Development of a Device for Detecting Helium Leaks From Canisters: Part 2 — Numerical Analysis of Temperature Behavior During Gas Leaks From a Canister of a 1/4.5 Scale Cask Model

2018 ◽  
Author(s):  
Kosuke Shimizu ◽  
Hirofumi Takeda ◽  
Masanori Goto
Keyword(s):  
Heat Transfer ◽  
Internal Pressure ◽  
Ambient Air ◽  
Ideal Gas ◽  
Helium Pressure ◽  
Leak Detector ◽  
Long Term Storage ◽  
Sealing Performance ◽  
Term Storage

In the concrete cask, the canister is sealed with lids by welding, and has high sealing performance. But considering long-term storage, there is a concern about loss of the sealing performance due to stress corrosion cracking (SCC). In the concrete cask, unlike the metal cask, it is not mandatory to constantly monitor helium pressure between the lids. However, it is useful from the viewpoint of improving safety during the long-term storage to install a helium leak detector in the canister inside the concrete cask. Currently, we are developing the leak detector utilizing the phenomenon that the surface temperature of the canister changes when helium leaks out of the canister. As part of developing the leak detector of the canister, leak tests were performed using a small canister model as a pressurized vessel and a 1/4.5 scale cask model of the actual cask including the canister. This leak detector utilized the phenomenon that canister bottom temperature (TB) increases and canister lid temperature (TT) decreases when the internal pressure of the canister decreases. In computational fluid dynamics (CFD) calculation, focused on this phenomenon, the influence of the internal pressure and physical properties of internal gas in the canister were examined by calculating conditions of three kinds of pressure and two types of gas (air and helium). The main purpose of the CFD calculation was to confirm the results of the experiment, and we grasped the phenomenon occurring in the canister and elucidated its mechanism. For the CFD calculation, a commercial CFD software, STAR-CCM+® (ver.12.06.010) by Siemens PLM Software Company, was used. A CAD file used for the calculation simulated also the shape inside the canister (e.g. basket, fuel rods). A polyhedral mesh was used for a calculation mesh. In the small canister model, a mesh of its ambient air was not generated, and heat transfer between the canister surface and the ambient air was calculated from a heat transfer correlation equation. On the other hand, in the 1 / 4.5 scale cask model, the mesh of its ambient air was generated, so that the heat transfer on the surface of the canister was calculated according to the actual heat transfer phenomenon. The internal gas and the ambient air of the canister were ideal gas, and buoyancy due to density change was taken into consideration. A realizable k-epsilon model was used for a turbulence model, and a DO model was used for a radiation model.

Development of Device for Detecting Helium Leak From Canister: Part 1 — Experiment on Temperature Behavior During Gas Leak From Canister of 1/4.5 Scale Cask Model

2018 ◽  
Author(s):  
Hirofumi Takeda ◽  
Masanori Goto
Keyword(s):  
Performance Monitoring ◽  
Temperature Data ◽  
Detection Methods ◽  
Helium Pressure ◽  
Leak Detector ◽  
Long Term Storage ◽  
Sealing Performance ◽  
Gas Leak ◽  
Term Storage

A concrete cask has an advantage in cost and period of manufacturing compared with a metal cask. In the metal cask, monitoring of helium pressure between a primary lid and a secondary lid of the cask is required by regulation. On the other hand, in the concrete cask, the lids of a canister are welded and have high sealing performance, so that the monitoring of helium leak from the canister is not required. However, a loss of the sealing performance of the secondary lid, which is caused by stress corrosion cracking (SCC), is concerned in the case of long-term storage by the concrete cask. In the view of this situation, it would be useful to install a helium leak detector in the concrete cask in order to improve the safety of the long-term storage. Thus, we have been developing the detector. The phenomenon that the temperature at the bottom of the canister (TB) increases and the temperature at the top of the canister (TT) decreases during the helium leak from the canister has been confirmed by the experiments in the previous study. We have proposed the performance monitoring by monitoring the temperature difference ΔTBT (= TB-TT) instead of pressure monitoring. This time, to make the installation and maintenance of the helium leak detector easier in consideration of practical use, we proposed a new detection technique using only the temperature of either the lid or the bottom of the canister. We performed leak tests by using a 1/4.5 scale cask model based on a similarity law of thermal hydraulics. In the experiments, air was used for an inner gas of a canister of the model, and a heat flux of a canister surface had the same value as that of the actual canister surface. In this model, Ra* number can be made to coincide with that of the actual canister. Besides, Gr* number and Bo* number are almost equal to those of the actual canister. Temperature data at respective canister parts were obtained under condition of canister internal pressure from 6 atm to 1 atm (atmosphere pressure). Also, the new and old leak detection methods were evaluated by using the obtained temperature data.

Experimental Measurement of Vacuum Assisted Drying of Spent Nuclear Fuel

2015 ◽  
Author(s):  
Matthew Rivera ◽  
Randall Manteufel
Keyword(s):  
Nuclear Fuel ◽  
Spent Nuclear Fuel ◽  
Ambient Air ◽  
Vacuum Drying ◽  
Drying Process ◽  
Dry Storage ◽  
Long Term Storage ◽  
Drying Techniques ◽  
Term Storage

A prevalent issue within extended long term dry storage units for spent nuclear fuel has always been fuel and cask contamination. This contamination can be the result of the helium within the cask leaking into the atmosphere or inadequate vacuum drying techniques. Once the cask integrity has been compromised, the helium starts to leak, and the resulting space once occupied by helium in the casks is replaced with ambient air. One of the other prominent gases found within ambient air besides oxygen is water vapor which can be a result of both helium leaking and poor vacuum drying techniques. Contact between water and the fuel rods/assemblies for a prolonged amount of time can result in corrosion of the fuel cladding, and the canister if exposed. The potential of corrosion of the fuel cladding increases risk of radioactive fission fragments contaminating the environment, increases the radioactive period of spent nuclear fuel, and decreases the potential for fuel rod repurposing within the future if U.S. law permits. With literary findings showing liquid water within the inner cask in a long term storage unit of fifteen years or longer, proper drying techniques have not been fully developed. There are a number of projected theories about how water is entering the cask without an external crack or imperfection within the inner cask walls. This case study aims to solve this issue by inspecting the vacuum drying process of the fuel rods/assemblies from the temporary on-site storage pools to their respective long term dry storage casks. The purpose of this case study is to conduct a laboratory experiment of a scale replica of one dry storage cask and the vacuum drying process before long term storage. The experiment will be focused around the process of applying several cycles of vacuum and backfilling the cask with Helium. The purpose of several cycles of backfilling gas is to simultaneously introduce more of a pressure gradient for water evaporates to depart the pressure vessel and to avoid thermodynamic temperatures that would otherwise freeze the top layer of water. To do this, the vacuuming process must be properly understood, as pulling a vacuum drops pressures instantaneously. There are possibilities of freezing water vapor into its solidified form due to its thermodynamic triple point during this vacuum process. Once water is trapped under a layer of ice within the vessel, water will remain throughout storage time due to restrictions to its own geometries. The importance of developing a scale model and improving the drying process that precedes long term storage of spent nuclear fuel is a necessary solution to existing contamination results for practical future applications within the United States and other countries moving towards long term storage of spent nuclear fuel.

scholarly journals Sequential Controlled Atmosphere Storage for `McIntosh' Apples

HortScience ◽  
2006 ◽  
Vol 41 (5) ◽  
pp. 1322-1324 ◽  
Author(s):  
P. Guy Lévesque ◽  
Jennifer R. DeEll ◽  
Dennis P. Murr
Keyword(s):  
Ambient Air ◽  
First Year ◽  
Controlled Atmosphere ◽  
Ripening Period ◽  
Long Term Storage ◽  
Lower Temperature ◽  
Atmosphere Storage ◽  
Term Storage

Sequential decreases or increases in the levels of O2 in controlled atmosphere (CA) were investigated as techniques to improve fruit quality of `McIntosh' apples (Malus ×sylvestris [L.] Mill. var. domestica [Borkh.] Mansf.), a cultivar that tends to soften rapidly in storage. Precooled fruit that were harvested at optimum maturity for long-term storage were placed immediately in different programmed CA regimes. In the first year, CA programs consisted of 1) `standard' CA (SCA; 2.5–3.0% O2 + 2.5% CO2 for the first 30 d, 4.5% CO2 thereafter) at 3 °C for 180 d; 2) low CO2 SCA (2.5–3.0% O2 + 2.5% CO2) at 3 °C for 60 d, transferred to low O2 (LO; 1.5% O2 + 1.5% CO2) at 0 or 3 °C for 60 d, and then to ultralow O2 (ULO; 0.7% O2 + 1.0% CO2) at 0 or 3 °C for 60 d; and 3) ULO at 3 °C for 60 d, transferred to LO at 0 or 3 °C for 60 d, and then to SCA or low CO2 SCA at 0 or 3 °C for 60 d. In the second year, the regimes sequentially decreasing in O2 were compared with continuous ULO and SCA. After removal from storage, apples were held in ambient air at 20 °C for a 1-week ripening period. Fruit firmness was evaluated after 1 and 7 d at 20 °C, whereas the incidence of physiological disorders was assessed only after 7 d. Lowering the temperature while decreasing O2 was the best CA program with significant increased firmness retention during storage and after the 1-week ripening period. Reduced incidence of low O2 injury in decreasing O2 programs and absence of core browning at the lower temperature were also observed.

Failure Pressure Simulations for 3013 Inner Can Under Room Fire Conditions

2003 ◽  
Author(s):  
Narendra K. Gupta
Keyword(s):  
Internal Pressure ◽  
Upper Bound ◽  
Fissile Material ◽  
Acceptance Criteria ◽  
Failure Pressure ◽  
Long Term Storage ◽  
C 30 ◽  
Term Storage ◽  
Fire Conditions

The 3013 container is widely used for long-term storage and transporting of the fissile material (PuO2) in the DOE complex. The design of 3013 container is governed by the DOE Standard 3013. Thermal and structural analyses were performed to assess the integrity of a closed 3013 inner can assembly during a postulated room fire transient. The inner can assembly is engulfed in a 932°F (500°C) 30-minute long room fire. The fire transient results in a can temperature of about 900°F and an upper bound internal pressure of 641 psi due to the evaporation of moisture and generation of gases in the stored PuO2. The structural analyses show that the inner can assembly can withstand a pressure of 641 psi and meet the ASME B&PV Code stress acceptance criteria for one time accident loading. The failure pressures of the 3013 inner can at can metal temperatures of 900°F, 1200°F, and 1400°F are estimated to be 1435 psi, 1051 psi, and 705 psi respectively.

Modelling of Moisture Movement in Wood during Outdoor Storage

2001 ◽  
Vol 6 (2) ◽  
pp. 3-14 ◽  
Author(s):  
R. Baronas ◽  
F. Ivanauskas ◽  
I. Juodeikienė ◽  
A. Kajalavičius
Keyword(s):  
Experimental Data ◽  
Finite Difference ◽  
Climatic Conditions ◽  
Two Dimensional ◽  
Moisture Movement ◽  
Finite Difference Technique ◽  
Long Term Storage ◽  
Space Formulation ◽  
Term Storage

A model of moisture movement in wood is presented in this paper in a two-dimensional-in-space formulation. The finite-difference technique has been used in order to obtain the solution of the problem. The model was applied to predict the moisture content in sawn boards from pine during long term storage under outdoor climatic conditions. The satisfactory agreement between the numerical solution and experimental data was obtained.

Trehalose: a cryoprotectant that enhances recovery and preserves function of human pancreatic islets after long-term storage

Diabetes ◽  
1997 ◽  
Vol 46 (3) ◽  
pp. 519-523 ◽  
Author(s):  
G. M. Beattie ◽  
J. H. Crowe ◽  
A. D. Lopez ◽  
V. Cirulli ◽  
C. Ricordi ◽  
...  
Keyword(s):  
Pancreatic Islets ◽  
Human Pancreatic Islets ◽  
Long Term Storage ◽  
Term Storage
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