A wrapper tube for a fuel subassembly of a nuclear reactor core and method for protecting fuel against overheating in case of coolant boiling

Simple SummaryContent extracted from patent full text and abstract with AI.

This invention describes an improved design for the wrapper tube surrounding fuel rods in sodium-cooled fast nuclear reactors. By adding strategically placed openings in each wrapper tube, the system allows sodium coolant to bypass blockages caused by sodium vapor (boiling) during accidents. This prevents overheating and melting of the fuel by ensuring continuous coolant flow, even when vapor zones form, thus enhancing the reactor's safety during emergency conditions.

Use CasesContent extracted from patent full text and abstract with AI.

• Sodium-cooled fast nuclear reactors to enhance core safety
• Other nuclear reactor designs where coolant boiling can cause flow blockage and overheating
• Any heat-generating system (e.g., industrial heaters) requiring robust cooling in the event of coolant vaporization or blockage
• Research reactors or small modular reactors utilizing liquid metal coolants

BenefitsContent extracted from patent full text and abstract with AI.

• Improves nuclear reactor safety during coolant boiling accidents by maintaining coolant flow to the fuel rods
• Prevents the propagation of vapor blockages toward sensitive core regions, reducing risk of runaway reactions and damage
• Minimizes the likelihood of fuel rod cladding dryout and subsequent fuel melting
• Provides a passive, mechanical solution that does not require active monitoring or control
• Can be integrated into existing or future sodium-cooled fast reactor designs with minor modifications
• Helps localize and limit the effects of coolant boiling, making accident management easier

Technical Classifications (CPCs)

Inventors & Applicants

Patent Abstract

The present invention discloses an innovative design of the sodium-cooled fast reactor subassembly wrapper tube ( Figure 1(b) ) and a method for protecting the sodium-cooled fast reactor core against overheating and melting in case of the accidents accompanied by a sodium boiling. More generally, the invention is considered to be valuable in any field of technology where a heat generating fuel, heater or the like need to be cooled sufficiently to prevent the resources involved from damage caused by overheating and/or melting. The innovation of the wrapper tube design compared to the traditional wrapper tube design of a sodium-cooled fast reactor fuel subassembly ( Figure 1(a) ) consists in an introduction of openings (5). The openings are made in all faces of the wrapper tubes of all fuel subassemblies at the same axial location. The goal of the openings (5) is to provide the sodium flow bypath between the neighbouring subassemblies, in the case when the sodium vapour obstructs or fully blocks the liquid sodium flow at the top of the fuel subassembly (i.e. above the axial level of the openings). Due to this bypath, the sodium flow rate at the inlet of the subassembly, where the boiling occurs, does not significantly drop ( Figure 2(b) ). As a result, the sodium vapour does not propagate downwards to the core centre, where the void reactivity coefficient is positive, but rather in radial direction from one channel to another, being always kept in the region of low or even negative void reactivity coefficient. Moreover, the availability of the sodium flow rate through the subassembly, where boiling occurs, is beneficial for preventing the cladding dryout, because a part of sodium will flow through the boiling region in the form of a liquid film on the surface of the claddings.