Characterising U-232 and Tl-208 Buildup and Decay on Thorium-fuelled RGTT200K

Thallium-208 (Tl-208), a decay daughter of uranium-232 (U-232), is a strong 2.6 MeV gamma emitter present in significant amount in thorium fuel cycle. Its existence enhances the anti-proliferation characteristics of thorium fuel cycle, but at the same time complicates the fuel handling system. In order to ensure that radiation hazard is properly contained, the buildup and decay characteristics of both U-232 and Tl-208 need to be understood. This paper aimed to provide a characterisation on U-232 and Tl-208 buildup in the thorium-fuelled RGTT200K, a 200 MWt very high temperature reactor (VHTR) developed by BATAN, using ORIGEN2.1 depletion code. Pure and impure U-233 were used as the fissile nuclide for comparison. The result showed that U-232 buildup rate is faster in pure U-233, but its Tl-208 buildup is slower. Nonetheless, pure U-233 always has its U-232 and Tl-208 activity lower than impure U-233. Accordingly, both U-232 and Tl-208 radioactivity post-discharge in pure U-233 are lower than impure U-233, although the difference become somewhat negligible after 300 years of decay. Tl-208 activity peaked after 10 years of decay, necessitating different approach in managing post-discharge fuel management.

Multiphasic value biases in fast-paced decisions

Perceptual decisions are biased toward higher-value options when overall gains can be improved. When stimuli demand immediate reactions, the neurophysiological decision process dynamically evolves through distinct phases of growing anticipation, detection and discrimination, but how value biases are exerted through these phases remains unknown. Here, by parsing motor preparation dynamics in human electrophysiology, we uncovered a multiphasic pattern of countervailing biases operating in speeded decisions. Anticipatory preparation of higher-value actions began earlier, conferring a “starting point”-advantage at stimulus onset, but the delayed preparation of lower-value actions was steeper, conferring a value-opposed buildup rate bias. This, in turn, was countered by a transient deflection toward the higher value action evoked by stimulus detection. A neurally-constrained process model featuring anticipatory urgency, biased detection, and accumulation of growing stimulus-discriminating evidence, successfully captured both behavior and motor preparation dynamics. Thus, an intricate interplay of distinct biasing mechanisms serves to prioritise time-constrained perceptual decisions.

Study on mechanical properties of titanium alloy drill pipe and application technology

With the increasing intensity of oil and gas field exploration and development, oil and gas wells are also drilling into deeper and more complex formations. Conventional steel drilling tools can no longer meet the requirements of ultra-deep, high-temperature and high-pressure wells. The paper first analyzes the advantages of titanium alloy drill pipe based on basic performance of titanium alloy drill pipe. The experimental results show that the basic properties of titanium alloy drill pipes meet the operating standards of the petroleum industry. Then the buckling performance of titanium alloy drill pipe and steel drill pipe is compared, the calculation results show that the buckling performance of titanium alloy drill tools is slightly lower than that of steel drill tools. Secondly, the maximum allowable buildup rate of titanium alloy drill pipe and steel drill tool is studied. The research shows that under the same condition of the drill pipe outer diameter, titanium alloy drill pipe can be used for a smaller curvature radius and greater buildup rate. This advantage of titanium alloy drill pipe makes it more suitable for short radius and ultra-short radius wells. Finally, taking a shale gas horizontal well as an example, with the goal of reducing drill string friction and ensuring drill string stability, a comparative study on the application of titanium alloy drill pipe and steel drill pipe is carried out. The results show that titanium alloy drill pipe has a wider application in the field, and is suitable for operations under various complex working conditions.

Development of technologies and tools for drilling additional wells from artificial bottom-hole with whipstock of continuous action in hard and very hard rocks

Background. Various approaches are currently used to create borehole curvature depending on associated methodological and practical geological problems. Continuous action whipstockes are considered to be the most modern and accurate among these approaches. The efficiency of such devices may decrease under difficult mining and geological conditions.Aim. To increase the efficiency of drilling a curved borehole in hard and very hard rocks by reducing the speed of drilling out an artificial bottom.Materials and methods. We studied the operating principles of various types of continuous action whipstocks. Empirical results were determined by studying the operation of continuous milling whipstocks in difficult rock conditions and by studying the materials used for manufacturing artificial bottom holes. The study included optimization of the efficiency of drilling a well in hard rocks from an artificial bottom hole in a new direction.Results. The main factors decreasing the whipstock efficiency were found to be the mechanism of buildup rate, and the different strength of the rock and artificial bottom-hole. A feature of the work of a milling type whipstocks is that the creation of a deflecting force is carried out due to the constant influence of the axial load, the value of which proportionally affects the speed of drilling. A review of the materials used to create an artificial bottom led to the conclusion that at present there are no curable materials that would have a hardness higher than category 8 for drillability, which means that when trying to drill a new direction of a well in rocks more than 8 grade for drillability, the speed drilling with a continuous action whipstocks will exceed the optimum and reduce the intensity of the buildup rate whipstock.Conclusion. Since the rate of drilling an artificial bottom hole is difficult to regulate using the drilling mode parameters, it is necessary to develop technical solutions that would limit the rate of deepening a new direction of the wellbore.

Pressure Activated Sealant to Restore Tubing Integrity – Case Study of Well Tn-X in Mahakam

Pressure activated sealant is used to repair tubing leak and restore tubing integrity without the need to install downhole devices which yield additional restriction inside tubing and reduce tubing ID. Leak on tubing was detected in early production phase from the continuous increase of A annulus pressure. The leak point was indicated from Production Logging Tool (PLT) at 183 m suspected from tubing thread connection, with annulus pressure buildup rate 435 psi/24 hrs. Pressure activated sealant was selected as the means to cure the leak. Retrievable plug was set below the leak point and sealant was pumped on top of plug, followed by inhibited water. Then pressure was applied at surface to squeeze and activate the sealant. The remaining fluid inside tubing remained liquid, allowing the plug to be retrieved. A total of 59 L sealant mixture and 750 L of inhibited water was pumped to the well. Hesitation pressure was performed to activate the sealant, and got indication of chemical sealing at 1000 psi. The tubing was then pressure tested to 5000 psi and pressure was holding in 1 hour, indicating positive isolation has been established between tubing-annulus. From continuous annulus pressure monitoring, pressure in A annulus has been stable at ~40 psi for the last 8 months after sealant injection has been performed. Pressure activated sealant is proven as a reliable method to cure small leak in tubing. Since the sealant will only be hardened inside the leaking point, there will be no additional restriction in the tubing, thus Internal Diameter (ID) reduction will not be a concern for future well intervention operations. Pressure activated sealant could become one of the alternatives to cure tubing leaks, especially in the cases where tubing ID reduction is not favored.

Converting InSAR- and GNSS-derived strain rate maps into earthquake hazard models for Anatolia

<p>Geodetic measurements of crustal deformation rates can provide important constraints on a region’s earthquake hazard that purely seismicity-based hazard models may miss. For example, geodesy might show that strain (or a deficit of seismic moment) is accumulating faster than the total rate at which known earthquakes have released it, implying that the long-term hazard may include larger earthquakes with long recurrence intervals (and/or temporal increases in seismicity rates). Conversely, the moment release rate in recent earthquakes might surpass the geodetic moment buildup rate, suggesting that the long-term-average earthquake activity and hazard may in fact may be more quiescent than might be estimated using the earthquake history alone. Such geodetic constraints, however, have traditionally been limited by poor spatial and/or temporal sampling, resulting in ambiguities about how the lithosphere accommodates strain in space and time that can bias estimates of the resulting hazard. High-resolution deformation maps address this limitation by imaging (rather than presuming and/or modelling) where and how deformation takes place. These maps are now within reach for the Alpine-Himalayan Belt – one of the most populous and seismically hazardous regions on Earth – thanks to the COMET-LiCSAR InSAR processing system, which performs large-scale automated processing and timeseries analysis of Sentinel-1 data provided by the EU’s Copernicus programme. We are pairing LiCSAR products with GNSS data to generate high-resolution maps of interseismic surface motion (velocity) and strain rate for the Anatolia region. Here we quantitively investigate what these strain rate distributions imply for seismic hazard in this region, using two approaches in parallel.</p><p>First, building on previous work, we develop a fully probability-based method to pair geodesy and seismic catalogs to estimate the recurrence times of large, moderate and small earthquakes in a given region. We assume that earthquakes 1) obey a power-law magnitude-frequency distribution up to a maximum magnitude and 2) collectively release seismic moment at the same rate that we estimate it is accumulating from the strain rate maps. Iterating over various magnitude-frequency distributions and their governing parameters, and formally incorporating uncertainties in moment buildup rate and the magnitudes of recorded earthquakes, we build a probabilistic long-term-average earthquake model for Anatolia as a whole, including the most likely maximum earthquake magnitude. Second, we estimate how seismic hazard may vary from place to place within Anatolia. Using insights from dislocation models, we identify two key signatures of a locked fault in a strain rate field, allowing us to convert the newly developed strain maps to “effective fault maps.” Additionally, we explore how characteristics of earthquake magnitude-frequency distributions may scale with the rate of strain (or moment) buildup, and what these scaling relations imply for the distribution of hazard in Anatolia, using the seismic catalog to evaluate these hypotheses. We also explore the implications of our findings for seismic hazard and address how to expand these approaches to the Alpine-Himalaya Belt as a whole.</p>

Plastic Shrinkage Cracking of Self-compacting Concrete: Influence of Capillary Pressure and Dormant Period

This research investigates the effect of capillary pressure and the length of the hydration dormant period on the plastic shrinkage cracking tendency of SCC by studying specimens produced with different w/c ratios, cement types and SP dosages. A relationship between the capillary pressure rate and the length of the hydration dormant period is defined, which can explain the cracking severity of the concrete when the volumetric deformation is unknown. The results show, that the cracking tendency of SCC was the lowest in case of w/c ratio between 0.45 and 0.55, finer and more rapid hardening cement, and lower dosage of SP. The dormant period was prolonged by increasing the w/c ratio, using coarser cement, and higher SP dosage. It was concluded that the cracking tendency of concrete is a function of the capillary pressure buildup rate and the length of the dormant period.

OPTIMALISASI PEMBORAN MENGGUNAKAN TEKNOLOGI PEMBORAN BERARAH

Pemboran berarah di Indonesia diperlukan untuk menjawab tantangan dari build-up bagian 8.5in dilakukan dengan menggunakan teknik kerekayasaan. Tantangan tersebut termasuk kebutuhan High Dogleg dengan Dogleg severity(DLS) 9o/100ft sampai 11o/100ft, panjang interval lapisan shale yang reaktif, kualitas lubang bor, kendali lintasan, pembersihan lubang dan pemasangan casing liner. Semua tantangan tersebut dapat memengaruhi pembengkakan Authorization For Expenditure (AFE) sumur dan pada kasus yang lebih ekstrim maka akan dapat mengakibatkan hilangnya satu sumur. Jenis perencanaan sumur telah didesain untuk pemboran vertical di bagian 12.25in, kemudian build pada bagian 8.5in dari vertikal ke inklinasi 90o dengan buildup rate 11o/100ft untuk memasuki zona reservoir.<br />Kerjasama antara operator dan perusahaan penyelenggara pemboran berarah memberikan kemudahan bagi para insinyur pemboran untuk mengahadapi tantangan conventional steerable motor assemblies. Bagian 12.25in dibor vertikal dengan menggunakan motor dan bagian 8.5in dibor dengan menggunakan Rotary Steerable System (RSS). Teknologi ini ditujukan untuk membandingkan rasio penetrasi menggunakan motor dan RSS. Solusi ini memudahkan operator untuk membor bagian 8.5in dengan aman dan efisien tanpa hambatan, selama proses mengebor dan pemasangan casing, juga dapat menghemat waktu sampai dengan 3 hari dari perencanaan. Teknologi baru ini mebuktikan bahwa ada kemungkinan untuk membor dengan Dogleg Severity (DLS) sampai 17o/100ft dengan putaran penuh. Rasio penetrasi pada bagian ini juga tidak membutuhkan sliding.