Authors:Larisa Mariut, Elena Helerea, and Ioan Felea
Gill Y. Development of an electrical cable replacement simulation model to aid with the management of ageing underground electric cables. IEEE Electrical Insulation Magazine , Vol. 27, No. 1, 2011, pp. 31
Authors:M. Beneš, V. Pla?ek, G. Matuschek, A. A. Kettrup, K. Györyová, W. D. Emmerich, and V. Balek
Thermal behavior of commercial PVC cable insulation both before and after extraction of plasticizers, fillers and other agents
were tested by TG/DTG and DSC during heating in the range 20-800C in air. The ultrasound enhanced hexane extraction and dissolution
in THF with subsequent precipitation of PVC were used to prepare 'extracted' and 'precipitated' samples. The total mass loss
measured for the 'non-treated', 'extracted' and 'precipitated' PVC samples was 71.6, 66.6 and 97%, respectively. In the temperature
range 200-340C the release of dioctylphthalate, HCl and CO2was observed by simultaneous TG/FTIR. From TG results measured at different heating rates (1.5, 5, 10, 15 K min-1) in the range 200-340C the non-isothermal kinetics of the PVC samples degradation was determined. Activation energy values
of the thermal degradation processes calculated by ASTM E 698 method, for 'non-treated', 'extracted' and 'precipitated' PVC
samples were 174.617 kJ min-1, 192.819 kJ min-1, 217.120 kJ min-1, respectively. These kinetic parameters were used for the lifetime simulation of the materials.
Degradation of polymeric materials used in nuclear power plants (NPP), especially polymeric cable insulation materials, in
the course of their service can be monitored by measuring their properties by DSC, mainly oxidative induction time — OIT.
The studied materials were in-laboratory aged by applying main stressors that act in NPP — ionising radiation and temperature.
The dependence of OIT on radiation and thermal degradation of polymeric material was determined. The OIT values have been
compared to elongation at break as a property that directly reflects the functionality of the studied material. The comparison
of monitored OIT of real cable samples taken from NPP with dependencies on how the OIT values change with the elongation at
break, makes possible to establish the extent of cable degradation. This method can be considered as a suitable and effective
technique for lifetime assessment not only of cable insulations but also of many other plastics.
Authors:M. Beneš, N. Milanov, G. Matuschek, A. Kettrup, V. Plaček, and V. Balek
Thermogravimetry (TG/DTG) coupled with evolved gas analysis (MS detection) of volatiles was used to characterize the thermal
behavior of commercial PVC cable insulation material during heating in the range 20-800C in air and nitrogen, respectively.
In addition, simultaneous TG/FTIR was used to elucidate chemical processes that caused the thermal degradation of the sample.
A good agreement between results of the methods was found. The thermal degradation of the sample took place in three temperature
ranges, namely 200-340, 360-530 and 530-770C. The degradation of PVC backbone started in the range 200-340C accompanied
by the release of HCl, H2O, CO2 and benzene. The non-isothermal kinetics of thermal degradation of the PVC cable insulation in the temperature range 200-340C
was determined from TG results measured at heating rates of 1.5, 5, 10, 15 and 20 K min-1 in nitrogen and air, respectively. The activation energy values of the thermal degradation process in the range 200-340C
of the PVC cable insulation sample were determined from TG results by ASTM method.
A cikk olyan általánosított rácsos tartók állapotváltozóinak meghatározásával foglalkozik, amelyeket a rudakon kívül kötelek és dúcelemek alkotnak, vagyis amelyek csak húzásra, illetve csak nyomásra vehetők igénybe. Az elmozdulások és az igénybevételek meghatározására egy nemlineáris egyenletrendszert vezetünk le, melyet a Newton–Raphson-féle iterációs eljárás módosításával oldunk meg. A javasolt eljárást numerikus példákkal szemléltetjük.
A simple technique for measurement of the soil-atmosphere radon flux has been developed by fastening a charcoal canister inside a PVC cylindrical container. This device, which is deployed at the ground surface for approximately 16 hours, captures radon emanating from the soil by adsorption onto the charcoal surface. After recovery of the canister and measurement of the radon daughter activity on a NaI detector, the radon flux may be calculated if the adsorption efficiency of radon onto the charcoal is known. This parameter was determined by exposure of charcoal canisters to226Ra-spiked barium palmitate filter sources for timed intervals. Since this compound is known to emanate 100% of the222Rn generated during radium decay, it forms a useful flux standard. The accuracy of our flux measurements was assessed by comparison to a more established technique, the enclosed-chamber or accumulator method. Concentration measurements were made for the chamber over a less than 2-hour period while the canister flux measurements were based on single overnight deployments. The experiment was repeated 5 times at two different sites and the two techniques generally agreed within a 95% confidence interval.
Authors:D. Corbett, W. Burnett, P. Cable, and S. Clark
Determination of sedimentary fluxes of222Rn via diffusion was required as an input for a mass balance model of radon in a freshwater lake. We obtained these fluxes
by: (1) direct measurement in the laboratory using a simulated sediment bed and water column; (2) a “sediment equilibration”
technique; and (3) porewater modeling. The first method, analogous to an in situ benthic chamber approach, uses direct observation
of the increasing222Rn activity in water overlying a sediment bed packed in plastic columns. This allows one to directly measure the fluxes and
determine the effective wet bulk sediment diffusion coefficient (Ds). Radon flux estimates using these three techniques agreed to within approximately 10–15%.
Authors:S. P. LaMont, C. R. Shick, P. Cable-Dunlap, D. J. Fauth, and T. R. LaBone
A new high-sensitivity plutonium bioassay program employing thermal ionization mass spectrometry (TIMS) has been developed to monitor Savannah River Site employees for intakes of PuO2. The U.S. Department of Energy requires bioassay laboratories which have the ability to detect a 100 mRem, 50-year committed effective dose equivalent (CEDE) intake of radioactive material. For PuO2, traditional alpha-spectrometry methods are not sensitive enough to meet this specification. To comply with this requirement, a radiochemical TIMS method was developed to determine Pu in urine bioassay samples. Four radiochemical separation steps were used to purify Pu from urine to ensure samples were free from matrix effects that interfere with TIMS analysis. These included precipitation, ion-extraction chromatography, electrodeposition, and ion-exchange chromatography. A batch of reagent blanks determined the detection limit for this method was 0.59 fg 239Pu/l (1.3 µBq 239Pu/l). The 239Pu concentration was also measured in 20 urine blank samples to determine the minimum 239Pu concentration that would indicate an occupational intake. A Probit plot was constructed for the results and the 99 th percentile of the urine blanks showed that the minimum 239Pu concentration that would indicate an uptake was 2.4 fg/l (5.5 µBq/l).
Authors:K. Hofstetter, P. Cable, D. Beals, J. Noakes, J. Spaulding, M. Neary, and R. Peterson
Researchers from the Savannah River Technology Center, the Center for Applied Isotope Studies (CAIS) and Sampling Systems
have developed a prototype Field Deployable Tritium Analysis System (FDTAS) for near-real-time measurements of environmental
levels of tritium in ground and surface water. The device consists of a modified liquid scintillation counter coupled to an
automatic sampler which incorporates on-line water purification. The FDTAS has been field tested at several Savannah River
Site locations and has produced results comparable to laboratory analyses for low concentrations of tritium. Figures of merit
obtained in the field include an average tritium background count rate of 1.5 counts per minute (cpm), tritium detection efficiency
of ≈25%, and a detection limit of <10 Bq/l for a 100 minute count.