Models of high-temperature corrosion of graphites in radiation fields and oxidizing environments and models for predicting the resource of materials in the reactors of the IV generation :: SPE RESST

Models of high-temperature corrosion of graphites in radiation fields and oxidizing environments and models for predicting the resource of materials in the reactors of the IV generation


During developing and choice of reactor graphites for high-temperature gas-cooled reactors (HTGR) generation IV, it is important to predict, by means of simulation tests of change of constructional properties and fuel materials, caused by high-dose radiation by neutrons or charged particles. Imitating modeling of reactor radiation in NSC KIPT NAS of Ukraine is performed with the help of charged particle accelerators, in which the rate of formation of radiation defects is 2..4 orders of magnitude higher than in the environment of the simulated reactor.

For increase the effectiveness of simulation studies of oxidation of reactor graphites under irradiation, an analysis of physical phenomena during their thermal and radiation oxidation was carried out. The model of the combined influence of radiation fields and oxidizing environment on carbon materials which at a task of the corresponding phenomenological parameters allows to describe is developed:

	dimensional changes in graphite samples;

	Young's modulus;

	strength and coefficient of thermal expansion of graphite in dosing.

The economic-mathematical analysis of the choice of constructional materials of the HTGR is made

Design, construction and operation of nuclear power plants (NPP) are initially associated with high capital costs. At the same time, the main price load is borne by the reactor vessel, inner-body elements and pipelines, which are made of radiation-resistant steels and alloys.

"The strategy of development of nuclear power in Ukraine until 2030 and for the future" offers a research of the possibilities of using the HTGR of the IV generation in the nuclear power complex of Ukraine. The HTGR various projects were developed in Germany (AVR, THTR-300, HTR-500, HTR-Module), the USA (Peach Bottom, Ft.St. Vrain, Fulton, MHTGR, MPBR, NGNP), old USSR / the Russian Federation (VGR-50, VGM, VG-400, GT-MHR), Japan (HTTR, HTR-GT, GTHTR-300), People's Republic of China (HTR-10, MHTGR-IGT), Republic of South Africa (PBMR), France (ANTARES), Netherlands (ACACIA). When choosing a specific nuclear power plant HTGR for Ukraine, it is necessary to consider all possible technical options for their implementation, including, and taking into account expected cost indexes of the main components of the nuclear reactor.

For justification of economically expedient choice of materials most of the HTGR metal-consuming components and, in particular, the nuclear reactor case, materials research and expected approach is offered. It consists in forecasting of cost of components case staly VTGR, non-stationary temporary ranks presented in the form, and, on their basis, determination of expected cost of the case of the nuclear reactor.

The information technology (IT) of non-stationary time series forecasting with a risk assessment was developed. Unlike the existing forecasting technologies, it allows to carry out the detailed analysis of the non-stationary time series components and justifies transition to the optimal forecasting method, having previously excluded methods that do not satisfy to the original data statistical description. IT also includes risk assessment of the constructed forecast.

Approbation of the proposed approach and the developed IT on the example of the solution of the scientific and practical task of justifying the HTRP case was carried out.

	For carrying out predictive calculations, steel was chosen that have a positive experience of more than 30 years of operation as a part of the casing of differen nuclear reactors: 15H2NMFA, A-336 Code Case 1236, A 533GR B 1989, A-508 Class 2 1989, 16 MnD5 RCC-M 2111 , 20 Mn Mo Ni 5 5 1990, 15Х2В2ФА 2000, 15Х2МФА.

	The assumption is accepted that considered case steels are close on operational parameters values, therefore additional rating of the compared values is not required. Comparison was made only cost indexes case steels without production costs, which are approximately the same for the HTGR casing types.

	Initial data for forecasting of exchange quotations on components (Si, Mn, Fe, Cu, Cr, Ni, Mo, W, V, Nb) of nuclear reactor case steels are taken from the official sites of the US Geological Survey National Minerals Information Center, the London Metal Exchange, the US Department of Labor. All reactor case steels components costs have been specified to the uniform system of measures (US $ per metric ton) and, taking into account inflation, to comparable prices in 1998.

	With the help of the created information technology of forecasting with a risk assessment, creation of forecasting models and calculation of forecast estimates from 2009 to 2014-2019 for the components which are a part of the HTGR cases is executed (see Fig. 1-2).

Figure 1 - Current and prediction estimates of the case steels components cost in 2014 - 2019, in US dollars per metric ton in comparable prices in 1998

Figure 2 - Current and prediction estimates of the case steels cost in 2014 - 2019, in US dollars per metric ton in comparable prices in 1998

	The average absolute percentage error of the forecast is 12.94%. The forecast risk is 14.5%.