The Risø Mesoscale PUFF model (RIMPUFF) predicts dispersion of released hazardous material and plays an important role in the emergency response system of many Chinese nuclear power plants (NPPs). The wind field over the calculation domain is a critical input of RIMPUFF, which dominates the performance of RIMPUFF. Due to the complex topography of most Chinese NPP sites, it remains challenging to provide a refined wind field for RIMPUFF prediction. To solve the problem, California Meteorological Model (CALMET) is coupled with RIMPUFF for wind field calculation in this study. Moreover, the computing scope and capability of RIMPUFF are enhanced in order to obtain more accurate prediction for the emergency response and source term inversion in nuclear accidents. Except for that the unlimited amount of grid with higher resolution is supported, a new sampling module is added to RIMPUFF for predicting the concentration of radioactive materials and dose at number-unbound arbitrary location. To verify the CALMET-RIMPUFF method, a wind tunnel experiment that replicates the topography of one Chinese NPP site within 10 km-range, is conducted. In the experiment scenario, the speed and vertical profile of the incoming flow is carefully set according to the annual mean wind speed and wind profile data measured in recent years on the meteorological tower of this NPP. The results demonstrate that the wind field calculated by CALMET is consistent with the topography. With this wind field, the RIMPUFF-predicted concentration distribution matches the measurements well both qualitatively and quantitatively. Moreover, the calculation of U.S. Environmental Protection Agency (EPA) statistical evaluation metrics indicate that the random scatter is within a factor of 1.8 and the FAC2 is nearly 80%. It proves the acceptability of CALMET-RIMPUFF over the complex topography of Chinese NPP sites.

The Nuclear Power Plants (NPPs) have been built on the concept of Defense in depth. The severe accident causes the failure of fission product barriers and let the fission products to escape into environment. The containment is the last barrier to the fission products. Thus, the containment is installed with engineering safety features (ESFs) i.e. spray system, heat removal system, recirculation filtration system; containment filtered venting system (CFVS), and containment exhaust filtration system. In this work, kinetic study of the containment retention factor (CRF) has been carried out for a large dry PWR containment considering 1000 MWe PWR. The computational modeling and simulation have been carried out by developing a kinetic code in MATLAB, which uses the fractions of activity airborne into the containment after the accident. The Kinetic dependency of CRF on containment filtration systems, spray system with caustic and boric acid spray has been carried out. For noble gases, iodine and aerosols, the CRF increases with the increase in exhaust rate. While, CRF for iodine first increases then start reducing with containment spray flow rate. The Kinetic dependency of CRF has also been studied for boric and caustic spray.

Sodium-water reaction (SWR) is a design basis accident of a Sodium Fast Reactor (SFR). A breach of the heat transfer tube in a steam generator (SG) results in contact of liquid sodium with water. Typical phenomenon is that the pressurized water blows off, vaporizes and mixes with the liquid sodium. The consequence of the accident are: thermal-hydraulic and chemical impact on the heat transport equipment and structure induced by the heat of exothermic reaction and caustic reaction product. The purpose of the present paper is to delineate the mechanism and process of the SWR by a counter-flow diffusion flame experiment and a numerical simulation. Based on the numerical simulation, the most appropriate and optimum condition in which stable and continuous diffusion flame of sodium and water vapor is obtained. Key idea is to perform the experiment in a depressurized reaction vessel. According to the experiment, spatial distributions of chemical reactants and products, temperature and particles are measured in detail. The characteristics of the SWR are explained from the present study and the chemical reaction model currently used in the analytical tool of the SWR is appropriate.

Los Alamos National Laboratory currently possesses between 500 and 800 fiberglass-reinforced plywood crates that contain hazardous materials that need to be decontaminated. To access the hazardous material, a system is needed to dismantle the crate. Currently, crates are dismantled by workers using hand-held tools. This technique has numerous disadvantages. One disadvantage is that it is difficult for a worker to hold the tool for an extended period of time in the awkward angles and positions necessary to fully size-reduce the crate. Other disadvantages of using hand tools include managing power cords and vacuum hoses, which become entangled or can act as tripping hazards. In order to improve the crate opening and size-reduction task, Florida International University’s Hemispheric Center for Environmental Technology (HCET) is developing a manually operated crate dismantlement system. This versatile system is expected to greatly increase worker efficiency while decreasing fatigue and the possibility of accidents.

While long-term monitoring and stewardship means many things to many people, DOE has defined it as: “The physical controls, institutions, information, and other mechanisms needed to ensure protection of people and the environment at sites where DOE has completed or plans to complete cleanup (e.g., landfill closures, remedial actions, and facility stabilization).” Across the United States, there are thousands of contaminated sites with multiple contaminants released from multiple sources where contaminants have transported and commingled. The U.S. government and U.S. industry are responsible for most of the contamination and are landowners of many of these contaminated properties. These sites must be surveyed periodically for various criteria including structural deterioration, water intrusion, integrity of storage containers, atmospheric conditions, and hazardous substance release. The surveys, however, are intrusive, time-consuming, and expensive and expose survey personnel to radioactive contamination. In long-term monitoring, there’s a need for an automated system that will gather and report data from sensors without costly human labor. In most cases, a SCADA (Supervisory Control and Data Acquisition) unit is used to collect and report data from a remote location. A SCADA unit consists of an embedded computer with data acquisition capabilities. The unit can be configured with various sensors placed in different areas of the site to be monitored. A system of this type is static, i.e., the sensors, once placed, cannot be moved to other locations within the site. For those applications where the number of sampling locations would require too many sensors, or where exact location of future problems is unknown, a mobile sensing platform is an ideal solution. In many facilities that undergo regular inspections, the number of video cameras and air monitors required to eliminate the need for human inspections is very large and far too costly. HCET’s remote harsh-environment surveyor (RHES) is a robotic platform with SCADA capabilities equipped with a sonar-imaging scanner, a high-resolution color CCD camera, and various combinations of sensors. The RHES is controlled remotely via a PC. This paper will discuss the development and application of this system.

Although nuclear power appears to be expanding as a major global energy source, the disposal of radioactive waste from the nuclear fuel cycle still poses formidable challenges to the full expansion of the nuclear enterprise. The perception that nuclear wastes represent unique and insoluble threats to humans is ill founded. The risk from these radioactive materials is comparable and many ways less severe than other more familiar hazardous materials that are ubiquitous in the biosphere. Radioactive materials decay and reduce in time unlike stable elements. Besides the reduction of radioactive materials through decay, the dilution and dispersion of all hazardous materials by natural forces and events provides the reduction required to make adequate and safe disposal of nuclear waste possible. The ultimate sink for essentially all of these hazardous wastes will prove to be the oceans with their great capacity of dilution and containment.