Environmental qualification of equipment for nuclear power plants
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This is the second edition of CSA N290.13, Environmental qualification of equipment for nuclear power plants. It supersedes the previous edition, published in 2005 under the title Environmental qualification of equipment for CANDU nuclear power plants.
Changes to this edition include the following:
a) The scope of the Standard has been updated to clarify the Standard’s applicability to design basis accidents (DBAs) that create harsh environment conditions [i.e., exclusion of equipment in a mild environment from environmental qualification (EQ)].
b) The Standard has been updated to align with CNSC REGDOC-2.5.2, and to better align with current industry standards.
c) Further clarification regarding the application of EQ principles including condition-based qualification, combined qualification, and reassessment of qualified life have been provided.
d) The informative Annex A (Arrhenius methodology in predicting material aging) was removed.
e) The informative Annex B (Harsh environment conditions) has been updated to clarify the basis for typical screening criteria for a harsh environment and provide further guidance on implementation of these criteria, and is now located in Annex A.
f) The informative Annex C (Bibliography) was removed. A new informative Annex B [Equipment survivability assessments for design extension conditions (DEC)] has been included.
CSA N290.13 has been written as a general Standard for the establishment and maintenance of an EQ program for safety-related equipment in nuclear power plants (NPPs) that are within its scope. It provides generic requirements and methods for such qualification.
Safety-related equipment is qualified to ensure performance of its required safety functions under harsh environmental conditions that result from a DBA. Adherence to this Standard can result in improved public health and safety. The integrated performance of the process systems, instrumentation, and electrical systems limits the consequences of accidents.
A NPP safety analysis considers, in part, facilities and their safety system designs in terms of postulated service conditions. Inherent in each analysis are two presumptions that are evaluated. First, designs are such that equipment can actually perform designated safety functions in postulated harsh environments. Second, safety-related components are not degraded by in-service aging to the point where they cannot perform their designated safety functions when required.
Production testing, normal service testing, and surveillance might not be able to determine the equipment’s vulnerability to failure resulting from inadequate design, in-service time, or environmental conditions, because of the special environmental stresses associated with some postulated service conditions. Under these circumstances, common-cause failure of redundant safety-related equipment might occur at a time when its safety function is required. It is the fundamental role of EQ to provide reasonable assurance that both design and manufacture permit the equipment to perform its required safety function(s) during normal and accident service conditions.
The CSA N-Series Standards provide an interlinked set of requirements for the management of nuclear facilities and activities. CSA N286 provides overall direction to management to develop and implement sound management practices and controls, while the other CSA Group nuclear Standards provide technical requirements and guidance that support the management system. This Standard works in harmony with CSA N286 and does not duplicate the generic requirements of CSA N286; however, it might provide more specific direction for those requirements.
This Standard reflects the operating experience of the Canadian nuclear power industry.
Users of this Standard are reminded that the design, manufacture, construction, commissioning, operation, and decommissioning of nuclear facilities in Canada are subject to the provisions of the Nuclear Safety and Control Act and its supporting Regulations.
This Standard specifies the requirements for an EQ program for nuclear power plants (NPPs) (see Figure 1). The EQ program comprises a set of planned and coordinated activities establishing auditable assurance that equipment will
a) perform safety functions in a harsh environment following the DBA(s) for which it is credited; and
b) meet or exceed its functional and performance requirements, taking into consideration the effects of normal service.
Equipment demonstrated to be in a mild environment after a DBA are not subject to the requirements of this Standard.
Note: Post-DBA harsh environment conditions addressed by an EQ program are a subset of service conditions required to be addressed as part of overall equipment qualification. Service conditions can also include seismic, severe weather, external floods, electromagnetic interference and radio frequency interference, and fire. Equipment qualification to demonstrate performance in these conditions is outside of this Standard’s scope. For further guidance on the equipment qualification process, see IEC/IEEE 60780-323.
This Standard presents the requirements for establishing and preserving EQ to confirm the adequacy of the equipment to meet its design intent.
This Standard addresses the effects of aging on equipment required to mitigate the consequences of a DBA. This Standard addresses the need to minimize common cause failure under accident conditions.
The requirements established herein are to be used for the preservation of EQ during maintenance or modification of equipment and systems and are to be used in the procurement of equipment and parts.
DEC survivability assessments are outside the scope of an EQ program. However, this Standard provides optional guidance (see Annex B) on how to demonstrate, with reasonable confidence, that equipment and instrumentation credited to operate during DEC will be capable of performing their intended safety function(s) under the expected environmental conditions.
Note: For general requirements on beyond design basis accidents (BDBAs), see CSA N290.16.
In cases of conflict between this Standard and other Standards which it references, this Standard takes precedence.
In this Standard, shall is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; should is used to express a recommendation or that which is advised but not required; and may is used to express an option or that which is permissible within the limits of the Standard.
Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material.
Notes to tables and figures are considered part of the table or figure and may be written as requirements.
Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.
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