Process safety analysis criteria

There are a large number of studies showing that when a program is instituted to reduce the frequency of unsafe behaviors, a reduction in incident rate coincides with a reduction in unsafe behaviors. Krause, Seymore, and Sloat (1999) report a meta-analysis of 73 firms that implemented behavior-based safety programs for up to five years. Reductions in accident rates from pre-implementation baselines averaged 29 percent after one year and up to 69 percent by the fifth year. Thus, there is criterion-based validity when incidents are the criterion. We are not aware of any studies that have used process safety incidents or fatalities as a criterion. 

The fourth criterion assesses the ability of the full complement of plant systems to perform their safety functions. By application of this criterion, the plant is shown to be Within the bounds of the existing safety envelope for SRS reactors. Further, this process aids in identifying specific areas for improving the documentation of the SRS safety analysis. 

As a part of the Unreviewed Safety Question (USQ) review, the proposed activity must be evaluated to the criteria set forth in the Technical Specifications and the Safety Analysis Report (SAR). Seismic concerns and designs are both covered by the Technical Specifications and the SAR and are addressed by the USQ process. The procedure further requires that the USQ evaluation be approved by DOE prior to implementation of the activity when a USQ is determined to exist. The requirement to use the USQ process applies to all systems thereby enveloping the requirements of restart criterion 3. 

The analysis and evaluation problem involves modeling the alternatives in an appropriate fashion and then developing an evaluation criterion so that one can compare them to each other. Developing a suitable criterion is often a nearly impossible task. How does one compare the safety of two processes For the problem of reaction path synthesis, how does one compare alternative chemical routes to the same molecule when one cannot predict kinetics If it proves possible to develop a suitable evaluation function, then one must still be able to do the analysis and evaluation quickly. One is usually faced with an enormous number of alternatives in synthesis, and a trade off is necessary between analysis and evaluation speed and accuracy. 

One example of a component-based testing method is the Vehicle Related Pedestrian Safety Index (VERPS) [73, 74]. This index utilizes a linear scale for both active and passive safety measures. The pedestrian head impact in frontal passenger vehicle collisions is assessed using the Head Injury Criterion (HIC) as metric. The method delivers specific results for a given vehicle and pedestrian combination. The evaluation process includes accident data analysis for relevant scenarios, kinematic analysis (via multi-body simulation), hardware component testing, and a procedure to obtain the VERPS index [73, 74]. The VERPS index takes only the probability for AIS3+ head injuries due to impact on the vehicle into account, since this probability can be derived from the HIC measurement. 

Large-break accident analysis of CSRIOOO was performed using the advanced process simulation software (AFROS) code to clarify its characteristics and to evaluate the capability of its safety system (Dang et al., 2013). At the cold-leg large-break accident, the maximum cladding temperature is lower than the criterion 1260°C by approximately 340°C, which appears during the blow-down phase. 

---