Preliminary hazard analysis features

Two types of analytical methods are used to evaluate hazards 1) preliminary hazards analysis (PHA), and 2) failure modes and effects analysis (FMEA). PHA is an accident scenario-based form of analysis. The FMEA is a complementary type of evaluation that utilizes a system failure-based form of analysis. Generally, FMEAs were only accomplished for equipment which was perceived to have a significant safety role, i.e. SSCs which were anticipated to be designated as safety significant in accordance with DOE-STD-3009. Unlike PHA, the first objective of FMEA is to subdivide the facility into several different (and, to the maximum extent possible, independent) system elements. Failure modes of each system element are then postulated and a structured esramination of the consequences of each failure mode follows. However, similar to PHA, FMEA. documents preventive and mitigative features (failure mechanisms and compensation) and anticipated accident consequences (failure effects). This appendix documents the FMEA for the HCF. 

The GPCA safety requirements were designed on the basis of a preliminary hazard analysis for the controller of the pump. We found that almost half of the requirements can be related to user interface functionalities, and correctly capture basic human factors concerns. However, a hazard analysis specifically addressing user interface functionalities is needed to cover a more complete set of aspects related to human factors. We are currently starting this hazard analysis. Some examples of safety features and constraints that are currently not considered in the GPCA safety requirements and can potentially make the user interface design safer follows. 

A formal hazard analysis of the anticipated operations was conducted using Preliminary Hazard Assessment (PHA) and Failure Modes and Effects Analysis (FMEA) techniques to evaluate potential hazards associated with processing operations, waste handling and storage, quality control activities, and maintenance. This process included the identification of various features to control or mitigate the identified hazards. Based on the hazard analysis, a more limited set of accident scenarios was selected for quantitative evaiuation, which bound the risks to the public. These scenarios included radioactive material spills and fires and considered the effects of equipment failure, human error, and the potential effects of natural phenomena and other external events. The hazard analysis process led to the selection of eight design basis accidents (DBA s), which are summarized in Table E.4-1. 

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