Safety design rationale

Safety Design Rationale for Venting the Reactor Vessel Head... 

The design constraints identified as necessary to control system hazards are passed to the implementers and assurers of the individual system components along with standards and other requirements. Success is determined through feedback provided by test reports, reviews, and various additional hazard analyses. At the end of the development process, the results of the hazard analyses as well as documentation of the safety-related design features and design rationale should be passed on to the maintenance group to be used in the system evolution and sustainment process. 

The vertical intent dimension has seven levels. Each level represents a different model of the system from a different perspective and supports a different type of reasoning about it. Refinement and decomposition occurs within each level of the specification, rather than between levels. Each level provides information not just about what and how, but why, that is, the design rationale and reasons behind the design decisions, including safety considerations. 

In a traditional System Safety program, much of this information is found in or can be derived from the hazard log, but it needs to be pulled out and provided in a form that makes it easy to locate and use in operations. Recording design rationale and assumptions in intent specifications allows using that information both as the criteria under which enforcement of the safety constraints is predicated and in the inevitable upgrades and changes that will need to be made during operations. Chapter 10 shows how to identify and record the necessary information. 

The design of the operational safety controls are based on assumptions about the conditions during operations. Examples include assumptions about how the operators will operate the system and the environment (both social and physical) in which the system will operate. These conditions may change. Therefore, not only must the assumptions and design rationale be conveyed to those who will operate the system, but there also need to be safeguards against changes over time that violate those assumptions. 

Once again, audits and performance assessments should start from the safety constraints and design assumptions and rationale. The goal should be to determine whether the safety constraints are being enforced in the operation of the system and whether the assumptions underlying the safety design and rationale are still true. Audits and performance assessments provide a chance to detect whether the behavior of the system and the system components still satisfies the safety constraints and whether the way the controllers think the system is working—as reflected in their process models—is accurate. 

Design Rationale The design of a deep draft navigation project must result in a safe, efficient, reliable and least cost plan with appropriate consideration of environmental and social aspects. However, the factors of safety, efficiency and reliability must be accommodated before the cost is optimized. Costs include construction, maintenance and replacement. 

Recent development highlighted a shift in FDA position and interpretation of the market exclusivity clause. Under the orphan designation, three interferon products, Betaseron (IFN-pib), Avonex (IFN-pia) and Rebif (IFN-pia) are currently approved for treatment of multiple sclerosis (MS). The interplay in drug safety and efficacy consideration, business strategies, and regulatory rationale permitting approval of the three drugs for MS treatment is discussed in Box 3.5. 

The Maintenance of Wakefulness Test (MWT) was developed as an alternative, physiologically based test of sleepiness (1). The test was designed for use with patients whose sleepiness during the day might adversely affect performance or safety. Reasoning on the basis of face validity, a person who has little difficulty with falling asleep inappropriately should be able to stay awake in a quiet, sedentary situation such as during MWT trails. Beyond the procedure s face validity, there are other rationales for the use of the MWT, as discussed below. 

Additional safety studies may be required to support the movement into new indications, and the complex designer biopharmaceuticals will continue to require creative approaches to safety assessment. In either case, the requirement for, and design and execution of, those studies should be driven by sound scientific rationale. Ultimately, the objective of preclinical safety evaluation is well articulated in ICH S6 ... 

In this paper, we provided the rationale and definition of a benchmark test called BMTl to look at the implications of THM couplings on safety parameters in the near field of a hypothetical repository. This hypothetical repository possesses composite features since it is based on a Japanese design, with a Japanese bentonite used as buffer material and the heat output characteristics of Japanese spent fuel. However, the permeability and strength characteristics of the rock mass are based on typical properties of granites of the Canadian Shield. 

The obvious need to avoid undue disclosure of internal issues and business methods, names, distribution lists and the like, as well as to avoid transmitting information extraneous or strictly tangential to the technical matter at hand, must not be confused with undue reticence. If others are expected to properly implement in-house process know-how or to use it as the basis for an activity to be done on our behalf or as part of an agreement or license, the disclosure of the technical information must be no less than sufficient what works and what does not work, the technical rationale for the prior decisions, our best understanding of the process issues and sufficient detail of methods, process design calculations, and data. In particular, data on thermochemical safety, industrial hygiene, and environmental profile need to be fully disclosed. 

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