[Nuclear Systems Volume 1 Solutions Zip
Tilo Chopin
The decontamination of Tritium (T) is particularly problematic: it is a special form of hydrogen that creates tritiated water (HTO vs. H2O), which does not lend itself to removal by conventional technologies.
Tritium is routinely released into the environment by commercial nuclear power plants. Until now, no technology existed to remove low levels of tritium contamination economically. We are changing the paradigm by blending complex innovation and simple economics.
The MDS is a Tritium management tool for processing large volumes of light water across a range of concentrations. This technology is based on the working principle of combined electrolysis catalytic exchange (CECE) and releases only clean oxygen and hydrogen with no liquid effluent. The technology builds on proven heavy water solutions, and although developed with a focus on light water, it can also be adapted for use in heavy water detritiation.
The system is designed to reduce the volume of tritiated water which allows for reuse and recycling of Tritium instead of its release into the environment. This process takes diluted tritium and concentrates it so it can be recycled or reused while reducing the amount of Tritium released to the environment.
The chemical water purification process uses ion exchange columns to remove ionic contaminants from water by absorbing the containments onto ion-exchange resin. Through a mixture of cation and anion-type resins, fluids are purified. The resins remove metal ions, organic acids, organic bases and biomolecules and can act as a deep bed filter. We also provide off-the-shelf columns for different ion exchange media, offering fully customizable solutions.
The Westinghouse reverse osmosis (RO) system can be used to concentrate liquid waste to reduce its volume or purify a liquid stream to reduce contaminants. The RO system can operate at high pressures to concentrate spent advanced scale conditioning agent (ASCA) solvents and rinse waters, or at lower pressures to remove silica from borated water.
On its first project, the RO system reduced the waste volume inventory after an ASCA process application from 80,000 gallons of spent solvent and 80,000 gallons of rinse water to less than 15,000 gallons of concentrate which was shipped to a waste facility for disposal.
Westinghouse has a two-phased approach to combat biological fouling in cooling systems. The first phase uses an oxidation step that kills the majority of the organisms responsible for the bio-fouling. The second phase uses chelating agents in a reducing environment to decompose and remove typical cooling water scales comprised of inorganic metal oxides and cemented fouling detritus. An added benefit is decomposition of a large fraction of the protective biomass that permits unimpeded solvent access to the metallic corrosion products beneath.
The transfer of fuel from the reactor to the spent fuel pool (SFP) is delayed until the decay heat reaches
a point where the SFP cooling can handle the heat produced. To eliminate lost time and cost, Westinghouse developed a comprehensive program tailored to minimize reliance on plant systems for decay heat removal.
This unique system consists of portable equipment skids that are designed to be installed quickly and easily in convenient locations. The modular design of the pumps, filters and heat exchangers permits safe and reliable operation with redundant capability.
Chemical decontamination is used to support the as- low-as-reasonably-achievable (ALARA) principle by general dose reduction. Any size system, from full reactor plant to small waste tanks and drain lines (hot spots), can be decontaminated.
We can perform chemical decontaminations for operating nuclear plants, plants planning for decommissioning and decommissioned plants. Chemical decontaminations are proven to more than offset cost by reducing all of the following: dose to workers, waste classification of removed components, transport and burial costs, and the administrative burden of managing higher dose exposures.
Along with our portfolio of field services, the Richland Service Center facility can be used for a variety of fabrication projects, chemical mixing, maintenance, repair of hot equipment and laboratory testing. The facility includes the following:
All Richland Service Center equipment is stored field ready and is designed for expedited mobilization. The equipment is skid mounted and modular to reduce the amount of time required for setup on-site. Engineers and technicians who fabricate and maintain the equipment also are trained and experienced in operating it in all field applications. Lessons learned from operating experience are quickly incorporated into equipment modifications or new system fabrication to address safety and ALARA concerns. Most skids also contain automated controls to further reduce operator exposure. Our equipment has the following advantages:
For the various nuclear sites in the United States and abroad operated by government entities, our services can be implemented as part of a strategy to overcome past, current and future nuclear and environmental challenges. Our experience includes:
The need to eliminate site specific hot spots and treat small components cost effectively is an issue. This is due to effluent treatment containing contamination from utility operating processes or complex radionuclides from legacy decommissioning, which share similar challenges in addressing activation levels.
The addition of the Mini System Decontamination system allows Westinghouse to address challenges with elevated radiation levels in a cost-effective way. The MSD equipment is designed for use on small problem areas such as sample sinks and sample lines, drain lines and vent lines with volumes up to 50 gallons.
The entire system is designed and constructed to fit on a single, moveable cart. It fits into a standard elevator and is easy to move, set up and demobilize. The system is shipped in one small container and set up and operated by an engineer and technician. The system can be operated on a single shift or the engineer and technician can split responsibilities to allow for continuous 24-hour operations, as needed. An individual plant system can normally be decontaminated in about one day, allowing for several systems to be cleaned in a week.
The skid may be operated in a recirculation or a once-through (flush) mode depending on the plant system and cleaning requirements. This allows for multiple location and type applications within a single design.
From one of our most recent operations utilizing the MSD, Westinghouse performed a chemical decontamination on portions of a sample line system including the delay coil. The utilities desire was to see a >10 Decontamination Factor (DF). The average results were:
For used fuel designated as high-level radioactive waste (HLW), the first step is storage to allow decay of radioactivity and heat, making handling much safer. Storage of used fuel may be in ponds or dry casks, either at reactor sites or centrally. Beyond storage, many options have been investigated which seek to provide publicly acceptable, safe, and environmentally sound solutions to the final management of radioactive waste. The most widely favoured solution is deep geological disposal. The focus is on how and where to construct such facilities.
Used fuel that is not intended for direct disposal may instead be reprocessed in order to recycle the uranium and plutonium it contains. Some separated liquid HLW arises during reprocessing; this is vitrified in glass and stored pending final disposal.
Some countries are at the preliminary stages of their consideration of disposal for ILW and HLW, whilst others, in particular Finland, have made good progress. Finland's Onkalo repository is expected to start operating in 2024. It will be the first deep geological repository licenced for the disposal of used fuel from civil reactors.
The following table sets out the commonly accepted disposal options. When considering these, it should be noted that the suitability of an option or idea is dependent on the wasteform, volume, and radioactivity of the waste. As such, waste management options and ideas described in this section are not all applicable to different types of waste.
These facilities will be affected by long-term climate changes (such as glaciation) and this effect must be taken into account when considering safety, as such changes could disrupt these facilities. This type of facility is therefore typically used for LLW and short-lived ILW with half-lives of up to 30 years.
The long timescales over which some waste remains radioactive has led to the idea of deep disposal in underground repositories in stable geological formations. Isolation is provided by a combination of engineered and natural barriers (rock, salt, clay) and no obligation to actively maintain the facility is passed on to future generations. This is often termed a 'multi-barrier' concept, with the waste packaging, the engineered repository, and the geology all providing barriers to prevent the radionuclides from reaching humans and the environment. In addition, deep groundwater is generally devoid of oxygen, minimising the possibility of chemical mobilization of waste.
Deep geological disposal is the preferred option for nuclear waste management in most countries, including Argentina, Australia, Belgium, Canada, Czech Republic, Finland, France, Japan, the Netherlands, Republic of Korea, Russia, Spain, Sweden, Switzerland, the UK, and the USA. Hence, there is much information available on different disposal concepts; a few examples are given here. The only purpose-built deep geological repository that is currently licensed for disposal of nuclear material is the Waste Isolation Pilot Plant (WIPP) in the USA, but it does not have a licence for disposal of used fuel or HLW. Plans for disposal of spent fuel are particularly well advanced in Finland, as well as Sweden, France, and the USA, though in the USA there have been political delays. In Canada and the UK, deep disposal has been selected and the site selection processes have commenced.
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