Reliability-based assessment of integrity of bonded prestressed concrete containment structures

The main function of a nuclear containment structure is to prevent the leakage of radioactive materials from the reactor in the event of a serious failure in the process system. To maintain a high level of leak integrity, prestressed concrete is widely utilized in containment construction. In bonded prestressing systems, excessive prestressing losses caused by unexpected material deformations and degradation of tendons could result in the loss of leak integrity under an accident. To safeguard against this, the Canadian Standard, CSA N287.7 (1995), recommends periodic inspection and evaluation of prestressing systems of CANDU containments. As bonded tendons are not amenable to direct inspection, the evaluation is based on the testing of a set of beams with features identical to the containment. The paper presents a quantitative reliability-based approach to evaluate the containment integrity in terms of the condition of bonded prestressing systems. The proposed approach utilizes the results of lift-off, destructive, and flexural tests to update the probability distribution of prestressing force, and to revise the calculated reliability against through-wall cracking of containment elements. An acceptable criterion for the results of beam tests is established on the basis of maintaining adequate reliability throughout the service life of the containment.     

Exposure assessment to Sudan dyes through consumption of artificially coloured chilli powders in India

In view of detection of Sudan dyes in chillies, the Spices Board of India formulated a mandatory testing programme in all chilli consignments exported from India. However, no surveillance data on use and levels of Sudan dyes in domestic chilli products are available in India. Hence chilli powders were monitored to check the magnitude of artificial coloration and the likely exposure assessment of Sudan dyes. Among 800 non‐branded, loose chilli powder samples, over 66% were found to employ artificial colouration while only 33% were free from Sudan dyes. None of the branded chilli powder samples was found to contain Sudan dyes. The maximum content of Sudan I noted was as high as 11.8 mg g^?1, which at the rough per capita consumption estimates of 0.5–1.0 g chilli powder per day amounts to an intake of 5.8–11.8 mg of Sudan I. This may lead to unwarranted health consequences, hence regular monitoring of the chilli powder samples is advisable to safeguard the health of unsuspecting consumers.     

Energy auditing of diversified rice–wheat cropping systems in Indo-gangetic plains

The field investigations were carried out for energy use analysis in terms of different input requirements and outputs harvested under the diversified rice–wheat cropping systems at the research farm of Project Directorate for Cropping Systems Research, Modipuram, Meerut, India during the year 2000–2004. The experiments were conducted on rice (Oryza sativa L.)–wheat (Triticum aestivum L. emend. Fiori and Paol) system involving 8 sequences using diversification, furrow irrigated raised bed system (FIRB) of sowing wheat, use of summer period for deep ploughing or raising legume crops for seed or green manure to study the energy dynamics of different diversified cropping systems. Results revealed that total energy use was highest in rice–potato–wheat (i.e. 77,601 MJ/ha in flat bed & 75,697 MJ/ha in raised bed) followed by rice–wheat–sesbania (i.e. 48,770 MJ/ha in flat & 47,830 MJ/ha in raised bed) and rice–wheat–greengram (i.e. 48,414 MJ/ha in flat & 47,482 MJ/ha in raised bed). In overall, the raised bed sowing of wheat in the cropping system consumed 6–11% less fertilizer energy than flat bed while saved up to 4.2% energy through irrigation. The total output energy of the system was recorded significantly higher in rice–potato–wheat system (i.e. 222,836 MJ/ha in flat bed & 218,065 MJ/ha in raised bed) in comparison to rice–wheat–greengram (i.e. 177,477 MJ/ha in flat bed & 175,125 MJ/ha in raised bed), rice–wheat–sesbania (i.e. 172,000 MJ/ha in flat bed & 168,919 MJ/ha in raised bed) and rice–wheat system (i.e. 156,085 MJ/ha in flat bed & 151,862 MJ/ha in raised bed). The significantly higher net return of energy was obtained in rice–potato–wheat system as compared to other systems. This system required about 75% more input energy but provided about 42% more output energy compared to conventional rice–wheat system. About 10% higher output energy was obtained through growing greengram in summer for grain and foliage incorporation while 14% gain obtained by green manuring sesbania, when compared to deep summer ploughing after wheat harvest.     

Phenomenon of barrelling in aluminium solid cylinders during cold upset-forming

Experiments were carried out to generate data on the upset forging of solid cylinders of annealed aluminium. The curvatures of the barrelled aluminium cylinders measured physically were found to conform closely with the values calculated using the experimental data. The calculations were made on the assumption that the curvature of the barrel followed the geometry of a circular arc. It was further found that the measured radius of curvature of the barrel exhibited a straight-line relationship with the new geometrical shape-factor, irrespective of the aspect ratios of the cylinders. Further empirical relationships were found to exist between the measured radius of curvature of the barrel and other variables such as the hydrostatic stress and the stress-ratio parameter.     

Profit evaluation of a two-unit system with internal and external repairs, inspection and post repair

In practice, systems do not always fail with a major breakdown, needing a heavy repair from some external source. Quite often, systems have a minor fault for which an immediate internal repair is more appropriate, in terms of availability of the system and economy, than calling a repairman from some external repair facility, waiting idly for his arrival or making a call with a higher cost. The present work discusses two non-identical unit systems with two types of repair, the internal and the external one. The external repair is called only when the internal staff fail to do the job. In the case of external repair, there is a provision of inspection, wherein if the repair is found unsatisfactory, it is sent for post repair. Using the regenerative point technique, various reliability characteristics of system effectiveness have been obtained.     

Multi-stage point estimation of the common location parameter of several exponential distributions

The problem of point estimation of the common location parameter of several exponential distributions is considered. The scale parameters are assumed to be unknown and unequal. Consideration is given to a family of loss functions. Non-existence of the fixed sample size procedure is established to deal with the present estimation problem. Purely sequential, accelerated sequential, three-stage and two-stage procedures are developed to handle the situation. Relative advantage and disadvantage of these estimation approaches are established.     

Development of elastomer blends for specific defence application

Several aspects of butyl (CIIR)-polychloroprene (CR) rubber blends viz (i) phase morphology evolution with respect to varied blend ratios and the effect of compatibilizer, (ii) processing characteristics, (iii) vapour impermeability and flame retardancy, (iv) mechanical properties, (v) ageing characteristics and (vi) the effect of addition of fillers into these blends have been studied. Scanning electron microscopy (SEM) has been used as a tool to investigate the phase morphology and also the failure mechanism. Blends based on CR and CIIR are likely to be important to Defence services for developing several rubber products with the above properties and characteristics. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995