Study of gas pipelines cracks using transmission and Compton scattering

Most of the natural gas production is transported through pipelines that require periodic inspections to evaluate the structural integrity of the pipelines due to possible defects caused by degradation that can rupture causing leakage of the fluid causing major disasters. Based on this, the project presents a methodology for predicting cracks in pipe used in gas pipelines. The approximation is based on the principles of gamma densitometry to calculate the density of the pipe wall in order to investigate possible cracks. The natural gas fluid is found in such systems and interferes in the density calculations and therefore will be considered in the simulations. The detection system uses a narrow beam geometry appropriately, comprising gamma ray source (137Cs) and NaI(Tl) 3"x3" detectors for calculating transmitted and scattered photons. Different positioning angles of the detector are investigated. In this study, the MCNP-X code is used to perform the simulations, in order to develop a counting geometry. Simulations of different thicknesses of the crack were also used to determine the minimum thickness detected by the two NaI(Tl) detectors. Having equipment that can estimate cracks present in pipes used in gas pipelines, in addition to predicting their location can reduce costs and make a major contribution to this sector.

Production of 128I Atoms through 127I (n,γ) 128I Reactions in some Solid Iodocompounds using an (241Am-Be) Neutron Source

Present work reports the production of 128I atoms through 127I (n,g) 128I reactions in six iodine containing compounds (viz. NaI, NaIO3, NaIO4, KI, KIO3 and KIO4) in solid state. An 241Am-Be neutron source has been used for the production of 128 I atoms. The radioactivities produced have been measured by a thin end-window G.M. Counter. The irradiation time and counting geometry were constant throughout the present sets of experiments. Results obtained have been analyzed through time-decay analyses. From the decay curves, the half life of 128I has been estimated ~25 minutes. The average zero time activities of 128I from three independent measurements in each of NaI, NaIO3.H2O, NaIO4, KI, KIO3 and KIO4 target, have been found 116 ± 2, 92 ± 4, 88 ± 6, 102 ± 6, 98 ± 1 and 93 ± 5 cpm respectively. It is interesting to note that the activities show a decreasing trend while passing through either from NaI to NaIO4 or from KI to KIO4. Results are attributed to the quantity of 128I produced in a specified volume element and, self absorption and self scattering of radiations within the target compounds studied. Keywords: Iodocompounds; 128I; 241Am-Be neutron source; Chemical effects of nuclear transformation.© 2011 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi:10.3329/jsr.v3i2.6385 J. Sci. Res. 3 (2), 357-366 (2011)

New Free-Release and Sorting Monitors Developed for NPP A-1 Decommissioning, Slovakia

A pilot free-release monitoring post with a 600 L container monitor was developed and metrological tested within the 2nd stage of NPP A1 decommissioning project. In order to reduce the volume of contaminated soil monitoring a conceptual design of fast sorting loader shovel monitor (loader’s spoon) was proposed and tested within the project as well. The free-release monitoring post makes use of a pair of electrically cooled lead shielded semiconductor detectors placed into a mounting rack ensuring measurements in either horizontal (container monitoring) or vertical (drum monitoring) counting geometry. For evaluation of measured HPGe spectra the Canberra – Packard ISOCS detection efficiency calculation code was used. A loader is used to change the measured side of the 600 L container. For metrological certification of this monitor a special prototype test container with 24 rod sources inside a regular grid was necessary to design and to use. The mentioned above vertical counting geometry together with an additional drum rotator ensures standard free release monitoring of materials in 200 l rotating drums. Successful metrological qualification of the both counting geometries at SMU Bratislava showed 20% accuracy class. A pair of NaI(Tl) detectors and a measurement and navigation frame ensuring loader shovel fixation in counting position are used for the fast sorting monitoring. The navigation of loader and its shovel to the counting geometry should be as fast as possible. The monitored results shall be indicated by a prompt light indication system (apart from storing on HDD). MCNP 5 calculation code was used for assessment of gross gamma 137Cs detection efficiency. The estimated MDA for a pair of 2″ × 2″ Na(Tl) detectors and 30 s acquisition time is about 90 Bq/kg. However, due to the counting geometry deviations from calculated values the uncertainty of measurements can be relatively high. Hence, the system is applicable for sorting monitoring only.

Uncertainty Analysis of Activity Measurement of New Monitoring System for Free-Release for NPP A-1 Decommissioning, Slovakia

New free release monitoring post with a large volume 600 L container counting geometry was designed and developed. The monitoring system is able to monitor a material also in standard counting geometry of 200 L drum. Using counting geometry of 600 L rectangular container that is equipped with self-discharger is able to increase the total monitoring capacity. The monitoring system is based on a pair of electrically cooled semiconductor HPGe detectors that are placed into a modifiable vertical or horizontal pair of lead collimators. The monitoring system is integrated with an industrial scale for determination of massic activities of measured materials and in addition by a rotating table in the case of 200 L drums monitoring. Monitoring system is integrated into transportable ISO container with constant environmental conditions that are ensured by air-condition unit. Full-energy peak detection efficiency (FPE) polynomial curves for various densities of measured material were in both cases determined by ISOCS calibration code based on designed counting geometry and delivered ISOCS/LabSOCS detector characterization. Uncertainty analysis of massic activity measurement by container and drum monitoring system in designed counting geometry is introduced below in more detail.