Safety by design

A HAZOP (Hazard and Operability Study) involves a fonual review of proeess and instrumentation diagrams by a speeialist team using a stmetured teehnique, based upon key words. These eomprise property words and guide words , e.g. as in Table 12.4. 

Where possible plants of intrinsleahy safe design are prefeiTed, i.e. those whieh have been designed to be self-eorreeting rather than those where equipment has been added on to eontrol hazards. Some eharaeteristies of intrinsleahy safe plants are  

Are unstable reactions and side reactions possible, e.g. spontaneous combustion or polymerization  

Could poor mixing or inefficient distribution of reactants and heat sources result in undesirable side reactions, hot spots, runaway reactions, fouling, etc  

Can hazards from the reaction be reduced by changing the relative concentration of reactants or other operating conditions Can side reactions produce toxic or explosive material, or cause dangerous fouling  

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Safety by design should always be the aim, but it is often impossible or too expensive and we then have to rely on procedures. Key features of all procedures are as follows-. 

Safety first has always been and continues to be the basic policy of the nuclear industry. This includes reactor safety by design as well as activities to discourage the proliferation of nuclear weapons and to prevent sabotage of nuclear facilities. This policy has been successful the chance of death from a nuclear accident is over a million times less than death... 

Safety by Design. Safety concerns are the other half of the approval process. Surely sound statistical criteria should be used to quantify this critical process and ensure that public health concerns are addressed appropriately, both before and after approval. Safety is of concern for both the clinical trial participants and the future subjects if the product is approved. Yet the simple questions How much safety data is enough and Where do the greatest risks lie are usually answered based on regulatory precedent rather than any statistical modeling of risk or variability. 

Donaldson K et al (2011) Identifying the pulmonary hazard of high aspect ratio nanoparticles to enable their safety-by-design. Nanomedicine (Lond) 6(1) 143-156 Doshi DA, Gibaud A, Goletto V, Lu M, Gerung H, Ocko B, Han SM, Brinker CJ (2003) J Am Chem Soc 125 11646... 

Increasing the defence-in-depth by implementing a safety by design approach ... 

Thus, IRIS has adopted the internal CRDMs as reference (traditional CRDMs remaining as backup) because (1) they eliminate the corrosion problem, (2) they are one more implementation of the safety-by-design IRIS philosophy, and (3) current advancements which have occurred in Japan in regard to the electromagnetic concept, while internally to the IRIS project. Polytechnic of Milan has further advanced the hydraulic drive concept. IRIS is currently evaluating candidate concepts for the internal CRDMs to proceed with the preliminary design of the chosen one. 

The IRIS design provides for multiple levels of defence for accident mitigation (in-depth-in-depth (DID)), resulting in extremely low core damage probabilities. In addition to the traditional DID levels (barriers, redundancy, diversity, etc.) IRIS introduces a very basic level of DID, i.e., elimination by design of accident initiators or reduction of their consequences/probability. This is implemented through the safety-by-design IRIS philosophy, which was briefly presented in the introduction. 

Several features of the design form the basis of the safety-by-design approach. These features are summarized in Table 3 and are discussed in the following. Table 4 provides an overview of how the safety-by-design features listed in Table 3 will impact the typical design basis events. 

TABLE 3. IMPLICATIONS OF SAFETY-BY-DESIGN IRIS PHILOSOPHY... 

Class rV design basis event IRIS design characteristic Results of safety-by-design IRIS philosophy... 

To complement its safety-by-design IRIS features limited and simplified passive systems as shown in Fig. 6. They include ... 

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