PRELIMINARY POWER TRANSIENT ANALYSIS OF THE SUPER FR WITH AXIALLY HETEROGENEOUS CORE

The Super FR is one of the SuperCritical Water cooled Reactor (SCWR) concepts with once-through direct cycle plant system. Recently, new design concept of axially heterogeneous core has been proposed, which consists of multiple layers of MOX and blanket fuels. To clarify the safety performance during power transient, safety analyses have been conducted for uncontrolled control rod (CR) withdrawal and CR ejection at full power. RELAP/SCDAPSIM code was used for the safety analysis. The results show that the peak cladding surface temperature (PCST) is high in the upper MOX fuel layer. It is also shown that axial temperature gradient of cladding greatly increases in a short period. Suppressing such large temperature gradient may be a design issue for the axially heterogeneous core from the viewpoint of ensuring fuel integrity.

Study on slagging characteristics and prevention of biomass briquette

It is a high efficiency，energy-saving and emission reduction measure to replace coal with biomass briquette fuel in a layer combustion furnace, but in the combustion process, the serious slagging problem has been restricted the promotion of biomass fuel. By analyzing the combustion characteristics of biomass briquette, the ash fusion characteristics and slagging mechanism, combined with the combustion characteristics of a layer combustion furnace, the important influence of key combustion parameters (furnace temperature, excess air, fuel layer thickness) on the slagging in the furnace is obtained, which provides a scientific basis for taking measures to prevent and control the slagging in the design and operation of the biomass briquette layer combustion furnace.

Role of Horizontal Eddy Diffusivity within the Canopy on Fire Spread

Wind profile observations are used to estimate turbulent mixing in the atmospheric boundary layer from 1 m up to 300 m height in two locations of pine forests characteristic of the southeast US region, and to 30 m height at one location in the northeast. Basic turbulence characteristics of the boundary layers above and within the canopy were measured near prescribed fires for time periods spanning the burns. Together with theoretical models for the mean horizontal velocity and empirical relations between mean flow and variance, we derive the lateral diffusivity using Taylor’s frozen turbulence hypothesis in the thin surface-fuel layer. This parameter is used in a simple 1D model to predict the spread of surface fires in different wind conditions. Initial assessments of sensitivity of the fire spread rates to the lateral diffusivity are made. The lateral diffusivity with and without fire-induced wind is estimated and associated fire spread rates are explored. Our results support the conceptual framework that eddy dynamics in the fuel layer is set by larger eddies developed in the canopy layer aloft. The presence of fire modifies the wind, hence spread rate, depending on the fire intensity.

Role of horizontal eddy diffusivity within the canopy on fire spread

<p>Wind profile observations are used to estimate turbulent properties in the atmospheric boundary layer from 1 m up to 300 m height above north Florida pine woods. Basic turbulence characteristics of the lower boundary layer are presented. Together with theoretical models for the mean horizontal velocity we derive the lateral diffusivity using Taylor's frozen turbulence hypothesis in the surface fuel layer (tens of centimeters). This parameter is used to predict the spread of surface fires in a simple 1D model. Initial assessments of sensitivity of the fire spread rates to the lateral diffusivity are made. Estimated lateral diffusivity with and without fire are made and associated fire spread rates are explored. Our results support the conceptual framework that eddy dynamics in the fuel layer is set by larger eddies developed in the canopy layer aloft. The presence of fire modifies the eddy structure depending on the fire intensity.</p>

Long-term changes in masticated woody fuelbeds in northern California and southern Oregon, USA

Mechanical mastication is a fuels treatment that shreds midstorey trees and shrubs into a compacted woody fuel layer to abate fire hazards in fire-prone ecosystems. Increased surface fuel loading from mastication may, however, lead to undesirable fire intensity, long-duration flaming or smouldering, and undesirable residual tree mortality. Two major questions facing fuels managers are: how long do masticated fuels persist, and how does the composition of masticated fuelbeds change over time? To evaluate these changes, we measured 25 masticated sites with a range of vegetation, species masticated and time since treatment (1–16 years) in the western US. Seven of the 25 sites were sampled nearly a decade earlier, providing a unique opportunity to document fuelbed changes. Woody fuel loading ranged from 12.1 to 91.9Mg ha−1 across sites and was negatively related to time since treatment. At remeasured sites, woody fuel loads declined by 20%, with the greatest losses in 1- and 10-h woody fuels (69 and 33% reductions in mass respectively). Reductions were due to declines in number of particles and reduced specific gravity. Mastication treatments that generate greater proportions of smaller-diameter fuels may result in faster decomposition and potentially be more effective at mitigating fire hazard.

Fire-extinguishing efficiency and environmental performance of foam for extinguishing a warehouse space with oil

This article analyzes the fire extinguishing efficiency of hydrocarbon and fluorinated film-forming foaming agent. It was revealed that fluorinated blowing agents have a number of significant advantages over hydrocarbon. The main ones are: ensuring inertness when feeding from foam of various heights and distances, long-term prevention of reignition, extinguished petroleum product, the possibility of extinguishing hydrocarbon flames by supplying foam to the base of the tank, directly into the fuel layer.

Fire extinguishing efficiency of hydrocarbon and fluorinated film-forming foaming agent

This article analyzes the fire extinguishing efficiency of hydrocarbon and fluorinated film-forming foaming agent. It was revealed that fluorinated blowing agents have a number of significant advantages over hydrocarbon. The main ones are: ensuring inertness when feeding from foam of various heights and distances, long-term prevention of reignition, extinguished petroleum product, the possibility of extinguishing hydrocarbon flames by supplying foam to the base of the tank, directly into the fuel layer