Atomic Energy Regulatory Board

This paper describes the development of the Safety Performance Indicators (SPIs), the methodology for assessment of the safety culture of radiotherapy institutions using SPIs and common strengths and common areas for improvement. SPIs were categorized into eight sections which all together contain 23 attributes and each attribute has scoring criteria from 0 to 2 (in steps of 0.5). The maximum absolute cumulative score of SPIs was 46. A relative cumulative SPIs score of >80% indicates an institution strong commitment towards safety while score <50% indicates need for additional guidance to enhance safety culture. The assessment using SPIs was conducted for 17 radiotherapy institutions. The methodology of assessment includes interactive discussion, direct observations and document analysis. The relative cumulative SPIs score of seven institutions was found to be >80% while it was found in the range of 67.0% to 80% for the remaining ten institutions. Institutions were communicated about the cumulative SPIs score, areas of strengths, and areas for improvement. SPIs were found to be a good tool for safety culture assessment and can be utilized by the radiotherapy institutes for self-assessment to identify the areas of improvement. Based on SPIs score, regulatory body can grade the institutions from a radiation safety compliance point of view.

To optimize the patient dose and image quality through quality assurance (QA) of diagnostic x-ray equipment and to ensure compliance with international and national standards in x-ray specification parameters, the use of contactless and quick non-invasive instruments has gained importance. Considering the importance of equipment qualification and the intervention level for equipment management, it is vital to account for uncertainties in the measurement of parameters in diagnostic radiology. However, the limits and measurement uncertainties associated with the parameter measurement are not well established and many technical and scientific literature provide different tolerance values, either as absolute or in terms of percentage. In this paper, the authors analyze non-invasive multi-parameter detector measurements with the aim to (i) improve the accuracy in measurement of x-ray parameters (kilovoltage, dose, and exposure time); (ii) estimate the uncertainty associated with such measurements; (iii) analyze the tolerance values prescribed by various professional and regulatory bodies and propose an improvised method of reporting the parameters. The approach adopted in this paper takes into account the uncertainties associated with traditional instruments and the subjectivity in the measurements. Estimated uncertainty for kV measurements in the range between 1.45 kV at 40 kV measurements and 4.88 kV at 150 kV measurements. The MU associated with the dose measurement is estimated to be 6.2% at 110 kVp, 100 mA, and 500 msec. Maximum MU estimated at 10 msec exposure time is 4.5% and with MU of 5% deviation added to 9.5%. The current practice of reporting the measured mean values deviation without considering the inherent measurement uncertainty may not be a correct quantification procedure in QA. This is evident from the case study that 3% addition to the measured kV, 6.2% addition in the measured dose, and 4.5% to the measured time accounts for measurement uncertainty.

The coupled natural circulation loops (NCLs) based passive systems have gained importance in nuclear industry due to their infinite grace time during severe accidents. However, the behavior of these systems is quite complex due to their regenerative feedback effects. In this connection, a numerical model to investigate the dynamics of single-phase coupled NCLs has been developed. The governing equations are solved using finite volume method. The model has additional features for wall conduction, fluid axial conduction, heater-cooler orientations, etc. Further, water-steam property subroutine is used for fluid properties instead of Boussinesq approximation. The model is validated against both single and coupled loop experimental facilities. It is then applied to investigate the transients of vertically coupled two identical NCLs. Results showed that Loop-1 flow is noted to be higher than Loop-2, the same is successfully explained based on temporal temperature profiles. A comparison of single and coupled NCLs revealed that their dynamics are different. The effects of aspect ratio, loop diameter, wall thickness, initial flow field on dynamics of coupled NCLs are investigated. Further, the flow is noted to be proportional to both loop diameter and aspect ratio. The influence of other parameters is also discussed to bring out their influence on dynamics of coupled NCLs.