12 Human Factors
ARTICLE 12 HUMAN FACTORS
Each Contracting Party shall take the appropriate steps to ensure that the capabilities and limitations of human performance are taken into account throughout the life of a nuclear installation.
Regulatory requirements
The safety criteria for nuclear power plants [3-1] stipulate as a matter of principle that high requirements have to be imposed on the design and quality of the nuclear installations.
Further, safety-enhancing operating principles are to be realised. These general requirements include, among others,
− ease of maintenance of the systems and plant components under special consideration of possible radiation exposure of the personnel,
− ergonomic measures at the workplaces, and
− reliable monitoring of the operating conditions.
Criterion 2.5 [3-1] requires that workplaces and work procedures are to be designed under ergonomic aspects in such a way that they create the prerequisites for the personnel’s optimal behaviour in terms of safety.
KTA safety standard [KTA 3501] requires that necessary manual initiations of protective actions for controlling incidents are not required before a time span of 30 minutes. This requirement has considerable influence on the automation of protective actions and the design of the control room.
The general requirements on man, technology and organisation are specified in guidelines and KTA safety standards.
The general procedure of maintenance measures is described in the guideline for the procedure for preparation and performance of maintenance and modifications at nuclear power plants [3-41].
KTA safety standard [KTA 1201] includes the requirements on the operating manual, KTA safety standard [KTA 1202] analogously the requirements for the testing manual.
KTA safety standard [KTA 3904] makes requirements on control room, emergency control room and local control stations in nuclear power plants.
Implementation and measures of the plant operators (according to their own statement)
The nuclear power plants are controlled and operated from a central control room. The control room is equipped with all the information, activation and communication systems that are necessary for normal operation and for coping with abnormal operation and design basis accidents. For the design of the control room, great importance was attached to ergonomic aspects.
German nuclear power plants are highly automated. In addition to the extensive instrumentation and control systems available for operation, many of the more complex
procedures are activated by automatic controls. This relieves the personnel from routine actions and the control room staff is able to concentrate on the monitoring of safety.
The concept of the reactor protection system design includes the automatic control of design basis accidents for a period of at least 30 minutes without the need for any manual action. In the case of abnormal operation or design basis accidents, the aim of this concept is to ensure sufficient time to diagnose the situation and take appropriate actions.
Computerised information systems support the operating personnel in all nuclear power plants. With regard to maintenance, especially as concerns in-service inspections, extensive technical measures are provided to prevent human errors or to minimise their effects. These measures range from permanently installed and unambiguously identifiable testing devices to testing computers and the automatic resetting of safety systems in the event of their inadvertent actuation by the reactor protection system in the course of an in-service inspection.
Irrespective of the numerous technical provisions for preventing human errors, tools were implemented to further optimise the man-machine interface. In addition to the human factors programme (optimisation of the man-machine interface), already established in the nineties, the analyses of events (also referred to as HF events) was further optimised by introducing optimised methods (safety through organisational learning). In this respect, the operators of the German nuclear power plants developed a guideline on an integrated event analyses within the framework of the VGB Power Tech e.V. (VGB). Apart from the reportable events, reports about other abnormal occurrences and voluntary reports made by staff members are also recorded and investigated. For the analysis and determination of the contributing factors that have led to an event, generally accepted ergonomic methods are applied. The investigations comprise the areas man, technology and the organisation.
With the introduction of the VGB guideline on safety culture in 1999, the operators of the German nuclear power plants also showed how they interpret and practise safety culture and by means of which criteria effectiveness can be assessed. Accordingly, a high safety culture results in an awareness of the persons involved in plant processes that the safety of the nuclear power plant has the highest priority, that allows an appropriate handling of errors and that there is a working atmosphere based on trust. Essential principles of this guideline have been integrated in the management principles, company concepts, etc. and thus binding for the company’s staff.
Regulatory review
The fulfilment of the requirements on the man-machine interface is checked by the licensing authority in the licensing procedures for construction and operation of the plant according to the requirements of the rules and regulations. To this end, verifications of the plant operator are subjected to extensive reviews on behalf of the authority. Modifications of safety-relevant plant components and written operating procedures are subject to regulatory review within the framework of the modification procedure. Scope and depth of the review depend on the safety relevance of the modification. For the handling of reportable events and other occurrences, the authority also considers the contributing factors from the areas man and organisation.
The concept of the plant operators on an integrated event analysis was reviewed for its suitability by the Länder authorities within the framework of their supervisory activities, partly with the support of the authorised experts. The plant operators give report to the supervisory authority on the application, results and effectiveness of their integrated event analysis.
Moreover, the supervisory authority reviews the methods of the plant operator for the
analysis of events and experience feedback in technical meetings. Main objective of the review is to ensure that the plant operator analyses the events in an integrated manner under consideration of all contributing factors from the areas man, technology and organisation and derives remedial measures with regard to the contributing factors.
In individual cases, the supervisory authority requires the performance of additional independent event analyses for in-depth assessment of contributing factors from the fields of man and organisation.