Advanced approach to the induced activity determination of VVER-440 structural components

• Published in: Nuclear engineering and design 2022-01, Vol.386, p.111571, Article 111571
• Main Authors: Šnírer, Michal, Krištofová, Kristína, Farkas, Gabriel, Hausner, Peter, Slugeň, Vladimír, Borák, Ján
• Format: Article
• Language: English
• Subjects: Boric acid; Decommissioning; Density; Fuel cycles; Fuels; Induced activity; Long-term operation; MCNP5 code; Neutral particles; Nuclear fuels; Nuclear power plant; Nuclear power plants; Plant shutdowns; Reactors; Shielding; Temperature distribution
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2021.111571

[Display omitted] •Original data from the V2 NPP were used to perform the induced activity calculation.•Code MCNP5 with ENDF/B-VII.1 effective cross-sectional library was used.•Inventory of induced activity of V2 NPP materials at the core level after 60 years.•The most important activation products in individual construction materials. The paper describes development and evaluation of the complex three-dimensional MCNP (Monte Carlo Neutral Particles) model of the VVER-440/V-213 reactor. The adapted, original data from the V2 NPP (Jaslovské Bohunice, Slovakia) were used to perform the induced activity calculations of structural components with respect to the planned 60-year period of operation. The survey of operational history defined a reference fuel cycle on the basis of which a neutron source term was developed. Parameters such as axial distribution of fuel and control assembly burnup, change in fuel density depending on burnup, moderator temperature distribution and moderator density change from temperature, boric acid concentration in the coolant and position of the 6th group of control assemblies were taken into account. A model of the V2 NPP reactor was developed at the core level. The calculation of the induced activity was performed using the code MCNP5 with ENDF/B-VII.1 effective cross-sectional library. In addition to the methods and model used in this analysis, the paper also summarizes the results that can be generally applied to the mentioned types of nuclear power plants. At the time of V2 NPP shutdown, the total activity of the steel components reached the level of 7.14E + 09 Bq/g. Reactor biological shielding concrete reached the level of 1E + 07 Bq/g. Calculation of the inventory of induced activity of V2 NPP materials at the core level after 60 years of operation are presented and analysed in details.