Chernobyl Nuclear Disaster 1986

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On April 26, 1986, a sudden surge of power during a reactor systems test destroyed Unit 4 of the nuclear power station at Chernobyl, Ukraine, in the former Soviet Union. Massive amounts of radioactive material from the accident and the fire that followed were released into the environment. Sand and boron were poured on the reactor debris by the emergency crews that responded. The sand was to stop the fire and additional releases of radioactive material; the boron was to prevent additional nuclear reactions. A few weeks after the accident, the crews completely covered the damaged unit in a temporary concrete structure, called the “sarcophagus,” to limit further release of radioactive material. The Soviet government also cut down and buried about a square mile of pine forest near the plant to reduce radioactive contamination at and near the site. Subsequently Chernobyl’s three other reactors were restarted but all eventually were shut down, with the last reactor closing in 1999. The disaster was a unique industrial accident due to the scale of its social, economic and environmental impacts and longevity. It is estimated that, in Ukraine and Russia alone, around 9 million people were directly affected resulting from the fact that the long lived radioactivity that was released more than 200 times than that of the atomic bombs dropped in Hiroshima and Nagasaki.

The Soviet nuclear power authorities presented their initial accident report to an International Atomic Energy Agency meeting in Vienna, Austria, in August 1986. After the accident, officials closed off the area within 30 kilometres (18 miles) of the plant, except for persons with official business at the plant and those people evaluating and dealing with the consequences of the accident and operating the undamaged reactors. The Soviet (Russian) government evacuated about 120,000 people from the most heavily contaminated areas in 1986, and another 220,000 people in subsequent years.

The concept of failure is crucial to understanding engineering as engineering design has as its first and foremost objective the anticipate failure. Thus, colossal or enormous disasters that do occur are ultimately failures of design. However the lessons learned from those disasters can do more and contributed greatly to advance knowledge of engineering. It has much more contribution than all the successful machines and structures in the world. Indeed, failures appear to be inevitable during the prolonged period success. Failure, in turn lead to greater safety margins and, hence leads to new successes.

Therefore, the various failures of engineering design has occurred in the many different fields of engineering which has cause massive disasters in the history of engineering. The engineering disaster that is studied in this report is the Chernobyl disaster.

CHRONLOGICAL SEQUENCE OF THE DISASTER

Background

The Chernobyl nuclear power station is located in Ukraine at the settlement of Pryp'yat, 16 km northwest of the city of Chernobyl and 104 km at the northern part of Kiev, Ukraine (20km south of the border with Belarus). The Chernobyl Nuclear Power Station includes four nuclear reactors, each capable of producing one gig watts of electric power. At the time of the accident, the four reactors produced about 10 per cent of the electricity used in Ukraine. Construction of the Chernobyl power station began in the 1970s. The first of the four reactors was commissioned in 1977, and Reactor No. 4 began producing power in December 1983. When the accident occurred in 1986, the other two nuclear reactors were under construction.

The Soviet-designed RBMK (Reaktor Bolshoy Moshchnosty Kanalny, high-power channel reactor) is a pressurised water-cooled reactor with individual fuel channels and using graphite as its moderator. It is also known as the light water graphite reactor (LWGR). It is very different from most other power reactor designs as it derived from a design principally for production of plutonium and was intended and used in Russia for both power production and plutonium fission. No other power reactors in the world use a combination of a graphite moderator and water coolant.

On April 26, 1986 operators of the power plant ran a test on an electric control system of one of the reactors. They shut down the reactor’s power-regulating system and its emergency safety systems, and they withdrew most of the control rods from its core while the reactor was still running. On April 26,1986 the chain reaction in the core went out of control due to other mistakes that compounded the problem at 1:23 AM. Several explosions triggered a large fireball; this and the raging fire in the reactor core released large amounts of radioactive material into the earth’s atmosphere. Most contamination occurred around the reactor in areas that are now part of Russia and Ukraine.

Chronological Schedule

May 1972

- A discussion took place in Kiev about the type of nuclear plant to be built at Chernobyl.

- Chernobyl's director supported construction of Pressurized Water Reactors (PWRs). He informed the Ukraine Ministry of Energy that an RBMK (a boiling water reactor) releases forty times more radiation than a PWR.

- However, the scientist in Ukraine, Alekzandrov opposed this, stating that the RBMK- 1000 was not only the safest reactor with pressure tube reactors.

December 1983

- The construction of Unit 4 at Chernobyl was completed

- On 20 December the nuclear power plant had become operational.

- The production of electricity started on 20 December was quite remarkable, because usually there is a time lapse of about six months between the completion of the construction and the plant becoming operational.

- Turbine had been tested, but without results. The question was still why the test was not repeated again immediately, but had to be left until April 1986.

May 1984

- Document notes deficiencies in the third and fourth block, and also of poor quality of some equipment sent from Yugoslav companies.

March 1985

- The Minister of Energy, Anatoly Mayorets, decreed that information on any adverse effects caused by the functioning of the energy industry on employees, inhabitants and environment, were not suitable for publication by newspapers, radio or television.

February 1986