On April 26, 1986, the No. 4 nuclear reactor at the Chernobyl Nuclear Plant near the city of Prypiat suffered from a catastrophic nuclear accident during a systems test. The resultant explosion and fire released large quantities of radioactive contamination into the atmosphere, which then spread over large areas in Europe. It is considered the worst nuclear power plant accident in history, and is one of only two classified as a level 7 event on the International Nuclear Event Scale.
Radioactive iodine and other dangerous radioactive elements released from the explosion and subsequent venting from the damaged containment structure rose into the air and spread across millions of square miles, polluting many European nations. Potassium iodide was distributed in the immediate areas surrounding the Chernobyl Nuclear Plant, including the Pripyat region where most of the workers lived. The distribution of the contamination was determined by the weather conditions at the time. The radioactive plume touched down many times in numerous populated areas as far out as 500 km (over 300 miles) from the plant site.
The disaster arose during a systems test of the No. 4 reactor. There was a sudden power output surge experienced during a procedure intended to determine how much power was needed to keep the reactor operating during a blackout. When an emergency shutdown was attempted a more extreme spike in power output occurred. It was this extreme spike incident that ultimately led to a reactor vessel rupture and a series of explosions. These catastrophic events were not correctly managed or contained and as a result the graphite moderator of the reactor was exposed to air, causing it to ignite. The explosion and fire ejected hot particles of nuclear fuel, fission products and contaminated material into the air, including caesium-137, iodine-131, strontium-90 and other radionuclides. The damaged reactor vessel released contaminated material into the compromised containment structure, a plume of radioactive smoke and debris particulate then vented into the atmosphere and dispersed over an extensive geographical area. Data released in the post-Soviet era indicates that about 60% of the fallout in USSR landed in Belarus, but large parts of eastern and northern Europe were affected. The analysis of the precipitating events remains controversial, but it seems the cause of the incident was essentially one of flawed reactor and operational systems design, flawed control rod tip design, defective operational training and an organisational culture that allowed breaking safety instructions for the experiment and rushing the test after last-minute problems.
Pripyat, the town closest to the reactor is only 3 km away and was home to 49,000 residents before the disaster, mostly the families of the plant workers. The city of Chernobyl is only 4 km to the south of the reactor. High radiation levels forced the evacuation of more than 100,000 people from the region surrounding Chernobyl, but although about 700 residents have since returned to live in the region, none have reoccupied the actual town of Pripyat.
Pripyat is a freeze-frame of 1980s Soviet life. Propaganda slogans still hang on walls, and children's toys and other items remain as they were. But buildings are rotting, paint is peeling and looters have taken away anything that might have been of value. Trees and grass are eerily reclaiming the land. Today, the Chernobyl Exclusion Zone is a tourist destination. In 2002, it opened for tourism, and in 2004 there were 870 visitors.
The accident that destroyed the Chernobyl 4 reactor is understood to have directly led to the death of 31 reactor operating staff, emergency responders and firemen within three months of the incident. An undetermined number of further deaths arose from exposure to radiation during the initial crisis and the ongoing contamination of the plant and environs.
Over twenty years after the accident, debate still rages about the number of directly related deaths. Fearing bad PR, the U.S.S.R. for several years forbade medical examiners from listing radiation as a cause of death. Estimates of deaths related to the accident range from 56 to thousands. The World Health Organization (WHO) suggests the final figure could reach 4,000 civilian deaths, a figure not including casualties amongst clean-up workers drawn from the Soviet military forces. The numbers presented for consequential death from radiation exposure induced illness and cancer vary considerably and range upward toward just short of 1,000,000 potential casualties. A Russian publication concluded that between 1986-2004 there were 985,000 premature cancer deaths worldwide as a result of radioactive contamination from Chernobyl.
- Svetlana Alexievich's Voices from Chernobyl: The Oral History of a Nuclear Disaster offers personal insight into the lives of residents before and after meltdown. ISBN 0312425848.
- UNSCEAR's assessments of the radiation effects .
To gain access to Pripyat, Chernobyl or any of the surrounding villages, you will need to enter the 30 km exclusion Zone - and to do that, you will need to arrange a day pass. The easiest way of obtaining one of these is through a tour operator, of which there are many based in Kiev.
Government agency with jurisdiction over the site in regulation №1157 stipulates that a request for a Zone permit must be applied for at least 10 office days (which can make up to 14 calendar days) prior to the planned visit.
- [dead link]Amazing Chernobyl Tour, Chervonoarmiiska St., 43, 01004 Kiev, ☎ , e-mail: email@example.com. Amazing Chernobyl tour organizes day trips to Chernobyl and Pripyat, for individuals and groups From $149 per person.
- Chaes-tour.com, 1/36, Bastionnaya str., Kiev, ☎ . ChAES-tour will allow you to know firsthand what happened in the now- closed zone of the Chernobyl NPP & Pripyat town, to touch its secrets and events, to find out what is an insidious radiation and learn how to win it. 1-, 2- or more day long scheduled group tours and tours on request, all types can be thematic. The price includes the maximum time in the Chernobyl zone (departure from Kyiv on 8.00, return on 20.00-21.00), an extensive program of visits of the Chernobyl Exclusion Zone, the author's supervision of Sergei Mirnyi, a liquidator and writer, or by guides specially trained by him, learning how to survive at elevated background radiation, watching documentaries about Chernobyl, as well as insurance, a comfortable air-conditioned bus, route maps, personal certificates proving your visit of Chernobyl. From $89 1-day trip to $787 5-day trip per person.
- [dead link]CheapChernobylTour.com, 43, Chervonoarmiis'ka St., Apt. 32, Kiev, ☎ , e-mail: firstname.lastname@example.org. CheapChernobylTour.com offers ecological tours to the Chernobyl zone and Pripyat. The CheapChernobylTour includes transfer to and from the Chernobyl zone, lunch in the cafeteria of the nuclear power plant, and an excursion in Chernobyl. Visitors get to see the reactor, the ‘dead town’ of Pripyat, and the ‘red forest’ where pine trees turned reddish orange because of radiation. Guests get 20% discount for their accommodation in the Mini Hostel Kiev in the night before and after the CheapChernobylTour. from USD 149 to USD 169.
- Chernobyl Tour, Polupanova str., 1, Chernobyl, ☎ . Mo-Fri, 10AM - 6PM. Trips are based on the most advanced knowledge about Chernobyl and radiation, and are user-friendly and enjoyable. They show in depth both rich Chernobyl history and nature of the Zone, and teach radiation survival skills. 1-, 2- or more day long scheduled group tours and tours on request, all types can be thematic. 1-day trip - $116-160, 2-day trip - $265-314 per person. The price includes official Zone access pass, an English-speaking guide, Kiev pick-up and drop-off, transportation, map of the route and Zone. Possibility to rent personal dosimeter-radiometer.
- ChernobylTrip.com, . Ecological tours to Chernobyl zone and Pripyat. You will travel with professional English-speaking guide. Chernobyl Tour includes transfer to and from Chernobyl zone, lunch and excursion in Chernobyl, and hostel in case of 2 days trip.
- Chernobylwel.com, . These tours provide opportunities to see places that usually stay unseen including cooling towers 5 and 6, meeting with local citizens and visiting the cemetery of technicians. They also offer 2 day trips for €200-250 for tours from Kiev.
- Kiev Lodging Chernobyl Tours (email@example.com), 5 Pushkinskaya str., Kiev, ☎ . The tour company has all legal documents required to conduct tours in a safe and correct way and is backpacker friendly. The tour includes an English speaking guide, Kiev pick-up and drop-off, official Zone access pass, transportation and food/drinks. Prices start from $195 per person.
- [formerly dead link]Lupine Travel, ☎ , e-mail: firstname.lastname@example.org. A UK based firm offering 1, 2 and 4 day Chernobyl tours including optional airport transfers and apartment stays in Kiev. For overnight stays food requirements are brought in from outside the Zone. Cost to join a group tour is from €139/person.
- Pripyat.com, . Organised tours to the Chernobyl exclusion Zone and Pripyat city conducted by former residents. Includes formal tours with testimonials, stories and memories about days of accident from people who lived in the region. They do very interesting, informative tours and everything is officially legalised.
- SoloEast Travel, office 105, #10 Proreznaya St., Kiev, ☎ . One of the first tour providers to Chernobyl. Mandatory insurance ($10 USD) and optional radiation monitor ($10 USD) are not included in the advertised price. $79 USD /person.
- Star Sky Travel, ☎ . Trips to Chernobyl zone for groups and individual tourists; airport and railway transfer; VIP service; tourist visa support, student invitation, business invitation.
- Tour2chernobyl.com, Illinska street 12, Kiev (They usually meet their groups at 9:00 AM at a meeting point in Kiev, get on a bus and leave for Chernobyl), ☎ , toll-free: , e-mail: email@example.com. Mon-Fri: 9 AM - 6 PM. You can check the available dates for group tours on our website. This tour includes the Chernobyl Zone, Ghost Town Prypyat and Radar Duga. This tour is official and was approved by the Ukrainian Ministry of Health. Skype: tour2chernobyl.com from 49$ per person.
- UkrainianWeb, . A North America based firm offering all-inclusive, English speaking guided tours to the Zone. Tours include a Kiev pick-up and drop-off, Zone access pass, transportation and lunch. Friendly service, fast and convenient booking with various payment options.
- Trip-to-Chernobyl.com, Dmitrova ST 24, Kiev, ☎ , e-mail: firstname.lastname@example.org. Oficial tour-operator of private 1 or few-days tours to Exclusion Zone. All the tours include visiting unique places (in addition to the usual Chernobyl and Pripyat walking tour) like Radar Duga (Chernobyl-2), old bus and railway stations, abandoned villages, communication with self-settlers of Chernobyl Zone. There is a possibility to organize the tour up to your program. Booking is allowed to be made 7 working days in advance. Every visitor is provided by the health insurance. Price depends on the number of people. Points included into the price: pick up from Kiev by mini-bus, accompaniment of English speaking guide, all the documents and permits from the State Agency of Chernobyl, meals, accommodation for the night in a hotel in Chernobyl, health insurance. From USD 110/person.
Chernobyl reactor 4
You'll not be able to get too close, but the nearest observation point is 200 m from the reactor sarcophagus. The only way to get into the reactor is if you are a scientist or a film maker that has had months of preparation in advance. Although radiation levels here will be much higher than elsewhere in the region, you will not be able to pick up a significant dose during your stay. Typical dose at the site seems to be about 5-9 microsieverts (0.5-0.9 mR/h) (winter), slightly higher in the summer. However, measurements done from the observation point in October 2008 only showed a value of 0.14 microsieverts (0.014 mR/h). There is a visitor's centre with a very interesting model of the damaged reactor, where the plans for improving the sarcophagus over the facility will be explained to you.
Chernobyl Nuclear Power Plant
The power plant itself, home to four decommissioned RBMK-1000 reactors, offers amazing insight into Soviet nuclear and architectural engineering practices for those able to arrange in-depth visits. Commercial tours stop only at the Reactor 4 observation pavilion. Visitors wishing to experience the interior of the plant must request permission via a letter faxed to the plant's general director (currently Igor Gramotkin) as outlined on the plant's website. The letter should introduce you or your group, and explain in detail what you want to see. Admission, by no means guaranteed, presumably favors professionals employed in relevant fields. Visitors are issued badges and indirectly-read TLD-type dosimeters at the power plant entrance, then pass through a modern security checkpoint in the ABK-1 administrative building, and thereafter are given cotton coats, caps, and booties in preparation for entering the radiological control zone. A higher standard of dosimetry and personal protective equipment may be issued for some areas, such as the "Sarcophagus." Visitors' own dosimetry devices are not allowed inside ChNPP. Always be mindful that this is a fueled nuclear facility and security is taken seriously. Strictly follow directions from plant personnel about photography, and never attempt to rest anything on the floor (it may be confiscated due to contamination). The exit portal monitors at ChNPP are thankfully much less sensitive than those found in most American nuclear plants, but still it's a good idea to wear fresh clothes and shoes rather than articles that may have been contaminated elsewhere in the Zone. In 2011, visitation was allowed to Unit 3 main circulation pump rooms, the live 750-kV switchyard control room, the Unit 1 control room, the Phase 1 dosimetry panel, and the memorial to engineer Valery Khodemchuk in the ventilation building between Reactors 3 and 4, among other places. The turbine hall was closed due to excessive radioactivity in 2011, but was accessible in 2010. A particularly interesting place is the bunker under ABK-1 that is used as an emergency response center (as it was in the 1986 accident).
The power plant has a cafeteria that serves freshly-prepared and appetizing Ukrainian food.
Some commercial tours may stop to feed bread to the monstrous catfish living in the condenser cooling channel that flows under the railroad bridge near ABK-1. Do not take pictures in the direction of the power plant from this location. (Your guide will probably make this rule abundantly clear.)
ChNPP has its own train station, Semikhody. Trains travel without stopping between Semikhody and Slavutych. The service is free. As there are no stops while the train passes through Belarus, there are no border controls. Visitors exiting the Exclusion Zone via Semikhody must pass through a portal monitor and their personal belongings may be frisked for radionuclide contamination.
Vehicle scrap yard
"Rossokha" village, cemetery of military machineries - In April 2008 the government prohibited access to this site and it has remained closed to visitors. The scrap yard contains the irradiated emergency vehicles which tended the disaster. There are a number of fire tenders, ambulances, trucks and helicopters in the vehicle graveyard, although some of the vehicles are now being sold as scrap metal. You will no longer be able to gain entry there, but as some of the vehicles are still carrying lethal doses of radiation, this isn't a bad thing. Since the closing of that site tours since 2008 have taken visitors to a collection of abandoned ships on a lake by the city instead.
The famous abandoned city, which once housed 50,000 residents. Sights to see are the schools, kindergarten, public buildings and the amazing cultural palace which contains a swimming pool, cinema and gymnasium, and overlooks the famous ferris wheel. Hazards are the crumbling buildings, and decaying wooden floors in places – so be careful. The government has deemed all buildings in the town as condemned, so most tours will not let you enter the buildings.
Minibus day-trips from Kiev typically stop in the town's center, at the west end of Lenin Street near the Palace of Culture. Short-term visitors are confined to the pavement at ground level; if you join one of these tours, your risk exposure is minimal, but so too is your exposure to the vast cultural reliquary that is Pripyat. A more in-depth visit (several days, staying overnight at the InterInform hotel in Chernobyl, eating meals at the InterInform stolovaya) costs about $200 per person per day in a group of four (2011). The long-term visitor is rewarded with considerably more freedom to explore, accompanied of course by an InterInform guide.
Decades of neglect have resulted in a physically-hazardous ex-urban environment in which radiation is of distant, secondary concern. Hazards include uncovered manholes in the middle of barely-recognizable streets, open elevator shafts, flooded basements, decayed wooden floors, collapsed roofs, large amounts of broken glass, challenging footpath obstructions in dark hallways, and quite possibly asbestos. Flashlights are essential to exploring interiors. Although radiation isn't a relatively major concern, the "hotter" spots in town would most certainly be off-limits to the public in the United States or Western Europe. As an example, the basement of the Polyclinic contains first responders' clothing (firefighters' clothes, boots, helmets, etc.) and presents external gamma exposure rates approaching one roentgen (R) per hour (June 2010). Note that as of October 2017, the only access into the hospital basement is by crawling through a hole dug after the basement access was deliberately buried. Some other hot spots are well-known to guides and they can either help you avoid these places or find them if so inclined. The hot spots most commonly visited by tours are mostly marked with radiation signage. These hot spots are generally either places that were not decontaminated previously, contaminated objects, or locations where radioactive materials have collected together due to rain runoff.The most important precaution concerning radioactivity is to avoid ingesting loose contamination. Although your guide might eat snacks or smoke in Pripyat, you should not – particularly if you have been handling things or visiting places like the hospital basement. Buy an ample supply of drinking water at one of the magazines in Chernobyl before going to Pripyat (obviously there is not potable water there). Water can also be used to rinse contaminated shoes before re-entering vehicles.
There is a great number of abandoned villages in the exclusion zone, and all are extremely interesting to view. Visitors can see farmhouses, small cottages and plenty of vegetation. Be careful entering any of these areas, as vegetation always carries far higher levels of residual radioactivity than concreted areas. Guides will always tell you not to step on the moss, and the dust in dried-out puddles tends to concentrate radioactivity. In addition, pay attention to where you are walking, as most buildings have been damaged due to a combination of neglect and due to being actively damaged by people.
Secret Radar Installation
Within the 10 km zone is a large former secret radar installation that the Soviet government used to detect missiles. From Priyapat, it is easy to see in the distance, if looking from a point of elevation.
Your tour will probably include food, but you're advised to bring your own snacks and drinks. However, some tours let you visit the only shop in Chernobyl where you can buy a beer for your meal. By the end of the tour, you just might need it.
If you get access to the Chernobyl administration centre, you will be able to buy souvenirs, such as books detailing the disaster.
In Chernobyl town there is a canteen for the maintenance crews that work in the exclusion zone. If you are on a guided tour, you can eat there, though depending on the tour, the scheduled lunch may not start until well in the afternoon. All day visitors to Chernobyl will likely dine at restaurants in the surrounding area.
If staying overnight the canteen in Chernobyl town is used to provide dinner, however, it does not stay open just for tourists. If there is a lack of workers than the Canteen may be closed by the time you return for dinner. In this instance your guides will usually walk you to the nearby shops which stock various cured meats, dried fish and canned vegetables as well as massive range of spirits and beers.
If you bring meals and drinks with you, make sure to keep them well sealed, and avoid opening/consuming any food or drinks in the open air within the 10 km area around the power plant. Clean your hands thoroughly before touching any food.
Tap water in the area remains unsafe for drinking or washing because of the radiation that leaked into surrounding dams, lakes and rivers, so stick to bottled water or mineral water - which in Ukraine is predominantly sparkling.
- ChornobylInterinform Agency Hotel, Bohdan Khmelnytsky Blvd 1A (at the former intersection of Khmelnytsky Blvd and Polupanova Street). Check-in: (by arrangement), check-out: (by arrangement). ~$40 (double occupancy), July 2011.
Visitors have one (legal) option for spending the night in the Chernobyl Exclusion Zone, and it is the government-run hotel in central Chernobyl. Any of the tour companies mentioned elsewhere on this page can, in principle, make bookings for visitors at the hotel as part of the process of registering the tour with the InterInform Agency. Rules are constantly in flux; if you want to stay overnight in Chernobyl, ask your tour operator about it and make sure to plan early.
If you are accustomed to lodging standards in Kiev, you will find the InterInform Agency hotel surprisingly affordable for the level of comfort provided. The buildings are prefabricated structures installed after the 1986 accident. Many rooms are actually suites, some larger than others. Some rooms have useful amenities like refrigerators, dining tables, sofas, or dishes--luck of the draw. Each room has its own bathroom and shower. Tap water is potable. No WiFi (2011). The buildings are not air-conditioned, but (hopefully!) the windows will be unlocked and screened in the summer. The main Interinform office building has the largest suites, while the annex to the east contains more rooms and even a chapel on the first floor with faux-stained-glass windows. Radiation levels at the InterInform Hotel are close to Kiev background.
Hotel guests are NOT PERMITTED TO LEAVE the premises without an authorized guide! This includes innocuously walking 500m down the street to buy drinks / snacks / batteries at one of the magazins. If the very-abundant police catch you out on the town without your guide, you can expect a pleasant little march over to the police station near the Lenin statue / old Dom Kulturi, where they have an open-air gazebo set up with folks like you in mind. There you'll wait in contrition until your guide retrieves you.
The InterInform Agency canteen, located on the ground floor of the west building, offers prix fixe dining by reservation only. Reservations made when the tour is booked with InterInform are about $10 for lunch or dinner, but if meals must be arranged on the day of service, higher prices are charged. The canteen serves three meals a day at fixed times. Dinner is a multi-course, freshly-prepared, traditional Ukrainian set meal with very large portions and typically paired with a traditional beverage like kompot; even after a day of strenuous exploration in Pripyat, it may be hard to eat all the food they bring you, at the pace they bring it. Chances are nobody will check you for contamination or remind you to wash up before eating, but that would be a very good idea to do on your own.
- See also: Nuclear tourism#Stay safe
If in Pripyat, exercise caution when entering buildings—the ground around entrances to, and inside buildings will generally be littered with broken glass, concrete and debris. Be sure to take care inside buildings as the flooring can be somewhat uneven (and sometimes unstable). Watch your footing—a decent pair of shoes/boots would be a good idea.
As of April 2012 tours are no longer allowed to enter the buildings due to an accident occurring involving a floor collapsing injuring several tourists. All visitors sign written acknowledgements of the Exclusion Zone rules, including the rules prohibiting structural access. However, it remains routine (2017) for in-depth custom tours to enter Pripyat structures and forested areas at the discretion of the guide.
Most forested areas should be avoided. Whereas areas accessible to tourists near the reactor and Pripyat generally has low radiations in most areas (but notably not in the hospital basement), forested areas may have higher levels of radiation, in part because no decontamination was attempted in those areas.
Do not ingest any material found within the exclusion zone as it may be radioactive. Food and drinks at the canteen does not come from the exclusion zone, so it should be safe.
Radiation hygiene is a very important consideration for in-depth visits, because radioactive contamination discovered on visitors at the Zone checkpoints is construed as prima facie evidence of rules violations (entering structures and straying from paved areas). If you go to the Zone with the goal of exploring and wallowing in the most contaminated areas (e.g. the Pripyat polyclinic or the "Red Forest"), pay attention! As of 2013, the Lelev checkpoint at the 10-km boundary is operational and all visitors must pass through the portal monitors while a police officer scans the vehicle and its interior contents with a scintillator; thus, it is no longer possible to plan on cleaning up at accommodations located in Chornobyl in order to pass inspection at the 30-km boundary. You must be radiologically pristine (well, almost!) before getting back in the vehicle after going exploring. Take the following hygiene equipment, which you should have in easy reach for when you return to your vehicle:
- Pancake thin-window Geiger-Muller survey instrument. Cover the probe with a plastic bag to avoid contaminating it.
- Disposable gloves
- An abundance of carbonated bottled water, purchased at one of the small stores in Chornobyl before you head out to explore
- A cleaning brush with long bristles
- Pocket knife for cutting contaminated spots out of shoe soles (disposable shoe covers are a nice idea but they always break)
- Scissors for cutting contaminated hair
- A change of clothes and / or a disposable Tyvek coverall
Wear gloves while exploring to avoid contaminating hands. After exploration in contaminated areas, remove any obviously-contaminated outerwear like coverall or gloves or street clothes and pack it out in your luggage like a good citizen (low levels of contamination on these articles will be detected by the personnel portal monitors, but will not be noticed in luggage by the wand detectors the police use). Pass the GM probe over your body slowly and identify any spots exceeding about 500 CPM. First, attempt to wash as much of the contamination in these areas off by means of water and brushing. Contaminated hair or shoelaces should simply be cut off, as washing these will prove futile. Shoe soles are sometimes resistant to washing, in which case the offending spots should be reduced by cutting off with a knife. Your goal during cleanup should be to eliminate any spots on your body where the count rate exceeds 500 CPM on the pancake instrument, with particular attention to feet and hands. Avoiding contamination in the first place would in theory be preferable, but if you're reading this, you probably didn't come to Chernobyl to sit around staying clean.
The levels of radiation on guided tours are relatively small; radiation levels in most places are less than those of being in an aircraft flying at 30,000 ft. The main danger is not in the radiation itself, but in particles of radioactive materials that may remain on your clothes or items. Those who actually follow the rules (stay on pavement, out of buildings) will almost never trigger the portal monitor alarms at Dytyatky and can safely ignore the in-depth "radiation hygiene" discussion above.
A lethal dose of radiation is in the range of 3-5 sieverts (300-500 roentgens) when administered within an hour. Levels on the tour reportedly range from 0.15 to several microsieverts per hour (15 to several hundred microroentgens an hour). A microsievert is one-millionth of a sievert.
Example: On a six-hour trip arranged in October 2008 the total dose was 4 microsieverts according to the meter (400 microroentgens). This was less than the total dose of the connecting two-hour flight, which was 6 microsieverts (600 microroentgens). Radiation levels by the power plant were 1.7 microsieverts per hour (170 microroentgens per hour) and they varied between 0.4 and 9.5 microsieverts per hour (40-950 microroentgens per hour) in the Pripyat amusement park. Thus, risks are pretty much non-existent as long as you don't get yourself contaminated.
The International Council on Radiation Protection has a recommended annual limit of 50 millisieverts (5 rem) (uniform irradiation of the whole body) for nuclear plant workers.
Clinical effects are seen at 750-2,000 millisieverts (75-200 rem) when administered in a short time scale.
Since the levels are microsieverts (10^-6) the exposure level is very low. But it is still possible to be in contact with some very hot surfaces, so caution should be stressed. Note: One rem is equal to 1.07 R (roentgen), or 0.01 sieverts or 10 millisieverts.