Initial checklists, analysis

ANALYSIS DOCUMENTATION. PrHA report documentation should include the PrHA worksheets, checklists, logic diagrams, human reliability analyses, and any other analysis made to better understand the scenarios. The PSM Rule requires that human factors that impact scenarios as cause or protection be expanded to analyze the basic cause of errors or response failures. For example, a cause may identify that an operator can turn the wrong valve to initiate an accident. The PSM Rule requires that basic causes also be identified. For example, valve is not labeled the operator has not been trained on the operation or the operator forgot the step. There may be more than one basic cause. (See also Section 3.2, paragraph on Human Factors.)... 

The determination of the undesired and initiating events depends on the area, to which a plant belongs, on the object and the objective of the analysis. It belongs to the qualitative part of the analysis and may be supported by checklists (vid. Sect. 9.1.2.1) or systematic methods like FMEA (vid. Sect. 9.1.2.4) or HAZOP (vid. Sect. 9.1.2.3). 

Potential external events were identified by reviewing previous Safety Analysis Reports of similar DOE facilities (Restrepo 1995) and the recommended list of external events used to evaluate commercial nuclear power plant risks (NRC 1983). In addition, an attempt was made to identify any other potential external-initiating event unique to the site that had not been considered in previous studies. It is important to note that operational accidents (e.g., criticality, internal fires) occurring inside the HCF and assodated radioactive material storage facilities are not considered in this screening process. These types of "internal initiating events are identified separately using preliminary hazard checklists (see Appendix 3A). 

All nodes of a RCA methodology can be examined to identify those that could relate to the antecedents and consequences of problematic behaviours. This information can be used in the form of checklists by incident investigators to lead them into the ABC analysis from their initial investigation using RCA. 

FEED stage At the initial FEED stage, PFDs, certain equipment, etc. are fixed and it is in the process of development of a P. ID. At this stage, preliminary hazard analysis, checklists, etc. are utilized for PHA. Then, slowly instrumentation is developed based on layers of protections desired as a safeguard and interlock. 

The application ofthe N18.2 checklist has been reviewed against the APIOOO design and PRA, and been appropriately updated to reflect the plant s specific design features. On this basis, while potential Anticipated Transient Without Scram (ATWS) faults are included in ANSI N 18.2, for the APIOOO no causes for these have been identified within the Design Basis (i.e. the initiating event frequency is less than 10-5 per reactor year). These faults are addressed via PRA and Severe Accident Analysis (as described in Section 5.4 and 5.5 of this chapter). This issue is discussed in sub-section 4.4.1.3 ofthe APIOOO Fault Schedule (Reference 5.1). 

One of the key issues in initiating the CRIOP analysis has been to select the relevant checklist items and scenarios during the planning and preparation phase. The identified issues should be further explored in the subsequent CRIOP analysis. The scenario analysis is an important arena for exploring challenging situations. Experienced CCR operators should be involved to identify scenarios to be explored. Given the limited time available for a CRIOP analysis, it is important not to include too many questions or too many scenarios. The CRIOP analysis must not be performed as a defence, or... 

During the workshops it was also mentioned that the checklist contained many questions and that the questions were somewhat academic or theoretical. Some of the questions were difficult to answer by a clear Yes or No. But even participants who initially were sceptical to CRIOP were positively surprised by the discussions and the results of the analysis. 

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