Graded approach

Grading Approach Fire Detection—based on defining fire detection performance requirements for sensitivity, response time, and availability based on risk of fire escalation. 

The fire detection grading approach is a coarse hazard assessment, which documents the credible fire hazards and defines and establishes acceptable fire detection performance requirements. The fire detection performance requirements are defined by determining what size of fire presents a credible escalation hazard. The systematic application ofthe grading process then develops an engineered detection system whose performance can be verified. The general process utilized to develop the detection layout is as follows ... 

The following comprehensive textbooks are suitable as introductions into biochemistry, and they allow a graded approach to more detailed levels of coverage. 

For a material species graded approach, several kinds of thermoelectric material of which the optimum operating temperature is different fi-om each other are laid in order. Concerning composition graded and dopant concentration graded... 

In many contact metamorphic aureoles, values of 5 0 and 5 C vary systematically. The coupled 0-C trend is towards lower and values at higher metamorphic grade approaching the igneous contact. Thus, 5-values decrease progressively as metamorphism increases. This trend may also correlate with bleaching of the rock, coarsening of calcite and the development of calc-silicate minerals. This may be the result of one or more volatilization reactions, variable temperature, or fluid infiltration. 

It is recommended that a graded approach be used in meeting this requirement. 

A graded approach shall be uses in the application of these nuclear safety design criteria to ensure that the depth of detail required and the magnitude of resources expended for the design are commensurate with each facility s programmatic importance and the potential environmental, safety, and/or health impact of normal operations. 

Graded Approach means a process by which the level of analysis, documentation, and actions necessary to comply with a requirement in this Part are commensurate with ... 

Some preliminary guidance on the use of the graded approach is available in a DOE draft Standard on Hazard Categorization. Further guidance on the graded approach with regard to classifying safety class SSCs is under development. 

In order to facilitate the implementation of this nuclear safety design criterion DOE 5480.28, NATURAL PHENOMENA HAZARDS MITIGATION, specifies the requirements for each new and existing DOE facility. The evaluation criteria for this DOE Order are built around a graded approach. DOE 5480.28 specifies that an NPH analysis will be performed for all new and existing dOE faciI ities. Specifically ... 

Appendix A, Criterion 38 - Containment Heat Removal, and Criteria 39 and 40 - inspection and Testing of Containment Heat Removai Systems shouid be inciuded as part of the graded approach assessment for the overall containment design,... 

Containment enhancement provisions may also be part of a graded approach as augmentation or in I ieu of 10 CFR 50 containment design criteria. For an example, a filtered vented containment or confinement system may adequate protection to the public and onsite a containment heat removal system may not be reduce ultimate risk to an acceptable level, containment design criteria are used, the ultimate goal of protecting the health and safety of the public and onsite workers should be assured. 

For small Category A reactors, all Category B reactors, and critical facilities, implementation of the graded approach to hazard analysis should be used to evaluate the application of containment related design criteria. 

As indicated in Table 3.3-6, the risk to the public and the environment from the internal isotope production and radioactive material storage accidents was assessed to be minor or very minor, and the application of a graded approach to the accident analyses is appropriate. Since no unique accidents are assessed to be of high risk, representative accidents are chosen to bound a number of similar accidente and form as complete a set of bounding conditions as possible to represent the accident risk to the public and the environment. Accidents from the hazard evaluation with the greatest potentiai consequences to the public are emphasized in the DBA selection process. 

The development of each DBA in the accident analyses is based on application of a graded approach, as provided for in DOE-STD-3009-94. The standard states that quantitative analyses are only required to the extent necessary to demonstrate that Evaluation Guidelines are not exceeded. Further. For nonreactor nuclear facilities, these considerations (hazard magnitude) do not support a need for probabilistic/quantitative risk assessment . Additionally, the Standard states that The use of bounding assumptions and less detailed physical modeling in accident analysis Is appropriate . 

It is important to realize that classification for the sake of classification or the assignment of preconceived requirements to SSCs could make the design and construction of new facilities or the modification of existing ones and their operational costs prohibitive for little risk reduction gained. Therefore, the classification of SSCs and the implementation of requirements should be applied in a graded approach. The classification is therefore based on results of hazard or accident analyses. 

Sinale Failure Criterion Graded approach is dependent on SSC classification and operational mode (passive vs. active). Any of the following Fail safe. Redundancy or diversity. Separation or isolation (including interfaces and boundaries). Evaluate for common failure modes, independence, and reliability. Backfit only if risk/cost effective. 

Processes to detect and prevent quality problems as well as ensure quality improvements are established in the RREP-QAPP and implemented through several QA Implementing Procedures. The extent to which each applies to the various activities, operations, projects, and experiments at the Hot Cell Facility is described in the HCF PEQP. Four grouping of safety importance (graded approach) are defined in that RREP ... 

RREP 2-1, Quality Levels. This RREP describes the implementation of the graded approach as required by 10 CFR 830.120. 

Work is performed under controlled conditions by using a graded approach as required by 10 CFR 830.120 and as implemented in the Org. 6431/6433 Work Control Instruction. This instruction requires the development of a Project/Experiment Quality Plan (PEQP) to ensure that all safety related work will be performed to meet the requirements of 10 CFR 830.120. 

The hazard classification of the facility dictates the QA levels that are assigned to the facility, structures, systems, and components (SSCs), based on the consequence of failure. The extent of requirements and depth of QA activity are commensurate with the scope, complexity, importance, and degree of risk of a SSC. Through the use of quality levels, the stringency of the requirements is applied in a graded approach to all SSCs within the facility. The most stringent requirements (Quality Level I) apply, by default, to all safety- class SSCs, which are specified in accordance with DOE Orders and Standards [i.e., DOE Order 5480.23 (DOE 1992) and DOE-STD-3009-94 (DOE 1994a). As described in Chapter 3, no safety class SSCs are identified for the HCF. 

The analysis described above is in part, based on engineering judgment and professional opinion. While these judgments are appropriate and valid in applying the graded approach to assessing the safety of HCF operations, one can examine the effects on the evaluated outcomes of judgments different than those made in this analysis. Some of these assessments, and specifically the assessment of confinement bam er failures, will be accomplished in evaluation of the BDBE, and thus will not be discussed here. 

IV.44. Items or services may be procured to different levels of quaUty, depending on their importance and impact on safety. A graded approach to quality, as described in Safety Series No. 113 [IV.3], may be used in the procurement of such items and services. 

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