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Energy and Environment
Published in T.M. Aggarwal, Environmental Control in Thermal Power Plants, 2021
A nuclear reactor is only part of the life-cycle for nuclear power. The process starts with mining (see Uranium mining). Uranium mines are underground, open-pit, or in-situ leach mines. In any case, the uranium ore is extracted, usually converted into a stable and compact form such as yellowcake, and then transported to a processing facility. Here, the yellowcake is converted to uranium hexafluoride, which is then enriched using various techniques. At this point, the enriched uranium, containing more than the natural 0.7% U-235, is used to make rods of the proper composition and geometry for the particular reactor that the fuel is destined for. The fuel rods will spend about 3 operational cycles (typically 6 years total now) inside the reactor, generally until about 3% of their uranium has been fissioned, then they will be moved to a spent fuel pool where the short lived isotopes generated by fission can decay away. After about 5 years in a spent fuel pool the spent fuel is radioactively and thermally cool enough to handle, and it can be moved to dry storage casks or reprocessed.
Spent Fuel Management
Published in James H. Saling, Audeen W. Fentiman, Radioactive Waste Management, 2018
James H. Saling, Audeen W. Fentiman
Before bringing new fuel into the core, the depleted fuel assemblies must be removed using the fuel handling system, as shown in Figure 3.3. The manipulator crane is positioned over the fuel assembly, and the assembly is lifted by engaging the grippers from the crane’s hoist in the upper nozzle of the fuel assembly and moved from the core area to the area of the fuel transfer system (Figure 3.4) and reactor core control assemblies (RCCA) change fixture. If the fuel assembly contains a thimble plug or spider rod assembly, the insert may be removed in the RCCA change fixture before the fuel assembly is placed in the carriage of the conveyor. The carriage is then lowered from the vertical position to the horizontal one by an upender and is moved through the tunnel. On the other end (spent fuel pit side) of the tunnel, the carriage is raised again by another upender. The fuel assembly is then removed from the carriage by a long-handled spent fuel tool and placed in the storage rack of the spent fuel pool. The spent fuel pool is full of water, which serves as radiation shielding and coolant for spent assemblies. Burnable poison rod assemblies are also transferred to the spent fuel pool.
Nonrenewable Energy Resources
Published in Julie Kerr, Introduction to Energy and Climate, 2017
After use in the reactor, fuel assemblies become highly radioactive and must be removed and stored at the reactor under water in a spent fuel pool for several years. Even though the fission reaction has stopped, the spent fuel continues to give off heat from the decay of radioactive elements that were created when the uranium atoms were split apart. The water in the pool serves to both cool the fuel and block the release of radiation. From 1968 through June 2013, 241,468 fuel assemblies had been discharged and stored at 118 commercial nuclear reactors operating in the United States.
A Global Model for Predicting Vacuum Drying of Used Nuclear Fuel Assemblies
Published in Nuclear Technology, 2022
Sudipta Saha, Jamil Khan, Travis Knight, Tanvir Farouk
In the United States, nearly 2000 tons of used nuclear fuels are removed from reactors annually.1 After removal from a reactor, these nuclear fuels are placed in a spent fuel pool for at least 5 years to allow the remaining radioactivity and heat to decay. After the radioactivity and the decay heat dissipate to a certain level2,3 the fuel assemblies are removed from the holding pool and loaded into dry casks for long-time storage purpose.4 Before the storage casks are sealed off, it is a requirement that the water and moisture content in the system be reduced to a specific target to reduce the possibility of physical- and chemical-driven degradation (e.g., corrosion and degradation of the fuel rods, storage assembly).5 Molecular dissociation of sufficient residual water via radiolysis could contribute to reaching a flammable condition during any possible future opening of the casks.6,7 In addition, hydrogen will also lead to the formation of hydrides in the cladding, reducing its mechanical strength, where fuel rods are required to maintain their integrity should later retrieval become necessary.8–11
Surrogate modelling to enable structural assessment of collision between vertical concrete dry casks
Published in Structure and Infrastructure Engineering, 2019
Majid Ebad Sichani, Jamie E. Padgett
The response of radioactive waste containers in impact scenarios has been explored by various researchers. For example, McCreesh, Duvall, and Sievwright (1995) and Petkevich et al. (2014) used stress, strain, deformation and acceleration responses in the structural assessment of radioactive waste containers in drop tests. The existing literature on dry casks explores the structural response of two major cask types: transport casks and storage casks. A transport cask is loaded with the canister at the spent fuel pool location and is transported to the ISFSI site where it is unloaded, and the canister is inserted into a storage cask for interim storage.
Issues of Safety Assessment of New Russian NPP Projects in View of Current Requirements for the Probability of a Large Release
Published in Nuclear Technology, 2021
V. B. Morozov, A. E. Kiselev, A. A. Kiselev, K. S. Dolganov, D. Yu. Tomashchik, S. N. Krasnoperov
Potential fuel damage in the spent fuel pool occurs due to a combination of loss of heat removal in a closed circuit, a concurrent failed connection of an alternative heat removal system and other available means of water injection into the spent fuel pool, and the impossibility of restoring the equipment operability. According to the qualitative classification of the consequences, this accident belongs in the category of accidents with late fuel melting.