Critical safety characteristic

Critical characteristic is any feature throughout the life cycle of a critical item, such as dimension, tolerance, finish, material or assembly, manufacturing or inspection process, operation, field maintenance, or depot overhaul requirement that if nonconforming, missing, or degraded may cause the failure or malfunction of the critical item. The term critical characteristic is synonymous with critical safety characteristic. ... 

Critical safety characteristic is any feature, such as tolerance, finish, material composition, manufacturing, assembly, or inspection process or product, which if nonconforming or missing could cause the failure or malfunction of a CSI. See Critical Safety Item (CSI) for additional related information. 

CSI is a part, assembly, installation, subsystem, or system with one or more critical safety characteristics that, if missing or not conforming to the design requirements, quality requirements, or overhaul, and maintenance requirements, would result in an unsafe condition leading to death or serious injury. It is typically a part that must be manufactured to specific tolerances and maintained within these tolerances for safe system operation. A CSI part is a controlled part where certain safety characteristics are critical and are therefore tightly controlled. 

Wires and cables that are utilized in enclosed spaces are usually required to have fire safety characteristics as described in various codes and standards. The codes and standards governing fire safety of wires and cables are highly complex and diverse, both by application and by geography, and play a critical role in determining selection and formulation of insulation and jacketing materials. Thus, careful review of applicable standards is essential prior to beginning formulation or product development. 

As discussed in para 418.1, during preparation of the certificate, care should be taken relative to the authorized quantity, type and form of the contents of each package because of the potential impact on criticality safety. Any special inspections or tests of the contents to confirm the characteristics of the contents prior to shipment should be specified in the certificate. This is of particular importance for any removable... 

As discussed in para. 418.1, care should be taken relative to the authorized quantity, type and form of the contents of each package because of the potential impact on criticality safety. Any inspections or tests of the contents that may be needed to confirm the characteristics of contents prior to shipment should be specified in the certificate. Measurements that satisfy the requirements of para. 674(b) may need to be performed prior to loading and/or shipment if the package contains irradiated nuclear fuel. The criteria that the measurement must satisfy should be specified or referenced in the certificate for the package (see related advisory material of para. 502.8). Similarly, if special features are allowed to exclude water in-leakage, specific inspections and/or test procedures to ensure compliance should be stated (or referenced) in the certificate. 

VII.22. The application for approval of a transportation package should demonstrate that the calculational method (codes and cross-section data) used to establish criticality safety has been validated against measured data that can be shown to be applicable to the package design characteristics. The validation process should provide a basis for the reliability of the calculational method and should justify the value that is considered the subcritical limit for the packaging system. 

At the Los Alamos Scientific Laboratory the need has been recognized for a program to provide an improved appreciation of criticality safety fundamentals to super visors of fissile material processes. Many of the senior people who have been with the Laboratory for many years are now retiring. These people, had the opportunity to develop their familiarity with criticality safety considerations as operations e3q>anded from the relatively small scale which was characteristic of the early days. Their successors are denied this opportunity, and some feel the need for an educational program having more. depth than is appropriate for every employee. 

Small mass critical configura ns have always been of interest and importance in criticality safety. Olson and Robkin have previously calcuUted crHical masses for thin flat foils of U and immersed in Urge Dfi reflectors. This study was based on the mathematical observation that an infinite sUb of fissionable materUl with 1) > 1, immersed in an infinite nonabsorbing reflector, would approach zero thickness. The temperature of the fissile core and DjO reflector was lowered to 4 K in the calculations to rethermalize neutrons striking the core and to take advantage of the absorption characteristics of the fuel. Under these conditions a minimum critical mass of 35 g was obtained for U and 22 g for Pu. The method of calculation was a two-group diffusion analysU of a thin, centrally located core. 

This standard provides criteria for the administration of a nuclear criticality safety program for operations outside of reactors in which there exists a potential for criticality accidents. Responsibilities of management, supervision, and the nuclear criticality safety staff are addressed. Objectives and characteristics of operating and emergency procedures are included. 

Another fascinating (but critical in terms of product safety) characteristic of bacteria is their capacity to grow extremely fast if the environmental cmiditions in terms of nutrient availability, moisture and temperature become favourable. 

Define the characteristics of the safety management programs necessary to ensure the safe operation of the facility, including a criticality safety program, where applicable. Depending on the type of nuclear facility and where it is in its life cycle, the DSA format will typically be one or more of the following ... 

Symptom based EOPs can resolve some of the limitations of the event based approach by formally defining and prioritizing the major critical safety functions. In symptom based procedures, the decisions for measures to respond to events should be specified with respect to the symptoms and the state of systems of the plant (such as the values of safety parameters and critical safety functions). This allows the operator to maintain optimal operating characteristics without the need to be concerned with the continuing accident scenario. The method for monitoring plant parameters used in the symptom based approach is in accordance with the needs of the plant staff in severe accident conditions. 

While additives meant to improve the SEl certainly constitute a major portion of the additive research for Li-ion batteries, many other additives aim to improve different aspects of the Li-ion batteries, such as the safety characteristics, ionic conductivity of the electrolyte, and high/low temperature performance of the electrolyte. For example, researchers have developed redox shuttle and overcharge shutdown additives to protect the battery from overcharge and the resulting thermal mnaway, flame retardant additives to reduce the flammability of the electrolyte, and anion receptors to enhance the ionic conductivity and increase the lithium transference number. These additives may not be critical to the cell performance, but may be very important and possibly necessary in commercial batteries. 

HA is the systematic examination of a system, item, or product within its life cycle, to identify hazardous conditions including those associated with human, product, and environmental interfaces, and to assess their consequences to the functional and safety characteristics of the system or product. In order to design-in safety, hazards must be designed-out (eliminated) or mitigated (reduced in risk), which can only be accomplished through HA. Hazard identification is a critical system safety function and is one of the basic required elements of an SSP. 

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