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CSA N285.8:15 (R2020) Technical requirements for in-service evaluation of zirconium alloy pressure tubes in CANDU reactors, Includes Errata 1 (2016), Errata 2 (2016), and Update No. 1 (2019)
standard by CSA Group, 07/01/2015
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REVISED OCTOBER 2019
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N285.8-15, Technical requirements for in-service evaluation of zirconium alloy pressure tubes in CANDU reactors
Update No. 1 — October 2019 | Revision symbol (in margin) |
Clauses 3.1, 4.3, 4.3.1, 4.3.2.1, 7.1.1, 7.1.5, 7.1.6, 7.3.1, 7.4.3.2, 7.4.3.3, A.2.1, A.2.2.1, A.2.2.2.1, A.2.2.2.3.1, A.2.2.2.4, A.2.3.1, B.2.2.2.5, B.2.2.3.3.4, C.1.3, C.3.2.3.4, C.3.3.4, C.3.3.4.3, D.5.3.2.2, D.13.2.3, and D.13.2.3.1 Annexes F and G Tables 1, C.1, D.26, D.27, and D.28 Figures A.30, A.31, and A.32 | ① |
Errata — July 2016 | Revision symbol (in margin) |
Clauses A.2.3.2.4 and B.2.2.2.5 Table D.22 | Δ |
Errata — January 2016 | Revision symbol (in margin) |
Clauses D.5.4.1 and D.8.2 Table C.1 | Δ |
N285.8-15
July 2015
Title: Technical requirements for in-service evaluation of zirconium alloy pressure tubes in CANDU reactors
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N285.8-15
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N285.8-15
Technical requirements for in-service evaluation of zirconium alloy
pressure tubes in CANDU reactors
Technical Committee on Periodic Inspection of CANDU Nuclear Power Plant Components 4
Subcommittee on Technical Requirements for In-Service Evaluation of Zirconium Alloy Pressure Tubes in CANDU Reactors 7
Technical Committee on Periodic Inspection of Nuclear Power Plant Components — Update 1 10
Subcommittee on Technical Requirements for In-Service Evaluation of Zirconium Alloy Pressure Tubes in CANDU Reactors — Update 1 13
Preface 16
Scope 18
Reference publications 19
Definitions, symbols, and abbreviations 19
Definitions 19
Symbols and abbreviations 24
General requirements 26
Scope 26
Evaluation of in-service inspection results 27
Evaluation of flaws detected by in-service inspection and evaluation of repair 27
Evaluation of pressure tube to calandria tube contact for inspected fuel channels 27
Assessment of reactor core 28
Applicability 28
Assessment of reactor core for flaws 28
Evaluation of reactor core for pressure tube to calandria tube contact 28
Evaluation of material surveillance measurements 28
Requirements of evaluations 29
Evaluation methods 29
Inspection uncertainty 29
Hydrogen equivalent concentration 29
Material properties 29
Loading conditions 30
Operating conditions 30
Records and notification 30
Evaluation of pressure tube flaws 31
General 31
Flaw characterization 31
General 31
Characterization of planar and laminar flaws 31
Characterization of volumetric flaws 31
Evaluation of planar and laminar flaws 32
General 32
July 2015 © 2015 Canadian Standards Association 1
N285.8-15
Technical requirements for in-service evaluation of zirconium alloy
pressure tubes in CANDU reactors
Flaw growth evaluation 32
Fracture initiation evaluation 32
Plastic collapse evaluation 33
Evaluation of volumetric flaws 33
General 33
Fatigue crack initiation evaluation 34
Delayed hydride cracking initiation evaluation 35
Plastic collapse evaluation 39
Evaluation of pressure tube to calandria tube contact 39
General 39
Classification of operating conditions 39
Evaluation of pressure tubes left in contact with calandria tubes 40
General 40
Evaluation for Sustained Operating Conditions 40
Evaluation for Limited Operating Conditions 40
Evaluation of pressure tubes removed from contact with calandria tubes 41
General 41
Evaluation for Sustained Operating Conditions 41
Evaluation for Limited Operating Conditions 41
Assessment of reactor core 42
General 42
Evaluation of service conditions for protection against fracture 43
General 43
Deterministic evaluation 43
Probabilistic evaluation 43
Assessment of degradation mechanisms in the reactor core 43
General 43
Assessment of degradation mechanisms related to flaws 44
Assessment of pressure tube to calandria tube contact 44
Evaluation of leak-before-break 44
General 44
Deterministic evaluation 45
Probabilistic evaluation 45
Evaluation of material surveillance measurements 46
General 46
Evaluation of hydrogen equivalent concentration 46
Evaluation of fracture toughness 47
Evaluation of delayed hydride cracking growth rate 48
Evaluation of threshold stress intensity factor for delayed hydride cracking 48
Annex A (informative) — Procedures for the evaluation of pressure tube flaws 71
Annex B (informative) — Procedures for the evaluation of pressure tube to calandria tube contact 180
Annex C (informative) — Procedures for the assessment of a reactor core 187 Annex D (informative) — Material properties and derived quantities 208 Annex E (informative) — Notification of in-service evaluation form 266
July 2015 © 2015 Canadian Standards Association 2
N285.8-15
Technical requirements for in-service evaluation of zirconium alloy
pressure tubes in CANDU reactors
Annex F (informative) — Guidance on calculating the maximum allowable pressure tube failure frequencies for use in probabilistic assessments for the reactor core 267
Annex G (informative) — Uncertainty analysis in probabilistic evaluations 269
July 2015 © 2015 Canadian Standards Association 3
N285.8-15
Technical requirements for in-service evaluation of zirconium alloy
pressure tubes in CANDU reactors
This is the third edition of CSA N285.8, Technical requirements for in-service evaluation of zirconium alloy pressure tubes in CANDU reactors. It supersedes the previous editions, published in 2010 and 2005.
This Standard specifies mandatory technical requirements and non-mandatory evaluation procedures for fitness-for-service assessments. Pressure tubes in Canadian CANDU® nuclear power plants are inspected in accordance with CSA N285.4, Periodic inspection of CANDU nuclear power plant components. When a detected flaw indication does not satisfy the criteria of acceptance by
examination, or when pressure tube to calandria tube contact is detected or predicted, Clause 12 of CSA N285.4 permits a fitness-for-service assessment to determine acceptability. Also, Clause 12 of CSA N285.4 requires evaluation of the results of specified material property surveillance measurements.
Note: CANDU (CANada Deuterium Uranium) is a registered trademark of Atomic Energy of Canada Limited.
This Standard is one of a series of CSA N285 Standards that provide consistent rules for the design, fabrication, installation, inspection, and assessment of pressure-retaining systems and components in CANDU nuclear power plants. The series outlines requirements that are particularly applicable to nuclear power plants in Canada and references the appropriate requirements of the ASME Boiler and Pressure Vessel Code. Users of this Standard are reminded that the site selection, design, manufacture, construction, installation, commissioning, operation, and decommissioning of nuclear facilities in Canada are subject to the Nuclear Safety and Control Act and its Regulations. The Canadian Nuclear Safety Commission might impose additional requirements to those specified in this Standard.
The CSA N-Series of Standards provides 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 may provide more specific direction for those requirements.
This Standard consists of a mandatory main body and five non-mandatory annexes. The main body contains the mandatory rules and acceptance criteria for in-service evaluation of zirconium alloy pressure tubes in CANDU reactors. The non-mandatory annexes are as follows:
Annex A — Procedures for the evaluation of pressure tube flaws;
Annex B — Procedures for the evaluation of pressure tube to calandria tube contact;
Annex C — Procedures for the assessment of a reactor core;
Annex D — Material properties and derived quantities; and
Annex E — Notification of in-service evaluation form.
Annexes A to C contain evaluation procedures that may be used to demonstrate compliance with the acceptance criteria in the main body of the Standard. Annex D contains the material properties and derived quantities that are required when performing an evaluation in accordance with Annexes A to C. Annex E contains a form for providing notification of the evaluation to the authority having jurisdiction (AHJ).
This Standard assumes that the typical evaluation process consists of
pressure tube inspection;
evaluation of the inspection results;
documentation of the inspection results and evaluation;
July 2015 © 2015 Canadian Standards Association 16
N285.8-15
Technical requirements for in-service evaluation of zirconium alloy
pressure tubes in CANDU reactors
notification of the AHJ regarding the inspection and evaluation; and
acceptance by the AHJ of the disposition of pressure tubes prior to returning the reactor to service.
This Standard is based in part on fitness-for-service guidelines developed by a Technical Task Team formed by the CANDU Owners Group (COG).
This Standard was prepared by the Subcommittee on Technical Requirements for In-Service Evaluation of Zirconium Alloy Pressure Tubes in CANDU Reactors, under the jurisdiction of the Technical Committee on Periodic Inspection of CANDU Nuclear Power Plant Components and the Strategic Steering Committee on Nuclear Standards, and has been formally approved by the Technical Committee.
Notes:
Use of the singular does not exclude the plural (and vice versa) when the sense allows.
Although the intended primary application of this Standard is stated in its Scope, it is important to note that it remains the responsibility of the users of the Standard to judge its suitability for their particular purpose.
This Standard was developed by consensus, which is defined by CSA Policy governing standardization — Code of good practice for standardization as “substantial agreement. Consensus implies much more than a simple majority, but not necessarily unanimity”. It is consistent with this definition that a member may be included in the Technical Committee list and yet not be in full agreement with all clauses of this Standard.
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July 2015 © 2015 Canadian Standards Association 17
N285.8-15
Technical requirements for in-service evaluation of zirconium alloy
pressure tubes in CANDU reactors
N285.8-15
1 Scope
1.1
This Standard specifies the technical requirements for the owner/operator to ensure structural integrity of cold-worked Zr-2.5 wt% Nb alloy pressure tubes in operating CANDU reactors. Clause 13 of CSA N285.0/N285.6 Series requires that when in-service inspection results or material surveillance results do not satisfy the requirements of the original inspection program, a fitness-for-service evaluation must be performed in accordance with CSA N285.4 to demonstrate acceptance. The requirements of this Standard address the specific fitness-for-service evaluation requirements of CSA N285.4, Clause 12.
1.2
This Standard applies only to cold-worked Zr-2.5 wt% Nb alloy pressure tubes in operating CANDU reactors and to evaluation of the volumetric inspection results, pressure tube to calandria tube contact, and material surveillance measurements listed herein. The definition of pressure tube material types is provided in CSA N285.0/N285.6 Series.
1.3
This Standard does not apply to evaluation of pressure tube dimensional changes (other than pressure tube to calandria tube contact), material property surveillance measurements beyond those defined in CSA N285.4, or to other reactor types. This Standard does not apply to pressure tube materials other than cold-worked Zr-2.5 wt% Nb.
1.4
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.
July 2015 © 2015 Canadian Standards Association 18