Several Research Methods Introduction on NPP Operators Reliability

International Journal of Nuclear Energy Science and Engineering, Volume 6, 2016 www.ijnese.org doi: 10.14355/ijnese.2016.06.001

Several Research Methods Introduction on NPP Operators Reliability Jiang Shengyao, Li Fu, Zhou Yangping, He Xuhong, Fang Jingxuan* Tsinghua University, Beijing 100084, China Beijing 101 Middle School, Beijing 100091, China zhouyp@mail.tsinghua.edu.cn; joannafjx@sina.com Abstract The paper introduces several relevant research methods on reliability to Chinese nuclear power plant operators in past over 10 years based on nuclear power plant (NPP) simulator platform. The relevant research methods including human cognition reliability model, fuzzy synthetic evaluation math model, and psychology quality research model etc. are introduced briefly.

The introduction is not only a fact record of past over 10 years research about operator reliability, but also a kind of summary about the research methods. The research methods on NPP operators’ reliability will be not only useful to the safe operation of nuclear power plant, but also referenced to the operator research of other industries.

Keywords Nuclear Power Plant Operator, HCR Model, Borda, Possibilistic Fuzzy Regression Model, Psychology Quality, Fuzzy Synthetic Evaluation, Psychology Evaluation

Introduction Electricity is the key source of power for socio‐economic development of any country. Almost every country needs a stable and powerful source which will be able to supply energy continuously for a very long period of time.

Nuclear energy can be the best solution to this problem. Primary sources of energy can’t provide that much of energy as nuclear energy. [26] So nuclear energy application leads to safety issue.

Among the serious events and accidents in nuclear power plant (NPP), the human beings related errors are over 50%. Now many countries in the world have taken more attention to the research of human being reliability. [1] As the most important factor to protect the safety of NPP, the NPP operators are highly regarded. The research methods on NPP operators are various. Several research methods on the reliability of Chinese NPP operators in past over 10 years have given out brief introduction and summary. The application of these methods is not only important to NPP safe operation but also referred to the research of the operators of other industries on reliability.

Several Research Methods on NPP Operators Reliability The safe operation of NPP includes equipments and operators two aspects. The equipments reliability research of NPP could be applied with some methods like Monte Carlo method to simplify the Bayes estimation of nuclear power plant equipment reliability. The method makes it possible to automatically and quickly analyze the reliability data and greatly simplify the computing procedure. [2] As brief introduction showed above, besides the equipment reliability research, the most important research should be focused on the NPP operators. The relevant research on Chinese NPP operators’ reliability mainly includes human cognitive reliability (HCR) model research, synthetic evaluation on operators, psychological evaluation on operators and etc. The relevant systematic research continued several steps and many aspects. The process and content of relevant research on NPP and NPP operators’ reliability can be showed as Figure 1.

Basic capacity of operators includes education background, working years, working position, license situation and etc. Position capacity of operators includes relevant position knowledge capability, accidents responding ability,

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cooperation capability and communication skill etc. Psychological evaluation of operators touches the most important factor affecting the safety of NPP or operators themselves. The relevant methods will be introduced briefly as below.

Reliability Research on NPP Reliability Research on Equipments Reliability Research on Operators

Basic Capacity Evaluation of Operators

Position Capacity Evaluation of Operators

Psychological Quality Evaluation of Operators

FIG.1 RELIABILITY RESEARCH ON NPP

Cognitive Model of Reliability Research on NPP Operators The research method on NPP operators’ reliability is focused on the quantitative research of event response under the restrained time based on NPP simulator. The simulated data is come from computer simulation like macro‐ computer and etc. Now with the computer technique rapid development, the simulator sever can take the role of plant and does various mathematical calculations to mimic the reactor in real time. [28] Among the serious events and accidents in NPP, the errors related to human beings are over 50%. [3] Now many countries in the world have taken more attention to the research of human reliability. There are many countries & regions such as USA, Hungary, Japan, Taiwan, making use of human cognitive reliability (HCR) model to do the quantitative research of NPP operators. [4‐8] The HCR model is one of the most useful models to study Human Reliability Analysis (HRA) quantitatively. As a cognitive model, it is also the most usually used method in NPP operator behavior research. The HCR method has the following six steps: [9] 1)

Identifying the actions that must be analyzed by the HRA, using, e.g., a task analysis method.

2) Classifying the types of cognitive processing required by the actions. This classification uses a sequence of binary choices, resulting in a classification in terms of skill‐based, rule‐based and knowledge‐based actions.

3) Determining the median response time (T0.5) of a crew to perform the required tasks.

4) Adjusting the median response time to account for performance influencing factors.

5) For each action, determining the system time window (Tsw) in which action must be taken.

6) Finally, dividing the Tsw by T0.5 to obtain a normalized time value. Based on this, the probability of non‐ response is found by using a set of time‐reliability curves.

It is clear from this description of the method that the reference is made to a specific operator model, i.e., the skill‐ based, rule‐based, knowledge‐based characteristics developed as an elaboration of the step‐ladder model. [10] This model is used in two different ways. One way is to classify the ‘cognitive processing’ required by the actions. The other way is to distinguish between three time‐reliability curves which provide different values for the probability of non‐response for each type of ‘cognitive processing’. [11] The HCR curves are shown in Figure 2. The reliability cognitive model of NPP operators is often described by the curves. These curves can be fitted by three‐parameter Weibull distribution [12], two‐parameter Weibull distribution [13] or logarithmic normal distribution.

The applied cognitive model of the research on the reliability of Chinese NPP operators is showed in formula as below: P(t)=exp‐[( t/ T0.5)/Ai] Bi (1) T0.5 is the median time that NPP operators execute an action;

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Ai, Bi are the related size, shape parameters of ith kind cognitive action, respectively; P(t) is the non‐response probability of NPP operator at t.

Non‐response Probability

10 0 Knowledge-based 10 - 1 Skill-based

Rule-based

10 - 2

10 ‐ 3 10 0 10 Normalized Time FIG.2 HCR CURVE

The research on the NPP operators’ reliability is often combined with the training of NPP operators in many countries of the world. [14] The experimental research on Chinese NPP operators’ reliability was also done together with the training on the NPP simulator.

Six accidents are selected in the reliability experiment research. They are steam generator tube rupture (SGTR), loss of coolant accident (LOCA), main steam line break (MSLB), external power network failure 1 (EPNF1), external power network failure 2 (EPNF2) and anticipated transient without scram (ATWS).

The experiments include wide‐ranging human‐system interaction (HI) based on HCR model. The six selected accidents were performed on a real NPP full size simulator of China. It is referred to a 300MW, two‐circular PWR NPP. The attendees are 38 operators who come from a NPP of China. The experimental parameters of the two‐ parameter Weibull distribution described with formula (1) are shown in Table 1.

TABLE 1 THE PARAMETERS OF TWO‐PARAMETER WEIBULL DISTRIBUTION (300MW)

Accident

Ai

Bi

T 0 . 5 (S)

SGTR

1.17

2.39

118.41

MSLB

1.11

3.4

15.88

LOCA

1.23

1.75

53.47

EPNF1

1.24

1.72

6.45

EPNF2

1.65

0.97

15.88

ATWS

1.32

1.11

62.94

Based on the experimental parameters, the fitting curves of the two‐parameter Weibull distribution to the six accidents can be obtained. The fitting curves of six accidents based on the two‐parameter Weibull distribution are shown in Figure 3.

From the research some conclusions could be found: 1) Through the academic analysis and experimental result on the reliability research of the Chinese NPP operators based on different kinds of simulators, the applied cognitive model on HCR is verified; 2) The cognitive type of Chinese NPP operators is a rule‐based type of HCR. The research method based on two‐parameter Weibull distribution can be used to verify cognitive model‐HCR model.

3) The median time can be used as a behavior indicator of the NPP operators.

4) The related results of the fitting curves based on two‐parameter Weibull distribution can be referred to laying down the real NPP operating regulations which apply to the response time of emergency accidents.

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Since all experiments were based on simulator platform, the data collection is very important. According to recent research results, in order to be against gross measurement errors, data reconciliation (DR) should be applied. [25] And for real time monitoring, distributed data acquisition system is also applied. [27] This will be a direction for future research.

Furthermore, in the research only rule‐based type conclusion was got based on 38 operators sample. For more Chinese NPP operators, the conclusion could be verified further in future research.

Non‐response Probability

1.0 0.8 0.6 0.4

HI1‐SGTR(+) HI2‐MSLB(ᇞ) HI3‐LOCA(□) HI4‐EPNF1(▽) HI5‐EPNF2(▲) HI6‐ATWS(■)

0.2 0.10 0.08 0.06

HI4 HI3

0.04

HI5 HI6

HI2 HI1

0.02 0.01 0.1

0.2

0.4

0.6 0.8 1.0

2.0

4.0

6.0 8.0 10.0

Normalized Time FIG. 3 6 HI FITTING CURVES BASED ON TWO‐PARAMETER WEIBULL DISTRIBUTION

Reliability Research on NPP Operators Based on Possibilistic Fuzzy Regression Model The reliability research of nuclear power plant (NPP) operators is focused on the non‐response probability of NPP operators under the restrained time. The response time to the accidents is very important. It can be influenced by the performance shape factors (PSF). Since PSF include many factors and uncertainties, it is very difficult to process quantitatively. Based on the probability distribution of the response time on HCR model, in order to solve the uncertainty problem on the non‐response probability, the response time is supposed as a single point value. This is the traditional research method of HCR model. However, the uncertainty of the median time to the accidents on HCR model can be influenced by PSF, it is not complete to regard the response time as only a simple point value.

The relevant method of fuzzy mathematics is utilized to do research on the NPP operator response time distribution related to PSF. The method describes the linear relations between response time and PSF. The relations can be described by the fuzzy definition of PSF that can be set up by a linear fuzzy system equation and made use of fuzzy linear regression to estimate related fuzzy parameters. Furthermore, the possibilistic distribution function of the response time to the accidents of NPP operators can be obtained.

The relevant formula is shown in formula 2 as below: [15] Y=A0+A1X1+…+ AnXn (2) Y is responding time described by fuzzy data. X1, X2…Xn are real number of PSF. A0 is a fuzzy constant. It describes parameter of responding time to the accidents of NPP operators. A1, A2…An are fuzzy data to express the PSF parameters that affect responding time of accidents such as urgent pressure, EOP procedure, cognitive level, HI design level, safety parameter display system(SPDS), structure of operators, communication, training and experience etc.

Considering Chinese NPP operators situation, the possibilistic linear model for the response time Yj is assumed to be as follows in formula 3: Yj＝A0+A1X1j+A2X2j+A3X3j (3)

where X1j, X2j, X3j denote age, experience outside a control room and education for the jth crew group, respectively.

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When Yj is the fuzzy observed value with respect to the jth input variable Xj =(X1… X3)j and Ai are fuzzy numbers， i = 0,…3，A0 denotes the accident response time represented by fuzzy parameter of NPP operators, A1, A2 and A3 denote age, experience outside a control room and education represented by fuzzy parameters.[16] Through the research to 24 Chinese NPP operators with 8 groups considering the average data including responding time to accident, age, control room experience and education etc, the possibilistic linear regression model for the response time Y is as below in formula 4: Y=(1417.2,10)L +(‐121.8,0)LX1+(82.27,0)LX2+(95.45,0)LX3 (4) where X1，X2，X3 denotes the variable of age, experience outside a control room and education respectively.

Based on formula (4), A0 is a positive value, and the accident response time of NPP operator has a basic fuzzy number constant. The function of PSF can be realized through A1, A2 and A3. The coefficient of age of operators A1 is negative, it makes clear that the older the age is, the more possibility the rapid response based on experience has.

The feedback is negative to the response time. Both the coefficient of the experience outside a control room of operators A2 and the coefficient of the education A3 are positive. It shows that rich working experience and good education can improve the synthetic quality and the judge ability.

The research method is based on 24 Chinese operators and some accidents. The key point is the possibilistic linear model could be used to do research on NPP operators’ reliability. However, the sample number is not more enough and the relevant PSFs also could be discussed moreover.

Synthetic Evaluation of NPP Operators Based on Borda Score Human being is a key factor to the safety of NPP operation. Synthetic evaluation of NPP operators is related to such as knowledge skill, psychological personality, organization design, behavior and environment etc. The human relevant experiments to NPP operators can reflect their synthetic ability to some extent. Considering the environment of NPP operators, the test results can be analyzed based on their background. Through making use of Fuzzy supervision, the evaluation to NPP operators can be obtained not only qualitatively, but also quantitatively.

Fuzzy synthetic evaluation supplies the method and tool of quantitative analysis to NPP operators. In this method, to the factor set U={u1 , u2 , …, un }, evaluation result can be expressed by different class, appraisal and data.

Assuming there are m kinds of evaluation class or appraisal, the relevant evaluation set is V={ v1 , v2 , …, vm }.

Because of the different extent of different evaluation factor, evaluation factor ui is arranged relevant weight factor n

ai , and  ai  1 . Different weight assignments can lead to different synthetic evaluation results. The weight i 1

assignment of various factors can be described as A={a1 , a2 , …, an }. After getting U, V and A, evaluation set can be obtained through combining Fuzzy transform (A(UV)) [17] Fuzzy performance evaluation factor set of NPP operators can be assigned as B={SGTR, LOCA, MSLB, EPNF1, EPNF2, ATWS}. The Borda score about experiment accidents of NPP operators is described in Table 2.

TABLE 2 BORDA SCORE OF ACCIDENTS RESPONSE PROBABILITY OF NPP OPERATORS (BP)

No.

SGTR

MSLB

LOCA

EPNF1

EPNF2

ATWS

1

0

1

1

0

0

2

7

0

0

0

1

3

5

5

3

2

4

3

7

4

4

1

5

3

5

6

6

2

6

6

4

2

2

0

7

2

3

5

5

3

8

1

1

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n

To each NPP operator, the sum of total weight factor is 1, or  i ( x)  1 . n is the number that NPP operator i 1

n

attends experiments. The overall Borda score of each NPP operator is Bt   i ( x) Bi ( x) . [18] The performance i 1

evaluation results of 8 NPP operators are showed in Table 3.

TABLE 3 PERFORMANCE EVALUATION RESULTS OF NPP OPERATORS

Operator No.

Bp

Ranks

1

0.3

8

2

2.4

6

3

3.9

2

4

3.5

3

5

4

1

6

2.6

5

7

3.4

4

8

1

7

Performance evaluation is a part of synthetic ability of NPP operators. In actual evaluation, the environment fact should be added. So the similar method can be used to analyze synthetic ability of NPP operators. Two factors including NPP operator’s working experience and education experience will be regarded as evaluation factors.

Fuzzy synthetic evaluation factor set of NPP operators is Bs={Working Experience, Education Experience, Performance Evaluation}. The synthetic ability rank of NPP operators is in Table 4.

TABLE 4 SYNTHETIC EVALUATION RESULTS OF NPP OPERATORS

Operator No.

Bs

Ranks

1

3

3

2

2

7

3

4.2

2

4

2.9

4

5

4.6

1

6

2.4

6

7

2.8

5

8

1.6

8

The Fuzzy synthetic evaluation of NPP operators is based on the value of accident response probability and environment factors such as working experience and education experience. The higher the value is, the bigger the Borda score is. The bigger the Borda score is, the stronger the synthetic ability that the NPP operator has. The synthetic evaluation result is influenced by many factors of NPP operators such as age, education background, psychological factor and environment etc.

Based on the ranks nine years ago, the present situation of 8 NPP operators can verify the related analysis method and model. Among 8 NPP operators, the top 4 ranks have been promoted or appointed important work. For example, the operator ranked 1 has been arranged to other country to control NPP operation. The operators ranking 2, 4 and 5 were also assigned to other country to operate NPP. The other operators stayed here to be responsible for NPP operation. The evaluation results in the past reflected their relevant ability. [19] The Fuzzy synthetic evaluation of NPP operators supplies a kind of tools or methods to evaluate capability of NPP operators. The method needs a long time to verify the experiment conclusion many years ago. So its efficiency is not good. However, the method could be used to other industry people.

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Psychology Quality Evaluation Research on NPP Operators With the modern psychological survey theory research development and psychology test applied in the personnel selection, the psychology selection system is playing a more and more remarkable part in the personnel selection and appraisal. It is becoming one of the most important contents to evaluate and forecast the human behavior.

The oversea research to the dangerous occupation starts relatively early. For example, pilot psychology selection system is used and leads to prominent result in pilot selection in Germany; the research on NPP operators from Prognoz Institute of Psychology of former Soviet Union indicates that the performance level is related to some certain specific psychological characteristics like sense of responsibility, emotional stability and so on. In addition, the psychological research also involved member of submarine, driver of express train, and management personnel of airplane etc.

To China nuclear domain, the dimensions to select NPP operator psychological quality have not been set up. The relevant research is not sufficient.

To Chinese NPP operators, 9 NPP accidents which are connected closely with NPP operators are selected to analyze. Chinese NPP operator psychology selection system including cognition ability, personality psychology characteristics and psychological health 3 aspects is obtained through the relevant research finally.

1) Cognition Ability The cognition ability of Chinese NPP operators includes capability of observation, operation ability, attention, memory ability, and quantity analysis ability and logic judgment ability 6 aspects.

2) Personality Characteristics Personality is a person who takes into action through special way including internal structure and process.

Personality psychology characteristics include Gregarious, Venturesome, Self‐Regulation, Emotional Stability, and Risk Taking and Achievement Motivation 6 dimensions.

3) Psychological Health Psychological health is a fundamental requirement to operator normal operation. The research includes Somatization, Obsessive‐Compulsive, Interpersonal Sensitivity, Depression, Anxiety, Hostility, Phobic Anxiety, Paranoid Ideation and Psychoticism 9 dimensions.

Cognition ability can be tested through professional psychology instrument; Personality psychology characteristics is mainly obtained through paper test and expert interview; Psychological health measurement can be got through SCL‐90 table. [20] TABLE 5 THE EXAMPLE OF CHINESE NPP OPERATORS PSYCHOLOGICAL CHARACTERISTICS DATA

z4

z5

z6

S1

S2

S3

S4

S5

S6

S7

S8

S9

61

54

54

55

1.1

1.3

1.3

1.1

1.1

1.2

1.1

1.2

1.2

64

62

50

58

56

1.1

1.4

1.3

1.1

1.1

1.2

1.0

1.3

1.4

46

58

50

45

52

1.5

2.5

2.2

2.2

1.5

1.7

1.3

2.5

1.3

z1

z2

z3

Normal

57

55

A

66

B

56

Note: z1 to z 6 is Gregarious, Venturesome, Self‐Regulation, Emotional Stability, Risk Taking and Achievement Motivation respectively; S1 to S9 is Somatization, Obsessive‐Compulsive, Interpersonal Sensitivity, Depression, Anxiety, Hostility, Phobic Anxiety, Paranoid Ideation and Psychoticism respectively.

Table 5 displays psychological characteristics data of 2 operators. Compared with the relevant standard which is showed in normal line in the Table 5, A is better than B in performance which can be easily found.

The NPP operators could be evaluated through the method relevant to psychological characteristics. Because the human being is complicated, different psychological characteristics data can display the capability of different NPP

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operators. The experiment is initial, the relevant research could be done to more NPP operators and other industry people.

Research of Psychological Characteristics and Performance Relativity of NPP Operators Psychological characteristics and performance relativity are two important aspects of psychology research of nuclear power plant operators. In order to get psychological characteristics and performance relativity, the relevant data of operators need to be got firstly. Then the relevant research model can be showed in Figure 4.

Analysis of Behavior Characteristics of Operators

Model of Psychological Characteristics of Operators

Model of Performance Appraisal of Operators

Selection and Draft of Suitable Measurement Table

Draft of Suitable Measurement Table of

Measurement of Psychological Characteristics of Operators

Performance Evaluation

Measurement of Performance Appraisal of Operators

Modudule of Measurement of Psychological Module of Measurement of Working Characteristics of Operators Performance of Operators

Analysis of Psychological Characteristics and Performance Relativity

FIG.4 THE RESEARCH METHOD OF RELATIVITY

36 Chinese NPP operators’ psychological characteristics data were obtained. The data including mean, standard deviation, maximum, minimum and normal model of each dimension of psychological characteristics table of 36 operators are showed in Table 6.

From Table 6, there is no much difference between nuclear power plant operators and normal model in the aspects including Gregarious, Venturesome and Achievement Motivation. The Self‐Regulation is lower than normal model.

Emotional Stability and Risk Taking are much higher than normal model. The other aspects including Somatization, Obsessive‐Compulsive, Interpersonal Sensitivity, Depression, Anxiety, Hostility, Phobic Anxiety, Paranoid Ideation and Psychoticism are lower than normal model.

In order to get the relationship between psychological characteristics of operators and performance, the relativity analysis result of 36 operators is shown in Table 7.

The dimensions can be divided into upper and down two parts from Table 7. The upper 6 personality characteristics dimensions basically are positive relativity to performance. The higher the score of dimension is, the better the performance is. The Gregarious, Self‐Regulation and Emotional Stability are obviously positive relativity to the working performance (The working performance is the average of task performance and satisfaction). The

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down 9 psychological health dimensions are negative relativity to performance. The higher the score of dimension is, the worse the performance is. The Obsessive‐Compulsive, Interpersonal Sensitivity and Depression are obviously negative relativity to the working performance.

TABLE 6 TESTING RESULT OF PSYCHOLOGICAL CHARACTERISTICS OF OPERATORS

Min

Max

Mean

Standard deviation

Normal model

Normal model standard deviation

Gregarious

47

68

56.7

5.0

56.02

7.77

Venturesome

40

66

54.6

6.0

/

/

Self‐Confidence

15

24

19.36

2.23

20.15

1.84

Self‐Regulation

44

74

59.7

7.4

62.36

8.83

Emotional Stability

39

68

53.5

7.0

47.12

9.40

Risk Taking

42

67

53.4

5.9

38.68

9.46

Achievement Motivation

45

69

54.3

6.2

53.26

5.88

Somatization

1.00

2.00

1.17

0.26

1.37

0.48

Obsessive‐Compulsive

1.00

2.50

1.36

0.41

1.62

0.58

Interpersonal Sensitivity

1.00

2.89

1.34

0.46

1.65

0.51

Depression

1.00

2.23

1.22

0.34

1.50

0.59

Anxiety

1.00

2.00

1.14

0.25

1.39

0.43

Hostility

1.00

2.33

1.25

0.41

1.48

0.56

Phobic Anxiety

1.00

1.71

1.09

0.16

1.23

0.41

Paranoid Ideation

1.00

2.83

1.28

0.47

1.43

0.57

Psychoticism

1.00

1.90

1.16

0.24

1.29

0.42

TABLE 7 RELATIVITY ANALYSIS OF PSYCHOLOGICAL CHARACTERISTICS AND PERFORMANCE

Task performance

Satisfaction

Working performance

Gregarious

0.405*

0.413*

0.503*

Venturesome

0.381*

0.118

0.235

Self‐Regulation

0.273

0.326

0.369*

Emotional Stability

0.194

0.427*

0.388*

Risk Taking

0.240

‐0.076

0.092

Achievement Motivation

0.258

0.245

0.309

Somatization

‐0.195

‐0.231

‐0.263

Obsessive‐Compulsive

‐0.192

‐0.343*

‐0.332*

Interpersonal Sensitivity

‐0.125

‐0.413*

‐0.338*

Depression

‐0.213

‐0.410*

‐0.388*

Anxiety

‐0.244

‐0.027

‐0.161

Hostility

‐0.086

‐0.319

‐0.255

Phobic Anxiety

‐0.013

‐0.056

‐0.044

Paranoid Ideation

‐0.179

‐0.344*

‐0.326

Psychoticism

‐0.035

‐0.128

‐0.102

*，P<0.05

The data of psychological characteristics and performance of 36 nuclear power plant operators are tested and analyzed. The conclusion is as below: 1. There are some differences between 15 psychological characteristics dimensions of nuclear power plant

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operators and normal model. The Self‐Regulation dimension is lower than normal model. The Emotional Stability and Risk Taking dimensions are obviously much higher than normal model. The 9 psychological health dimensions including Somatization, Obsessive‐Compulsive, Interpersonal Sensitivity, Depression, Anxiety, Hostility, Phobic Anxiety, Paranoid Ideation and Psychoticism are lower than normal model. It shows that the common quality of operators is better.

2. The 6 personality characteristics dimensions including Gregarious, Venturesome, Self‐Regulation, Emotional Stability, Risk Taking and Achievement Motivation are positive relativity to the working performance. The Gregarious, Self‐Regulation and Emotional Stability are obviously positive relativity to the working performance.

The 9 psychological health dimensions including Somatization, Obsessive‐Compulsive, Interpersonal Sensitivity, Depression, Anxiety, Hostility, Phobic Anxiety, Paranoid Ideation and Psychoticism are negative relativity to the working performance. The Obsessive‐Compulsive, Interpersonal Sensitivity and Depression are obviously negative relativity to the working performance. It shows when the higher the score of Gregarious, Self‐Regulation and Emotional Stability etc 6 personality characteristics dimensions is, the higher the relevant working performance is; when the higher the score of Obsessive‐Compulsive, Interpersonal Sensitivity and Depression etc 9 psychological health dimensions is, the lower the relevant working performance is.

3. There are tight relationship between psychological characteristics and performance among risky occupation people. The people who have high performance usually have good cooperation, daring to do things, calmness and psychological health. Nuclear power plant operators are also in line with the rule. [21] Since NPP operators belong to risky occupation people. The experiment shows what kind of people should be searched for doing this kind of job, because different type people will lead to different results to some extent based on different psychological characteristics.

Other Application in the Reliability Research of NPP Operators The reliability research of NPP operators includes many aspects and dimensions such as basic quality, position capability and relevant psychological factors etc evaluation. The process is very complicated. While human being, time and related environment etc factors being added up together, the system will be more complicated. [22]Where the expert system could be utilized very well to make decision and judge efficiently. When the evaluation factors more complete, the evaluation rules more detail, the final results will be near to the real fact. [23] In order to support NPP operators to judge rapidly and correctly, fault diagnosis method had been studied deeply.

The relevant method like genetic algorithms is used. Since the imperfection of expert knowledge, illusive signals and multi‐faults diagnosing are serious problems to fault diagnosis of NPP, based on Genetic Algorithms (GA), and the method contraposed the characteristic of the fault diagnosis of NPP and integrated with classical probability theory. The method can diagnose several faults that happen at the same time and has comparative adaptability to the imperfection of expert knowledge, illusive signal and other instance. The application can support NPP operators very well in accidents diagnosis. [24] Summary The paper introduced the several research methods on Chinese NPP operators’ reliability in past over 10 years. All research methods including NPP operators HCR model, Fuzzy regress model to responding time calculation, Fuzzy synthetic evaluation and psychological evaluation system etc. surround the most important factor to NPP‐ NPP operators to do research.

The introduction of these methods shows the possible research dimensions to NPP operators. These dimensions include operation experiment capability, the capability being related to what kinds of factors, what kinds of factors affecting synthetic capabilities, different psychological characteristics data being related to different type people, moreover relevant to different performances and etc. The combination of these methods will help evaluate NPP operators very well.

The relevant research is not only to play important part to NPP safe operation, but also to give reference to other industries on both research methods and operators reliability.

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