scholarly journals MATERIAL ISSUES FOR CURRENT AND ADVANCED NUCLEAR REACTOR DESIGNS

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Peter Hosemann ◽  
Jasmina Vujić
Keyword(s):  
Nuclear Reactor ◽  
Prolonged Exposure ◽  
Liquid Metals ◽  
Radiation Environment ◽  
High Radiation ◽  
Nuclear Systems ◽  
Temperature And Pressure ◽  
Pressure Stress ◽  
Liquid Salts ◽  
Lifetime Extension

In all engineering applications, design and materials together determine the functionality and reliability of a device. This is particularly important in nuclear systems where the materials are pushed to their limits and phenomena not present anywhere else occur. In nuclear systems a combination of high temperature and pressure, stress, corrosive environment and high radiation environment combined causes significant materials challenges. Majority of commercial LWRs today are licensed for 40 years of operation, but many of them undergo lifetime extension to 60 or possibly 80 years. Materials degradation has always been a significant issue. However, due to the lifetime plant extension, finding materials that could sustain prolonged exposure to these extreme conditions has become a significant problem. In addition to the materials challenges in current LWRs, advanced reactors usually deal with even more difficult issues due to their operational requirements. Unusual heat transport media, such as liquid metals, liquid salts or other types of coolants, lead to a whole new set of material challenges. While corrosion has been the main issue, much higher operating temperatures create additional difficulties. In this paper, we present an overview of materials issues for current and advanced nuclear reactor designs.

scholarly journals Survival of Radioresistant Bacteria on Europa’s Surface after Pulse Ejection of Subsurface Ocean Water

Geosciences ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 9 ◽  
Author(s):  
Anatoly Pavlov ◽  
Vladimir Cheptsov ◽  
Denis Tsurkov ◽  
Vladimir Lomasov ◽  
Dmitry Frolov ◽  
...  
Keyword(s):  
Vacuum Chamber ◽  
Deinococcus Radiodurans ◽  
Radiation Environment ◽  
Ocean Water ◽  
High Radiation ◽  
Viable Cells ◽  
Subsurface Ocean ◽  
Temperature And Pressure ◽  
Radiation Conditions ◽  
Accumulated Dose

We briefly present preliminary results of our study of the radioresistant bacteria in a low temperature and pressure and high-radiation environment and hypothesize the ability of microorganisms to survive extraterrestrial high-radiation environments, such as the icy surface of Jupiter’s moon, Europa. In this study, samples containing a strain of Deinococcus radiodurans VKM B-1422T embedded into a simulated version of Europa’s ice were put under extreme environmental (−130 °C, 0.01 mbar) and radiation conditions using a specially designed experimental vacuum chamber. The samples were irradiated with 5, 10, 50, and 100 kGy doses and subsequently studied for residual viable cells. We estimate the limit of the accumulated dose that viable cells in those conditions could withstand at 50 kGy. Combining our numerical modelling of the accumulated dose in ice with observations of water eruption events on Europa, we hypothesize that in the case of such events, it is possible that putative extraterrestrial organisms might retain viability in a dormant state for up to 10,000 years, and could be sampled and studied by future probe missions.

scholarly journals The potential for climate-driven bathymetric range shifts: sustained temperature and pressure exposures on a marine ectotherm, Palaemonetes varians

2015 ◽  
Vol 2 (11) ◽  
pp. 150472 ◽  
Author(s):  
J. P. Morris ◽  
S. Thatje ◽  
D. Cottin ◽  
A. Oliphant ◽  
A. Brown ◽  
...  
Keyword(s):  
Metabolic Pathways ◽  
Prolonged Exposure ◽  
Range Shifts ◽  
Environmental Constraints ◽  
Bathymetric Range ◽  
Surface Warming ◽  
Marine Crustacean ◽  
Physiological Limit ◽  
Temperature And Pressure ◽  
Macromolecular Damage

Range shifts are of great importance as a response for species facing climate change. In the light of current ocean-surface warming, many studies have focused on the capacity of marine ectotherms to shift their ranges latitudinally. Bathymetric range shifts offer an important alternative, and may be the sole option for species already at high latitudes or those within enclosed seas; yet relevant data are scant. Hydrostatic pressure (HP) and temperature have wide ranging effects on physiology, importantly acting in synergy thermodynamically, and therefore represent key environmental constraints to bathymetric migration. We present data on transcriptional regulation in a shallow-water marine crustacean ( Palaemonetes varians ) at atmospheric and high HP following 168-h exposures at three temperatures across the organisms’ thermal scope, to establish the potential physiological limit to bathymetric migration by neritic fauna. We observe changes in gene expression indicative of cellular macromolecular damage, disturbances in metabolic pathways and a lack of acclimation after prolonged exposure to high HP. Importantly, these effects are ameliorated (less deleterious) at higher temperatures, and exacerbated at lower temperatures. These data, alongside previously published behavioural and heat-shock analyses, have important implications for our understanding of the potential for climate-driven bathymetric range shifts

scholarly journals Variational methods and speed-up of Monte Carlo perturbation computations for optimal design in nuclear systems

2019 ◽  
Vol 34 (3) ◽  
pp. 211-221
Author(s):  
Zafar Koreshi ◽  
Hamda Khan ◽  
Muhammad Yaqub
Keyword(s):  
Monte Carlo ◽  
Variational Methods ◽  
Nuclear Reactor ◽  
Critical Mass ◽  
Reactor Core ◽  
Radiation Shielding ◽  
Optimization Simulation ◽  
Nuclear Systems ◽  
Optimal Mix ◽  
Optimal Material

Seeking optimal material distribution in a nuclear system to maximize a response function of interest has been a subject of considerable interest in nuclear engineering. Examples are the optimal fuel distribution in a nuclear reactor core to achieve uniform burnup using minimum critical mass and the use of composite materials with an optimal mix of constituent elements in detection systems and radiation shielding. For such studies, variational methods have been found to be useful but, they have been used for standalone analyses often restricted to idealized models, while more elaborate design studies have required computationally expensive Monte Carlo simulations ill-suited to iterative schemes for optimization. Such an inherent disadvantage of Monte Carlo methods changed with the development of perturbation algorithms but, their efficiency is still dependent on the reference configuration for which a hit-and-trial approach is often used. In the first illustrative example, this paper explores the computational speedup for a bare cylindrical reactor core, achievable by using a variational result to enhance the computational efficiency of Monte Carlo design optimization simulation. In the second example, the effect of non-uniform material density in a fixed-source problem, applicable to optimal moderator and radiation shielding, is presented. While applications of this work are numerous, the objective of this paper is to present preliminary variational results as inputs to elaborate stochastic optimization by Monte Carlo simulation for large and realistic systems.

Scoping Analyses of Parameterized Cool-Down Transients Associated With Reactor Shutdown

2007 ◽  
Author(s):  
T. L. Dickson ◽  
M. T. EricksonKirk
Keyword(s):  
Nuclear Reactor ◽  
Structural Integrity ◽  
Operating Temperature ◽  
Nuclear Regulatory Commission ◽  
The United States ◽  
Pressure Vessels ◽  
Operating Conditions ◽  
Temperature And Pressure ◽  
Reactor Operating ◽  
Technical Basis

The current regulations, as set forth by the United States Nuclear Regulatory Commission (NRC), to insure that light-water nuclear reactor pressure vessels (RPVs) maintain their structural integrity when subjected to planned startup (heat-up) and shutdown (cool-down) transients are specified in Appendix G to 10 CFR Part 50, which incorporates by reference Appendix G to Section XI of the ASME Code. The technical basis for these regulations contains many aspects that are now broadly recognized by the technical community as being unnecessarily conservative. During the past decade, the NRC conducted the interdisciplinary Pressurized Thermal Shock (PTS) Re-evaluation Project that established a technical basis to support a risk-informed revision to current PTS regulations (10CFR Part 50.61). Once the results of the PTS reevaluation are incorporated into a revision of the 10 CFR 50 guidance on PTS, it is anticipated that the regulatory requirements for the fracture toughness of the RPV required to withstand a PTS event (accidental loading) will in some cases be less restrictive than the current requirements of Appendix G to 10 CFR Part 50, which apply to normal operating conditions. This logical inconsistency occurs because the new PTS guidelines will be based on realistic models and inputs whereas existing Appendix G requirements contain known and substantial conservatisms. Consequently, a goal of current NRC research is to derive a technical basis for a risk-informed revision to the current requirements of Appendix G to 10 CFR Part 50 in a manner that is consistent with that used to develop the risk-informed revision to the PTS regulations. Scoping probabilistic fracture mechanics (PFM) analyses have been performed for several hundred parameterized cool-down transients to (1) obtain insights regarding the interaction of operating temperature and pressure parameters on the conditional probability of crack initiation and vessel failure and (2) determine the limits on the permissible combinations of operating temperature and pressure within which the reactor may be brought into or out of an operational condition that remains below the acceptance criteria adopted for PTS of 1 × 10−6 failed RPVs per reactor operating year. This paper discusses the modeling assumptions, results, and implications of these scoping analyses.

Development of Robots Working in High Radiation Environment for Decommissioning Fukushima Daiichi Nuclear Power Plant

2018 ◽  
Vol 2018.23 (0) ◽  
pp. A112
Author(s):  
Takuya FUKUMOTO ◽  
Kouji ISHIZAWA ◽  
Satoshi OKADA ◽  
Katsuhiko HIRANO ◽  
Kouichi KUROSAWA ◽  
...  
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Radiation Environment ◽  
High Radiation ◽  
Fukushima Daiichi

scholarly journals Performance and operation experience of the ATLAS Semiconductor Tracker

2014 ◽  
Vol 31 ◽  
pp. 1460295
Author(s):  
Zhijun Liang ◽  
Keyword(s):  
Hadron Collider ◽  
High Energy ◽  
Radiation Environment ◽  
High Luminosity ◽  
Track Reconstruction ◽  
High Radiation ◽  
Leakage Currents ◽  
On Line ◽  
And Performance ◽  
The Ideal

We report on the operation and performance of the ATLAS Semi-Conductor Tracker (SCT), which has been functioning for 3 years in the high luminosity, high radiation environment of the Large Hadron Collider at CERN. We also report on the few improvements of the SCT foreseen for the high energy run of the LHC. We find 99.3% of the SCT modules are operational, the noise occupancy and hit efficiency exceed the design specifications; the alignment is very close to the ideal to allow on-line track reconstruction and invariant mass determination. We will report on the operation and performance of the detector including an overview of the issues encountered. We observe a significant increase in leakage currents from bulk damage due to non-ionizing radiation and make comparisons with the predictions.

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