Safety significant item

Safety-related is used as a general overarching term applied to any item that is related to safety. In this usage it is inclusive of than safety-critical and safety-significant items (SSIs). 

The lower trigger level (alert) should be close to SL-1 (usually associated with operational limits), at which significant damage to safety related items is not expected. If the overall seismic capacity of the plant is lower than SL-1 (e.g. during the seismic re-evaluation), the lower trigger level should be referred to the actual seismic capacity of the plant. 

When a safety significant event is identified, an attempt is made to deteimine why the event happened. Was it the result of an unsafe condition (latent failure) or an unsafe act (active failure) The active failure(s) may stem from an unsafe condition(s). The investigators drill down imtil no other items remain (the last underlying factor). An example of a sequence of events diagram is given in Figure 3.3. 

At a system level, die items that need to be included in the EMIT schedule are those on which the technical specifications impose availability requirements, because such requirements come from the underlying nuclear safety case An EMIT schedule will be produced, containing all EMIT activities, using a structured maintenance task analysis process. Each task in die schedule will be classified according to its nuclear safety significance. 

Six items are started when placing the Primary-Secondary Cooling system in operation. The sequence in which the items are started has no safety significance except that ... 

The appropriate classification of SSCs, including software, that are items important to safety, on the basis of their safety significance ... 

Anomalous behavior is deviation from a general rule or regime it is inconsistent behavior deviating from what is usual, normal, or expected. In systems applications, anomalous behavior is behavior of an item that is not in accordance with the documented requirements or specifications for the item. It is unexpected behavior, and it is generally undesired behavior. System safety is concerned with anomalous behavior because it can typically be the cause of a mishap, or be part of a sequence of events leading to a mishap. Safety HA typically looks for anomalous behavior that is safety-essential or safety-critical in outcome. When performing an HA, potential anomalous behavior should be considered in hardware actions, hardware functions, software functions, and human tasks. For example, inadvertent rudder movement on an aircraft, without a valid command to move, is considered anomalous behavior with safety significance. 

Typically, if an item is safety-critical, it is then referred to as being safety-critical, as opposed to safety-related. Items less than safety-critical in severity are referred to as safety-related. When safety-critical and SR items are being compared together, safety-related refers to items whose failure to operate, or incorrect operation, will contribute to a mishap that could result in injury, minor system loss, or minor environmental damage (the same as safety-significant), whereas safety-critical hazards refer to hazards with catastrophic or critical severity. 

An SPF is the failure of a single item or component that would, in turn, directly lead to the occurrence of a specified UE. The intent is to identify component safety significance and criticality in order to understand where potential design safety weaknesses exist, so they can be eliminated or mitigated. Typically, the UE is a critical-safety condition, such as loss of life, loss of the system, loss of mission, and environmental damage. The particular UE depends upon the particular system and its objectives. 

Where the relevant safety requirements can be complied with, the Hazard Consequence Report continues to be processed in a nominal manner. If, for some reason, a defined safety requirement cannot be satisfactorily implemented, or its implementation cannot be verified as complying with the intent of the requirement, then once again the relevant report is identified as potentially unresolved. Furthermore, if risk assessment determines that, in spite of compliance with defined requirements, significant risk contributors remain in the design, then the relevant report is also identified as potentially unresolved. At this stage, additional safety critical items may also be identified. 

Appropriate arrangements should be in place to ensure that safety related activities are adequately controlled to minimize the risks to health and safety. The level of control should depend on the safety significance of the task. Activities with a high level of safety significance may require a specially authorized person to carry out the task, such as the reactor operator. In addition, certain critical activities such as tests and experiments will need to be authorized in advance and will involve the use of a permit to work system. Other control measures may include the use of hold points and verification stages during complex tasks and the control of stores items and test equipment. 

Progress has been satisfactory on the SAR upgrade program however, the amended K-Reactor chapters have yet to be delivered and approved by DOE. SAR upgrades will remain an open item until WSRC has reviewed and upgraded the safety-significant chapters and resolved all applicable pre-restart comments as well as any other significant comments. DOE staff will evaluate the resolution of those comments to ensure that the SAR meets the restart criteria and will report on that evaluation in a supplement to the SER. 

One of the most significant laser safety standards is that developed by the Z-136 committee of the American National Standards Institute (ANSI) (55). Although it is voluntary, many organi2ations use the ANSI standard. It contains a number of items including a recommendation for maximum permissible levels of exposure to laser radiation for various wavelengths, exposure durations, and different parts of the body separation of lasers into four different classes according to the level of ha2ard they present and recommendation of safety practices for lasers in each of the classes. 

Material control and traceability This item could have a higher priority if raw material or product losses are high or represent a significant safety or environmental risk. 

If the PrHA team is quite experienced, they may rank the action items according to the anticipated time and resources needed to implement changes. Or the team may make safety improvement and implementation recommendations. Ranking of action items or safety improvement recommendations may be valuable to management in several ways. It shows the significance that the PrHA team places on each item. It also allows management to prioritize the immediate efforts of corrective action and resolution. If resources are scarce, the ranking may affect the implementation schedule. 

PHAs are performed using the software program Leader 4.0, from EQE International, Inc., in Knoxville, Tennessee. These analyses typically yield action items that have the potential to significantly affect safety and recommendations that address minor safety concerns or increased efficiencies. Per the plant procedure, action items must be acted upon and recommendations must, at minimum, be evaluated by the Facility Manager. 

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