Methodology for failure analysis of complex technical systems and prevention of their consequences

The paper presents a study on the methodology of failures and their possible consequences analysis. Analysis of failures and their consequences is carried out for newly developed or modernized products and it is one of main activities in the reliability assurance system. The methodology is applied to the analysis of all designed systems, starting from the earliest stage of development, in order to evaluate the approach to development and compare the advantages of the design solution. The considered analysis of failures and their consequences of components is a part of the complex analysis of reliability of the whole product. Depending on the complexity of the design and the available data, a particular approach may be chosen for the analysis. In one case, it is a structural approach, in which a list of individual elements and their possible failures is compiled. In another case, it is the functional approach, which is based on the statement that each element must perform a number of functions that can be classified as solutions. The results provide a scheme for conducting the analysis and finding solutions to prevent them. The conclusions say that the level of detail determines the level at which failures are postulated

Esitmation of effective doses for barium meal fluoroscopic examinations

The aim of the current study is to establish conversion coefficients (CCs) from dose-area product to effective dose for barium meal (BM) fluoroscopic examinations. The study is based on data collected at a major University hospital in St-Petersburg, Russia. The structure of the BM examinations was evaluated and a computational model for effective dose estimation, using PCXMC 2.0 software, was developed. Resulting values of CCs estimated in the study were comparable with previously published data for BM examinations

Результаты контроля доз облучения хрусталиков глаз у медицинского персонала г. Санкт-Петербурга

Results of individual monitoring for personnel of X-ray surgical teams in several clinics of St. Petersburg are presented and analyzed. Measurements of the operational quantities – individual dose equivalents Hp (3) and Hp (10) were performed by thermoluminescent dosimetry method. Dosimeters designed to measure Hp (3) were located in the operators forehead area, and to determine Hp (10) both above the operator ‘s individual protective apron in the collar or chest area and under the protective apron in the chest area. The results of 34 measurements of the annual values of Hp (3) and Hp (10) measured above the apron and 24 values of Hp (10) measured below the apron were processed and analyzed. The results after the statistical treatment show that the probability of exceeding the annual values of Hp (3) in the personnel of X-ray surgical teams of the new dose limit 20 mSv is small, less than 1%. Exceeding the current dose limit of the equivalent exposure dose of the lens of the eye (150 mSv) is hardly possible at all under normal conditions. The best solution for evaluating the radiation dose of the lens of the eye is to measure the individual equivalent of the dose Hp (3), using a suitably calibrated TL-dosimeter (thermoluminescent dosimeter) located near the worker’s eyes. However, this additional dosimeter is only necessary when the values of eye lens equivalent dose can approach the new value of dose limit of 20 mSv. According to the results of the study, it is possible to introduce such an additional dosimeter if the annual value of Hp (10) recorded by the dosimeter located above the protective apron is more than 10 mSv.В работе представлены и проанализированы результаты индивидуального дозиметрического контроля персонала рентгенохирургических бригад нескольких клинических больниц г. Санкт-Петербурга. Измерения операционных величин – индивидуальных эквивалентов доз Нр (3) и Нр (10) проводились методом термолюминесцентной дозиметрии. Дозиметры, предназначенные для измерения Нр (3), располагались в области лба оператора, а для определения Нр (10) – как над индивидуальным защитным фартуком оператора в области воротничка или груди, так и под защитным фартуком в области груди. Были обработаны и проанализированы результаты 34 измерений годовых значений Нр (3) и Нр (10), измеренных над фартуком, и 24 значений Нр (10), измеренных под фартуком. Результаты статистической обработки показали, что вероятность превышения годовых значений Нр (3) у персонала рентгенохирургических бригад нового предела дозы 20 мЗв мала, – менее 1%. Превышение же существующего в настоящее время дозового предела эквивалентной дозы облучения хрусталика глаза (150 мЗв) вообще вряд ли возможно в нормальных условиях. Наилучшим решением для оценки дозы облучения хрусталика глаза является измерение индивидуального эквивалента дозы Нр (3) с помощью соответствующим образом откалиброванного ТЛ-дозиметра (термолюминесцентный дозиметр), расположенного вблизи глаз работника. Однако этот дополнительный дозиметр необходим только в случае, когда значение эквивалентной дозы облучения хрусталика глаза может приблизиться к новому значению предела дозы 20 мЗв. По результатам проведенного исследования введение такого дополнительного дозиметра возможно, если годовое значение Нр (10), регистрируемое дозиметром, расположенным над защитным фартуком, больше 10 мЗв

Application of monolithic foam concrete in building envelopes of a cottage, used in conditions of intermittent heating

The paper focuses upon the peculiarities of application of monolithic foam concrete as a heat-insulating layer in building envelopes of houses used in conditions of intermittent heating. The researchers analyze thermal characteristics, review literature describing the application of foam concrete in construction and demonstrate this material applicability at outer walls insulating, taking buildings and constructions with variable thermal behaviour as an example. The paper outlines main criteria that building envelopes of such structures should meet. To assess the effectiveness of monolithic foam concrete in building envelopes application, the authors carried out thermo-technical calculation of the outer walls, insulated with monolithic foam concrete. The graphs of dependence of multilayer building envelope heating time upon thickness of a heat-insulating layer and upon heat transmission resistance of the construction was obtained on the basis of these calculations. The dependence of specific energy consumption upon the heating time is also given in the paper. The study reveals the optimal range of thickness and density of monolithic foam concrete for insulating outer walls of buildings, used in in conditions of intermittent heating. This calculation also proves that the application of foam concrete as an insulant on the inside of the outer wall makes it possible to reduce the load on the building foundation

Application of monolithic foam concrete in building envelopes of a cottage, used in conditions of intermittent heating

The paper focuses upon the peculiarities of application of monolithic foam concrete as a heat-insulating layer in building envelopes of houses used in conditions of intermittent heating. The researchers analyze thermal characteristics, review literature describing the application of foam concrete in construction and demonstrate this material applicability at outer walls insulating, taking buildings and constructions with variable thermal behaviour as an example. The paper outlines main criteria that building envelopes of such structures should meet. To assess the effectiveness of monolithic foam concrete in building envelopes application, the authors carried out thermo-technical calculation of the outer walls, insulated with monolithic foam concrete. The graphs of dependence of multilayer building envelope heating time upon thickness of a heat-insulating layer and upon heat transmission resistance of the construction was obtained on the basis of these calculations. The dependence of specific energy consumption upon the heating time is also given in the paper. The study reveals the optimal range of thickness and density of monolithic foam concrete for insulating outer walls of buildings, used in in conditions of intermittent heating. This calculation also proves that the application of foam concrete as an insulant on the inside of the outer wall makes it possible to reduce the load on the building foundation

Comparison of organ absorbed doses in whole-body computed tomography scans of paediatric and adult patient models estimated by different methods

This study aimed to identify the uncertainty in estimations of organ absorbed dose using dedicated software by comparing with corresponding doses measured in physical phantoms. The comparison was performed for whole-body computed tomography (CT) obtained as part of positron emission tomography. Whole-body CT scans provide an advantage in terms of comparison because all organs are in the primary beam of the irradiated area. Organ doses estimated by the different software programs (CT-Expo, VirtualDose and NCICT) were compared by thermoluminescent detector measurements in anthropomorphic phantoms in 1-y-old, 5-y-old and adult patients. Differences were within ~15% in 12 major organs. However, differences of ~30% were observed in organs located at slightly different positions in the computational models compared to the physical phantoms. All investigated programs were deemed suitable for accurate estimation of organ absorbed dose

Estimation of conversion coefficients from dose-area product to effective dose for barium meal examinations for adult patients

The aim of the current study was to establish conversion coefficients (CCs) from dose-area product to effective dose for most common barium meal (BM) fluoroscopic examination. The study was based on data collection in two X-ray rooms in a major university hospital in St-Petersburg, Russia that allowed evaluating a structure of BM fluoroscopic examinations and developing a computed model of effective dose estimation using PCXMC 2.0 software. Results indicate that effective doses and the CCs were mainly influenced by the structure (contribution of different projections) and by the parameters (field size and energy characteristics of the X-ray beam) of the fluoroscopic examination. Resulting values of CCs estimated in the study were comparable with the published data for BM examinations

Potential for the establishment of national CT diagnostic reference levels in the Russian Federation

Computed tomography (CT) is a widespread diagnostic modality that is commonly associated with relatively high patient doses. Hence, optimization of radiation protection of the patients from CT examinations is extremely important. An integrant part of radiation protection in medicine is a system of diagnostic reference levels (DRLs). The aim of the study was to evaluate the possibility of establishing DRLs for typical CT examinations on national level in the Russian Federation. The study is based on the dose surveys performed in different regions of Russia in 2009-2017. Data was collected on the mostcommon native and multiphase CT examinations as well as whole body CT as a part of positron emission tomography combined with computed tomography (PET/CT) examinations. Establishment of DRLs on the region level in Russia iscomplicated due to the high number of regions and limited availability of dose data. Comparison between typical dose distributions indicated no significant regional differences, hence allowing establishing DRLs on the national level. The 75% percentiles of both DLP and effective dose distributions were proposed as the preliminary values of national DRLs. It was proposed to establish DRLs for whole native CT examinations or for one phase of multiphase CT examination

Estimation of the effective doses from typical fluoroscopic examinations with barium contrast

The current study aimed to estimate the effective doses and conversion coefficients (CCs) for typical barium swallow (BS), barium meal (BM) and barium enema (BE) protocols and to evaluate the impact of different examination parameters on the resulting CCs. Data were collected in surgical and therapy departments in St. Petersburg Urban Mariinsky Hospital. Computational models were developed using PCXMC 2.0 software. CCs (μSv × μGy-1 × m-2) were estimated, as follows, for over couch and under couch exposure geometries, respectively: 2.3 and 1.7 for BS (surgical department); 2.4 and 2.0 for BM (surgical department); 2.6 and 2.1 for BE (surgical department) 2.5 and 3.8 for BM (therapy department). The effective doses and CCs are mainly influenced by the combination of different fluoroscopic series and X-ray images taken in different projections, the irradiation field size and the energy characteristics of the X-ray beam