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The BREST reactor is a Russian concept of
lead-cooled fast reactor The lead-cooled fast reactor is a nuclear reactor design that features a fast neutron spectrum and molten lead or lead-bismuth eutectic coolant. Molten lead or lead-bismuth eutectic can be used as the primary coolant because especially lead, and ...
aiming to the standards of a
generation IV reactor Generation IV reactors (Gen IV) are six nuclear reactor designs recognized by the Generation IV International Forum. The designs target improved safety, sustainability, efficiency, and cost. The most developed Gen IV reactor design is the sodium ...
. Two designs are planned, the BREST-300 (300 MWe) and the BREST-1200 (1200 MWe). Main characteristics of the BREST reactor are
passive safety Automotive safety is the study and practice of design, construction, equipment and regulation to minimize the occurrence and consequences of traffic collisions involving motor vehicles. Road traffic safety more broadly includes roadway design ...
and a
closed fuel cycle The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the ''front end'', which are the preparation of the fuel, steps in the ''service period'' in ...
. The reactor uses nitride uranium-plutonium fuel, is a
breeder reactor A breeder reactor is a nuclear reactor that generates more fissile material than it consumes. Breeder reactors achieve this because their neutron economy is high enough to create more fissile fuel than they use, by irradiation of a fertile mate ...
and can burn long-term
radioactive waste Radioactive waste is a type of hazardous waste that contains radioactive material. Radioactive waste is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, rare-earth mining, and nuclear weapons r ...
. Lead is chosen as a coolant for being high-boiling, radiation-resistant, low-activated and at atmospheric pressure.


BREST-300

The construction of the BREST-300-OD in
Seversk Seversk ( rus, Се́верск, p=ˈsʲevʲɪrsk) is a closed city in Tomsk Oblast, Russia, located northwest of Tomsk on the right bank of the Tom River. Population: It was previously known as ''Pyaty Pochtovy'' (until 1949) and ''Tomsk-7'' ...
(near
Tomsk Tomsk ( rus, Томск, p=tomsk, sty, Түң-тора) is a city and the administrative center of Tomsk Oblast in Russia, located on the Tom River. Population: Founded in 1604, Tomsk is one of the oldest cities in Siberia. The city is a not ...
) was approved in August 2016. The preparatory construction work commenced in May 2020. Construction started at . The first BREST-300 will be a demonstration unit, as forerunner to the BREST-1200. The combination of a heat-conducting nitride fuel and the properties of the lead coolant allow for complete plutonium breeding inside the core. This results in a small operating reactivity margin and enables power operation without prompt neutron reactor power excursions. In simpler terms, the uranium 238 in the core is converted to plutonium, which itself will undergo an effective fission in the fast spectrum. This is in contrast to other fast reactor designs, where an outside blanket of uranium is required; placing too much uranium in the core section would lead to subcritical operation. In doing so, a substantial number of neutrons is required for breeding. This implies in turn, that in the reactor operation, there are "just enough" neutrons to operate, and no excess is present.


Advantages of lead as coolant

The use of lead as a coolant has several advantages if compared to other methods for reactor cooling. * Molten lead does not significantly
moderate Moderate is an ideological category which designates a rejection of radical or extreme views, especially in regard to politics and religion. A moderate is considered someone occupying any mainstream position avoiding extreme views. In American ...
neutrons. Moderation occurs when neutrons are slowed down by repeated collisions with a medium. When the neutron collides with atoms that are much heavier than itself, almost no energy is lost in the process. Thus, the neutrons are not slowed down by lead, which ensures that the neutrons keep their high energy. * Molten lead acts as a reflector for neutrons. Neutrons escaping the core of the reactor are to some extent directed back into the core, which allows a better
neutron economy Neutron economy is defined as the ratio of an adjoint weighted average of the excess neutron production divided by an adjoint weighted average of the fission production. The distribution of neutron energies in a nuclear reactor differs from the f ...
. This in turn enables more spacing between the fuel elements in the reactor, allowing better heat removal by the lead coolant. * Lead undergoes almost no activation by neutrons. Thus, virtually no radioactive elements are created by absorption of neutrons by the lead. This is in contrast to the
Lead-bismuth eutectic Lead-Bismuth Eutectic or LBE is a eutectic alloy of lead (44.5 at%) and bismuth (55.5 at%) used as a coolant in some nuclear reactors, and is a proposed coolant for the lead-cooled fast reactor, part of the Generation IV reactor initiative. It h ...
which was used in other fast designs, including in Russian submarines. The bismuth in this mixture (which has a lower melting point, 123.5 °C, than that of pure lead) is activated to some degree to polonium. * Although virtually no neutrons are absorbed by the lead, lead is very effective at absorbing
gamma rays A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
and other ionizing radiation. This ensures that radiation fields outside the reactor are extremely low. * In contrast to another relatively popular coolant that is used in fast reactors, molten sodium metal, lead does not have issues with flammability (although the combustion of sodium in air is a mild reaction), and will solidify from a leak. * The very wide temperature range at which lead remains liquid (more than 1400 K or °C) implies that any thermal excursions are absorbed without any pressure increase. In practice, the operational temperature will be kept at around , mainly because of other material properties. * As with all fast reactor designs, because of the high temperature and the high thermal inertia,
passive cooling Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or no energy consumption. This approach works either by preventing heat from ...
is possible in emergency situations. Thus, no electrical pumping is required, natural air convection is sufficient to remove residual heat after shutdown. To achieve this, the reactor is equipped with a dedicated passive heat removal system, that requires no electrical power. * All fast reactor designs operate at substantial higher temperatures in the core than water cooled (and moderated) reactors. This allows a significantly higher thermodynamic efficiency in the steam generators. Thus, a larger portion of the nuclear energy is converted into electricity, more than 40% efficiency, compared to around 30% in water cooled reactors. *Similarly, as with all fast spectrum reactors, the coolant is not pressurized. This means that no pressure vessel is required, and the piping and ducts can be constructed with non-pressure resistant steel and alloys.https://aris.iaea.org/PDF/BREST-OD-300.pdf Any leak in the primary coolant circuit will not be ejected at high pressures. * Lead has a high thermal conductivity (35 W/m.K) compared to that of water (0.58), which means that heat transport from the fuel elements to the coolant is effective.


Disadvantages of lead as coolant

* Lead has a high melting point of which means that the entire reactor and all the lead present in piping, heat exchangers etc. must be heated to a temperature substantially higher than this to allow reactor operation to start. * Lead has a substantially lower heat capacity than sodium, which means that more flow is required for heat removal of the core. *Lead also has a lower heat conductivity than sodium, which means that the heat transport is more effective in a sodium cooled fast reactor. * Lead is toxic to humans. * Lead as coolant can lead to corrosion of the reactor internals.


Technical data

* Thermal power: 700 MW * Electrical power 300 MW * Average lead coolant temperature: on entry, on exit of the steam generator * Loop number: 4 * Core height: * Fuel load: * Fuel campaign: 5 years


See also

*
Fast breeder reactor A breeder reactor is a nuclear reactor that generates more fissile material than it consumes. Breeder reactors achieve this because their neutron economy is high enough to create more fissile fuel than they use, by irradiation of a fertile mate ...
*
Fast neutron reactor A fast-neutron reactor (FNR) or fast-spectrum reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons (carrying energies above 1 MeV or greater, on average), as opposed ...
*
Generation IV reactor Generation IV reactors (Gen IV) are six nuclear reactor designs recognized by the Generation IV International Forum. The designs target improved safety, sustainability, efficiency, and cost. The most developed Gen IV reactor design is the sodium ...
*
Siberian Chemical Combine The Siberian Chemical Combine (russian: Сибирский химический комбинат) was established in 1953 in Tomsk-7 now known as Seversk, in the Tomsk Region as a single complex of the nuclear technological cycle for the creation o ...


References


External links


Design Features of BREST Reactors and Experimental Work to Advance the Concept of BREST Reactors

Lead-Cooled Fast-Neutron Reactor (BREST)
IAEA. 2015 {{authority control Liquid metal fast reactors Nuclear power reactor types Nuclear reactors Nuclear research reactors Small modular reactor