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[en] The use of flammable gas and high voltage in detector systems is common in most experiments at Fermilab. To ''mitigate the hazards associated with these systems'' Fermilab Engineering Standard SD-45B was adopted. As part of their mission the Research Facilities Department and the Site Operations Department have assisted the fixed target experiments in satisfying some of the requirements of SD-45B. This note describes the devices that are available to experiments that will satisfy points of SD-45B. This note is meant to be used as a guide and not a mandatory standard, each experiment is reviewed for compliance with SD-45B by the flammable gas safety subcommittee. This note describes a generic system that should fit the majority of class 1, 2 and low pressure class 3 systems (less than 15 psi)
[en] For the first time, information on the surface relief of undoped GaS and doped GaS:Yb single crystals subjected to gamma irradiation was obtained using atomic force microscopy (AFM). It was found that GaS is characterized by a non-uniform distribution of irregularities with different heights and periodicities, and when doping crystals with Yb atoms, the distribution of irregularities becomes more orderly, the height and periodicity of irregularities decreases. Irradiation with gamma-quanta of GaS at doses of Φγ 140 krad and doping with Yb atoms lead to rearrangement of defects, resulting in a decrease in a single free volume of irregularities, and in doses above Φγ > 140 krad increase single crystals are the most radiation-resistant.
[en] The proactive maintenance of the spring-loaded-self-actuated Pressurizer Safety Valve (PSV) has caused frequent concerns pertaining the spring self actuated reliability due to set point drift, spurious openings, and seat leakage. The exhaustive testing performed on a Crosby PSV model 6M6 has revealed that the principal cause of these malfunctions is the spring compression elastic instability during service. The spring lateral deformations measurements performed validated the analytical shapes for spring compression: symmetrical bending - for coaxial supported ends - restraining any support displacement, and asymmetrical bending induced by the potential misalignment of the supported top end. The source of the spring compression instability appears on the tested Crosby PSV induced by the top end lateral displacement during long term operation. The testing with restrained displacement at the spring top has shown consistent set-point reproducibility, less than +/- 1 per cent. To eliminate the asymmetrical spring buckling, a design review of the PSV is proposed including the guided fixture at the top and the decrease of spring coil slenderness ratio H/D, corresponding to the general analytical elastic stability for the asymmetrical compression. (authors)
[en] Highlights: • Study of the dynamic characteristics of a pressure relief valve. • Transient CFD simulations using the mesh deformation technique. • Key internal structural parameters of the valve during valve opening. • Experimental results are verified by CFD simulation. • Analysis of the reason for delayed opening of a pressure relief valve. - Abstract: The opening characteristics of a 3-D power operated pressure relief valve were studied experimentally and numerically. The experimental results were used to study the mechanism controlling the valve opening time. The CFD simulations used the trimmed volume mesh deformation technique to study the full transient opening dynamic characteristics of the valve. The pressure and velocity fields were obtained including the small scale flow features. The CFD results were used to analyze the upper surface average pressure, surface velocity, resultant force and displacement of the disc during opening. The inlet and outlet mass flow of the valve was in a stable state when the valve opening time was 1.43 s. Moreover, the influence of the size structural parameters on the valve opening time was studied. The simulation results compare well with test data including the shock wave during the valve opening. The results show that the geometric factors affecting the valve opening time can be modified to reduce the valve opening time. It shows that the area of the region between the relief hole (orifice D) connected to the solenoid valve and the vertical tube has the greatest influence on the valve opening time. Due to the upward movement and misalignment of the disc, the valve opening time is delayed during the operation of pressure relief valves. The conclusions of this paper provide guidance for the optimal design of safety valves.
[en] Fitting the SEBIM Pilot-Operated Safety-Relief-Valve in a tandem arrangement is a well established way of upgrading PWR pressurizer safety valves. An improved version of the SEBIM system, called the ''hot solution'', has now been developed. Its main features are outlined. (Author)