Chemical Plant Explosions – 2005, Jilin

In China's northeastern Jilin Province, on November 13, 2005, a petrochemical plant explosion released 100 tons of toxic waste into the Songhua River. The Songhua leak of 2005 gained prominence in large part due to the inadequate reaction capacity displayed by central and local state agencies. Representatives from China's State Environmental Protection Agency (SEPA) visited the UN Environmental Programme (UNEP) in Nairobi and the UN offices in Beijing on November 26 in order to provide detailed information regarding the Songhua spill. SEPA then continued to send the UN updates on a regular basis. Despite being a bold step on the side of the Chinese government, it didn't seek the UN until two full weeks after the first explosion in Jilin Province, when the pollution slick had already reached Harbin. It is likely safe to assume that this was the longest the Chinese government could wait without running the risk of conflict with Russia, whose border was downriver, even though the central government went public primarily because it could no longer keep information about the incident from its own citizens. This chemical explosion had an effect on different cities some are summarized below:

1. Effects on Jilin City 

An industrial water plant in Jilin City was shut down on the day of the blasts. Several hydroelectric plants upstream started releasing extra water about the same time in an effort to dilute the chemical that had flown into the Songhua River. Songhua River water deliveries were stopped on November 15, and other water deliveries were stopped on November 18. On November 23, the water supplies were resumed.

To Read About : Chemical Pollution in China: What The Heck's Going On? Click here

2. Effects On The Province Of Heilongjiang

Harbin, the capital of Heilongjiang, was negatively impacted when the local Harbin administration announced a shutdown of the water infrastructure for maintenance on November 21. Harbin is heavily reliant on the Songhua River for its water supply. Other water sources in the city had already been cut off without warning from the Harbin local government, which caused panic among the city's inhabitants.

3. Effects on Russia

The poisonous slick entered Russia on December 16 and affected the city of Khabarovsk there. The slick was now considerably less thick. However, Russia had extra wells drilled and citizens are given instructions to store water before the slick reached the city as a precaution against contamination.

Contaminant water

Following the explosions, more than 100 tons of pollutants with toxic ingredients, including benzene and nitrobenzene, entered the Songhua River, an arm of the Amur River. Pollutants from Jilin province went through a number of cities and counties before entering the Songhua River. The Heilongjiang province and its city, Harbin, were then negatively impacted. The slick traveled through Jiamusi city in eastern Heilongjiang before entering the Amur River near the Sino-Russian border. The Amur River formerly had benzene levels that were 108 times higher than what was considered acceptable for human consumption. The poisonous sleek then traveled through a number of Russian territories, including the Jewish Autonomous Oblast and the Khabarovsk Krai districts of the Russian Far East, notably the cities of Khabarovsk and Komsomolsk-on-Amur. The slack then made its way into the Pacific Ocean through the Strait of Tartary. Among the regions where water pollution was a problem.

To Read About: Bhopal Disaster

The Three Mile Island nuclear disaster

Accidents happen, but when they upset nature's delicate equilibrium or result in significant human suffering, they turn into disasters. Here I am going to write about one of the biggest catastrophes brought on by human activities in American history, "The Three Mile Island nuclear disaster".

The Three Mile Island power plant, located close to Harrisburg, Pennsylvania, had the worst nuclear reactor disaster in American history on March 28, 1979. When coolant (the liquid that keeps a machine cool) escaped from the reactor core owing to a mix of mechanical failure and human mistake, no one was killed and very little radiation was spilled into the air.

About the Nuclear plant

The Three Mile Island (TMI) nuclear power plant is located in Pennsylvania, not far from Harrisburg. Two pressurized water reactors were present. Until its closure in 2019, TMI-1, an 880 MWe (or 819 MWe net) PWR, was one of the best-performing units in the USA. It went into operation in 1974. At the time of the disaster, TMI-2 had a 959 MWe (880 MWe net) capacity and was essentially brand new.

What happened that day?

A number of water pumps in the TMI-2 unit "tripped" at 4:00 in the morning of March 28, 1979. When the pumps failed, the water supply to the steam generators ceased, which led to an increase in the reactor coolant's temperature. Water that was rapidly heating up expanded as a result of the rising pressure. The pressurizer's top valve opened as it was intended to, but the pressure kept building. Just as it was intended to, the reactor "scrammed," and the control rods descended into the core to halt the nuclear fission reaction. When the pressure gradually returned to normal levels, the valve ought to have closed, but it didn't.

What might merely have been a minor annoyance was made worse by a confluence of mechanical and human faults. Because they feared the core "turning solid"—having too much water and losing control of pressure—they seized physical management of the water system. Alarms were sounding but no valuable information was given to the operator. Due to measuring devices sending erroneous data to the control room; technicians started keeping an eye on rising radiation readings at around 5:00 a.m. Around 6:30 a.m., an on-site emergency was declared. The facility remained in crisis for a few days after that, and eventually, radiation was purposely released into the atmosphere to release pressure within the system and prevent the potential of a hydrogen bubble explosion, which was then suspected but later disproved. 

Chain of Events

The reactor cooling system's pilot-operated relief valve (PORV) opened as it was meant to shortly after the shutdown. It ought to have shut down after about 10 seconds. But it remained open, dripping essential reactor coolant water into the drain tank for the coolant. Instruments showed the operators that a "close" signal was transmitted to the relief valve, which led them to believe the valve had closed. However, they lacked a tool for determining the valve's precise location. High-pressure injection pumps automatically injected replacement water into the reactor system in response to the loss of cooling water. Cooling water gushed into the pressurizer, boosting the water level while water and steam escaped through the relief valve.

In response, operators decreased the flow of replacement water. Their training had taught them that the only reliable indicator of the amount of cooling water in the system was the level of water in the pressurizer. They believed the reactor system was overloaded with water since they noticed an increase in the pressurizer level. According to their training, employees should use every effort to prevent the pressurizer from becoming flooded. If it filled, they wouldn't be able to control the cooling system's pressure, and it might even burst. The reactor's primary cooling system then started to produce steam. The pumps employed in the reactor cooling system vibrated when pumping a steam-and-water mixture. Operators turned off the pumps because the high vibrations may have destroyed them and rendered them useless. This put a stop to the reactor core's forced cooling. Because the pressurizer level remained high, the operators continued to believe the system was almost full of water. The fuel core of the reactor was exposed and heated up considerably more when the reactor cooling water boiled away. Due to the damage to the fuel rods, radioactive material was released into the cooling water.

To Read about: The Three Mile Island nuclear disaster

And lastly, workers shut a block valve between the relief valve and the pressurizer at 6:22 a.m. By taking this action, the relief valve-related coolant water loss was stopped. However, the core cooling system's water flow was obstructed by superheated steam and gases. Operators tried to pump more water into the reactor system throughout the morning in an effort to condense steam bubbles that they thought were obstructing the flow of cooling water. Operators tried to lower the pressure in the reactor system throughout the afternoon so that a low-pressure cooling system could be employed and emergency water supplies could be added to the system.

Finally, at about 8 o'clock, plant managers recognized they needed to restart the pumps in order to get water flowing through the core once more. Pressure in the reactor decreased as the temperature started to drop. Less than an hour separated the reactor from total meltdown. Although more than half of the core was damaged or in the process of melting, the core's protective shell was intact, and no radiation was leaking out. It appeared that the problem was over.

But on March 30, two days later, a bubble of extremely flammable hydrogen gas was found inside the reactor structure. When exposed core materials reacted with extremely hot steam two days prior, a bubble of gas resulted. Some of this gas had erupted on March 28 and some radiation had been dispersed into the environment. Plant staff members were not aware of the explosion at the time because it sounded like a ventilation door closing. Upon learning of the radioactive leak on March 30, locals were told to stay inside. As a precaution, Governor Thornburgh recommended: "pregnant women and pre-school age children to evacuate the region within a five-mile radius of the Three Mile Island facility until further notice." Experts were unsure whether the hydrogen bubble would cause further melting or even a massive explosion. As a result, the governor's attempt to prevent panic was successful; within days, more than 100,000 residents had left the nearby towns.

40 Years Later TMI Shut down on September 20, 2019

TMI-2 had a difficult time recovering from the mishap. Since then, TMI-1 has continued to function normally. The power plant started consistently and dependably losing money since it was initially built to run two cores, TMI-1 and TMI-2. It was revealed that the power plant would finally shut down in 2017 after the current owner, Exelon, was unable to persuade Pennsylvania state legislators to appropriate the required cash to maintain the power plant's competitiveness versus less expensive energy sources, like natural gas. The TMI-1 program ended formally on September 20, 2019. On the day of the closure, Exelon issued a statement in which it expressed sadness that "state legislation does not permit the ongoing operation of this safe and reliable source of carbon-free power" at a time when "our communities are seeking more clean energy to address climate change." Decades will pass throughout the decommissioning procedure, which is expected to cost at least $1 billion.

Health issues:

The acute health consequences described by certain locals and documented in two books cannot be explained by the official figures because they call for exposure to at least 100,000 millirems (100 rems) to the full body, which is 1000 times higher than the official estimates. Although there are many other possible reasons, the documented health impacts are consistent with high doses of radiation and analogous to the experiences of cancer patients receiving radiotherapy. Metal taste, erythema, nausea, vomiting, diarrhea, hair loss, farm, and wild animal deaths, and plant damage were some of the side effects. In Dauphin County, where the Three Mile Island plant is located, the death rate among infants under one year represented a 28 percent increase over that of 1978, and among infants under one month, the death rate increased by 54 percent. These local statistics demonstrated dramatic one-year changes among the most vulnerable. These figures were included in the 1981 version of physicist Ernest Sternglass' book Secret Fallout: low-level radiation from Hiroshima to Three-Mile Island. Sternglass is an expert in low-level radiation. The Pennsylvania Department of Health concluded that the TMI-2 disaster did not contribute to any local newborn or fetus deaths in its final 1981 report after looking at death rates in the 10-mile radius around TMI for the six months following the event.

As the Kemeny Commission had determined that this was the only effect on public health, scientific research continued in the 1980s but concentrated mainly on the mental health effects of stress. The TMI Public Health Fund eventually reviewed the data and supported a thorough epidemiological study by a team at Columbia University after a 1984 survey of 450 local residents by a local psychologist revealed acute radiation health effects (as well as 19 cancers among the residents in 1980–84 against an expected 2.6.

Other Chemical Disaster: Chernobyl Tragedy (Nuclear Annihilation )

Bhopal Disaster- Chemistry

Methyl isocyanate (MIC), a chemical, leaked from a pesticide facility owned by Union Carbide India Ltd. (UCIL) on December 2, 1984, turning the city of Bhopal into a massive gas chamber. India's first significant industrial tragedy. More than 600,000 workers were harmed and more than 15,000 individuals died as a result of at least 30 tonnes of methyl isocyanate gas. The Bhopal gas tragedy is regarded as the greatest industrial accident in history.

What caused the methyl isocyanate leak?

Three 68,000-liter liquid MIC storage tanks were located in Union Carbide India's Bhopal facility: E610, E611, and E619 MIC manufacture were underway and the tanks were being filled months prior to the accident. Each tank was pressurized with inert nitrogen gas and could not be filled more than 50% of the way. Each tank's liquid MIC might be blasted out thanks to the pressurization. However, one of the tanks (E610) was no longer able to withstand the pressure of nitrogen gas, making it impossible to pump liquid MIC out of it. Each of the tanks could hold no more than 30 tonnes of liquid MIC in accordance with the regulations. However, this tank weighed 42 tonnes. Due to this incident, UCIL was compelled to stop producing methyl isocyanate at Bhopal, and the plant was partially shut down for maintenance. On December 1, an attempt was made to repair the broken tank, but it proved unsuccessful. By that time, the majority of the safety systems at the factory that dealt with methyl isocyanate were broken. According to sources, water entered the failing tank on December 2 eve, causing a chemical reaction to go out of control. By night, the tank's pressure had multiplied five times. The effects of the MIC gas on the workers in the MIC region began to manifest by midnight. A few minutes later, the decision was made to stop the leak. The chemical reaction in the tank had, however, already reached a critical stage at that point. Within one hour, about 30 tonnes of MIC broke free from the tank and into the atmosphere. The majority of Bhopal people were exposed to the gas, which alerted them to the leak.

An alarm sounds before a calamity

Methyl isocyanate was used as an intermediary in the production of Sevin, a pesticide, at the UCIL factory in 1969. Trade unions in Bhopal raised concerns about contamination inside the facility in 1976. A few years later, a worker died a few hours after unintentionally inhaling a significant amount of poisonous phosgene gas. A journalist who was seeing the occurrences started looking into the facility and then published his findings in the local Bhopal newspaper with the headline "Wake up citizens of Bhopal, you are on the edge of a volcano." About 45 workers who had been exposed to phosgene were admitted to a hospital two years prior to the tragedy in Bhopal. There was leakage of phosgene, carbon tetrachloride, methyl isocyanate, and mono methylamine between 1983 and 1984.

To Read About: The Three Mile Island nuclear disaster

Effects of a leak of methyl isocyanate

The incident's correct treatment options were not known to the doctors. More than 600,000 workers were affected and over 15,000 individuals died as a result of the methyl isocyanate gas leak. Neonatal mortality and the stillbirth rate both rose by up to 300% and 200%, respectively. Trees and animals are also affected by gas leaks. The neighboring trees quickly become barren within a few days. Animal carcasses that were bloated had to be discarded. In the streets, people fled while throwing up and dying. The city's supply of crematoriums ran exhausted.

GOVT's response to the disaster in Bhopal

The Indian government had never before faced such a catastrophe. Immediately following the disaster, legal processes between India, UCC, and the US were initiated. In order to advocate victims' interests in court, the government passed the Bhopal Gas Leak Act in March 1985. The UCC initially offered India a $5 million assistance fund, but the government rejected it and requested $3.3 billion instead. In the end, a settlement outside of court was struck in February 1989, and Union Carbide agreed to pay $470 million in losses. The Supreme Court of India also established rules for the money, mandating that the deceased's relatives get between Rs 100,000 and Rs 300,000. Additionally, individuals who were totally or partially incapacitated were to get between Rs 50,000 and Rs 500,000, while those who had a temporary injury were to receive between Rs 25,000 and Rs 100,000. The top court urged UCIL to "voluntarily" support a hospital in Bhopal to care for the tragedy's victims. Seven former UCIL employees, all of whom were citizens of India, were found guilty of causing death by carelessness and given two years in prison in June 2010. They were eventually released on bond, though. Bhopal following the catastrophe of more than three decades.

UCC was successfully taken over by Dow Chemical Company in 2001, and as the legal disputes between India and the US continued, it became a wholly-owned subsidiary. Then, according to Dow, UCC was legally a new firm with new ownership and had no involvement in the catastrophe. Ingrid Eckerman quotes a sufferer as saying, "Death would have been a wonderful comfort," in his book The Bhopal Saga. To be a survivor is worse. There has been no resolution to the lawsuit thirty years later. Numerous survivors of the Bhopal gas disaster still struggle with a shortage of medical resources. Whatever was left inside the factory after it was shut down was sealed and stored there. Welfare organizations representing gas victims have been requesting its removal for years. There are numerous applications pending before the SC and high court to get the plant's poisonous leftovers removed.

What is MIC, or methyl isocyanate?

A colorless liquid called methyl isocyanate is used to create insecticides. When maintained properly, MIC is safe. The substance reacts with heat quite quickly. The chemicals in MIC interact with one another when exposed to water, producing a heat reaction. Although it is still used in pesticides, methyl isocyanate is no longer produced. The sole MIC storage facility that remained in existence today is at the Bayer CropScience facility in Institute, West Virginia.

Effects of methyl isocyanate chemical reaction on health

Ulcers, photophobia, respiratory problems, anorexia, chronic stomach discomfort, hereditary conditions, neuroses, decreased hearing and vision, impaired reasoning, and many other conditions are among the immediate health impacts. Chronic conjunctivitis, diminished pulmonary function, increased pregnancy loss, higher newborn mortality, increased chromosomal abnormalities, poor associative learning, and other conditions are long-term health impacts.

To Read About: Chemical Plant Explosions – 2005, Jilin

Chernobyl Tragedy (Nuclear Annihilation )

What's up folks? Today; lets get back to the past tragic incident of Chernobyl.

  On April 26, 1986 the Soviet Union’s Chernobyl Power Complex nuclear reactor 4 exploded. The explosion was caused by major fundamental flaws in the reactor design on top of a total disregard for protocol by some of the higher ranking people in charge, despite some serious reservations from more junior members of the staff. But before we get into all of that, let’s start at the beginning, with nuclear energy. 

Nuclear energy is created by splitting apart certain types of large isotopes, called fissile isotopes. Isotopes are variations of an element that have different numbers of neutrons, and some are more stable than others. A fissile isotope breaks apart when a neutron hits it, and even once in a while on its own. When it breaks apart, that’s called nuclear fission, and it’s the isotope’s way of trying to become more stable. When it does, kinetic energy that’s converted to heat is released. And that energy is ultimately what powers an electrical grid. So, why would we use nuclear energy and not just fossil fuels? Well, the energy released from one fission reaction is around a million times greater than the energy released when one fossil fuel molecule is burned. 

Now back to Chernobyl. There were many reasons Chernobyl exploded. To understand them let’s first take a look at how the reactor worked and how it was controlled. The Chernobyl RBMK-1000 reactor is a model specific to the former Soviet Union--it has never been used anywhere else. Nuclear power is considered safe--as long as protocols are followed, proper materials are used, and the reactor is designed to keep itself at a stable power level. All reactors in operation today have this design feature, but the reactors at Chernobyl didn’t. Like all modern reactors, Chernobyl used uranium-dioxide fuel enriched with uranium-235, an isotope of uranium that’s really prone to undergo fission. When uranium-235 is hit by a neutron it splits into two other atoms, plus 2-3 other neutrons. One of the atoms sometimes produced by uranium-235’s fission is Xenon-135, which played an important role in the accident. So we’ll get back to that shortly. Those 2-3 neutrons released are important because some go on to hit other atoms of uranium-235, continuing the chain reaction and continuing to create energy in the reactor. The RBMK-1000 reactor used large graphite blocks to moderate the speed of the neutrons, slowing them down by reducing their energy. Although it may sound counterintuitive, fast-moving neutrons are less likely to hit and break apart uranium-235, they simply whizz by too fast. By slowing them down it increased the chance that each neutron would hit uranium-235 and cause it to undergo fission, keeping the reaction going and releasing energy needed to heat water in the reactor. And that water is essential. The whole point of uranium-235 fission is to create enough energy to boil water in the reactor into steam. That steam is what spins the turbines that drive the electricity generators to power the electrical grid. 

Ok, so now we have a good idea of how we can keep a reactor generating energy, but what about if we want to slow it down or even stop it? The general way to slow down a reactor is to have fewer neutrons hitting and splitting apart uranium-235. And the way to do that is by having neutron absorbers. So, in addition to being used to create steam, water was also used in the reactor to act as a neutron absorber. Every element absorbs neutrons to some degree, even the hydrogen and oxygen in water. While each individual hydrogen and oxygen atom aren’t that likely to absorb neutrons, there is so much water in the reactor that combined, the water acts as a good absorber. If that water were to disappear, it would throw the neutron balance out of whack. Another absorber is xenon-135, the uranium-235 fission product we mentioned earlier. Xenon-135 is a very good absorber - one of the best of all the isotopes in the universe. Just a tiny bit can completely stop a nuclear chain reaction. And finally, boron carbide control rods. Boron carbide absorbs neutrons extremely well, slowing down the nuclear chain reaction. The RBMK-1000 reactor had over 200 of them, and they were moved in and out to decrease and increase the rate of fission. So, all of these things work together to keep fission going while still controlling it. Let’s, very briefly, turn to physics to explain why Chernobyl’s reactor was so different from the ones in operation today. Today’s nuclear reactors are designed to have a negative void coefficient, which might sound very complicated, but here’s the basic premise: it’s a negative feedback loop. If the water in a reactor starts to run low the reactor power drops so that it doesn’t get out of control. That was NOT the case with Chernobyl. To cut costs, the RBMK reactors were the only commercial reactors in the world designed with a positive void coefficient, which isa positive feedback loop. So, unlike other reactors, as water boiled into steam or leaked out and that void was created, instead of power decreasing, it increased, which caused more water to boil, more steam to form, and the cycle to continue. Ok, so, I’ll admit that there are a lot of things going on here, but we are about to bring them all together. 

What exactly happened the night of April 26,1986? Well the irony of that night was that they were actually doing a safety test on Chernobyl’s reactor 4. They wanted to see if, in the event that the reactor lost power, it could keep its own safety systems running until the backup generator kicked in. That safety test was, as you’d imagine, never completed. The safety test required that the nuclear reactor’s power be turned down, and it was, by lowering the control rods--but it was turned down below what normal operating protocol allowed. Turning it down so low was an issue because Xenon-135 was still being created and absorbing neutrons. Some Xenon-135 is unavoidable -- but you don’t want too much of it, because it can keep the power too low. And that’s what happened on the night of April 26, 1986. That night, the power was way too low, and they knew it. But because of all the xenon built up they were in a bind--the only way to raise the power was to start removing control rods, which are there to absorb neutrons and keep uranium-235 fission from happening too often. Under orders from shift supervisor and deputy chief engineer Anatoly Dyatlov, the operators made the disastrous mistake of removing all but 8 of the over 200 control rods, in blatant violation of safety procedures. What they should have done was raise the power slowly and safely over the course of a couple days, to get it to a place where the things moderating and controlling the reaction were again balanced and there wasn’t a danger of too much pressure building. With the control rods out the power went up, but only slightly. And xenon continued to build, keeping reactor power low. The next step in the safety test was to shutdown the pumps that would normally be sending water through the reactor. Without that water, uranium fission increased, and without the control rods in, there was no stopping the next series of events. Power began to increase, and with that, water at the bottom of the reactor core boiled and turned to steam. With the water pumps shut down for the safety test no water rushed in to replace it. That positive void coefficient that we mentioned earlier was making things worse. And steam pressure was building in the reactor; too fast. As power shot up, at least one of the workers at Chernobyl responded as they were trained to--they hit the emergency shutdown button, which inserts all of the control rods at once to stop the reaction. But they were past the point of no return--too much pressure from the steam had built up. On top of that, when those control rods started to go in, they ran into another major design flaw. The tips of the control rods were made of graphite, which keeps uranium fission going. So before the control rods could help, that graphite made the power level sky-rocket. And, just moments later, the crazy amount of pressure that built up caused the reactor to explode. As it did, atmospheric oxygen rushed in and reacted with the hot graphite blocks. Graphite was now the fuel in a combustion reaction, causing a second, fiery, explosion. The damage of the immediate explosion was minor compared to what was to come. The world became aware of the events at Chernobyl when radiation was first noticed outside a reactor in Sweden--much of eastern Europe was being exposed to the radioactive cloud. The night of the explosion only two plant workers died, but over 200 people, many of whom were fire-fighters who eventually putout the fire, came down with acute radiation syndrome. Within 2 weeks, 28 of them were dead. Chernobyl serves as a reminder of what can happen when a safety culture becomes unhinged. In the words of the late Dr. Valery Legasov, a Soviet inorganic chemist and chief of the commission investigating the Chernobyl disaster, “I advocate the respect for human engineering and sound man-machine interaction. This is a lesson that Chernobyl taught us”. The ruins of the Chernobyl reactor now sit under a metal shell--but some of the radioactive isotopes under that shell and in the surrounding areas have a half-life in the tens of thousands of years, which means they’ll exist long after we, and dozens of generations after us, are gone. 

Read Also: Ammonium Nitrate - Common Fertilizer or A Dynamite?

Ammonium Nitrate - Common Fertilizer or A Dynamite?

On August 4, a major fire broke out in a Port of Beirut warehouse and spread to 2,750 tonnes of ammonium nitrate which had been impounded and stored for six years after it was seized from an abandoned ship in 2014. Yes, the common fertilizer ammonium Nitrate was exploded. How do fertilizers which we often think of as just natural elements good for the earth, explode so violently and considered as more dangerous than dynamite. Let's begin with slightly background on fertilizer itself.

Plants need a few of basic nutrients to grow and most of them are found within the air and water things like oxygen, carbon and hydrogen. Of course; they also need another elements which will or might not be rich in the soil they grow in that's where fertilizer comes in. It packs the dirt with the secondary elements needed to form a plant flourish. One of the main components in manufactured fertilizer is ammonium nitrate. Atmospheric nitrogen has a really strong chemical bond that plants can't easily break. So fertilizer companies create a nitrogen-based substance that's much easier for plants to take apart. Ammonium nitrate is one such compound and it's used for good reason. The ammonium part sticks around longer without evaporating. So it's great for decent summer fields and the nitrate is easily used by plants. Even more compelling within the agricultural industry, it's inexpensive to manufacture. You mix ammonia and nitric acid and you're done but what makes nitrate capable of such lethal explosions? Surprisingly, not much truly ammonium nitrate is a comparatively stable compound. In other words, when it's just sitting quietly somewhere ammonium nitrate isn't that big of a problem because it needs a relatively high energy of activation. The energy needed to cause a reaction to explode. However if an accident where some quite detonation sort of a spark or some kind of energy occurs you better believe that nitrate is deadly. The compound essentially makes its own fuel from the ammonium and oxidizer from the nitrate. 

So its reaction is violent and long lasting. Once a reaction is sparked ammonium nitrate explodes violently. The explosive force occurs when solid ammonium nitrate decomposes very rapidly into two gases nitrous oxide and water vapor. Quite 100 people were killed and nearly 4 000 people were injured on August 4th during a massive explosion in Lebanon's capital Beirut. The explanation for the explosion was due to 2 700 tons of ammonium nitrate which was stored for 6 years in the warehouse of the port. The impact was felt 200 kilometers radius leading to a huge 3.5 magnitude earthquake. 

For More: Chernobyl Tragedy (Nuclear Annihilation )