PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY
Series: Nuclear and Reactor Constants

since 1971

Русский (РФ)

ISSN 2414-1038 (online)

Authors & Affiliations

Zagorulko Yu.I., Ganichev N.S., Konovalov M.A., Ilicheva N.S.
A.I. Leypunsky Institute for Physics and Power Engineering, Obninsk, Russia

Zagorulko Yu.I. – Leading Researcher. Contacts: 1, Bondarenko sq., Obninsk, Kaluga region, Russia, 249033. Tel.: +7 (484) 399-80-84; e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..
Ganichev N.S. – Head of Laboratory.
Konovalov M.A. – Junior Researcher.
Ilicheva N.S. – Senior Researcher.

Abstract

At carbon concentration in sodium of 30 ppm in temperature interval 400–550 °C the system «sodium-carbon» is two-phase system, consisted of carbon solution in sodium (with share from 0.005 to 0.12 of overall concentration) and particulate carbon phase, transported by sodium flow. The latter will be subjected to phase transitions (dissolution or crystallization) in circuits with temperature gradients. Except, mechanisms of carbon phase transitions could be dependent on scale factor, defined as ratio of sodium mass flow rate to specific wetted surface of the circuit pipelines and equipment units. It follows, that carbon activity in sodium circuit should be considered as an essentially local characteristic.
To carry out adequate experimental investigation of structural materials carburization/decarburization processes it is necessary to provide stable carbon activity in sodium in the test zone of the material.
The results of investigation on austenitic stainless steels carbonization in high-temperature sodium in dependence on the carbon thermodynamic activity in sodium are presented in the article. It was demonstrated, that at carbon activity near to 0.1, carburization of austenitic steels in sodium at 700–750 °C exceeds ~ 1.2 mass %. An equilibrium carbon activity in st. steels 04Cr16Ni15Mo3Nb, 08Cr16Ni15Mo3Nb at 700–750 °C is close to 5·10–3, that is characteristic to st. steels 304, 316.
It was established experimentally time irreversibility in kinetic of st. steels carburization/decarburization processes. It follows that at elevated temperatures short-time carbon activity «shocks», e.g. at abnormal or accidental sodium coolant pollution could cause st. steels very high carburization, which could be reserved subsequently for a long time in sodium with low-level carbon activity.

Keywords
fast reactor, mass transfer, carbon-containing impurities, sodium, carbon source, carbon activity, suspensions, carburization, austenitic steel, equilibrium samples-standards, diffusion sensor of carbon activity

Article Text (PDF, in Russian)

References

Problems of Atomic Science and Technology. Series: Nuclear and Reactor Constants, 2022, issue 1, 1:16