The Nuclear Weapons Asst. Prof. Dr. Doonyapong Wongsawaeng 2111201 ความร้ทั่วไปทางด้านรังสีและพลังงานนิวเคลียร์ู Nuclear Technology Department Chulalongkorn University 1 Presentation outline • History of nuclear weapon uses • Types of nuclear weapons • How nuclear weapons work • Amount of materials needed for nuclear weapons • Consequences and health risks • Commercial nuclear power plants and the atomic bombs • Stockpiles of nuclear arsenal in the world • Two countries of concerns (Iran, N. Korea) 2 Introduction • A nuclear weapon release vast quantities of energy from small amounts of matter • A well-designed nuclear weapon weighing total ~ 1 tons can produce an explosive force comparable to > 109 kilograms of conventional high explosive such as TNT • Nuclear weapons deliver damage by blast, fire and radiation • They are considered weapons of mass destruction (WMD) (biological and chemical weapons are considered WMD too) • There are international policies and efforts to control the weapons (NPT treaty, IAEA’s Comprehensive Safeguards Agreements and Additional Protocol, UNSCR 1540, etc.) 3 4 History of nuclear weapon uses • Only two nuclear weapons have been detonated successfully and offensively near the end of World War II • Hiroshima – 6 August 1945 – “Little Boy” – U-235 gun-type device • Nagasaki – 9 August 1945 – “Fat Man” – Pu-239 implosion-type device 5 The Manhattan Project • The Manhattan Project was the codename for a project conducted during World War II to develop the first atomic bomb. • The project was led by the United States, and included scientists from the United Kingdom and Canada. • The scientific research was directed by American Berkeley physicist J. Robert Oppenheimer. 6 The Manhattan Project • The Hiroshima bomb, Little Boy, was made from uranium-235. • Most of the uranium enrichment work was performed at Oak Ridge. • The gaseous diffusion technique was scaled up in a large separation plant at Oak Ridge. • During the war this method was important primarily for producing partly enriched material to feed the EM separation process, developed by Ernest Lawrence at the University of California Radiation Laboratory at the University of California at Berkeley. • The electromagnetic isotope separation was implemented in Oak Ridge at the Y-12 Plant, employing devices known as calutrons, which were effectively mass spectrometers. 7 The Manhattan Project 8 The Manhattan Project • Control panels and operators for calutrons at the Oak Ridge Y-12 Plant. • During the Manhattan Project the operators, mostly women, worked in shifts covering 24 hours a day. • Gladys Owens, the woman seated at right closest to the camera, was unaware of the purpose and consequence of her work until seeing the photo of herself while taking a public tour of the facility nearly 60 years later. 9 The Manhattan Project • In a mass spectrometer, a vaporized quantity of a sample is bombarded with high energy electrons which causes them to become positively charged ions. • They are then accelerated and subsequently deflected by B fields. • They then collide with a plate, producing a measurable electric current. The mass of the ions can be calculated according to the strength of the field and the charge of the ions. 10 The Manhattan Project 11 The Manhattan Project • Copper was originally intended for electromagnet coils, but there was an insufficient amount available due to war shortages. • The project engineers were forced to borrow silver from the U.S. Treasury. • A total of ~ 30,000 tons of silver from the U.S. Treasury reserves was used for coils, and was returned after the project ended. • Initially the method seemed promising for large scale production but was expensive and produced insufficient material and was later abandoned after the war. 12 The Manhattan Project • The bombs used in the first test at Trinity Site on July 16, 1945, in New Mexico, and in the Nagasaki bomb, were made primarily of Pu-239, a synthetic element. • U-238 + n U-239 Np-239 Pu-239 • The production and purification of Pu used techniques developed in part by Glenn Seaborg while working at Berkeley and Chicago. • Beginning in 1943, huge plants were built to produce plutonium at the Hanford Site. • However, reactor-bred plutonium was far less isotopically pure than cyclotron-produced plutonium. 13 14 The Manhattan Project • The presence of Pu-240 meant that the simple "gun type" model of bomb design would not work; the presence of extra neutrons from spontaneous fission (the spontaneous fission rate of Pu-240 is 40,000 times greater than that of Pu-239) meant that the weapon would pre-detonate with a greatly reduced yield. • The insolubility of this problem was concluded on June 17, 1944 and led to a redesign of the bomb as an "implosion" device in which a spherical core of plutonium would be compressed using conventional explosives, which would increase the plutonium's density and thus create a critical mass. 15 The Trinity Test • The Trinity Test was conducted by the United States on July 16, 1945, at a location 35 miles southeast of Socorro, New Mexico on the White Sands Proving Ground, headquartered near Alamogordo. • Trinity was a test of an implosion-design plutonium bomb. • Using the same conceptual design, the Fat Man device was dropped on Nagasaki, Japan, on August 9. • The Trinity detonation was equivalent to the explosion of around 20 kilotons of TNT and is usually considered the beginning of the Atomic Age. 16 The Trinity Test 17 The Trinity Test 18 The 30 m tall tower constructed for the test The Trinity Test The bomb fully assembled and ready for the test 19 The Trinity explosion, 0.016 seconds after detonation. The fireball is about 200 meters wide. Trees may be seen as black objects in the foreground.20 21 The Trinity Test Crater 24 hours after the test. The dark area is the fused soil. The small crater22 in the southeast corner was from the earlier test explosion of 108 tons of TNT. The Trinity Test 23 The atomic bombing of Hiroshima • In the early morning hours of August 6, 1945, a B-29 bomber named Enola Gay (named after Colonel Tibbets' mother) took off from the island of Tinian in the West Pacific, about six hours flight time from Japan, and headed north by northwest toward Japan, accompanied by two other B-29s • The bomber's primary target was the city of Hiroshima. • Hiroshima had a civilian population of almost 300,000 and was an important military center, containing about 43,000 soldiers. 24 25 Enola Gay’s crew The atomic bombing of Hiroshima 26 The atomic bombing of Hiroshima • The bomber, piloted by the commander of the 509th Composite Group, Colonel Paul Tibbets, flew at low altitude on automatic pilot before climbing to 31,000 feet as it neared the target area. • At approximately 8:15 a.m. Hiroshima time, the Enola Gay released "Little Boy," its 4.4 ton uranium bomb, over the city. • Tibbets immediately dove away to avoid the anticipated shock wave. • Forty-three seconds later, a huge explosion lit the morning sky as Little Boy detonated 1,900 feet (580 m) above the city, directly over a parade field where soldiers of the Japanese Second Army were doing exercises. • Though already eleven and a half miles away, the Enola Gay was rocked by the blast. 27 Little Boy contained 64 kg of uranium, of which 0.7 kg underwent nuclear fission, and of this mass only 0.6 g was transformed into energy. This is equivalent to an efficiency of only about 1.5% It exploded with a destructive power equivalent to between 13 - 18 kilotons of TNT (estimates vary). 28 29 The T-shaped Aioi Bridge, in the upper portion of the photograph, was the aim point for the Enola Gay. Only reinforced concrete buildings remain and 30 all have sustained significant structural damage. 31 The atomic bombing of Hiroshima • The burst temperature was estimated to reach over 106 oC, which ignited the surrounding air, forming a fireball some 250 m in diameter. • Eyewitnesses more than 8 km away said its brightness exceeded the sun tenfold. • Those closest to the explosion died instantly their bodies turned to black char. • Nearby birds burst into flames in mid-air, and dry, combustible materials such as paper instantly ignited as far away as 2 km from ground zero. • The white light acted as a giant flashbulb, burning the dark patterns of clothing onto skin and the shadows of bodies onto walls. 32 The atomic bombing of Hiroshima • Survivors outdoors close to the blast generally describe a literally blinding light combined with a sudden and overwhelming wave of heat. (The effects of radiation are usually not immediately apparent.) • Within minutes 9 out of 10 people < 1 km from ground zero were dead. • People farther from the point of detonation experienced first the flash and heat, followed seconds later by a deafening boom and the blast wave. 33 The atomic bombing of Hiroshima • Nearly every structure within 1.6 km of ground zero was destroyed, and almost every building within 5 km was damaged. • Less than 10% of the buildings in the city survived without any damage, and the blast wave shattered glass in suburbs 20 km away. 34 The Red Cross building was very close to the hypocenter. Note the depressed roof caused by the explosion occurring overhead. 35 36 37 38 The atomic bombing of Hiroshima • Small ad hoc rescue parties soon began to operate, but roughly half of the city's population was dead or injured. 39 The burns are in a pattern corresponding to the dark portions of the kimono she was wearing at 40 the time of the explosion. 41 A burned victim of the Hiroshima atomic bomb 42 The atomic bombing of Hiroshima • Long-range health dangers associated with radiation exposure, such as an increased danger of cancer, would linger for the rest of the victims' lives, as would the psychological effects of the attack.