Free Marine Nuclear Reactors Term Paper Sample

Sodium-cooled Fast Reactors (SFR)

The sodium-cooled fast reactor is a 4th generation reactor project that provides a basis upon which the design of an advanced fat neutron reactor is developed. The project relies on two projects called the LMFBR and integral fast reactor. The objective of the project is to produce a fast spectrum reactor that can be cooled by sodium. Nuclear power plants use these reactors for the production of nuclear power using nuclear fuel (Lee & Brun, 2014). The nuclear fuel cycle has two options from the actinide recycle. The first option involves the intermediate size of sodium-cooled reactor. The size range between 150 MWe and 600 MWe. The reactor consist of allow made of plutonium, uranium, minor actinide and zirconium. Pyrometallurgical reprocessing takes place inside facilities that are integrated inside the reactor. The second option is a medium to large reactor that ranges from 500 to 1500 MWe (Le coz, et al., 2011). This reactor is mixed with an oxide fuel that combines uranium and plutonium.

Design

The design of sodium-cooled fast reactors is done is such a way that it doesn’t compromise the design goals. For example, the operating temperature does not exceed the melting temperature of the fuel. A problem in the design can cause this to occur. A proper design takes cognizance of fuel to cladding chemical reaction (FCCI). This reaction occurs due to eutectic melting between fuel and cladding (Le Coz et al., 2011). When uranium and plutonium inter-diffuse with iron of the cladding, an alloy is formed. This alloy has reduced eutectic melting temperature. The chemical interaction causes a reduction in strength in the cladding. The production of plutonium from uranium regulates the transmutation of transuranic. Thus, a design that has inert matrix such as magnesium oxide is suitable for such reactors. The magnesium oxide is said to have a little chance of interacting with neutrons.
The design of sodium-cooled fast reactor is for the management of high-level wastes. These wastes include plutonium and actinides. In this regard, the system has long thermal time response. This feature serves as a safety feature. SFR has large coolant boiling and a system that operates close to atmospheric pressure. In addition, there is an intermediate sodium system. This system is found between radioactive sodium and the steam inside the power plant. Other design features include modular design, integration of pump and heat exchanger, removal of primary loop makes SFR a suitable technology for the generation of electricity (Tenchine et al., 2012). The reactor’s first spectrum is advantageous since it uses available fissile in more efficient ways than thermal spectrum reactors. Examples of SFR include BN-350 reactor, BN-800 reactor, Fermi 1 and Rapsodie.
Using liquid sodium as a coolant has various advantages. It has a high heat capacity that makes it possible to minimize overheating. The high heat capacity offers thermal inertia which lowers significantly the chances of overheating. When water is used as a coolant for a fast reactor, it takes the role of a neutron moderator. Consequently, it slows the fast neutrons into thermal neutrons. Superficial water can be used as a coolant for a fast reactor. However, it requires high pressure (Le Coz et al., 2011). The use of sodium is due to the existence of heavier sodium atoms relative to the hydrogen and oxygen atoms that constitute water molecules. In this regard, neutrons lose energy when they collide with sodium atoms. Unlike water, sodium does not need to be subjected to high pressure. This is because its boiling point is higher than the operating temperature of the reactor. Another benefit for using sodium as a coolant is because it does not corrode various parts of steel reactors. Electromagnetic pumps can be used to pump molten sodium since it is has the ability to conduct electricity. Additionally, the coolant reaches high temperatures relative to water. This allows for higher thermodynamic efficiency.
Despite the gains in using sodium as a coolant, it has various disadvantages too. Sodium has high chemical properties. This implies that precautions must be enhanced to ensure that fires are prevented and suppressed. Sodium explodes when it touches water. It also burns when it comes to contact with air (Le Coz et al., 2011). A case in point is the nuclear power accident that occurred in Monju. It has radioactive properties when it meets neurons even though it has a shorter half life. Due to the delicate nature of this element, care must be taken to ensure that it serves the purpose for which it is intended.

Lead-Cooled Fast Reactors

This reactor involves the use of molten lead as a coolant inside a nuclear reactor. Lead-bismuth eutectic can also be used in this process. The use of lead is preferred because lead has relatively low absorption of neutrons. It also has low melting points. Thus, the interaction between neutrons and heavy nuclei is less severe than sodium (Wolniewicz, 2014). This property of lead makes it a fast-neutron reactor. The coolant serves the role of neutron reflector in which escaping neutrons are taken to the core. Marine nuclear reactors have proposed the use of lead as a coolant.
Design
Like SFR, lead-cooled fast reactor is a 4th generation nuclear reactor. Its design comprises a fast neutron spectrum and molten lead as a coolant. The various options in this case include range of plant ratings and pre-manufactured cores. There are modular arrangements that are rated at 300 to 400 MWe as well as a large monolithic plant with a rating of 1200MWe. Fertile uranium and transuranics provide fuel needed in the reactor. There is a smaller design of LFR that can be naturally cooled by convection. However, larger designs including ELSY utilize forced circulation in normal power operation. Thermochemical production of hydrogen is done with temperatures exceeding 800 degree Celsius (Wolniewicz, 2014). LFR operates on a closed fuel cycle. It has a long refueling interval that takes between 15 and 20 years. The features of this reactor meet existing opportunities in the market such as generation of electricity and production of small grids. Developing countries can use this reactor at the expense of deploying indigenous fuel cycle infrastructure. LFE can be used to distribute energy products such as potable water and hydrogen.
Using lead-cooled fast reactor in the nuclear reactor has numerous advantages. It is possible to replace the whole core after it has been exhausted following a long period of use. This increases the efficiency of the core. In this regard, nations that have no plan of commissioning their nuclear infrastructure can utilize this reactor. LFR does not require electricity to cool after it has been shut down. Thus, LFR is safer compared to the use of water as a coolant. Due is a dense element. This makes it ideal for the prevention of gamma rays (Sienicki, 2012). The nuclear properties of lead make it possible for lead to hinder positive voice efficient. This makes lead fact reactor better for use than sodium fast reactor. The operating pressure for lead is low. The high boiling point of lead makes reduces the chances of overheating in the nuclear reactor. In this regard, SFR and LFR reduce chances of overheating. In the event of leakage, liquid lead does not cause explosions. This property makes lead a less reactive metal compared to sodium. Hence, the use of lead has lesser precautions compared to the use of sodium. Its reaction with water and air is less significant. This makes it possible for an easier and safer containment of lead.
However, the use of lead as a coolant is accompanied by some disadvantages too. The weight of the system usually requires additional support due to heavy weight of lead. It also requires seismic protection which implies an increase in the construction costs. The equipment may be damaged by frequent leakages of the coolant (Sienicki, 2012). The reactor may not operate when molten lead-bismuth solidifies. Despite cheap and abundant lead, bismuth involves high costs because it is expensive. Thus, using a lead-bismuth requires huge quantities of bismuth relative to the size of the reactor.
Against this backdrop, the centrality of SFR and LFR in the nuclear reactors cannot be undermined. The use of LFR is more beneficial than the use of SFR due to availability of lead. The sensitive nature of sodium poses dangers such as the risk of radiation and explosion. In light of the foregoing, it is indubitable that using these types of marine nuclear reactors is instrumental in the production of electricity.

References

Le Coz, P., Sauvage, J. F., & Serpantié, J. P. (2011). Sodium-cooled fast reactors: the ASTRID plant project.
Lee, Y. K., & Brun, E. (2014). Investigation of Nuclear Data Libraries with TRIPOLI-4 Monte Carlo Code for Sodium-cooled Fast Reactors. Nuclear Data Sheets, 118, 433-436.
Sienicki, J. (2012). Lead-Cooled Fast Reactors. In Fast Spectrum Reactors (pp. 513-532). Springer US.
Tenchine, D., Baviere, R., Bazin, P., Ducros, F., Geffraye, G., Kadri, D., & Tauveron, N. (2012). Status of CATHARE code for sodium cooled fast reactors. Nuclear Engineering and Design, 245, 140-152.
Wolniewicz, P., Hellesen, C., Jansson, P., Ane, H., Jacobsson Svärd, S., Österlund, M., & Qvist, S. (2014). Reactivity changes in lead-cooled fast reactors due to bubbles in the coolant.