BN-600

The BN-600 reactor is a sodium cooled fast breeder reactor built at the Beloyarsk Nuclear Power Station, in Zarechny, Sverdlovsk Oblast, Russia. Designed for 600 MW (electric), it produces 560 MW (electric) dispatching energy to the Middle Urals power grid. It has been in operation since 1980.

The plant is a poll-type reactor, where the reactor, coolant pumps, and intermediate heat exchangers and associated piping are all located in a common liquid sodium pool. The reactor system is housed in a concrete rectilinear building, and is provided with filtration and gas containment features. There have been incidents involving sodium/water interactions from tube breaks in the steam generators, a sodium fire from a leak in an auxiliary system, and a sodium fire from a leak in a secondary coolant loop while shut down. All of the incidents were classified as the lowest level on theInternational Nuclear Event Scale, and none of the events prevented restarting operation of the facility after repairs.

The reactor core is 1.03 meters tall and has a diameter of 2.05 meter. It has 369 fuel assemblies, mounted vertically, which each consist of 127 fuel rods with an enrichment of 17–26% ²³⁵U. In comparison, the normal enrichment in other Russian reactors is between 3–4% ²³⁵U. The control and scram system comprises 27 reactivity control elements including 19 shimming rods, two automatic control rods, and six automatic emergency shut-down rods. On-power refuelling equipment allows for charging the core with fresh fuel assemblies, repositioning and turning the fuel assemblies within the reactor and changing control and scram system elements remotely.

The unit employs a three-circuit coolant arrangement; the primary and secondary circuits coolant is sodium. Water and steam flow over the third circuit. The sodium is heated to 550 °C in the reactor. This heat is transferred from the reactor core via three independent circulation loops each comprising a primary sodium pump; two intermediate heat exchangers a secondary sodium pump with an expansion tank located upstream; an emergency pressure discharge tank. These feed a steam generator which in turn supplies a condensing turbine which turns the generator.

There is a lot of international interest for the fast-breeder reactor in Beloyarsk. Both Japan and France have their own fast-breeder reactors in operation, though only as test versions. Japan has paid 1 billion for the technical documentation on the reactor in Beloyarsk. It is an international study in progress where Russia, France, Japan, and the United Kingdom participate.

VVER

VVER (Voda-Vodyanoi Energetichesky Reaktor = Pressurized water reactor) is the Soviet (and now, Russian Federation) designation for light water pressurized reactor. In western countries, the PWR is used as the acronym. For the general public, the perception may be that all Soviet-designed reactors are identical to (or at least similar to) the reactors at Chernobyl. The Chernobyl reactor, however, is a light-water cooled, graphite-moderated reactor (LGR). It is considered by many experts to be a flawed design that is vulnerable to fire. Around the time LGRs were coming on line in the Soviet Union, early VVERs were also coming on line, many with safety innovations based on western designs.

The international community has encouraged the shutdown of various LGRs, but the need for electric power and the employment the power plants provide have made this a lengthy process. After unit 4 was destroyed by fire at Chernobyl, the other 3 units were returned to service and one continued to operate into the 21^st century. Recently, Lithuania agreed to shut down its two LGR units at Ignalina. The units provide nearly 80 percent of the country’s electricity, making this a very difficult economic decision.

The Russian Federation continues to build VVER units. While any Russian-built unit may suffer from the image of the disaster to Chernobyl 4, the new units conform to international standards and have developed an export market. More information on the safety and characteristics of VVER and other Russian models is available on another web site.

RMBK

RMBK (Reaktor Bolshoy Moshchnosti Kanalniy = High Power Canal Type Reactor) merupakan jenis reaktor generasi awal buatan Uni Soviet. Reaktor ini tergolong jenis reaktor nuklir sederhana. Reaktor ini menggunakan grafit sebagai moderator reaksi. Meski demikian reaktor ini menghasilkan energi yang cukup besar. Pada varian awal buatan era 1950-an yang bernama Atom Myrni (Atom Damai), reaktor ini mampu menghasilkan 50 MW energi. Pada varian lanjutan yaitu RMBK 1000, reaktor ini mampu menghasilkan 1000 MW energi. Sedangkan pada varian terakhir yaitu RMBK 1500, reaktor ini mampu menghasilkan 1500 MW energi. Selain energi yang cukup besar, reaktor ini juga menghasilkan pluntonium sebagai produk sampingan yang dapat digunakan sebagai bahan baku senjata nuklir.
Akan tetapi di samping keuntungan-keuntungan tersebut, reaktor ini menyimpan sejumlah ancaman berbahaya. Ketika reaktor ini bekerja dengan reaksi fisi, reaktor ini akan memanas. Ancaman muncul ketika reaktor ini tidak dikontrol dengan baik. Bila kerja reaktor tidak terkontrol dengan baik, akan terjadi overheating pada reaktor yang menculnya resiko fuel meltdown (melelehnya tongkat bahan bakar nuklir). Hal ini disebabkan oleh digunakannya grafit sebagai moderator sehingga moderator tidak mampu menjadi moderator sekaligus pendingin reaktor. Bila fuel meltdown terjadi, lelehan bahan bakar akan menyebabkan air yang dipanaskan dalam reaktor berubah menjadi uap bertekanan tinggi yang dapat memicu ledakan reaktor yang kemudian memicu kebakaran. Bila kebakaran terjadi, limbah nuklir dapat tersebar oleh asap kebakaran dan menyebar terbawa angin serta mengontaminasi daerah yang dilewatinya. Hal ini dapat berdampak fatal pada lingkungan dan kehidupan hewan dan manusia. Selain itu, kebakaran yang terjadi akan sulit dipadamkan karena adanya grafit yang mampu menjadi bahan bakar pada kebakaran tersebut. Hal ini pernah terjadi pada Pembangkit Listrik Tenaga Nuklir (PLTN) Chernobyl di Ukraina, Uni Soviet pada tahun 1986. Oleh karena faktor-faktor itulah, kini banyak reaktor RMBK yang telah dinonaktifkan.