[en] A safety device is claimed for a correct air flow in an enclosure in case of low pressure variations. This device is incorporated: to the air inlet adjusting the flow rate, increasing available room inside the glovebox

[en] For large ventilation networks, it is necessary to make a safety evaluation of their responses to perturbations such as blower failure, unexpected transfers, local pressurization. This evaluation is not easy to perform because of the many interrelationships between the different parts of the networks, interrelationships coming from the circulations of workers and matetials between cells and rooms and from the usefulness of air transfers through zones of different classifications. This evaluation is all the more necessary since new imperatives in energy savings push for minimizing the air flows, which tends to render the network more sensitive to perturbations. A program to evaluate safety has been developed by the Service de Protection Technique in cooperation with operators and designers of big nuclear facilities and the first applications presented here show the weak points of the installation studied from the safety view point

[en] The parameters of the ventilation flow rate, depression, arrangement of the premises, dimensioning of the equipment, energy sources are determined in order to reach the target fixed in the best technical and economic conditions throughout the whole life of the system

[en] The response of a ventilation network to disturbances either mechanical or thermal is difficult to evaluate when the network becomes complex as is the case in nuclear power plants and other nuclear facilities. Several teams from the CEA GROUP have joined together to elaborate a computation code able to simulate the behavior of any classical ventilation network. Such a code allows the study of a ventilation system in its design stage, pointing out safety problems and helping to solve them; the basis model generated in the design stage may be used to follow the operating life of the system, up to dismantling. The code, called PIAF, solves the set of equations which simulate a ventilation network in steady state: the numerical network is composed of nodes connected with various components. The unknowns of such a problem are pressure and temperature at the nodes and flow rates in the links. The problem induces a weakly nonlinear system, that PIAF solves by an iterative matricial newtonian method. PIAF has been validated in several facilities in France for various mechanical disturbances: some of those validation cases are considered