David Schrire - Academia.edu (original) (raw)
Papers by David Schrire
TopFuel 2022 Light Water Reactor Fuel Performance Conference
TopFuel 2022 Light Water Reactor Fuel Performance Conference
TopFuel 2022 Light Water Reactor Fuel Performance Conference
TopFuel 2022 Light Water Reactor Fuel Performance Conference
Nuclear fuel undergoes several thermo-mechanical changes during irradiation in a nuclear react... more Nuclear fuel undergoes several thermo-mechanical changes during irradiation in a nuclear reactor, such as change of density, caused by solid and gaseous swelling. This affects the heat transport within the pellet and, when leading to the pellet-cladding gap closure, it also affects the gap conductance, causing stress in the cladding. The density of irradiated fuel pellets can be measured in post-irradiation examination using several methods. In this work, a feasibility study was made using the gamma-ray transmission micro-densitometry technique. This is based on the comparison of two intensity measurements, with and without a sample with well-characterized thickness. Using a collimated source, a local examination of the density can be performed, scanning a pellet slice radially. The proposed technique aims to obtain a spatial resolution of cca. 100 microns. In this work, the parameters of the setup, such as the source activity, detector counting time, slit dimensions, colli...
Presently there is a clear trend of increasing demands on in-pile performance of nuclear fuel. Hi... more Presently there is a clear trend of increasing demands on in-pile performance of nuclear fuel. Higher target burnups, part length rods and various fuel additives are some examples of this trend. Together with an increasing demand from the public for even safer nuclear power utilisation, this implies an increased focus on various experimental, preferably non-destructive, methods to characterise the fuel.This thesis focuses on the development and experimental evaluation of such methods. In its first part, the thesis presents a method based on gamma-ray spectroscopy with germanium detectors that have been used at various power reactors in Europe. The aim with these measurements is to provide information about the thermal power distribution within fuel assemblies in order to validate core physics production codes. The early closure of the Barseback 1 BWR offered a unique opportunity to perform such validations before complete depletion of burnable absorbers in Gd-rods had taken place. T...
In the vicinity of nickel alloy spacers or other components, ”shadow corrosion” is seen on Zr-all... more In the vicinity of nickel alloy spacers or other components, ”shadow corrosion” is seen on Zr-alloys in BWRs. This shadow corrosion oxide is prone to flake off the Zr-alloy cladding. These flakes have, more often than not, straight edges, and these edges often correlate to pre-existing axial scratches. In this work, we have investigated the oxide on un-flaked and flaked areas, in and close to the axial scratches, with FIB-SEM. This method gives the possibility to explore cross-sections of the material with both high precision and high resolution. In the paper the mechanisms behind shadow corrosion and the flaking oxide are discussed based on the results from the FIB-SEM-investigations. There is an incentive for fuel vendors to avoid axial scratches in the manufacturing process since this is expected to reduce the risk of oxide flaking.
Presently there is a clear trend of increasing demands on in-pile performance of nuclear fuel. Hi... more Presently there is a clear trend of increasing demands on in-pile performance of nuclear fuel. Higher target burnups, part length rods and various fuel additives are some examples of this trend. Together with an increasing demand from the public for even safer nuclear power utilisation, this implies an increased focus on various experimental, preferably non-destructive, methods to characterise the fuel.This thesis focuses on the development and experimental evaluation of such methods. In its first part, the thesis presents a method based on gamma-ray spectroscopy with germanium detectors that have been used at various power reactors in Europe. The aim with these measurements is to provide information about the thermal power distribution within fuel assemblies in order to validate core physics production codes. The early closure of the Barseback 1 BWR offered a unique opportunity to perform such validations before complete depletion of burnable absorbers in Gd-rods had taken place. T...
Nuclear Engineering and Technology, 2018
A series of simulated reactivity-initiated accident (RIA) tests on irradiated fully recrystallize... more A series of simulated reactivity-initiated accident (RIA) tests on irradiated fully recrystallized boiling water reactor Zircaloy-2 cladding has been performed by means of the expansion-due-to-compression (EDC) test method. The EDC method reproduces fuel pelleteclad mechanical interaction (PCMI) conditions for the cladding during RIA transients with respect to temperature and loading rates by out-of-pile mechanical testing. The tested materials had a large variation in burnup and hydrogen content (up to 907 wppm). The results of the EDC tests showed variation in the PCMI resistance of claddings with similar burnup and hydrogen content, making it difficult to clearly identify ductile-to-brittle transition temperatures. The EDC-tested samples of the present and previous work were investigated by light optical and scanning electron microscopy to study the influence of factors such as azimuthal variation of the Zr-hydrides and the presence of hydride rims and radially oriented hydrides. Two main characteristics were identified in samples with low ductility with respect to hydrogen content and test temperature: hydride rims and radial hydrides at the cladding outer surface. Crack propagation and failure modes were also studied, showing two general modes of crack propagation depending on distribution and amount of radially oriented hydrides. It was concluded that the PCMI resistance of irradiated cladding under normal conditions with homogenously distributed circumferential hydrides is high, with good margin to the RIA failure limits. To further improve safety, focus should be on conditions causing nonfavorable hydride distribution, such as hydride reorientation and formation of hydride blisters at the cladding outer surface.
EPJ Nuclear Sciences & Technologies, 2017
A previously published investigation of an irradiated fuel rod from the Ringhals 2 PWR, which was... more A previously published investigation of an irradiated fuel rod from the Ringhals 2 PWR, which was bowed to contact with an adjacent rod, identified a significant but highly localised thinning of the clad wall and increased corrosion. Rod fretting was deemed unlikely due to the adhering oxide covering the surfaces. Local overheating in itself was also deemed insufficient to account for the accelerated corrosion. Instead, an enhanced concentration of lithium due to conditions of local boiling was hypothesised to explain the accelerated corrosion. Studsvik has developed a hot cell coupled LA-ICP-MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometer) equipment that enables a flexible means of isotopic analysis of irradiated fuel and other highly active surfaces. In this work, the equipment was used to investigate the distribution of lithium (7 Li) and boron (11 B) in the outer oxide at the bow contact area. Depth profiling in the clad oxide at the opposite side of the rod to the point of contact, which is considered to have experienced normal operating conditions and which has a typical oxide thickness, evidenced levels of ∼10-20 ppm 7 Li and a 11 B content reaching hundreds of ppm in the outer parts of the oxide, largely in agreement with the expected range of Li and B clad oxide concentrations from previous studies. In the contact area, the 11 B content was similar to the reference condition at the opposite side. The 7 Li content in the outermost oxide closest to the contact was, however, found to be strongly elevated, reaching several hundred ppm. The considerable and highly localised increase in lithium content at the area of enhanced corrosion thus offers strong evidence for a case of lithium induced breakaway corrosion during power operation, when rod-to-rod contact and high enough surface heat flux results in a very local increase in lithium concentration.
TopFuel 2022 Light Water Reactor Fuel Performance Conference
TopFuel 2022 Light Water Reactor Fuel Performance Conference
TopFuel 2022 Light Water Reactor Fuel Performance Conference
TopFuel 2022 Light Water Reactor Fuel Performance Conference
Nuclear fuel undergoes several thermo-mechanical changes during irradiation in a nuclear react... more Nuclear fuel undergoes several thermo-mechanical changes during irradiation in a nuclear reactor, such as change of density, caused by solid and gaseous swelling. This affects the heat transport within the pellet and, when leading to the pellet-cladding gap closure, it also affects the gap conductance, causing stress in the cladding. The density of irradiated fuel pellets can be measured in post-irradiation examination using several methods. In this work, a feasibility study was made using the gamma-ray transmission micro-densitometry technique. This is based on the comparison of two intensity measurements, with and without a sample with well-characterized thickness. Using a collimated source, a local examination of the density can be performed, scanning a pellet slice radially. The proposed technique aims to obtain a spatial resolution of cca. 100 microns. In this work, the parameters of the setup, such as the source activity, detector counting time, slit dimensions, colli...
Presently there is a clear trend of increasing demands on in-pile performance of nuclear fuel. Hi... more Presently there is a clear trend of increasing demands on in-pile performance of nuclear fuel. Higher target burnups, part length rods and various fuel additives are some examples of this trend. Together with an increasing demand from the public for even safer nuclear power utilisation, this implies an increased focus on various experimental, preferably non-destructive, methods to characterise the fuel.This thesis focuses on the development and experimental evaluation of such methods. In its first part, the thesis presents a method based on gamma-ray spectroscopy with germanium detectors that have been used at various power reactors in Europe. The aim with these measurements is to provide information about the thermal power distribution within fuel assemblies in order to validate core physics production codes. The early closure of the Barseback 1 BWR offered a unique opportunity to perform such validations before complete depletion of burnable absorbers in Gd-rods had taken place. T...
In the vicinity of nickel alloy spacers or other components, ”shadow corrosion” is seen on Zr-all... more In the vicinity of nickel alloy spacers or other components, ”shadow corrosion” is seen on Zr-alloys in BWRs. This shadow corrosion oxide is prone to flake off the Zr-alloy cladding. These flakes have, more often than not, straight edges, and these edges often correlate to pre-existing axial scratches. In this work, we have investigated the oxide on un-flaked and flaked areas, in and close to the axial scratches, with FIB-SEM. This method gives the possibility to explore cross-sections of the material with both high precision and high resolution. In the paper the mechanisms behind shadow corrosion and the flaking oxide are discussed based on the results from the FIB-SEM-investigations. There is an incentive for fuel vendors to avoid axial scratches in the manufacturing process since this is expected to reduce the risk of oxide flaking.
Presently there is a clear trend of increasing demands on in-pile performance of nuclear fuel. Hi... more Presently there is a clear trend of increasing demands on in-pile performance of nuclear fuel. Higher target burnups, part length rods and various fuel additives are some examples of this trend. Together with an increasing demand from the public for even safer nuclear power utilisation, this implies an increased focus on various experimental, preferably non-destructive, methods to characterise the fuel.This thesis focuses on the development and experimental evaluation of such methods. In its first part, the thesis presents a method based on gamma-ray spectroscopy with germanium detectors that have been used at various power reactors in Europe. The aim with these measurements is to provide information about the thermal power distribution within fuel assemblies in order to validate core physics production codes. The early closure of the Barseback 1 BWR offered a unique opportunity to perform such validations before complete depletion of burnable absorbers in Gd-rods had taken place. T...
Nuclear Engineering and Technology, 2018
A series of simulated reactivity-initiated accident (RIA) tests on irradiated fully recrystallize... more A series of simulated reactivity-initiated accident (RIA) tests on irradiated fully recrystallized boiling water reactor Zircaloy-2 cladding has been performed by means of the expansion-due-to-compression (EDC) test method. The EDC method reproduces fuel pelleteclad mechanical interaction (PCMI) conditions for the cladding during RIA transients with respect to temperature and loading rates by out-of-pile mechanical testing. The tested materials had a large variation in burnup and hydrogen content (up to 907 wppm). The results of the EDC tests showed variation in the PCMI resistance of claddings with similar burnup and hydrogen content, making it difficult to clearly identify ductile-to-brittle transition temperatures. The EDC-tested samples of the present and previous work were investigated by light optical and scanning electron microscopy to study the influence of factors such as azimuthal variation of the Zr-hydrides and the presence of hydride rims and radially oriented hydrides. Two main characteristics were identified in samples with low ductility with respect to hydrogen content and test temperature: hydride rims and radial hydrides at the cladding outer surface. Crack propagation and failure modes were also studied, showing two general modes of crack propagation depending on distribution and amount of radially oriented hydrides. It was concluded that the PCMI resistance of irradiated cladding under normal conditions with homogenously distributed circumferential hydrides is high, with good margin to the RIA failure limits. To further improve safety, focus should be on conditions causing nonfavorable hydride distribution, such as hydride reorientation and formation of hydride blisters at the cladding outer surface.
EPJ Nuclear Sciences & Technologies, 2017
A previously published investigation of an irradiated fuel rod from the Ringhals 2 PWR, which was... more A previously published investigation of an irradiated fuel rod from the Ringhals 2 PWR, which was bowed to contact with an adjacent rod, identified a significant but highly localised thinning of the clad wall and increased corrosion. Rod fretting was deemed unlikely due to the adhering oxide covering the surfaces. Local overheating in itself was also deemed insufficient to account for the accelerated corrosion. Instead, an enhanced concentration of lithium due to conditions of local boiling was hypothesised to explain the accelerated corrosion. Studsvik has developed a hot cell coupled LA-ICP-MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometer) equipment that enables a flexible means of isotopic analysis of irradiated fuel and other highly active surfaces. In this work, the equipment was used to investigate the distribution of lithium (7 Li) and boron (11 B) in the outer oxide at the bow contact area. Depth profiling in the clad oxide at the opposite side of the rod to the point of contact, which is considered to have experienced normal operating conditions and which has a typical oxide thickness, evidenced levels of ∼10-20 ppm 7 Li and a 11 B content reaching hundreds of ppm in the outer parts of the oxide, largely in agreement with the expected range of Li and B clad oxide concentrations from previous studies. In the contact area, the 11 B content was similar to the reference condition at the opposite side. The 7 Li content in the outermost oxide closest to the contact was, however, found to be strongly elevated, reaching several hundred ppm. The considerable and highly localised increase in lithium content at the area of enhanced corrosion thus offers strong evidence for a case of lithium induced breakaway corrosion during power operation, when rod-to-rod contact and high enough surface heat flux results in a very local increase in lithium concentration.