RU2442235C2 - The method of localization of the active zones of channel-type nuclear reactors - Google Patents

Abstract

FIELD: nuclear physics.

SUBSTANCE: invention relates to the method of the immediate interference with emergency situations at the channel-type nuclear reactor units: LWGR - 1000, LWGR - 1500 and the foreign analogs; the method of localization of the active zones of channel-type nuclear reactors is that spherical granulas (diameter 0.5-2.0) of melted together saline mixture of Na₂B₄O₇ - 84% of the total mass, Са3(Р0₄)₂ - 16 % of the total mass is inducted into the damaged active zone of the reactor.

EFFECT: innovation allows to promptly and reliably localize the processes developing under emergency situations, radically reduce the dissipation of the oxide fuel containing uranium, plutonium, extinguish graphite, stabilize temperature, secure long-lasting power unit conservation.

1 cl

Description

The invention relates to measures that can be taken to eliminate the extremely dangerous consequences of accidents during the operation of channel type nuclear power reactors (RBMK - 1000, RBMK - 1500 and foreign analogues). It can be used for any damage, high temperatures and high levels of radioactivity of fuel assemblies (fuel assemblies), fuel elements (fuel elements), channels, graphite moderator and core control devices, as well as for stopping and preserving spent reactor units.

Known actions that were taken to eliminate the consequences of the accident at the fourth RBMK-1000 reactor block of the Chernobyl nuclear power plant, in particular to localize core damage, were unprepared, untimely, extended for a long period, ineffective and wasteful. Moreover, among these actions were those that exacerbated the situation. So, dumping lead, dolomite and sand onto a dilapidated reactor (“sealing”) led to even greater destruction of fuel assemblies and fuel elements, i.e. to additional environmental pollution by plutonium and fission radionuclides. In addition, dolomite and sand worsened heat removal conditions, thereby contributing to an increase in temperature in the core covered by them. None of these actions can serve as a prototype of the proposed method.

The present invention is directed to the fast and reliable localization of processes that develop during an accident and become uncontrollable due to depressurization of fuel assemblies, deformation of channels and controls.

The objective of the proposed method is a sharp limitation of the dispersion of oxide fuel containing uranium, plutonium, fission radionuclides and radioisotopes of secondary origin, termination of fission reactions of uranium and plutonium nuclei, quenching of graphite, temperature stabilization, ensuring long-term conservation of the block, eliminating environmental pollution by solid substances and their aerosols .

This goal is achieved by the fact that granules of fused salt mixture with a melting point of 400-700 ° C, wetting uranium oxides, other components of irradiated nuclear fuel, graphite, zirconium and stainless steels, as well as a large cross section for neutron capture by nuclei, are introduced into the damaged reactor core. one or more components of the salt mixture.

It is proposed to use the system as a salt mixture:

84 wt.% Na ₂ B ₄ O ₇ - 16 wt.% Ca ₃ (PO ₄ ) ₂ in the form of granules with a diameter of 0.5-2.0 mm

The properties of this system are well understood; it meets the requirements: it has a melting point of 475 ° C, it well moistens uranium dioxide, graphite, zirconium, stainless steels, and has a low vapor pressure over the melt in a wide temperature range. It contains boron, which intensively absorbs neutrons. The natural mixture of B ¹⁰ s B ¹¹ has a high thermal neutron capture cross section σ _a = 755 barn.

The amount of boron introduced with the salt mixture is more than enough to effectively terminate the fission reactions. A thin layer formed during melting of the salt mixture on solid surfaces prevents the dispersion of oxides and stops the burning of graphite. The thickness of the salt layer decreases with increasing temperature. This ensures self-regulation of the heat transfer intensity during temperature fluctuations and eliminates the need for artificial cooling of the emergency zone for the entire cooling period of the unit.

Immediate creation at a nuclear power plant with channel reactors of stocks of salt pellets of the proposed composition and devices for their injection, for example, a nitrogen stream into the accident site, will reliably localize possible damage and dramatically reduce the cost of decontamination of territories adjacent to the nuclear power plant.

Claims (1)

A method for localizing accidental destruction of the core of nuclear channel reactors, characterized in that spherical granules of fused salt mixture of 84 wt.% Na ₂ B ₄ O ₇ - 16 wt.% Ca ₃ (PO ₄ ) _{2 with a} diameter of 0, are introduced into the damaged core of the reactor. 5-2.0 mm.