Evaluation of CANDU Spent Nuclear Fuel Bundle Structural Integrity During Normal Transport Conditions

2003 ◽  
Author(s):  
Greg Morandin ◽  
Eric Araujo ◽  
David J. Ribbans
Keyword(s):  
Plastic Deformation ◽  
Nuclear Fuel ◽  
Dynamic Load ◽  
Spent Nuclear Fuel ◽  
Spent Fuel ◽  
Shell Elements ◽  
Fuel Bundle ◽  
End Caps ◽  
The Impact ◽  
Transport Tube

The International Atomic Energy Agency requires that the transport of spent nuclear fuel in containers be able to handle certain loads in the axial, lateral and vertical direction under normal off-site handling scenarios. During transport, CANDU nuclear fuel bundles may experience axial impact loads due to possible sliding within a transport tube resulting in impact with the container wall. This paper presents a series of postulated fuel bundle impact scenarios in order to determine the enveloping dynamic g load that a bundle can experience before possible plastic deformation to the bundle fuel sheath. The IAEA load factors for envelope design are used as a reference to ramp the impact velocities and are not equivalent to the dynamic loads used in the analysis. Based on the transportation induced g loads outlined in the IAEA regulations for safe transport of spent fuel under normal handling conditions (IAEA 1985), these g loads are used to calculate a terminal velocity for the bundle whose motion impacts a rigid plate. One type of CANDU nuclear fuel bundle consists of 28 Zircaloy-4 fuel pencils loaded with Uranium Dioxide fuel pellets. The ends of the pencils are fitted with end caps and each end cap is spot welded to a Zircaloy-4 end plate at either end. The finite element model of the fuel bundle consists of 4-noded shell elements representing the fuel sheaths and end plates and 8-noded continuum elements representing the Uranium Dioxide pellets. For the purpose of the analysis, the fuel bundle is housed inside a transport tube, which limits the bundle lateral and vertical motion during impact rebound. The impact target is conservatively modelled as an infinitely rigid plate. Contact surfaces are modelled between the fuel bundle and transport tube, between the fuel bundle and impact plate and between each individual fuel pencil. Two bundle scenarios are considered. The first is a single fuel bundle impacting the plate and the second is two fuel bundles in series in a single transport tube impacting the plate. The second scenario considers the interaction between the two bundles during initial impact and rebound. The analysis covers these scenarios under various magnitudes of applied dynamic loading including 2g, 5g, and 8g. The objective is to determine at what applied load the fuel bundle will experience plastic damage to the fuel pencil sheath. This will effectively provide a bounding g load for CANDU spent fuel transport. The results of the analysis show that for a single bundle in a transport tube, a dynamic load of 8g results in plastic deformation of and the target are modeled using 4-noded shell elements. The pencil end caps are attached to the endplates using an area of common nodes (Fig. 3). Although the actual endcap to endplate connection is through a round spot-welded cross section, for modeling ease the interface is several fuel pencil sheaths. For the two-bundle case, a dynamic load of 8g does not result in any plastic deformation in the fuel pencil sheaths. Thus, a limiting dynamic load between 5g and 8g is determined for the fuel handling scenarios. This paper presents the methodology and models used in the analysis as well as the results of the simulations.

Analysis of the Impact of a Tunnel Fire Environment on a Spent Nuclear Fuel Transportation Cask

2003 ◽  
Author(s):  
Christopher S. Bajwa
Keyword(s):  
Pacific Northwest ◽  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
Thermal Conditions ◽  
Nuclear Regulatory Commission ◽  
Radioactive Material ◽  
Spent Fuel ◽  
Tunnel Fire ◽  
Accident Conditions ◽  
The Impact

On July 18, 2001, a train carrying hazardous materials derailed and caught fire in the Howard Street railroad tunnel in Baltimore, Maryland. Due to this accident, questions were raised about the performance of spent nuclear fuel transportation casks under severe fire conditions, similar to those experienced in the Baltimore tunnel fire. The U.S. Nuclear Regulatory Commission (NRC) evaluates the performance of spent fuel transportation casks under accident conditions. Title 10 of the Code of Federal Regulations Part 71 section 73(c)(4), (10 CFR 71.73(c)(4)) requires that transportation packages used to ship radioactive material must be designed to resist an engulfing fire of a 30 minute duration and prevent release of radioactive material to the environment. The staff of the NRC, in cooperation with the National Transportation Safety Board, the National Institute of Standards and Technology, Pacific Northwest National Labs and the Center for Nuclear Waste Regulatory Analysis, have undertaken an analysis to determine the thermal conditions present in the Howard Street tunnel fire, as well as analyze the effects that such a fire would have on a spent fuel transportation cask. This paper describes the analytic models used in the assessment and presents a discussion of the results.

Scenarios for the Transmutation of Actinides in CANDU Reactors

2010 ◽  
Author(s):  
Bronwyn Hyland ◽  
Brian Gihm
Keyword(s):  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
Spent Fuel ◽  
Candu Reactors ◽  
Used Nuclear Fuel ◽  
Decay Heat ◽  
Fuel Bundle ◽  
Loading Ratio ◽  
Heat Period ◽  
Actinide Transmutation

With world stockpiles of used nuclear fuel increasing, the need to address the long-term utilization of this resource is being studied. Many of the transuranic (TRU) actinides in nuclear spent fuel produce decay heat for long durations, resulting in significant nuclear waste management challenges. These actinides can be transmuted to shorter-lived isotopes to reduce the decay heat period or consumed as fuel in a CANDU® reactor. Many of the design features of the CANDU reactor make it uniquely adaptable to actinide transmutation. The small, simple fuel bundle simplifies the fabrication and handling of active fuels. Online refuelling allows precise management of core reactivity and separate insertion of the actinides and fuel bundles into the core. The high neutron economy of the CANDU reactor results in high TRU destruction to fissile-loading ratio. This paper provides a summary of actinide transmutation schemes that have been studied in CANDU reactors at AECL, including the works performed in the past [1–4]. The schemes studied include homogeneous scenarios in which actinides are uniformly distributed in all fuel bundles in the reactor, as well as heterogeneous scenarios in which dedicated channels in the reactor are loaded with actinide targets and the rest of the reactor is loaded with fuel. The transmutation schemes that are presented reflect several different partitioning schemes. Separation of americium, often with curium, from the other actinides enables targeted destruction of americium, which is a main contributor to the decay heat 100 to 1000 years after discharge from the reactor. Another scheme is group-extracted transuranic elements, in which all of the transuranic elements, plutonium (Pu), neptunium (Np), americium (Am), and curium (Cm) are extracted together and then transmuted. This paper also addresses ways of utilizing the recycled uranium, another stream from the separation of spent nuclear fuel, in order to drive the transmutation of other actinides.

The Impact of Alpha-Radiolysis on the Release of Radionuclides from Spent Fuel in a Geologic Repository

1983 ◽  
Vol 26 ◽  
Author(s):  
Ivars Neretnieks
Keyword(s):  
Nuclear Fuel ◽  
Uranium Oxide ◽  
Spent Nuclear Fuel ◽  
Crystalline Rock ◽  
Reducing Agents ◽  
Spent Fuel ◽  
Geologic Repository ◽  
Oxidizing Agents ◽  
Dissolved Iron ◽  
The Impact

ABSTRACTSpent nuclear fuel buried in deep geologic repositories may eventually be wetted by water. The alfa-radiation will radiolyse the water and produce hydrogen and oxidizing agents, mainly hydrogen peroxide and oxygen. The hydrogen will escape by diffusion and the oxidizing agents may attack the canister materials, oxidize the uranium oxide matrix or diffuse out and oxidize reducing agents in the surrounding rock.The rate of radiolysis has been computed recently within the Swedish nuclear fuel safety projects KBS. It is strongly influenced by the amount of available water and by the presence of dissolved iron. The movement of the oxidizing agents out from the canister and their reaction with the reducing agents (mainly ferrous iron) in the Swedish crystalline rock has been modelled as well as the movement of the radionuclides within and past the redox front. Some substances such as uranium, neptunium and technetium will precipitate at the redox front and will be withdrawn from the water to a considerable extent.

Chemical Effects at the Reaction Front in Corroding Spent Nuclear Fuel

2006 ◽  
Vol 985 ◽  
Author(s):  
Jeffrey A. Fortner ◽  
A. Jeremy Kropf ◽  
James L. Jerden ◽  
James C. Cunnane
Keyword(s):  
Transition Zone ◽  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
Aqueous Environment ◽  
Spent Fuel ◽  
Aqueous Corrosion ◽  
Reduction Potentials ◽  
Chemical Effects ◽  
Before And After ◽  
X Ray Absorption

AbstractPerformance assessment models of the U. S. repository at Yucca Mountain, Nevada suggest that neptunium from spent nuclear fuel is a potentially important dose contributor. A scientific understanding of how the UO2 matrix of spent nuclear fuel impacts the oxidative dissolution and reductive precipitation of Np is needed to predict the behavior of Np at the fuel surface during aqueous corrosion. Neptunium would most likely be transported as aqueous Np(V) species, but for this to occur it must first be oxidized from the Np(IV) state found within the parent spent nuclear fuel. In this paper we present synchrotron x-ray absorption spectroscopy and microscopy findings that illuminate the resultant local chemistry of neptunium and plutonium within uranium oxide spent nuclear fuel before and after corrosive alteration in an air-saturated aqueous environment. We find the Pu and Np in unaltered spent fuel to have a +4 oxidation state and an environment consistent with solid-solution in the UO2 matrix. During corrosion in an air-saturated aqueous environment, the uranium matrix is converted to uranyl (UO22+) mineral assemblage that is depleted in Np and Pu relative to the parent fuel. The transition from U(IV) in the fuel to a fully U(VI) character across the corrosion front is not sharp, but occurs over a transition zone of ∼ 50 micrometers. We find evidence of a thin (∼ 20 micrometer) layer that is enriched in Pu and Np within a predominantly U(IV) environment on the fuel side of the transition zone. These experimental observations are consistent with available data for the standard reduction potentials for NpO2+/Np4+ and UO22+/U4+ couples, which indicate that Np(IV) may not be effectively oxidized to Np(V) at the corrosion potential of uranium dioxide spent nuclear fuel in air-saturated aqueous solutions.

scholarly journals The Need for Integrating the Back End of the Nuclear Fuel Cycle in the United States of America

MRS Advances ◽  
2018 ◽  
Vol 3 (19) ◽  
pp. 991-1003 ◽  
Author(s):  
Evaristo J. Bonano ◽  
Elena A. Kalinina ◽  
Peter N. Swift
Keyword(s):  
United States ◽  
Nuclear Fuel ◽  
United States Of America ◽  
Spent Nuclear Fuel ◽  
Fuel Cycle ◽  
Nuclear Fuel Cycle ◽  
The United States ◽  
Spent Fuel ◽  
Dry Storage ◽  
The Us

ABSTRACTCurrent practice for commercial spent nuclear fuel management in the United States of America (US) includes storage of spent fuel in both pools and dry storage cask systems at nuclear power plants. Most storage pools are filled to their operational capacity, and management of the approximately 2,200 metric tons of spent fuel newly discharged each year requires transferring older and cooler fuel from pools into dry storage. In the absence of a repository that can accept spent fuel for permanent disposal, projections indicate that the US will have approximately 134,000 metric tons of spent fuel in dry storage by mid-century when the last plants in the current reactor fleet are decommissioned. Current designs for storage systems rely on large dual-purpose (storage and transportation) canisters that are not optimized for disposal. Various options exist in the US for improving integration of management practices across the entire back end of the nuclear fuel cycle.

Burnup Credit in the Criticality Safety Analysis of Spent Fuel in Storage Systems

2014 ◽  
Author(s):  
Vladyslav Soloviov
Keyword(s):  
Isotopic Composition ◽  
Nuclear Fuel ◽  
Beta Decay ◽  
Spent Nuclear Fuel ◽  
Storage Systems ◽  
Multiplication Factor ◽  
Spent Fuel ◽  
Neutron Multiplication ◽  
Initial Fuel ◽  
Effective Neutron

In this paper accounting of spent nuclear fuel (SNF) burnup of RBMK-1000 with actinides and full isotopic composition has been performed. The following characteristics were analyzed: initial fuel enrichment, burnup fraction, axial burnup profile in the fuel assembly (FA) and fuel weight. As the results show, in the first 400 hours after stopping the reactor, there is an increase in the effective neutron multiplication factor (keff) due to beta decay of 239Np into 239Pu. Further, from 5 to 50 years, there is a decrease in keff due to beta decay of 241Pu into 241Am. Beyond 50 years there is a slight change in the criticality of the system. Accounting for nuclear fuel burnup in the justification of nuclear safety of SNF systems will provide an opportunity to increase the volume of loaded fuel and thus significantly reduce technology costs of handling of SNF.

Developing a Concept for a National Used Fuel Interim Storage Facility in the United States

2013 ◽  
Author(s):  
Donald Wayne Lewis
Keyword(s):  
United States ◽  
Nuclear Fuel ◽  
Nuclear Waste ◽  
Spent Nuclear Fuel ◽  
The United States ◽  
Yucca Mountain ◽  
Storage Facility ◽  
Spent Fuel ◽  
Geological Repository ◽  
Interim Storage

In the United States (U.S.) the nuclear waste issue has plagued the nuclear industry for decades. Originally, spent fuel was to be reprocessed but with the threat of nuclear proliferation, spent fuel reprocessing has been eliminated, at least for now. In 1983, the Nuclear Waste Policy Act of 1982 [1] was established, authorizing development of one or more spent fuel and high-level nuclear waste geological repositories and a consolidated national storage facility, called a “Monitored Retrievable Storage” facility, that could store the spent nuclear fuel until it could be placed into the geological repository. Plans were under way to build a geological repository, Yucca Mountain, but with the decision by President Obama to terminate the development of Yucca Mountain, a consolidated national storage facility that can store spent fuel for an interim period until a new repository is established has become very important. Since reactor sites have not been able to wait for the government to come up with a storage or disposal location, spent fuel remains in wet or dry storage at each nuclear plant. The purpose of this paper is to present a concept developed to address the DOE’s goals stated above. This concept was developed over the past few months by collaboration between the DOE and industry experts that have experience in designing spent nuclear fuel facilities. The paper examines the current spent fuel storage conditions at shutdown reactor sites, operating reactor sites, and the type of storage systems (transportable versus non-transportable, welded or bolted). The concept lays out the basis for a pilot storage facility to house spent fuel from shutdown reactor sites and then how the pilot facility can be enlarged to a larger full scale consolidated interim storage facility.

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