Series: Nuclear and Reactor Constants

since 1971

Русский (РФ)

ISSN 2414-1038 (online)

Authors & Affiliations

Makhin V.M., Podshibyakin A.K.
Experimental and Design Organization “GIDROPRESS”, Podolsk, Russia

Makhin V.M. – Chief Expert, Dr. Sci. (Tech.). Contacts: 21, Ordzhonikidze st., Podolsk, Moscow region, Russia, 142103. Tel.: +7 (496) 769-29-42; e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it..
Podshibyakin A.K. – Chief Expert for WWER, Cand. Sci. (Tech.).


Phenomena are considered with signs of “cliff edge effects” as per definitions of IAEA and NP-001-15: degradation of the protective barrier – fuel rod claddings in surface boiling mode with depositions of impurities and borates on their surface and heating – up of claddings as well as the mode with departure from nucleate boiling on the fuel rod cladding. In spite of the fact that the first phenomenon was previously unknown, safety of the Unit is ensured by decisions made in the project. The mode with DNB was studied and measures were taken in project of reactor plant not allowing DNB under normal operating conditions and anticipated operational occurrences. Protection against DNB is obviously ensured by decrease in the reactor power due to operation of control systems and scram. The phenomena do not take place until they reach the state of “cliff edge effects” (as per terminology of IAEA and federal RF NP) and they are prevented at the initial stages. The reactor self-protection against DNB development can be implemented for a small size reactor, which is partial washing out of fuel with insertion of negative reactivity with subsequent decrease in power and DNB termination.

reactor, safety, emergency protection, heat exchange crisis, fuel element cladding, threshold effect, dispersive fuel, negative reactivity

Article Text (PDF, in Russian)


UDC 621.039.58

Problems of Atomic Science and Technology. Series: Nuclear and Reactor Constants, 2022, issue 1, 1:2