IDENTIFICATION OF ELECTROREFINER AND CATHODE PROCESSING FAILURE MODES AND DETERMINATION OF SIGNATURE-SIGNIFICANCE FOR INTEGRATION INTO A SIGNATURE BASED SAFEGUARDS FRAMEWORK FOR PYROPROCESSING

The traditional method of safeguarding nuclear facilities, nuclear material accountancy (NMA), faces many challenges when applied to pyroprocessing facilities. To aid in the safeguarding of these facilities, process monitoring (PM) is being investigated as a complementary method to NMA. PM takes general process data, such as density, current etc., and applies it to safeguards through the use of a statistical framework. Signature Based Safeguards (SBS), a proposed statistical framework for the application of PM techniques, identifies anomalous scenarios and subsequently identifies and detects their respective PM signatures from a system of sensors. This work focuses both on assisting SBS through identifying anomalous scenarios, and on the computer modeling of these failure modes and the PM signatures for them. The anomalous scenarios investigated were mechanical failure modes with potential safeguards-significance as they could lead to the deposition of plutonium and other actinides in the final uranium product ingot. The signatures of these anomalous scenarios were primarily radiation signatures from a coincidence counter that is used to analyze the final ingots. Several different failure modes were identified for both the electrorefiner and the cathode processor. The signatures for these failure modes were then determined by coupling two separate computer models. The first model is a FORTRAN-based electrorefiner code named ERAD capable of modeling the mass transport of metals within an electrorefiner. The second model was an MCNP-based simulation of the Canberra JCC-31 High Level Neutron Coincidence Counter. First, the identified failure modes were simulated by changing ERAD inputs. ERAD calculated an elemental mass composition at the cathode which was then used as the final ingot composition. The final ingot composition was analyzed for single and double neutron coincidence count rates using the MCNP model. The results demonstrate significant radiation signatures for the presence of plutonium as a result of the electrorefiner failure modes. Signatures from cathode processor failure modes were weak and thus warrant future investigation of better detectors for integration into a SBS framework

Candidate Measurement Technique Application as a Method for Materials Accountancy in Electrochemical Reprocessing

Electrochemical reprocessing is a promising method to recover useful fissile material from spent nuclear fuel. Due to the recent attention surrounding electrochemical reprocessing as a complement or alternative to aqueous methods, necessary safeguards must be developed. However, the process requires high temperatures and an inert atmosphere thus complicating the prospect of making material accountancy measurements. Thus, to be deployed commercially, viable material accountancy and process monitoring methods must be designed and tested to meet safeguard standards. This work focuses on gamma spectroscopy and total neutron counting methods, which have previously been applied to aqueous reprocessing. These signatures are simulated in a previously developed flowsheet model. By tracking the isotopic mass concentrations at a given time and location, proper emission rates can be calculated that yield accurate representations of the material. Furthermore, notional diversion scenarios were simulated to evaluate the sensitivity of the measurement simulations to slight changes in material mass. Confirmatory measurements at key locations allowed for identification and differentiation of normal and off-normal operating conditions

Emission control in rotary kiln limestone calcination using Petri net models

Indiana University-Purdue University Indianapolis (IUPUI)The idea of emission control is not new. Different industries have been putting in a lot of effort to limit the harmful emissions and support the environment. Keeping our earth green and safe for upcoming generations is our responsibility. Many cement plants have been shut down in recent years on account of high emissions. Controlling SO2, NOx and CO emissions using the Petri net models is an effort towards the clean production of cement. Petri nets do not just give a pictorial representation of emission control, but also help in designing a controller. A controlled Petri net can be potentially implemented to control the process parameters. In Chapter 2, we discuss the Petri nets in detail. In Chapter 3, we explain the modeling of emissions using the Petri nets. A controlled emission model is given in Chapter 4. A general Petri net model is considered to design the controller, which can be easily modified depending on the specific requirements and type of kiln in consideration. The future work given at the end is the work in progress and a neural network model will likely be integrated with the Petri net model

Developing Software Tools to Characterize Electrochemical Loss Scenarios via Gamma Detection for Various Measurement Points, Source Geometries, and Process Times

Faithful modeling of the expected gamma signals inside an electrochemical facility at various key measurement points is important for understanding what detection limits are available for the next generation of safeguards technologies. Gamma Detector Response and Analysis Software (GADRAS) and the Separation Safeguards Performance Model (SSPM) were used to build software tools for predicting the difference in radiation signatures between normal plant use and plutonium diversion scenarios, for various operational configurations. These tools allow for automated analysis of the large data sets generated by the SSPM, producing tables and charts for both total gamma counts over time, and channel-by-channel gamma spectrum analysis for specified time-slices. Preliminary application of this analysis suite shows a 99% confidence in detecting a 0.2 SQ protracted electrorefiner diversion over the course of one year, and a 99% confidence in detecting a 1.4 SQ protracted transuranic diversion over the course of one year

Global Nuclear Energy Partnership Technology Development Plan

This plan describes the GNEP Technology Demonstration Program (GNEP-TDP). It has been prepared to guide the development of integrated plans and budgets for realizing the domestic portion of the GNEP vision as well as providing the basis for developing international cooperation. Beginning with the GNEP overall goals, it describes the basic technical objectives for each element of the program, summarizes the technology status and identifies the areas of greatest technical risk. On this basis a proposed technology demonstration program is described that can deliver the required information for a Secretarial decision in the summer of 2008 and support construction of facilities

Development of a novel electrochemical pyroprocessing methodology for spent nuclear fuels

Nuclear power remains the most dense and reliable primary form of energy supply worldwide. Electricity generation via fission is also inherently carbon free, with environmental footprints rivalling modern renewable options. However issues arise from the production of highly irradiated spent fuels, with current management options limited to geological repository storage or, more desirably, closing of the fuel cycle by partitioning to recover fissionable species. Extensive research has been pursued over the past half century in an effort to address an accumulating oxide spent fuel inventory and to circumvent shortcomings of raw uranium supplies. Pyrochemical reprocessing or ‘pyroprocessing’ using molten salt electrolysis for the recovery of desirable spent fuel components is an increasingly sought after solution to the above issues. First developed in the late 1990’s, the FFC Cambridge Process has shown to be a cornerstone in the electrochemical reduction of metal oxides and potentially offers a new iteration of pyroprocessing by introducing a direct conversion of spent oxide fuels to metals. These metals are easier to reprocess and specifically recovered elements can be used directly in advanced civilian nuclear reactors and metallic fuel cycles. This thesis considers the role that an FFC based process could play in establishing a more sustainable, efficient and safer method for the select recovery of key metals from mixed oxide composites. Using an array of surrogate materials, the appropriation of an effective procedure was investigated in both CaCl2 and LiCl-CaCl2 Eutectic (LCE) molten salts at 810oC and 600oC respectively. At all stages of the process, feeds and electrolysis products have been examined by an assortment of ex-situ analytical tools, primarily SEM, EDS and XRD. A process engineering approach was taken to designing suitable reactors and cells with the aim of improving operational characteristics, greater electrochemical reduction efficiency and high yields of pure products. Preparation of electrolyte and feed oxide electrodes (surrogate or spent fuel) was investigated, including unique electrochemical treatment for the two molten salts and precedent for the creation of the oxide electrode via cold pressing or slip casting to kinetically aid optimal reduction. A series of investigations considering the thermodynamic performance of CaCl2 from a standpoint of electronic conduction were carried out, and considerable improvements found via the implementation of a simple cathodic sheath. Selective partitioning was shown possible by the intended mechanism of partial direct reduction and anodic dissolution in the 2NiO-CeO2 binary. Partitioning of Zr from ZrO2-CeO2, and Ti from TiO2-CeO2 was also achieved, however in both cases it was via the gradual chemical dissolution of partially reduced Ce(III) into the molten salt or phase separation between liquid Ce and solid Zr. Extensive CV experiments were performed to enhance understanding of redox chemistry for each species investigated. CeOCl was found to be the only semi-stable phase of Ce present at potentials between -1.0 V vs. Ag/AgCl and its final reduction potential at approximately -1.95 V in CaCl2 at 810oC. Active CV experiments using PuO2 and a MOX fuel sample containing 5% PuO2 were initiated, revealing remarkably similar electrochemical behaviour of PuO2 and the CeO2 surrogate. Both PuO2 and the bulk UO2 content MOX could be reduced in CaCl2 and in the lower temperature LCE whilst avoiding any decomposition of the electrolyte. Consequently a route for the direct electrochemical reduction of spent oxides fuels was shown plausible and offers a promising alternative to current pyroprocessing technology, with beneficial implications to the wider materials processing field