the other two recommendations.
If you don't increase continuing, you have to take into account that you loose an acclimatisation elevation of 300-500 meter per day if your sleeping elevation goes down fast (faster than 500 m per day).
So a trip should be checked before booking due to this recommendations.
But the Altitude Tutorial does not take into account the Death Zone which is the zone above 7500 m (some sources say 7000, some 8000 m), where the amount of oxygen cannot sustain human life and where no human body can acclimatize. So for very high altitudes other recommendations, e. g. an oxygen mask, must be used.

The dose rate on the ground was about (0.1 ± 0.015) µSv/h per kilometer height, like at aconcagua.
The common death rate at Damavand is about 0.02 % and about 40 % of the tourists make it to the summit.


Trip from Aalen to the highest summit of Europe, Elbrus and back in 2012

gammascout on the kibo summit


Elbrus (west) summit 2012-07-26, Dose rate: around 0.65 µSv/h.
The common death rate at Elbrus is about 0.25 % and about 70 % of the about 4000 tourists per year do reach the summit.
The company which organised the trip in the Caucasus was elbrustours.ru. The trip in the Caucasus did cost 850 Euro.

dose rate on Elbrus



The trip started in Aalen at 0.19 µSv/h, was at 0.34 in the hotel in the Baksan valley at 2200 m, at 0.36 at the Barrels huts (3800 m), 0.5 at 5000 m and 0.65 at the summit (6542 m). The acclimatisation tours to an altitude about 1 km higher (than the sleeping altitude) and the change from the valley to Barrels huts can not be clearly seen because of the activity of the underground. This is consistent with the fact that volcanoes, and Elbrus is a vulcano while Aconcagua is not, usually have more radioactivity, because of their higher Potassium content Because the gammascout switched from hourly logging to seven day logging, the record ends at 5000 m. So because the gammascout has no "HOLD" key, for logging it should only be used only in a hard case like the pelicase, although this increases the weight by 200 %.

temperature, pressure, humidity


Temperature, air pressure, air humidity and accelerations at the trip.

Doubling the sensitivity with a bigger tube, 2013-06

gammascout with big tube, backside gammascout with big tube, side


After six years i changed the battery and the tube to get a doubled sensitivity and therefore clearer results. Depending on the calibration of the original tube the sensitivity is not exactly doubled but that can be taken into accout by measuring an old known activity and back-calculation.
The old battery has a voltag of 3.66 V and a short-circuit current of 120 mA, which indicates about 50 % capacity.
This LND 72314 did cost me about 190 Euro and has twice the sensitivity of the old tube (ZP 1401). An additional advantage is that the LND 72314 background is only 1.8 times higher than the background of the old tube, so that the signal/background ratio is better.
After the modification the Gammasout is glued together with transparent tape and now therefore lesss robust and about 1 cm thicker, but that's no problem because it still fits into a pelicase 1040 (after removing the black rubber at the bottom).
To get the new tube into the case i removed the ray selection. With a sheet of paper, a small and a big pack of paper (or a smartphone) you have the same function.
Another modification was shorting one of the 4.7 MOhm resistors from the HV supply to the tube, because the new tube needs a lower resistance to the HV supply. At medium high doses of 150 µSv/h i could see the current pulses of the HV supply in the display by a lower contrast, caused by the temporary reduced supply voltage. So i added a 6800 µF / 35 V capacitor at the battery to stabilise the supply voltage.


Outdoor measurement results i found in the web

Dose rate at the Gasteiner Heilstollen 2009, source http://www.gasteiner-heilstollen.com/tl_files/pdf-dateien/Wissenschaftliche%20Informationen%20Radon-Therapie%20LOW.pdf :

0.2 mSv/h
Dose rate at the beach of Lake Karachay 2007, source http://en.wikipedia.org/wiki/Lake_Karachay#Current_status :

6 Sv/h

Comments:
The main source of the activity in the Gasteiner Heilstollen is Radon with an actitivy of 44 kBq/m3. About 50 % of the dose is caused by alpha rays, which have a Relative Biological Effectiveness [RBE] of 20.
At the beach of Lake Karachay the dose is nearly as high as the dose rate at the burning Chernobyl reactor (1986); you get a deadly dose in one hour!
Therefore Lake Karachay is called the dirtiest place on earth (Lenssen, "Nuclear Waste: The Problem that Won't Go Away," Worldwatch Institute, Washington, D.C., 1991: 15).
Some sources say that at the Lake Karachay by the nearby Kyshtym Disaster has been released more radioactivity than by the Chernoby disaster, which released between 5 and 12 Exa-Becquerel (EBq). An official investigation in 1997 says that the nuclear fuel reprocessing plant Mayak, which caused the pollution of Lake Karachay and the Kyshtym Disaster, released 8,9 Exa-Becquerel (EBq) of Strontium-90 und Caesium-137: http://de.wikipedia.org/wiki/Kerntechnische_Anlage_Majak#Unf.C3.A4lle_und_Umweltzerst.C3.B6rung.

So the Chernobyl desaster in 1986 was the most famous nuclear accident and the one with the greatest impact, but the radioactivity from Mayak has caused nearly the same damage, but more locally, over a longer period and more hidden by the government.

Ghosttowns like Prypiat can be found at some other places around the world. An example is the japan Hashima Island. A more modern version, with real radioactive contamination, is the 2011 made Fukushima alienation zone, but it will be opened for tourists in several years, around 2020 or later.

Nuclear accidents on earth are not the worst case of ionizing radiation on earth: A Supernova in a distance of a few hundred light-years or a Gamma-Ray-Burst or jet from a Hypernova in a distance of a few million lightyears would expose the earth to a radiation dose which would destroy the Earth's ozone layer: http://en.wikipedia.org/wiki/Gamma-ray_burst#Rates_and_impacts_on_life. And if these novas are much closer, their radiation is deadly for one half of the earth. Because the gamma rays do travel with light speed, these events do come without warning; when you see them, you are already hit. Because of the light speed, even a warning system with satellites which do search for gamma ray bursts would not help.


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