The EDF failure reporting system process, presentation and prospects

This paper describes the procedure Electricité de France uses to exploit the information on pressurized water reactor operation it receives back from the field (operation feedback).The first requirement in analyzing such data is a knowledge of past records. The first step, therefore, is to record the data, particularly events occurring on the plant and failures occurring on equipment, in large reliability data banks.However, the ‘raw’ information stored is rarely usable directly. The first step in the second stage—analysis—is to review and qualify the data before using it for any purpose. This difficult, but essential, review provides valuable information on the improvement of equipment reliability.The greater knowledge of plant and equipment behaviour, and the damage mechanisms involved, allows:

• safety to be kept at a high level: operation feedback is also essential for probabilistic safety studies,

• improvement of availability and preventive maintenance practices,

• correction of the initial design (design changes) and help for designing future plants.

Finally, operation feedback is a source of progress. Although it requires heavy initial investment, it is also a source of profit. It is a source of learning. The analysis results make it possible to define more suitable procedures and better preventive maintenance practices and thus improve the operation and safety of existing and future plants.     

Diversity in computerized reactor protection systems

Based on engineering judgement, the most important measures to increase the independency of redundant trains of a computerized safety instrumentation and control system (I&C) in a nuclear power plant are evaluated with respect to practical applications. This paper will contribute to an objective discussion on the necessary and justifiable arrangement of diversity in a computerized safety I&C system. Important conclusions are:

(i) diverse equipment may be used to control dependent failures only if measures necessary for designing, licensing, and operating a computerized safety I&C system homogeneous in equipment are neither technically nor economically feasible;

(ii) the considerable large operating experience in France with a non-diverse equipment digital reactor protection system does not call for equipment diversity. Although there are no generally accepted methods, the licensing authority is still required to take into account dependent failures in a probabilistic safety analysis;

(ii) the frequency of postulated initiating events implies which I&C functionality should be implemented on diverse equipment. Using non-safety I&C equipment in addition to safety I&C equipment is attractive because its necessary unavailability to control an initiating event in teamwork with the safety I&C equipment is estimated to range from 0.01 to 0.1. This can be achieved by operational experience.

Generic probabilistic safety analysis: application to the comparison of the emergency feedwater system designs of three PWRs and to the modernisation and backfitting of older Swedish NPPs

The relationship between configuration characteristics of safety systems and their unavailabilities was examined on the basis of the results of 25 PSAs for PWR and BWR plants [1 and 2]. The results of the evaluations provide groupings of configuration characteristics and associated ranges of unavailabilities that can be expected for the various groups. The safety functions

• residual heat removal at BWR plants

• coolant make-up at BWR plants

• auxiliary/emergency feedwater supply to steam generators at PWR plants

• emergency core cooling, including containment spray injection/recirculation, at PWR plants

were considered.Two applications are reported:

• evidence of validation of the generic approach, based on the results of a blind prediction of the unavailability of the emergency feedwater function at the plants N4, Sizewell-B and Konvoi, and subsequent comparison with results obtained by conventional reliability analysis;

• outline of the use of the approach in the framework of the modernisation and backfitting programme for Swedish nuclear power plants.

In the early discussions of safety objectives for the modernisation programme, the generic approach provided input to the exploration of possible target values for safety systems. In the process of reviewing proposed technical solutions, Swedish Nuclear Power Inspectorate (SKI) is using the generic approach as one of the tools for assessing safety function unavailabilities.     

Application of Bayesian statistical decision theory for a maintenance optimization problem

Reliability-centered maintenance (RCM) is a rational approach that can be used to identify the equipment of facilities that may turn out to be critical with respect to safety, to availability, or to maintenance costs. Is is dor these critical pieces of equipment alone that a corrective (one waits for a failure) or preventive (the type and frequency are specified) maintenance policy is established.But this approach has limitations:

• •when there is little operating feedback and it concerns rare events affecting a piece of equipment judged critical on a priori grounds (how is it possible, in this case, to decide whether or not it is critical, since there is conflict between the gravity of the potential failure and its frequency?);

• •when the aim is propose an optimal maintenance frequency for a critical piece of equipment - changing the maintenance frequency hitherto applied may cause a significant drift in the observed reliability of the equipment, an aspect not generally taken into account in the RCM approach.

In these two situations, expert judgments can be combined with the available operating feedback (Bayesian approach) and the combination of risk of failure and economic consequences taken into account (statistical decision theory) to achieve a true optimization of maintenance policy choices.This paper presents an application on the maintenace of diesel generator component.     

Occurrence of common mode failure

In technical facilities, for example in nuclear power plants, redundant systems are used to prevent random failures from deleting the complete system function. However, although this redundancy concept is adequate to cope with random failures in single redundancies, its applicability is limited in case of multiple failures due to a systematic failure cause to which all redundancies are submitted due to their identical features.Some general considerations have been formulated to rule out the occurrence of such common mode failure (CMF) in redundant systems under certain circumstances. CMF means that in more than one redundancy the systematic failure cause is activated at the same time, or within the same frame of time (e.g. during the mission time for an accident). It therefore has to be distinguished between the systematic cause and the actual occurrence of CMF: a latently existing systematic cause does not necessarily lead to simultaneous failure; it must be activated and therefore is only the prerequisite for CMF.A systematic cause results in simultaneous failure if

• —the systematic cause is activated by specific circumstances associated with the accident: a triggering effect to which the redundancies are subjected due to their identical features.

• —previous failures have accumulated undetectedly before the accident.

They now appear on demand due to the accident.For exclusion of CMF, both exclusion of a triggering effect and of accumulation is necessary. A trigger can be excluded, if the components are not affected by the accident at all, or are not submitted to any ‘abnormal’ operation. Accumulation can be ruled out by self annuciation.From this a matrix for excluding CMF-susceptibility has been derived.     

Japan’s intellectual property strategy

Initiated by a speech by the Japanese Prime Minister in 2002, an improved strategy for the creation, protection and use of intellectual property in the Japanese economy has rapidly evolved. The author outlines the major elements and achievements of the new strategy under five categories:

– Creativity and inventiveness (e.g. facilitating technology transfer from universities to the private sector).

– Protection (e.g. trilateral sharing of search and examination results, speedier examination, and the establishment of an IP high court).

– Exploitation (e.g. widening the range of organisations allowed to assist SMEs).

– Contents (mainly aspects of IP in the movie industry).

– Cultivating human resources (e.g. increased emphasis on IP education in universities).

Future work, in phase 2 through to 2009, in making Japan an ‘IP Rich Country’, will concentrate on building on these changes to integrate IP more fully into business growth.     

Identifying driver modules based on multi‐omics biological networks in prostate cancer

The development of sequencing technology has promoted the expansion of cancer genome data. It is necessary to identify the pathogenesis of cancer at the molecular level and explore reliable treatment methods and precise drug targets in cancer by identifying carcinogenic functional modules in massive multi‐omics data. However, there are still limitations to identifying carcinogenic driver modules by utilising genetic characteristics simply. Therefore, this study proposes a computational method, NetAP, to identify driver modules in prostate cancer. Firstly, high mutual exclusivity, high coverage, and high topological similarity between genes are integrated to construct a weight function, which calculates the weight of gene pairs in a biological network. Secondly, the random walk method is utilised to reevaluate the strength of interaction among genes. Finally, the optimal driver modules are identified by utilising the affinity propagation algorithm. According to the results, the authors’ method identifies more validated driver genes and driver modules compared with the other previous methods. Thus, the proposed NetAP method can identify carcinogenic driver modules effectively and reliably, and the experimental results provide a powerful basis for cancer diagnosis, treatment and drug targets.

Abbreviations

CNV

Copy number variation

FN

False Negative

FP

False Positive

HPRD

Human protein reference database

JS

Jensen–Shannon

KL

Kullback–Leibler

NCG

A comprehensive catalogue of known and candidate cancer genes from cancer sequencing screens.

PRAD

Prostate adenocarcinoma

PPI

Protein–protein interaction

TCGA

The cancer genome Atlas

TN

True Negative

TP

True Positive

     

Survey of the annual technical reports on the industrial property information activities of IP offices in the year 2001

The activities in the year 2001 of some 46 intellectual property offices and organizations worldwide in the field of patent, trademark and industrial design information are summarized, based on the Annual Technical Reports (ATRs) provided by those offices and organizations. The summary for each country commences with filing statistics, followed by the most relevant, new features of their information activities. Both the filing and information activities vary enormously.The author concludes, inter alia, that

1. In most industrialised countries as well as some of the emerging countries, the number of IP rights applications continued to increase.

2. The granting/registration procedures have not kept up in many IP Offices with this increased number of applications.

3. Work on systems permitting electronic filing of applications, correspondence and fee payment is continuing at a great pace.

4. CD-ROM, DVD and the Internet are now the major vectors for disseminating IP information.

5. The value of the ATRs, and their chronological and geographical comparisons, is increasingly limited by the absence of many ATRs each year and the repetition of information already provided in previous ATRs.

     

The structure and dynamics of technological systems: a conceptual model

This paper focuses on the construction of an integrated model of technological systems. The model has two purposes:

1. (1) to clarify the scope and relations of various concepts in this field, especially the concepts of technology, of national systems of innovation, and of technological systems; and

2. (2) to provide a framework in which to study the conceptualization and construction of evolving technological systems.

These purposes require the creation of new concepts and the redefinitions of some familiar ones. The model is structured at four levels of aggregation:

1. (1)the individual;

2. (2)the organizational;

3. (3)the sectoral; and

4. (4)the national.

From within this structure we can identify parallaxes, or changes in the appearance of each of the four levels as the level from which observation takes place is changed. The structure of the model and the concept of parallax serve to clarify some important complexities of the dynamics of the system within which technological change takes place.     

DESIGN FOR MULTI-HIT CAPABILITY

We consider the general problem of multiple impacts onto a mosaic in which one or two cells is broken by each impact. Impact onto a broken cell or a cell interface defeats the array. Multiple impacts are defined statistically, and equations are given for calculations n₅₀, defined as the number of impacts for which the probability is 50% that:

1. one cell is hit more than once, or

2. an impact occurs on an interface between two cells. The value of n₅₀ is determined by the number of cells, the cell shape, and width of the interface zone.

Statistics and analysis of relevant citations in international search reports in the CPO

Since China acceded to the PCT in 1994, the Chinese Patent Office has been establishing examination search files to meet the requirements of the PCT minimum documentation. In order to have a basis for future work, this paper gives statistics and analysis by categories of the relevant documents cited in 159 PCT international search reports which the CPO finished in 1994 and 1995, including countries, number of documents and technical fields. The conclusions are as follows:

1. (1) the technical fields of the majority of Chinese patents seeking protection outside China in 1994 and 1995 claimed medical apparatus and instruments, and health care medicines;

2. (2) at present, the starting year for search files should be fixed temporarily at 1920;

3. (3) in PCT international search reports made in the CPO, US patents were cited most often, followed by Chinese documents, then European documents. Japanese documents were fourth and PCT documents fifth; and

4. (4) the most common languages used by the examiners carrying out these searches were English and Chinese.

     

A Gamma–normal series truncation approximation for computing the Weibull renewal function

This paper presents a series truncation approximation for computing the Weibull renewal function. In the proposed model, the n-fold convolution of the Weibull Cdf is approximated by a mixture of the n-fold convolutions of Gamma and normal Cdfs. The mixture weight can be optimally determined and fitted into a very accurate linear function of Weibull shape parameter β. Major advantages of the proposed model include:

(a) The proposed model and its parameters can be directly written out. Using the proposed model, the renewal density and variance functions can be easily evaluated.

(b) The proposed model includes Gamma and normal series truncation models as its special cases. It is easy to be implemented in Excel. The series converges fairly fast.

(c) Over the range of β(0.87,8.0), the maximum absolute error is smaller than 0.01; and over , the maximum absolute error is smaller than 0.0037.

(d) The model can be easily extended to non-Weibull case with some additional work.

Multi-state reliability demonstration tests

ABSTRACT

Reliability demonstration tests have important applications in reliability assurance activities to demonstrate product quality over time and safeguard companies’ market positions and competitiveness. With greatly increasing global market competition, conventional binomial reliability demonstration tests based on binary test outcomes (success or failure) at a single time point become insufficient for meeting consumers’ diverse requirements. This article proposes multi-state reliability demonstration tests (MSRDTs) for demonstrating reliability at multiple time periods or involving multiple failure modes. The design strategy for MSRDTs employs a Bayesian approach to allow incorporation of prior knowledge, which has the potential to reduce the test sample size. Simultaneous demonstration of multiple objectives can be achieved and critical requirements specified to avoid early/critical failures can be explicitly demonstrated to ensure high customer satisfaction. Two case studies are explored to demonstrate the proposed test plans for different objectives.     

The modelling of degraded and critical failures for components with dormant failures

The failures reported in reliability data bases are often classified into sseverity classes, e.g., as critical or degraded failures. This paper presents models for the failure mechanism causing the degraded and critical failures, and estimators for the failure intensities of the models are provided. The discussions mainly focus on dormant (hidden) failures of a standby component. The suggested models are based on exponentially distributed random variables, but they give non-exponential (phase-type) distributions for the time to failure, and thus provide alternatives to the more common Weibull model. The main model is adapted to the information available in modern reliability data bases. Using this model it is also possible to quantify the reduction in the rate of critical failures, achieved by repairing degraded failures. In particular the so-called ‘naked failure rate’ (defined as the rate of critical failures that would be observed if no repair of degraded failures was carried out) is derived. Further, the safety unavailability (Mean Fractional Deadtime) of a dormant system is obtained for the new model.     

Integration of computation and testing for reliability estimation

This paper develops a methodology to integrate reliability testing and computational reliability analysis for product development. The presence of information uncertainty such as statistical uncertainty and modeling error is incorporated. The integration of testing and computation leads to a more cost-efficient estimation of failure probability and life distribution than the tests-only approach currently followed by the industry. A Bayesian procedure is proposed to quantify the modeling uncertainty using random parameters, including the uncertainty in mechanical and statistical model selection and the uncertainty in distribution parameters. An adaptive method is developed to determine the number of tests needed to achieve a desired confidence level in the reliability estimates, by combining prior computational prediction and test data. Two kinds of tests — failure probability estimation and life estimation — are considered. The prior distribution and confidence interval of failure probability in both cases are estimated using computational reliability methods, and are updated using the results of tests performed during the product development phase.     

Practical investigations of two-stage bacon tempering

Bacon has to be tempered (part-frozen) before it can be sliced in a high-speed slicing operation. Traditionally the desired slicing temperature was achieved in a long single-stage process. Increasingly a two-stage process of heat removal followed by temperature equalisation is used to reduce processing time and weight loss. The objectives of the work described in this paper were:

To provide practical design data for a two-stage bacon-slicing operation.

To provide data that could be used in the development and verification of a model that would help optimise current and new tempering systems.

     

Sensibility of Bayesian inference methods for reliability prediction of ageing systems,case of Diesel locomotives

This paper addresses the problem of reliability analysis of in-service identical systems when a limited number of lifetime data is available compared to censored ones. Lifetime (resp. censored) data characterise the life of failed (resp. non-failed) systems in the sample. Because, censored data induce biassed estimators of reliability model parameters, a methodology approach is proposed to overcome this inconvenience and improve the accuracy of the parameter estimation based on Bayesian inference methods. These methods combine, in an effective way, system’s life data and expert opinions learned from failure diagnosis of similar systems. Three Bayesian inference methods are considered: Classical Bayesian, Extended Bayesian and Bayesian Restoration Maximisation methods. Given a sample of lifetime data, simulated according to prior opinions of maintenance expert, a sensibility analysis of each Bayesian method is performed. Reliability analysis of critical subsystems of Diesel locomotives is established under the proposed methodology approach. The relevance of each Bayesian inference methods with respect to collected reliability data of critical subsystems and expert opinions is discussed.     

Bayesian reliability analysis when multiple early failures may be present

Summary This paper discusses the Bayesian reliability analysis for an exponential failure model on the basis of some ordered observations when the firstp observations may represent “early failures” or “outliers”. The Bayes estimators of the mean life and reliability are obtained for the underlying parametric model referred to as theSB(p) model under the assumption of the squared error loss function, the inverted gamma prior for the scale parameter and a generalized uniform prior for the nuisance parameter.