Chapter11: Nuclear Icebreakers
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Chapter11: Nuclear Icebreakers The scope of nuclear civil vessels includes the following three types of vessels: 1. Nuclear Merchant Ships, 2. Nuclear Icebreakers, and 3. Nuclear Cruise Ships. This chapter is dedicated to Nuclear Icebreakers. 2. NUCLEAR ICEBREAKERS: An icebreaker ship requires three main faculties that most normal ships lack: A strengthened hull, an ice-clearing shape, and the power to push through ice-covered waters. Icebreakers ships designed to cruise on ice-covered water by breaking through the ice with their strong, heavy, steel bows. The main objective for constructing icebreakers was to keep routes open for commerce where either seasonal or permanent ice conditions exit. ss rr ee k aa ee rr b ee cc I rr aa l ee cc u N –– 11 An icebreaker ship powered by nuclear to break floating ice is known as nuclear 11 rr ee icebreaker and nuclear icebreakers are far more powerful than their diesel powered t pp counterparts. Icebreakers were constructed by Russia primarily to aid shipping in the aa h frozen Arctic waterways in the north of Siberia. C Edited by Dr. Mir F. Ali 1 Just to appreciate the severity of the conditions, during the winter, the ice along the northern seaways varies in thickness from 1.2 to 2.0 metres (3.9 to 6.5 feet). The ice inin central parts of the Arctic Ocean is on average 2.5 metres (8.2 ft) thick. Nuclear-powered icebreakers can force through this ice at speeds up to 10 knots (19 km/h 12 mph). In ice- free- waters the maximum speed of the nuclear-powered icebreakers is as much as 21 knots (35 km/h, 24 mph). Nuclear propulsion has proven technically and economically essential in the Russian Arctic where operating conditions are beyond the capability of conventional icebreakers.rs. The power levels required for breaking ice up to 3 metres thick, coupled with refueling difficulties for other types of vessels, are significant factors. The nuclear fleet has increased Arctic navigation from 2 to 10 months per year, and in the Western Arctic, to year-round. Greater use of the icebreaker fleet is expected with developments on the Yamal Peninsula and further east. The icebreaker reactors are bigger than the reactors in nuclear submarines. The fuel used in OK-900A reactors is enriched to 45-75 percent uranium-235, and each reactor core holds 241 fuel assemblies, including 200 kg of uranium-235. The fuel in KLT-40 reactors is enriched up to 90 percent; it too contains 241 fuel assemblies, with a total ofof approximately 150kg of uranium-235. Fuel is replaced every three to four years, and itt takes approximately 45 days to refuel a nuclear-powered icebreaker. Generally, one reactor acts as the primary propulsion, and the second operates at low power. Water in the pressurized closed water circuit is heated to 300 to 400 degrees Celsius to produce steam. The steam enters a system of four steam generators per reactor core. These generators run the turbines, which run the propellers. Because it is a closed water circuit, this water is recirculated to the steam generators. The cooling system of the icebreaker reactors is specially designed to use cold Arctic seawater. Russia has the most powerful icebreaker fleet in the world, as well as unique experience in the design, construction and operation of such ships. Russian experience with nuclear powered Arctic ships totals about 300 reactor-years in 2009. The Murmansk Shipping Company (MSC) for the Ministry of Transport previously operated Russia’s fleet of nuclear icebreakers. However, in August 2008 responsibility was transferred to Rosatom by presidential decree and the agency is now tasked with both making the fleet profitable s s r r e e and addressing legacy issues such as radioactive waste and the decommissioning of old k k a a e e ships. r r b b e e 2.1 NS Icebreaker Lenin: I I c c r r The nuclear icebreaking fleet was developing nearly in parallel with domestic nuclear a a l l e e c c power. The decision to build the first nuclear icebreaker was taken on November 20, 1953, u u N and the ship’s keel laying took place at Admiralteyskiy Zavod (shipy ard) in Leningrad on – – 1 August 24, 1956. The icebreaker Lenin was undergone sea trials in the Gulf of Finland in 1 r r e e September 1959 and was officially accepted for service on December 3, 1959. It was t t p p a a launched on December 05, 1959. The 510 manufacturing plants and organizations all over h h C the country were involved in its building. Vessel particulars include: 2 1.1. Length: 134 metres; 2.2. Beam: 27.6 metres; 3.3. Height: 16.1 metres; 4.4. Max speed: 18 knots, 5.5. Displacement: 16,000 metric tons without ballast; and 6.6. Propulsion by three DC motors driving three screw propellers. NS Lenin was both the world’s first nuclear powered surface ship and the first nuclear powered civilian vessel. The first nuclear propulsion unit (OK-150) on Lenin had three identical pressurized water reactors (PWR) with a maximum heat output of 90 MWt. The shaft power was 44, 000 horsepower. Enriched uranium was used as fuel (the content of ss rr ee kk U-235 was equivalent 85 kg), and distillate water was used as a moderator and for heat aa ee rr transfer. The reactor core was 1.6 meters high and measured one meter in diameter. The bb ee core consisted of 7,704 fuel pins in 219 fuel assemblies. II cc rr aa ll ee cc There have been two accidents, the first took place in February 1965, when Lenin was uu N undergoing repairs and refueling. The vessel sustained severe mechanical damages to the –– 1 fuel assemblies, some of which were broken in two pieces, and were detected during the 1 rr ee tt unloading of fuel from reactor number two. About 95 spent nuclear fuel assemblies were pp aa hh transferred to the nuclear service ship Lepse and unloading was halted. After C investigations as to why the spent nuclear fuel assemblies were deformed, it was 3 established that the nuclear reactor operators had made an error that left the reactor core without cooling water.. The partial deformation of the fuel assemblies had occurred due to overheating of the reactor core. About 60 percent of the assemblies were damaged. The second accident aboard the Lenin took place in 1967, when the pipe system of the third circuit sprung a leak following the loading of fresh nuclear fuel. The second accident resulted in one of the three OK-150 reactorss being damaged beyond repair. All three reactors were removed, and replaced by two OK-900 reactors; the ship returned to service in 1970. The Lenin was taken out of operation in November 1989 and laid up at Atomflot,, the base for nuclear powered icebreakers in the Murmansk Fiord before it was converted to a museum ship. The vessel was initially fitted with three OK-150 pressurized water reactors producing 90 MW each. Due to operational problems including a partial core melt in 1965, two OK-900 units producing 171 MW each replaced the units. Remained in service for 30 years in the Northern Sea Route, breaking ice for container ships to navigate. During this period, escorted 3,741 transport ships. Voyage covered 654,400 nautical miles, including 560,600 nautical miles in ice. ss rr ee kk aa ee rr bb ee II cc rr aa ll ee cc uu N –– 1 1 rr ee tt pp aa hh 2.2 Arktika-Class Nuclear Icebreakers: C 4 The nuclear icebreakers of the Arktika class are used to force through the ice for the benefit of cargo ships and other vessels along the northern seaway. The northern seaway comprises the eastern part of the Barents Sea, the Petchora Sea, the Kara Sea, the Laptev Sea and the Eastern Siberian Sea to the Bering Strait. Important ports on the northern seaway are, among others, Dikson, Tiksi, and Pevek. In addition to cruising on ice-covered water, the icebreakers have also been used for a number of scientific expeditions in the Arctic. On August 17, 1977, the NS Arktika was the first surface vessel in the world to reach the North Pole.. Since 1989, some icebreakers have been used for Arctic tourism cruises. ss rr ee kk There are six icebreakers classified as Arktika class icebreakers that represent the bulk of aa ee rr the Russian nuclear icebreaker fleet: bb ee 1.1. NS Arktika launched in 1959; II cc rr aa 2.2. NS Sibir launched in 1977; ll ee cc 3.3. NS Rossiya launched in 1985; uu N 4.4. NS Sovetskiy Soyuz launched in 1990; –– 1 5.5. NS Yamal launched in 1993; and 1 rr ee tt 6.6. NS 50 Let Probedy launched in 1993. pp aa hh C 5 Since these icebreakers have been built over a period of thirty years, there is a fair bit of variation between ships of the class; thus, specifications are listed as a range of values. In general, the newer ships are larger, faster, and require smaller crews. Specifications: 1.1. Length: 148 m to 159 m (approximately 136 m at the waterline); 2.2. Beam: 30 m (28 m at the waterline); 3.3. Draft: approximately 11.08 m.; 4.4. Height (keel to masthead): approximately 55 m; ss rr 5.5. Displacement: 23,000 to 25,000 tons; ee kk 6.6.