Materials Engineering for the next Nuclear Generation

Stephen J Garwood

Director Engineering & Technology

Rolls-Royce, Submarines

©2008 Rolls-Royce Group plc�The information in this document is the property of Rolls-Royce Group 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 Group plc.

This information is given in good faith based upon the latest information available to Rolls-Royce Group 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 Group plc or any of its subsidiary or associated companies.

Title - Arial 28pt

Rolls-Royce data – strictly private

Disclaimer!

• Tonight’s lecture is my personal view based on over 30 years working on material related matters for the UK’s nuclear industry at IC, TWI and RR.

​

• My comments therefore do not necessarily reflect the view of RR, TWI or IC

Filename

2

Rolls-Royce data – strictly private

Outline

• Days of Future Passed

​

​

• The Present

​

​

• The Future

Filename

3

Rolls-Royce data – strictly private

• Days of Future Passed

​

​

​

• The Present

​

​

​

• The Future

Filename

4

(On the Threshold of a Dream)

Or are we!

Rolls-Royce data – strictly private

Days of Future Passed - Timeline

• 1956 Calder Hall opened
• 1958 UK/US Enabling Agreement
• 1959 HMS Dreadnought (S5W)
• 1963 PWR1 (Valiant)
• 1963 AGRs
• 1974 SGHWR ordered
• 1975 PFR (connected to grid)
• 1986 PWR2 (Vanguard)
• 1987-1995 Sizewell B (1969 AGR, 1974 SGHWR,and UK’s first commercial PWR 1980)

Filename

5

Rolls-Royce data – strictly private

Filename

6

The Queen opened Calder Hall in October 1956

The Queen has opened the world's first full-scale nuclear power station, at Calder Hall in Cumberland.

A crowd of several thousand people gathered to watch the opening ceremony, which was also attended by scientists and statesmen from almost 40 different countries.

The Lord Privy Seal, Richard Butler, described the event as "epoch-making".

He added, "It may be that after 1965 every new power station being built will be an atomic power station."

​

​

Rolls-Royce data – strictly private

UK’s Nuclear Power Stations 1980��R W Nichols�26th Hatfield Lecture�1975� ‘Steels contribution to Nuclear Power - Its Problems & Promise’��(Willoughby & Garwood - Metal Construction�Oct 1980)

Filename

1980 Reactor Systems

Filename

8

Rolls-Royce data – strictly private

Filename

Historical perspective

Filename

10

Admiral Hyman G Rickover USN

“Father of the nuclear navy”

1900 – 1986

• US nuclear propulsion programme
• Rickover and Mountbatten
• 1958 bilateral agreement
• S5W and Dreadnought
• Rolls-Royce & Associates
• DS/MP

SSN 571 USS Nautilus

Rolls-Royce data – strictly private

Rickover on Rolls-Royce….

Filename

11

“I formed a very good impression of the Rolls-Royce team; the leading men in it are competent and imaginative and, in my view, are capable of doing a first class job.”

Rolls-Royce data – strictly private

Filename

12

RR Nuclear Engineering

Rolls-Royce data – strictly private

Filename

13

Operational support

The Rolls-Royce submarines business provides full range nuclear services to the UK Navy

●

●

●

●

●

Waterfront support

Prototyping of RN reactor plants

Faslane

Vulcan

Build yard - Astute

HPV, NMS

Core Manufacture

Submarines HQ

Submarines 2007

Turnover: £265m

People: 1738

Plymouth

Derby

Barrow

●

Bristol - JET

Rolls-Royce data – strictly private

Rolls-Royce on Raynesway

Filename

14

Rolls-Royce data – strictly private

Vulcan Naval Reactor Test Establishment�at Dounreay

Filename

15

Rolls-Royce data – strictly private

Reactor core development

Filename

16

0

B

Z

G

H

Normalised to S5W

Core type

Key:

Power

Lifetime

2

4

6

8

A(S5W)

Rolls-Royce data – strictly private

History of Submarine Build Programmes

Filename

Burdekin & Capability Study

Burdekin Review (2003)

• Commissioned by MoD CSA
• How to improve submarine availability?
• Main conclusion: Need for underlying research programme to inform periodic review

​

Filename

Nuclear Propulsion Capability Study

• Commissioned by MoD CSA
• What is required to keep nuclear propulsion sustainable?
• Main conclusion: unsustainable without research and future plant programmes to support key skills & infrastructure

​

Periodic Safety & Availability Review

​

Nuclear Propulsion Critical Technology

​

Next Generation Nuclear Propulsion Plant

​

The Present

• Keeping the Nuclear Fleet Operating

​

Material Factors influencing Reactor performance

​

PWR Reactor Pressure Vessel steels

​

Structural Integrity Assessment

​

• Decline of Nuclear Engineers and UK Capability

Filename

19

Rolls-Royce data – strictly private

Royal Navy nuclear submarine fleet

Filename

20

D

D

Rolls-Royce data – strictly private

Trafalgar class – Reactor Compartment

Filename

21

Rolls-Royce data – strictly private

Submarine - Nuclear Propulsion Plant

Filename

22

Rolls-Royce data – strictly private

Factors influencing reactor materials performance

Filename

23

material

loading

environment

composition

mechanical working

welding

thermal treatments

microstructure

defects

pressure

residual stress

thermal

structural

temperature

water chemistry

electrochemical potential

pH; cleanliness

radiation

corrosion

radiation hardening

fatigue

fracture

plastic deformation

embrittlement

radiation creep

environmentally assisted cracking

Rolls-Royce data – strictly private

Nuclear fission

Filename

24

Fission of U235 is caused by low energy “slow” neutrons. When fission occurs, fast neutrons are produced.

Fast neutrons are either converted to slow neutrons by collisions within the moderator (water) or are absorbed by surrounding materials where they cause radiation damage.

Rolls-Royce data – strictly private

Displacement cascade

Filename

25

Rolls-Royce data – strictly private

Primary circuit materials

Filename

26

ferritic steels

​

austenitic stainless steels

martensitic stainless steels

cobalt alloys (Stellite)

nickel-copper alloys

zirconium alloys

nickel alloys

Rolls-Royce data – strictly private

Materials performance in PWRs -��(Ted Darby RR Fellows Lecture – Materials Performance in Pressurised Water Reactors)

​

• Stainless steels

• Zirconium alloys

• RPV steel

​

​

Filename

27

Rolls-Royce data – strictly private

Factors affecting stainless steel component integrity

Filename

28

material

loading

environment

composition

thermal treatments

welding process

microstructure

cold work

residual stress

thermal

structural

strain rate

temperature

water chemistry

electrochemical potential

flow rate

radiation

corrosion

thermal ageing

sensitisation

fatigue

fracture

plastic deformation

environmentally assisted cracking

Rolls-Royce data – strictly private

Cracking in welded seal sample

Filename

29

IGSCC

TGSCC in weld HAZ

Rolls-Royce data – strictly private

Intergranular Stress Corrosion Cracking

Filename

30

Rolls-Royce data – strictly private

Sensitisation - Cr depletion at grain boundary

Filename

31

Rolls-Royce data – strictly private

IGSCC mechanism

Filename

32

Rolls-Royce data – strictly private

EAC mechanism understanding – crack tip studies

Filename

33

IGSCC in non-sensitised materials and “special” grain boundaries…

Rolls-Royce data – strictly private

PWR fuel assembly

Filename

34

ABB 17x17 PWR fuel assembly picture courtesy of ABB Atom AB

fuel rod bowing

Rolls-Royce data – strictly private

Zr performance: corrosion and hydriding

Zr + 2H₂O ZrO₂ + 4H

​

• ZrO₂ thermal resistance �causes fuel temperature rise
• Some hydrogen absorbed:
• Zircaloy-2 – 50-80%
• Zircaloy-4 – 10-20%
• Hydrogen diffuses rapidly �at operating temperatures
• Low hydrogen solubility: �brittle hydrides form

Filename

35

centreline

cladding

oxide

water flow

fuel rod temperature profile

Rolls-Royce data – strictly private

Zircaloy corrosion mechanism

Filename

36

Rolls-Royce data – strictly private

Zircaloy-4 corrosion & SPP dissolution�

Filename

37

(Garzarolli, ASTM STP 1423)

Rolls-Royce data – strictly private

Hydride blister in fuel cladding

Filename

38

Ref. A. M. Garde, G. P. Smith, and R. C. Pirek, “Effects of Hydride Precipitate Localization and Neutron Fluence

on the Ductility of Irradiated Zr-4”, ASTM STP 1295, 1996.

Rolls-Royce data – strictly private

DHC mechanism in zirconium alloys

Filename

39

Rolls-Royce data – strictly private

DHC initiated at notch in irradiated Zircaloy-2

Filename

40

grain boundary

Rolls-Royce data – strictly private

DHC threshold and crack growth rate

Filename

41

K_IH

1cm/day

Rolls-Royce data – strictly private

Hydrogen solubility in irradiated Zircaloy

Filename

42

80

70

60

50

40

30

20

10

0

100

125

150

175

200

225

250

275

300

325

350

Temperature ^oC

Hydrogen concentration (ppm)

Tssp

Tssd

hydride dissolution

hydride precipitation

Rolls-Royce data – strictly private

DHC mechanism and critical temperatures

Filename

43

T_MIN

Temperature

DHC growth

rate

T_DAT

T_RIT

T_MAX

Hydrogen diffusion

to crack tip

Hydride

precipitation

Hydride

fracture

Over-temperature

Rolls-Royce data – strictly private

CANDU reactor fuel channel

Filename

44

Rolls-Royce data – strictly private

DHC in CANDU pressure tubes

Filename

45

• Local crack

• Tube rupture (Pickering 2 G-16)

Rolls-Royce data – strictly private

Catastrophic failure of cylindrical pressure vessel

Filename

46

Rolls-Royce data – strictly private

MV Kurdistan�April 1979

Filename

47

Rolls-Royce data – strictly private

Filename

48

Rolls-Royce data – strictly private

Fracture Mechanics Concepts

• G = Pi(sigma 2) a / E

​

• K = sigma (pi x a)1/2

​

• G = (K)2 / E

​

• J = G

​

• J = M sigmaY CTOD

Filename

49

Rolls-Royce data – strictly private

Fracture Mechanics Concepts

Filename

50

J F Knott

Hatfield Lecture

“Quantifying The Quality of Steel”

Rolls-Royce data – strictly private

K I Reference Curve

Filename

51

Rolls-Royce data – strictly private

Master Curve

Filename

52

Rolls-Royce data – strictly private

Failure Probability

Filename

53

Rolls-Royce data – strictly private

Reactor pressure vessel

​

• Welded construction using ferritic steel plates (PWR1) and forgings (PWR2)

​

• Limiting region for structural integrity is the highly irradiated ‘beltline’

Filename

54

Rolls-Royce data – strictly private

RPV steel – �corrosion� fatigue

​

• Potential for up to 100x enhancement in crack growth rate in water due to EAC mechanism

​

• Sulphur content of steel and/or water established as key variable

Filename

55

Rolls-Royce data – strictly private

Ductile – brittle transition in ferritic steels

Filename

56

Temperature

Ductile / Brittle Transition

Stress

Impact Energy

Yield Strength

Fracture Strength

Upper Shelf�(Ductile)

Lower Shelf�(Brittle)

Temperature

DBTT – irradiation shift

irradiation hardening

Rolls-Royce data – strictly private

Reactor Pressure Vessel

Filename

57

OUST

​

ALARP

​

IOF

​

TAGSI

Rolls-Royce data – strictly private

Failure Analysis Diagram

Filename

58

Rolls-Royce data – strictly private

TWI - Biaxial Wide Plate�A533B

Filename

59

Rolls-Royce data – strictly private

Filename

60

TWI Biaxial Test A533B

Rolls-Royce data – strictly private

Biaxial & Uniaxial Wide Plates�A533B

Filename

61

Rolls-Royce data – strictly private

Filename

62

Rolls-Royce data – strictly private

Ductile-Brittle�Transition Curve��A533B��Effect of Constraint

Filename

63

Rolls-Royce data – strictly private

Factors affecting Actual to Predicted Fracture Behaviour

Filename

64

• Constraint (bend tension biaxial)
• Thickness/size
• Crack acuity
• Crack position
• Proof Loading
• Material issues

Rolls-Royce data – strictly private

Big Bang video

Filename

65

Rolls-Royce data – strictly private

Irradiation damage mechanism in steels

Filename

66

Irradiation shift results from hardening due to both matrix damage and solute, e.g. copper precipitation.

​

In addition, phosphorus segregation to grain boundaries can cause further embrittlement.

Rolls-Royce data – strictly private

Fracture mechanisms and mechanics

Filename

67

Rolls-Royce data – strictly private

3D Atom Probe data for RPV steel aged at 365˚C

• Higher density of Cu clusters formed in higher Ni alloy

Filename

68

Rolls-Royce data – strictly private

3D Atom Probe analysis of RPV steel aged at 365˚C

• A shell of Ni, Mn and Si formed around Cu clusters after ageing at 365˚C for 3000 hours
• Other solutes segregate weakly, or not at all

Filename

69

Cu Ni Mn Si

Rolls-Royce data – strictly private

Cu precipitates in RPV steel

Filename

70

5nm

P1

P2

P3

C

C

• C
• Cu
• Sn
• Ni
• Mn

Sn

Rolls-Royce data – strictly private

• For irradiation sensitive steels the through life shift in brittle fracture boundary can eventually impose operating restrictions

​

• In modern steels, shift is minimised by controls on potential embrittling elements: Cu, P, etc.

Filename

71

Consequences

“Boot diagram”

Rolls-Royce data – strictly private

Possible contribution by TJW to an SJG talk covering “Activities/issues on irradiation embrittlement of RPV materials and how industry will solve these in the future, base materials and welds” (SJG email 28/09/08).��Draft 2 10/10/08

©2008 Rolls-Royce Group plc�The information in this document is the property of Rolls-Royce Group 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 Group plc.

This information is given in good faith based upon the latest information available to Rolls-Royce Group 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 Group plc or any of its subsidiary or associated companies.

Title - Arial 28pt

Rolls-Royce data – strictly private

Current issues (1)

• There is a requirement to extend RPV lifetimes to 60 or 80 years, but
• Current empirical data are limited to about 20 year irradiation exposures
• There remains a potential for unexpected new (slow kinetics) damage mechanisms to emerge from longer-term irradiations
• Surveillance schemes did not anticipate lifetimes beyond 40 years, there are few specimens left in reactor to provide forewarning of such mechanisms
• Some implicit assumptions of current prediction methods are not validated

Filename

73

Rolls-Royce data – strictly private

Current Issues (2)

• All regulatory models used to predict irradiation shift are empirically fitted to surveillance data
• They cannot therefore be used to predict shifts for new materials or for different irradiation environments (e.g. operating temperatures, and neutron fluences and spectra)
• In a few cases the materials used in current RPVs are outwith the general population of surveillance data

Filename

74

Rolls-Royce data – strictly private

Current issues (3)

• Some major funding bodies worldwide have perceived that the “irradiation damage problem” has been resolved for Gen II and Gen III RPVs, resulting in a drastic reduction in research programmes.
• (The problems associated with justification of 80 year operation are now becoming recognized, but significant damage has already been done to the resource.)

Filename

75

Rolls-Royce data – strictly private

Potential solutions (1)

• A considerable amount of work has been done to develop understanding of irradiation damage through studies of irradiated microstructures at the nanometer scale and through analytical work.
• The results can be used to develop Mechanistically-Based Correlation (MBC) models, which are more robust than the current empirical or semi-empirical models.
• Such models are not yet widely used in safety justification
• A limited amount of work, generally involving international collaboration, to develop understanding continues. It is expected that this will be enhanced by the (€5M) NULIFE PC1 programme, which will bid for EC FP7 funding

Filename

76

Rolls-Royce data – strictly private

Potential solutions (2)

• There is a continuing major effort worldwide to develop predictive models of irradiation damage through analytical and numerical physical models across the time and length scales involved.
• Such multi-scale physics (MSP) models can in-principle be reliably extrapolated, but it is likely to be many years before they are sufficiently developed and validated for regulatory acceptance.
• However, they are already becoming useful to develop insight and understanding, and to improve MBC models.
• MSP modelling is being pursued for Gen II, Gen III, Gen IV and fusion reactors. For Gen II/III work has been done in the (€18M) EC PERFECT project and is about to resume in the (€12M) EC PERFORM60 project.

Filename

77

Rolls-Royce data – strictly private

Potential solutions (3)

• For new Gen III plant there are options to:
• Improve start of life toughness (for both base material and welds) by improved specifications, processing and fabrication, or by introducing new materials
• Introduce materials which are less sensitive to irradiation
• Reduce uncertainties (and therefore increase margins) by improved start of life toughness estimation, improved surveillance programmes and improved through-life toughness prediction methods

Filename

78

Rolls-Royce data – strictly private

Potential solutions (4)

• For some existing plant, it may be possible to increase confidence in RPV properties by extracting samples from the RPV wall, which are small enough not to compromise integrity
• Possible techniques for non-destructive monitoring of in-service degradation have been investigated
• For some existing plant (notably VVER reactors), it may be possible to reduce or remove irradiation damage through vessel annealing – already done successfully for VVER-440 reactors)

Filename

79

Rolls-Royce data – strictly private

Ductile – brittle transition in ferritic steels

Filename

Temperature

Ductile / Brittle Transition

Stress

Impact Energy

Yield Strength

Fracture Strength

Upper Shelf�(Ductile)

Lower Shelf�(Brittle)

Temperature

DBTT – irradiation shift

irradiation hardening

Irradiation shift – fracture toughness

Filename

shift

Irradiation damage mechanism in steels

Filename

Irradiation shift results from hardening due to both matrix damage and solute, e.g. copper precipitation.

​

In addition, phosphorus segregation to grain boundaries can cause further embrittlement.

Model of a displacement cascade ca 2002

Filename

With thanks to Brian Wirth, University of California, Berkeley

Solute atom

(e.g., Cr, Cu,

Mn, Ni)

Filename

Low Nickel Weld

​

0.073at% Ni

​

~ 0.5at% Cu

High Nickel Weld

​

1.58at% Ni

​

~ 0.5at% Cu

Irradiated to 33 mdpa

Irradiated to 30 mdpa

Atom Probe Data

3DAP micrograph

Filename

In addition to Cu, clusters also contain a large proportion of Mn and Ni, some Si, occasionally P. They may also contain up to 50% Fe (disputed). Mn and Ni tend to be segregated to the interface.

J.M. Hyde, and C.A. English, “An Analysis of the Structure of Irradiation induced Cu-enriched Clusters in Low and High Nickel Welds.” Materials Research Society Symposium: Microstructural Processes in Irradiated Materials, MRS Proceedings vol. 650 (2001), paper R6.6

Filename

Data from Mike Miller using the LEAP (IGRDM-12)

Simulated microstructure after irradiation

Filename

With thanks to Stéphanie Jumel, EDF, France

The Present

• Ageing Nuclear Legacy
• Decline of Nuclear Engineers and UK Capability
• Select Committee on Defence
• Select Committee on Nuclear Skills

​

Filename

Filename

Filename

Sheffield Forgemasters

The Future - On The Threshold of a Dream

• Next Generation of Nuclear Power Stations
• Next Generation of Nuclear Submarines
• Next Generation of Nuclear Engineers
• Nuclear Future

​

Filename

• NGNPP for Submarine propulsion
• Gen III+ for Power Generation

What the papers say!

Filename

UK’s Nuclear Power Stations�2008

Filename

Filename

Filename

Next Generation in the UK

• Gen 1
• Gen 2
• Gen 3
• 3P’s vs 3 E’s Chatham House Conference
• Gen 4?

Filename

I Want That One!

Filename

UK vs Rest of World

Filename

Filename

​

• Improved Safety
• Improved Availability
• Reduced Whole Life Cost

Design – Future Concepts

Filename

PILM - CADMID

Filename

‘Cradle to Graveside’

A533BclassI A508classIII HY80

Filename

Filename

Submarines Engineering Population - 2008

Filename

Skill

Graduate

Engineers -

Submarines

Applied Science

13

Controls

97

Design

150

Electrical

22

Materials

47

Mechanical

40

Nuclear

25

Product Definition

25

Safety & Reliability

68

Service

118

Support

28

Thermo Fluids

81

Test

28

Total

850

Age groups

The Elements of SQEP Resource

Filename

Engineering Competency Assessment

• Engineering split into 21 primary � skills
• 14 are key to submarines business
• Each skill managed by Naval Marine � Skill Owner
• Each individual is assigned to a skill
• Individuals competency is assessed and � recorded by the Skill Owner

Nuclear Training Requirements Plan

• Customer defines Nuclear Training� requirements
• NTRP defines our training plan to � meet these
• The plan also manages compliance to � the NTRP within the business

​

Suitably Qualified and Experienced Personnel (SQEP)

Local Management Assessment

• Local post profiling highlights specific job� requirements over and above NTRP or � Competency Assessments
• Audit of job holder against post profile

Nuclear Training Committee

• Review waivers
• Audit compliance with NTRP

Training Management Process Coordinates:

• Training requirements from � all sources
• Maintains training records � from all individuals within the � organisation
• Delivers and administers � training packages

Career Structure Boardings

• Identify competencies � required to progress through� the grading structure

Filename

University Technology Centres & Liaison Teams

Solid Mechanics

Oxford

Vibration

Imperial College

Combustion Aerodynamics

Loughborough

University Gas Turbine Partnership (UGTP)

Cambridge (Whittle lab)

Performance

Cranfield

Materials Partnership

Cambridge, Birmingham & Swansea

Heat Transfer and Aerodynamics

Oxford (Osney lab)

Control & Systems Engineering

Sheffield

Aero-thermal Systems

Sussex

Advanced Electrical Networks

Strathclyde

Gas Turbine Transmission Systems

Nottingham

Systems & Software Engineering

York

Materials Damping Technology

Sheffield

Design Partnership (with BAE)

Cambridge, Sheffield & Southampton

Computational Fluid Dynamics

Oxford

Noise

Southampton

Manufacturing Technology

Nottingham

Thermo-fluid Systems

Surrey

RR Submarines University Links

Manchester, Newcastle, Cambridge, Imperial, Bristol, Leeds, Nottingham, Loughborough, Oxford,

Birmingham, Sheffield.

Filename

A Nuclear Future

• Best approach for a safe Nuclear future is via a strong, well funded UK Nuclear Industry.
• Nuclear Power has to be viewed as a worldwide activity, its influence is global .
• Next Generation Plant must be designed for Safety, Regulatory developments should not dominate real Engineering enhancements.
• Wonderful opportunity for new Engineers across a range of disciplines. This will motivate a New generation of Material Scientists, Engineers,Physicists etc and also ensure safe decommissioning and disposal of our Nuclear legacy.

​

Filename

Filename

1956: Queen switches on nuclear power

The Queen�

Sir Edwin Plowden, chairman of the Atomic Energy Authority, also stressed the ground-breaking nature of the new power station.

"Nothing that comes after will be able to detract from the importance of this first great step forward," he said.

Her Majesty the Queen gave her speech in the shadow of the massive chimneys of the Windscale plant, where explosives were made for Britain's first atomic bomb, and she gave a timely reminder of the more sinister origins of the technology.

"This new power, which has proved itself to be such a terrifying weapon of destruction," she said, "is harnessed for the first time for the common good of our community."

At 1216 GMT, she pulled the lever which would direct electricity from the power station into the National Grid for the first time.

A large clock on the wall of the power station registered the first kilowatts of energy to be produced.

The town of Workington, 15 miles (24 km) up the Cumberland coast from Calder Hall, became the first town in the world to receive light, heat and power from nuclear energy.

Within four hours, the first nuclear-powered electricity was reaching London.

The government expects to save about 40 million tons of coal by investing in the new technology, and it is planning to supply about 10% of the country's electricity needs from nuclear power within less than 10 years.

Calder Hall is known as a gas-cooled, graphite-moderated reactor, and uses the nuclear reaction in uranium rods to generate power.

Two other nuclear power stations are already under construction - one alongside the existing Calder Hall plant, to be known as Calder Hall B, and the other at Chapel Cross in Scotland.

​

A huge clock registered the first power to be transferred to the National Grid�

xxx

Filename

xxx

Filename

Key points

• Dawn of an exciting new Nuclear Generation in Power and Propulsion
• Need for next generation of UK based Engineers & Material Scientists
• Separate focus on Engineering Safety and Regulatory Compliance
• Research in the development of next generation Materials & Systems

​

Filename

Going out with a bang!

Filename

To understand how safe a component is one needs to know its actual failure conditions!

Filename