Reactivity, monitoring

If storage space at a reactor site is at a premium, a spent fuel reactivity monitor could be used to expand the capacity of some storage modes- ANSl/ANS-57.7 permits credit for burnup in the analysis of storage rack designs. However, an allowable fuel assembly reactivity must be established, and each fuel assembly must be shown by measurement to meet this criterion. These measurements could be accomplished by either static or pulse techniques. 

Feasibility of LWR Soberitical Reactivity Monitoring Using the Cf-Driven Neutron Noise Method, J. T. Mihalczo, W. T. King,J. A. Renier (ORNL)... 

Incident investigation is considered to be part of a reactive monitoring system because it is triggered after an event. The range of events includes ... 

So far, this chapter has concentrated on measuring activities designed to prevent the occurrence of injuries and work-reiated iii-heaith (active monitoring). Faiiures in risk controi aiso need to be measured (reactive monitoring), to provide opportunities to check performance, iearn from faiiures and improve the heaith and safety management system. 

Reactive monitoring arrangements inciude systems to identify and report ... 

Data from reactive monitoring should be considered by senior managers at least once a month. In most organizations serious events would be closely monitored as they happen. 

Dutyholders should measure their performance to assess how effectively risks are being controlled. Active monitoring provides feedback on performance and a basis for learning to improve before an accident or incident, whereas reactive monitoring involves identifying and reporting on incidents to check the controls In place. Identify weaknesses and learn from failures. 

Reviews are a management responsibility. They need to take account of information generated by the measuring (active and reactive monitoring) and auditing activities, and how to initiate remedial actions. 

Ideally, an analysis of all injury, damage and near-miss accidents should be undertaken, so that underlying trends may be highlighted and effective control action - both organisational and physical in nature - taken. It should be borne in mind that the use of accident statistics is classed as reactive monitoring, whereas the use of audits and inspections is classed as active (or proactive) monitoring. 

Because of the unique conditions that exist during initial fuel loading, temporary neutron detectors may be used in the reactor pressure vessel to provide additional reactivity monitoring. Credit for the use of temporary detectors may be taken in meeting Tech-Specs requirements on the number of operable source range channels. 

CFR 50.55a Codes and Standards Provides requirements that reactor internals stmctures and components important to safety be designed to quality standards conunensurate with the importance of the safety functions to be performed. These safety functions include reactivity monitoring and control, core cooling, and fission product confinement (within both the fuel cladding and the primary reactor coolant system). [6.7]... 

Monitoring safety management systems >- Active monitoring - tours and inspections, health surveillance or air quality sampling >- Reactive monitoring - investigating safety events, reports, etc. 

When measuring safety performance, successful organisations use a combination of both proactive and reactive monitoring techniques. 

Ideally, as in the case of reactive monitoring, statistical evidence as to the proactive performance will also be provided in such reviews. 

The first and most important step in investigating an unpianned event is to recognise it when it happens. The HSE describe these events as adverse events . Effective reactive monitoring of systems shouid aiiow an organisation to react to such adverse events. The reaction is normaiiy triggered by the outcome of the event, for exampie ... 

Comparisons with more recent figures from the UK tend to indicate that Bird s original findings hold some validity. Table 12.2 shows figures from the HSE for accident rates in 2001/02 for skilled tradesmen and machine operators. The table includes an estimate of the rate of near misses that would have occurred over the same period and gives an indication of the opportunities for reactive monitoring of adverse events that do not result in actual injury or loss. 

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