HTGR nuclear fuel based on plutonium oxide microspheres

Chernikov, A. S.; Permyakov, L. N.; Kurbakov, S. D.; Cherkasov, A. S.; Degal'tsev, Yu. G.; Lyshov, L. L.; Макаров, В. М.

doi:10.1007/bf02673316

Cited by 2 publications

(3 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, buffer layer thicknesses less than 20 µm are too small to extinguish the kinetic energy of the recoil nuclei; the result is an unfavorable over-irradiation of the inner surface of the pyrocarbon layer, giving rise to anisotropic radiation-induced size changes in it [16]. In most requirements for HTGR fuel, it is assumed that the density of the pyrocarbon buffer layer must be ≤1.1 g/cm 3 [3][4][5][6]. Other requirements are not imposed.…”

Section: Of Htgr Fuel Elementsmentioning

confidence: 99%

“…For pyrocarbon density 1.8-2 g/cm 3 (this is density of the inner and outer pyrocarbon layers [5,6]), the fibrous component comprises the dominating fraction. The boundaries of contiguity of the secondary supermolecular formations, formed on the basis of such components, are quite arbitrary.…”

Section: Of Htgr Fuel Elementsmentioning

confidence: 99%

“…The specifications for the microsphere fuel for HTGR take account of the following essential characteristics: thickness, density, anisotropy of the pyrocarbon coating, contamination of the coatings by fissile materials, defects in the silicon carbide layer, and others [2][3][4][5][6].…”

mentioning

confidence: 99%

See 2 more Smart Citations

Formation of multifunctional barriers to increase the radiochemical resistance of the protective coatings of HTGR fuel elements

Kurbakov

2009

At Energy

Self Cite

View full text Add to dashboard Cite

The radiation-size changes of pyrocarbon protective coatings on HTGR microfuel elements are analyzed. It is shown that there is a relationship between the microstructural inner pyrolytic layers and the formation of cracks in these layers as the irradiation dose accumulates. The effect of cracks in the inner pyrocarbon layers on the damage to the silicon carbide layer is examined. It is determined that incorporating into the inner pyrocarbon layer or forming on the inner pyrocarbon-silicon carbide interface compositions, for example, silicon carbide-carbon, Ti 3 SiC 2 , ZrC, TiC, and nitrides of Zr, Ti, and Al creates an obstacle to interior cracks, increasing the radiation-chemical resistance of the carbide layer and the microfuel as a whole.The structure of the microfuel of high-temperature gas-cooled reactors has evolved from particles with a single-layer protective coating consisting of pyrocarbon with a laminar structure through a bilayer pyrocarbon coating with different density to a fuel microsphere with three layers made of, respectively, inner high-density isotropic pyrocarbon and silicon carbide and an outer layer of high-density isotropic pyrocarbon ( Fig. 1) [1].The specifications for the microsphere fuel for HTGR take account of the following essential characteristics: thickness, density, anisotropy of the pyrocarbon coating, contamination of the coatings by fissile materials, defects in the silicon carbide layer, and others [2-6].The operational parameters (temperature, degree of fuel burnup, fluence of fast neutrons, and others) which have been obtained on the experimental stand satisfied the technical requirements for uranium dioxide microspherical fuel based on multilayer coatings (see Fig. 1, position I) and even exceeded the requirements in individual cases (see Fig. 1, positions II and III).In connection with new problems arising in the development of fourth-generation nuclear-energy systems, the requirements for the operational parameters (nuclear fuel burnup, irradiation temperature, hast-neutron fluence, energy release from a fuel microsphere, and others) are increasing substantially. Probably the biggest problem will be due to the realization of deep burnup of fuel at high irradiation temperature -up to 20% h.a. and higher than 1100°C under stationary operating conditions of a very-high-temperature gas-cooled reactor (VHTR, Japan).One of the variants under consideration variant for improving the performance of multilayer coatings is replacing the silicon carbide load-bearing layer by a zirconium carbide layer. However, such a replacement will make it necessary to solve a multitude of materials-engineering problems, develop methods for monitoring the properties of carbide-zirconium coatings and rejecting microfuel based on them, and determine the capability of zirconium carbide to confine solid fission products at elevated irradiation temperatures taking account of the high neutron fluence for VHTR and GFR (see Fig. 1, positions IV, V).Laboratory investigations performed in the USA on micros...

show abstract

Section: Of Htgr Fuel Elementsmentioning

confidence: 99%

Section: Of Htgr Fuel Elementsmentioning

confidence: 99%

See 1 more Smart Citation

Formation of multifunctional barriers to increase the radiochemical resistance of the protective coatings of HTGR fuel elements

Kurbakov

2009

At Energy

Self Cite

View full text Add to dashboard Cite

show abstract

Experimental and computational study of the pyrocarbon and silicon carbide barriers of HTGR fuel particle

2008

Self Cite

View full text Add to dashboard Cite

HTGR safety is secured by a system of barriers limiting the emission of fission products from the core into the surrounding environment during normal operation and postulated anticipated accidents. An experimental-computational analysis of two fundamentally important barriers -fuel kernels and their coating, whose function is to contain radionuclides and to protect workers and the environment, is examined. The function of the barriers and the requirements which they must satisfy are examined for HTGR fuel particles. The results of post-reactor studies are analyzed. Mathematical models and computational codes simulating the behavior of fuel particles are analyzed. Probabilistic-statistical models and the GOLT code are being developed to evaluate the behavior of fuel particles under irradiation. Together with other models, this code is used for comparative test calculations of the behavior of particle fuel under normal irradiation conditions (<1300°C). The first results of such calculations are discussed.A system of barriers which limits the emission of radionuclides from the core into the surrounding environment during normal operation and postulated anticipated accidents secures the safety of HTGR. Two basic concepts for HTGR are currently being developed: spherical fill in the core and prismatic fill with a core assembled from graphite blocks. In both cases, fuel particles are the main fuel elements.There are five fundamentally important barriers in HTGR which confine radionuclides and provide protection for workers and the environment: fuel kernels, coatings on the fuel kernels, matrix graphite of spherical fuel elements, fuel compacts, graphite fuel blocks, airtight coolant loop which includes the reactor vessel, a connecting vessel, and a turbomachine vessel, and an outer protective shell of the reactor with a special ventilation system. Of these barriers, the multilayer coating of the fuel particles ( Fig. 1) is decisive and the silicon carbide layer, in turn, plays the main role.The capability of coatings to contain radionuclides depends on the fuel quality, which is taken to mean the minimum statistical variance of the prescribed characteristics of a large mass of fuel particles, for example, the number of particles in the core of GT-MGR, which is currently being designed [1], is ~10 10 , as well as the maximum possible stability of the coatings as the fuel burns up. The main damaging factors for the coatings of fuel particles are high fuel temperature, fast-neutron fluence, irradiation intensity, power density, and burnup as well as the chemical action of the fission products, increase of the internal pressure of CO and gaseous fission products, and other factors. The role of most of these factors can change because of a change in the fuel structure, including a change in the kernel size and composition and in the coatings of the fuel particles.

show abstract

HTGR nuclear fuel based on plutonium oxide microspheres

Cited by 2 publications

References 1 publication

Formation of multifunctional barriers to increase the radiochemical resistance of the protective coatings of HTGR fuel elements

Formation of multifunctional barriers to increase the radiochemical resistance of the protective coatings of HTGR fuel elements

Experimental and computational study of the pyrocarbon and silicon carbide barriers of HTGR fuel particle

Contact Info

Product

Resources

About