Materials and Manufacturing, Opportunities and Constraints, in New Nuclear Build

Transcription

1 Materials and Manufacturing, Opportunities and Constraints, in New Nuclear Build J.B. Borradaile, R.M. Mitchell, H.R. Dugdale (Rolls-Royce) Sustainable Nuclear Energy Conference 9-11 April 2014, Manchester 2013 Rolls-Royce plc The information in this document is the property of Rolls-Royce plc and may not be copied or communicated to a third party, or used for any purpose other than that for which it is supplied without the express written consent of Rolls-Royce plc. This information is given in good faith based upon the latest information available to Rolls-Royce plc, no warranty or representation is given concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc or any of its subsidiary or associated companies. Trusted to deliver excellence 10 April 2014

2 Agenda Introduction to Rolls-Royce Capability Design, Structural Integrity and Reliability Safety Classification of Components HIP in the Nuclear Industry: A Case Study Development of HIP Nickel Based Alloys Capability Conclusions 10 April 2014

3 3 Rolls-Royce is a global business providing integrated power systems for use on land, at sea and in the air. Rolls-Royce has supplied nuclear PWR plant and nuclear services for over 50 years supporting civil and naval applications Trusted to Deliver Excellence

4 Nuclear Sector business locations 10 April 2014

5 Design Process STAGE 0 Innovation & Opportunity Selection STAGE 1 Preliminary Concept Definition STAGE 2 Full Concept definition STAGE 3 Product Realisation STAGE 4 Production & Inservice Support STAGE 5 Continuing In- Service Support STAGE 6 End of life disposal Customer requirements and key drivers + Research and Capability requirements / investment Statement of Requirements + Preliminary Concept Design Scheme Full Concept Design Scheme + Draft Design Substantiation Report + Definition of Material Requirements Final Reference Design Scheme + Design Substantiation Report + Manufacturing Drawings + Manufacturing, installation, testing and commissioning procedures Verification of manufacturing, Installation, testing and commissioning procedures + DSR Review Revalidation and Inspection + Maintenance and Upkeep + DSR Review Lay-up + Surveillance In-Service Modification Design Definition (creation) Product Introduction and Lifecycle Management - GQP C.1.8 Component Design - GQP C.4 Product Change Control - GQP C.1.4 Design Definition (verification) Maintenance of Design Intent Configuration Management

6 Design Intent Material Stress Design Intent Requirements Environment Maintenance of Design Intent Design No unacceptable defects introduced during welding No environmentally No defect initiation assisted cracking inservice Weld location and Material selection Geometry and geometry (ease of surface finish welding / inspection) specification Stage in Life Cycle Manufacture Weld procedures and welder qualification Heat treatment control/stress relief Process controls and inspection Commission - Plant fill procedure - In-service Control of maintenance requiring welding Environmental controls (operational and maintenance) Operation within design envelope

7 Nuclear Safety Principles 7 Proven Engineering Practices: Nuclear power technology is to be based on engineering practises which are proven by testing and experience Equipment Qualification: Safety components and systems shall be chosen which are qualified for the environmental conditions Continuous Improvement: Operating organisations and designers shall seek to improve safety standards and safety performance in present and future plant. Techniques such as maintaining excellent material condition and component performance shall be employed 10 April 2014

8 ASME Classes ASME recognises different levels of importance of each component. It requires provision of a level structural reliability relative to the safety importance of the individual component (Class 1, 2 or 3). ASME does not provide guidance on the selection of a specific classification to assign a component. It is the owner s responsibility through provision of the Design Specification, to provide an appropriate classification for components.

9 Safety Classification Compliance with design codes such as ASME allows a structural reliability of ~10-5 /year to be claimed, based on failure statistics from non-nuclear pressure vessels. For those components with intolerable consequences of failure (uncontained release of fission products to the public) it needs to be demonstrated that failure is incredible, which in the UK is defined as a failure rate <10-7 /year. Consequently, a higher safety classification and demonstration of reliability is required for a catastrophic failure mode of the Reactor Pressure Vessel, compared with other Class 1 primary circuit components, with less severe consequences of failure. This introduces the concept of Incredibility of Failure or IoF.

10 IoF Concept Major principle in Nuclear Safety is Defence in Depth, provision of multiple layers of protection Some components it is not possible to provide this defence by physical means Multi- Layered REDUNDANCY DIVERSITY SEGREGATION DEFENCE IN DEPTH For these Incredibility of Failure (IoF) needs to be demonstrated, retaining the principle of Defence in Depth, through application of appropriate experience, testing, analysis and monitoring GOOD DESIGN & MANF TAGSI FORWARNING of FAILURE Conceptual Defence in Depth based on leg element structure UK Technical Advisory Group on Structural Integrity of High Integrity Plant TESTING FAILURE ASSESSMENT

11 NSRP Safety Classifications System, Structure, Component, Classification Consequences of Failure Approximate Failure rate / annum ASME III Code Classification Consequence of Failure IoF Failure leads inevitably to fuel failure and uncontained fission product release <10-7 Class 1 Catastrophic High Integrity Failure would inevitably lead to fuel failure 10-6 Class 1 Major Safety Critical Failure would lead to a demand for a safety system to operate to prevent fuel failure 10-5 Class1 Serious ASME III Safety Related In combination with other failures (including operator error ) failure would lead to the demand for a safety system 10-4 Class 2 Minor Non-Safety Failure would only lead to reduced plant availability 10-3 Class 3 Negligible Procedure is DETERMINISTIC probabilistic studies may be used to support the deterministic calculations

12 Stages in the Procedure Step 1 Define Component Safety Classification Step 2 Assess Damage Tolerance Step 3 Determine Risk Category Step 4 Identify Structural Integrity requirements

13 Material failure mode Likelihood of significant defects Loading/ Stress level Degradation mechanism High upper shelf toughness High tearing resistance (e.g. TIG) Non-welded components Within stress limits Secondary stresses low Stress relieved welds Known well understood degradation mechanism Judgements/uncertainties resolved by surveillance/monitoring programmes FUF<0.4 Assessment of Damage Tolerance Intermediate upper shelf toughness (e.g. MMA, Sub.Arc) Welds with simple geometry and easy access for welding and NDE Within stress limits Non-stress relieved ductile welds Dissimilar ductile welds Structural discontinuity 0.4<FUF<0.8 Score Moderate crack growth Degradation mechanism that results in reduction in toughness but no failure mode Transition toughness Limited tearing resistance Welds with complex geometry and difficult access for welding and NDE Gross structural discontinuity Rapid temperature changes Non-stress relieved non-ductile welds Dissimilar non-ductile welds FUF>0.8 High crack growth Degradation mechanism that brings about a change in failure mode

14 Ranking of Damage Tolerance Sum the Damage Tolerance scores Damage Tolerance Total Score High (H) 4 Medium (M) 5 to 8 Low (L) 9 to 12 Use Damage Tolerance Ranking in Conjunction With Consequence of Failure Ranking Matrix of Potential risk

15 Damage Tolerance Matrix of Potential Risk and Structural Integrity Requirements Low (9-12) Medium (5-8) High (4) 4 legged approach (Required) SMI (ASME V) + review of credible defects MAI to support a defect tolerance assessment R6 target reserve factors Safety Classification (Consequences of Failure) IoF HI SC SR NS A A B C C A B C C C B C C C C CATEGORY A CATEGORY B CATEGORY C ASME Class 1 ASME Class 1 ASME Class 1 4 legged approach (required for cat A, recommended for cat B) SMI (ASME V) R6 sensitivity study ASME Class 2 (SR), Class 3 (NS) 4 legged approach (useful) SMI (ASME V) SMI (Standard Manufacturing Inspections) - Confirm quality MAI (Manufacturing Acceptance Inspections) Qualified inspections that target defects of structural significance and supports the fracture assessment

16 Examples High Quality Butt Weld in Large Diameter Austenitic Stainless Steel Reactor Coolant Boundary Piping A postulated gross failure of this weld could result in fuel failure based on the assumption that a catastrophic failure would not be isolable or protectable. Consequence is Fuel Failure - Safety Classification is High Integrity Material failure mode = 1 Likelihood of defects = 2 Loading/stress level = 2 Degradation mechanism = 1 Total score` = 6 Damage Tolerance is Medium. The location is therefore in Risk Category B. Risk Category B welded location, has the following structural integrity requirements: Compliance with ASME III Code Class 1 Design and Fabrication requirements (including SMI) High Quality Butt Weld in Small Diameter Austenitic Stainless Steel Reactor Coolant Boundary Piping A postulated gross failure of this weld would not result in fuel failure as it could be protected by emergency core cooling system. Failure is protected - Safety Classification is Safety Critical Material failure mode = 1 Likelihood of defects = 2 Loading/stress level = 2 Degradation mechanism = 1 Total score` = 6 Damage Tolerance is Medium. The location is therefore in Risk Category C. Risk Category C welded location, has the following structural integrity requirements: Compliance with ASME III Code Class 1 Design and Fabrication requirements (including SMI) R6 defect tolerance sensitivity study TAGSI safety case structure

17 Safety Classification Summary The traditional approach to safety classification was to designate all safety significant components as ASME III Class 1. IAEA and UK safety assessment principles for nuclear plants require components to be classified based on their safety functions and then designed and constructed to achieve the required reliability level. A safety classification process has been developed which has five levels; the highest two levels, High Integrity and IoF require additional demonstration of reliability than can be gained from strict compliance with ASME III Class 1 rules. A multi-legged structural integrity case is adopted for those components that require high reliability demonstration ie High Integrity/IoF using the UK Technical Advisory Group on the Assessment of High Integrity Nuclear Plant (TAGSI) format. The two specific areas where the ASME III Class 1 requirements may need to be exceeded to achieve the additional reliability demonstration are: Explicit demonstration of defect tolerance Validation of inspection techniques to demonstrate that tolerable size of defects (plus an appropriate margin) can be reliability detected and characterized.

18 Advanced Nuclear Manufacturing Case Study : Hot Isostatic Pressing (HIP) of powder metals Initial step is to produce powder metal of desired composition. Molten metal is poured through ring of high pressure inert gas nozzles. This breaks up molten stream into fine droplets which rapidly solidify within the atomisation tower. Powder is then sieved to desired size distribution, which limits segregation and inclusion size. A low alloy steel can is filled with the powder, degassed and sealed. The filled can is then subjected to a high temperature (>1100 C) and pressure (>100 MPa) for a number of hours until powder fully consolidated, along with a shrinkage of ~ 30%. Can is removed by machining or pickling

19 Why HIP? Attractive manufacturing route for NSRP components, able to provide protection against manufacturing route obsolescence, improved mechanical properties, better control of defects and more reproducible results. Microstructures are isotropic, equiaxed with a small grain size, properties not normally achieved in heavy section components. This helps facilitate ultrasonic NDE examination - Additionally, inclusions are small and more benign compared to forgings. Turnaround times and costs can be reduced when compared to large forgings. Complex shapes can be created, which enables weld removal from the design, simplifying construction and NDT requirements

20 Introduction: Advantages of HIPping Fine, equiaxed grain size Improved inspectability Material cleanliness Repeatability Geometric complexity (near-net shapes) Cost Batch sizes Lead time 10 April 2014

21 Introduction: HIP in the Nuclear Industry 21 Fine, equiaxed grain size Improved inspectability Material cleanliness Repeatability Geometric complexity (near-net shapes) Cost Batch sizes Lead time 10 April 2014

22 RR Nuclear HIP Strategy Background To satisfy the Nuclear Safety Principles a gradual introduction strategy for HIP NSRP components evolved This included proving the technology for specific applications, and development of the specification, procurement and justification experience.

23 CAT A Components - Conceptual Strength in Depth Multi-legged structure (TAGSI 4 leg approach) LEG 1 LEG 2 LEG 3 LEG 4 Interpolation of experience (Design and Manufacture) Functional Testing Failure Analysis Forewarning of Failure Multifaceted, based on experience and sound engineering practice Tolerant to defects and fault conditions. Strength of the case is judged by the strength and independence of each leg For introduction of HIP, both Leg 1 and Leg 3 needed to be stronger Leg 3 is required to be strong for IoF and HI components

24 Gradual Introduction Strategy Demonstrate by mechanical testing to recognised standards that HIPped material is equivalent to wrought form Obtain manufacturing and in-service experience of the technology through HIP of non-pressure boundary components Further develop manufacturing and in-service experience pf the technology by applying it to leak limited pressure boundaries of isolable components Further develop manufacturing and in-service experience of the technology by applying it to isolable pressure boundary components Apply technology to un-isolable pressure boundary components

25 Gradual Introduction Strategy Demonstrate by mechanical testing to recognised standards that HIPped material is equivalent to wrought form Obtain manufacturing and in-service experience of the technology through HIP of non-pressure boundary components Further develop manufacturing and in-service experience of the technology by applying it to leak limited pressure boundaries of isolable components Further develop manufacturing and in-service experience of the technology by applying it to isolable pressure boundary components Apply technology to un-isolable pressure boundary components

26 MPa Gradual Introduction Strategy: Tensile properties of HIP and wrought 316L % Proof HIP 0.2% Proof Wrought UTS HIP UTS Wrought Temperature C 10 April 2014

27 Gradual Introduction Strategy Demonstrate by mechanical testing to recognised standards that HIPped material is equivalent to wrought form Obtain manufacturing and in-service experience of the technology through HIP of non-pressure boundary components Further develop manufacturing and in-service experience of the technology by applying it to leak limited pressure boundaries of isolable components Further develop manufacturing and in-service experience of the technology by applying it to isolable pressure boundary components Apply technology to un-isolable pressure boundary components

28 Rolls-Royce (nuclear) applications of HIP HIPing of hard-wearing Stellite 6 (Co-base) and Tristelle 5183 (Febase) bars and HIP bonding of inserts to austenitic 304LE and Monel 4070 small-bore globe valves since 1994 HIPped Stellite/Tristelle Seat machined from bar Seat HIPped to valve body billet Final machining HIPped back seat 28 Replaced oxy-acetylene deposit of Stellite Reduced non-conformance and removed bottleneck in route HIPped seat provided better grain structure and in-service longevity Rolls-Royce data Proprietary & Confidential Information Proceedings of PVP-2005, PVP HIPped main seat

29 Implementation of HIP 29 Manufacture and bonding of HIP Stellite 6 hard facings onto valves Oxy-acetylene Stellite 6 deposit on stainless steel x100 HIPped Stellite 6 powder bonded onto stainless steel x April 2014

30 Gradual Introduction Strategy Demonstrate by mechanical testing to recognised standards that HIPped material is equivalent to wrought form Obtain manufacturing and in-service experience of the technology through HIP of non-pressure boundary components Further develop manufacturing and in-service experience of the technology by applying it to leak limited pressure boundaries of isolable components Further develop manufacturing and in-service experience of the technology by applying it to isolable pressure boundary components Apply technology to un-isolable pressure boundary components

31 Gradual Introduction Strategy HIPped Stainless Steel 316L Omega Seals 31 Omega seals are welded to main component assembly No discernible difference between wrought/hipped welded material HIP offers smaller defect sizes and an ability to supply small quantities at acceptable cost and lead-time Over 500 omega seals manufactured, with over 200 in-service. Proceedings of ICAPP 2008 Paper 8110 Rolls-Royce data Proprietary & Confidential Information

32 Gradual Introduction Strategy HIPped 316L stainless steel machined and welded omega seals.

33 Microstructure of Forged and HIPped 316L Omega seal was first stainless steel HIP application, high level of material cleanliness required Type 316L structures (x100) Forging (ASTM No. 2) HIPped powder (ASTM No. 5)

34 Gradual Introduction Strategy Demonstrate by mechanical testing to recognised standards that HIPped material is equivalent to wrought form Obtain manufacturing and in-service experience of the technology through HIP of non-pressure boundary components Further develop manufacturing and in-service experience of the technology by applying it to leak limited pressure boundaries of isolable components Further develop manufacturing and in-service experience of the technology by applying it to isolable pressure boundary components Apply technology to un-isolable pressure boundary components

35 Gradual Introduction Strategy Isolable PC boundary Tee piece 2009 Full size Tee piece in Type 316L ~ 2 tons Destructively tested, isotropic mechanical properties confirmed Production components were introduced onto nuclear plant First use of HIP in a Primary Circuit pressure retaining application

36 Isolable PC boundary Tee piece 2009 Previously, forging of the Tee had used a three ram press and closed die process Typical issues experienced included large grain structures and surfacebreaking defects HIP proved an attractive alternative In addition to project savings, HIP offered advantages in both mechanical properties and improved inspectability

37 Gradual Introduction Strategy Isolable PC boundary HIP Pipework HIP pipework in 304LE austenitic stainless steel enables elimination of a number of large bore and small bore stub connection welds. Development work produced a stable and reproducible technique HIP pipework sections have also been introduced onto plant Current requirement to machine bore rules out elbows and diameters where access cannot be gained

38 Gradual Introduction Strategy Valve Body and Cylinder Demonstrators Valve body and cylinder technology demonstrators manufactured from Type 304LE powder.

39 Gradual Introduction Strategy Pump Bowl Demonstrator Thickest section component produced to date Traditionally sand cast No inclusions above 15 μm reported Grain size ASTM grade 5

40 Gradual Introduction Strategy Demonstrate by mechanical testing to recognised standards that HIPped material is equivalent to wrought form Obtain manufacturing and in-service experience of the technology through HIP of non-pressure boundary components Further develop manufacturing and in-service experience of the technology by applying it to leak limited pressure boundaries of isolable components Further develop manufacturing and in-service experience of the technology by applying it to isolable pressure boundary components Apply technology to un-isolable pressure boundary components

41 ASME Code Case N-834 In November 2011, a code case submission for the use of HIP Type 316L austenitic stainless steel on nuclear plant was made to ASME boiler and pressure vessel committee. Code case was approved on October 22, 2013 It was the opinion of the committee that, ASTM A988/A988M-11 UNS S31603 may be used for Section III, division 1, subsection NB, Class 1 components in construction

42 Future Nuclear HIP Strategy 10 April 2014

43 The Development of HIPped Nickel Based Alloys 43 Interest in developing HIP Alloy 625 began in 1990 Research programme examined both the potential of the HIP process and the opportunity to make use of new materials. Alloy 625 was identified as having the potential to offer benefits to a wide range of plant applications HIP process is especially relevant to alloys like Alloy 625, the same properties that make it appealing to a designer also made it difficult to fabricate and machine 10 April 2014

44 Development of HIP NBA: Valve Production 44 Single experimental project to demonstrate the feasibility of producing an Alloy 625 valve using HIP Design offers a degree of complexity without being overambitious Opportunity to combine a number of production stages into one: Body machining Seat installation Addition of stubs Fitting of liner Three sections: Optimisation of HIP process Production of valve bodies Rig testing of completed valve 10 April 2014

45 % of Particles Development of HIP Valve: Parameters 45 Element C Si Cr Ni Fe Mo Nb Mn P S Co Al Ta N O Composition % Particle Size Distribution Temperature ( C) Pressure (MPa) Time at Temperature ( C) < >420 Particle Size Range (μm) 10 April 2014

46 Development of HIP Valve: Optimisation of HIP Parameters Effect of HIP temperature on mechanical properties

47 Development of HIP Valve: Valve Production 47 Three valve bodies produced Can design optimisation Rig testing considered successful Major departure from conventional method of producing component 10 April 2014

48 Stress MPa Development of HIP Valve: Material Characterisation 48 Tensile test results compared with ASME wrought data Wrought 0.2% proof Wrought UTS HIP 0.2% proof HIP UTS Temperature C 10 April 2014

49 Development of HIP Valve: Material Characterisation 49 Fracture toughness values were lower than expected 10 April 2014

50 Development of HIP Valve: Material Characterisation 50 Results from rotating beam specimens are comparable to wrought material, whilst those from cantilever bend tests are superior 10 April 2014

51 Development of HIP Valve: Project Conclusions 51 Project was determined to have successfully demonstrated the feasibility of producing a valve using the HIP process Significant reduction in the number of production stages Mechanical properties of Alloy 625 require more work Extensive development work required to transition valve from prototype to production part 10 April 2014

52 Further Development of NBA 52 Interest in the HIPping of NBA has recently been ignited Development of Alloys 690 and 625 Basic test programme aiming to characterise materials and optimise HIP parameters Material properties are compared to their wrought equivalents: regulatory requirements Aiming to manufacture HIP NBA components for plant applications 10 April 2014

53 Further Development of NBA: Alloy University of Birmingham programme Production of 15 kg HIP bars Small powder size: 45 ± 15 μm HIP Conditions: 1160 C, 103 MPa for 240 mins Heat Treatments are being studied 10 April 2014

54 UTS (MPa) The Development of HIPped Alloy 625: Mechanical Properties 54 Tensile tests showed favourable mechanical properties when compared with wrought ASME data HIP UTS Wrought ASME UTS HIP 0.2% proof Wrought ASME 0.2% proof Temperature ( C) 10 April 2014

55 The Development of HIPped Alloy 625: Mechanical Properties Favourable hardness and Charpy impact test results Sample Vickers (H v0.3) Brinell Rockwell Equivalent Brinell hardness 10 mm C ball 3000 kgf (HB) Equivalent Rockwell hardness 150 kgf (HRC) Temperature L T RT RT RT RT RT RT Average 270 H v HB 25 HRC

56 HIP Development of NBA: Alloy 625 MA April 2014

57 HIP Case Study Summary 57 HIP powder processing has become a valuable manufacturing technique The use of stainless steel HIPped components has been extensively validated through both laboratory and prototype component testing Work is beginning to optimise the HIPping of Inconel alloys, including Alloy 625 The methodology established for taking HIP stainless steel components from design phase up to component safety case will be key for the introduction of other HIPped materials onto plant 10 April 2014

58 Size Matters: Propulsion components are significantly smaller than land based plant RPV Steam Generator Pressuriser Reactor Coolant Pump RPV Steam Generator Pressuriser RCP Sizewell B (Gen III size) Naval Propulsion Equivalent

59 Conclusions 59 HIP has been demonstrated for applications on Naval Propulsion Plant. An ASME Code Case has been achieved for the use of HIP Type 316L austenitic stainless steel on Class 1 components. HIP advantages include inspectability of the component, control of defects, batch sizes, lead times and are not only metallurgical. There is no reason that HIP should not be used on Civil Plant and Small Modular Reactors with their requirement for increased production rates may provide the impetus Rolls-Royce data Proprietary & Confidential Information