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

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

Results of eye lens doses control of medical personnel in St. Petersburg

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

Engineering and Analytical Method for Estimating the Parametric Reliability of Products by a Low Number of Tests

The paper provides an overview of methods for determining reliability indicators and, on the basis of the analysis, proposes a new method for assessing the parametric reliability of products based on a small number of tests. The determination of the parameters and double logistic distribution based on the test results is considered, a statistical experiment was carried out, which was based on the method of statistical modeling of Monte Carlo. An example of evaluating parametric reliability by a new method is also given, on the basis of which an engineering technique is proposed. In the conclusion, remarks are made regarding the advantages of the novel method

Engineering and Analytical Method for Estimating the Parametric Reliability of Products by a Low Number of Tests

The paper provides an overview of methods for determining reliability indicators and, on the basis of the analysis, proposes a new method for assessing the parametric reliability of products based on a small number of tests. The determination of the parameters and double logistic distribution based on the test results is considered, a statistical experiment was carried out, which was based on the method of statistical modeling of Monte Carlo. An example of evaluating parametric reliability by a new method is also given, on the basis of which an engineering technique is proposed. In the conclusion, remarks are made regarding the advantages of the novel method

Assessment of current exposure of the population living in the Techa River basin from radioactive releases of the Mayak facility

Current doses arising from external and internal pathways have been estimated for the residents of two villages, Muslumovo and Brodokalmak, alongside the Techa River, which was contaminated by radioactive releases from the Mayak production facility. The dose estimates are based on numerous environmental measurements supplemented by further human whole body measurements and studies on occupational and dietary habits of Slavic and Turkish ethnic groups. Estimated doses arise mainly from use of the contaminated floodplains alongside the Techa River. The current average annual effective dose attributable to Cs-137 and Sr-90 in the environment, under conditions where restrictions on some river-related activities are in place, may exceed the Russian national action level of 1 mSv only in the hypothetical critical group of herdsmen in Muslumovo. The dose to this critical group in Brodokalmak is assessed to be 3 times less than that in Muslumovo and 2 fold below the action level. The external and internal exposures give comparable contributions to the total dose in both settlements and population groups: 47% and 53% in Muslumovo and 40% and 60% in Brodokalmak, respectively. About one quarter to one half of the internal dose in adults arises from the intake of Sr-90. In order to avoid substantial increases in the dose received by Muslumovo residents, it is expedient to prolong the current policy of restriction of some river-related population activities in this village