Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 1

WHAT IS RELIABILITY ?
Military standard definition of reliability:
« The probability that an item will perform a required function without failure under stated conditions for a stated period of time »
Note:
• A functional definition of failure is needed. For example, a failure means different things to the user and to the person repairing the failure,
• The system's operating conditions must be specified (e.g. external temperature).
• A period of time is needed.
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 2

RELIABILITY: A MODERN CONCEPT, YOU SAID ?
« As concerns the gold ring set with an Emerald, we guarantee that for 20 years the emerald will not fall out of the gold ring. If the emerald should fall out of the gold ring before the end of 20 years, we shall pay unto Bel-Nadin-
Shumu an indemnity of 10 mana of silver. »
Record found on a clay tablet in Egypt - 429. BC …
Source :
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 3

« The probability that an item will perform a required function without failure under stated conditions for a stated period of time. »
When was the probability concept ‘born’ ?
1654: The Chevalier de Méré, a French nobleman, called Pascal's attention to an apparent contradiction concerning a popular dice game.
• The game consisted in throwing a pair of dice 24 times,
• The problem was to decide whether or not to bet money on the occurrence of at least one "double six" during the 24 throws. A well-established gambling rule led de Méré to believe that betting on a double six in 24 throws would be profitable, but his own calculations indicated just the opposite …
Then followed an exchange of letters between Pascal and Fermat in which the fundamental principles of probability theory were formulated for the first time.
The Dutch scientist Christian Huygens learned of this correspondence and shortly thereafter (in 1657) published the first book on probability; entitled De Ratiociniis in Ludo Aleae , which was a treatise on problems associated with gambling
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 4

FIRST STEPS OF RELIABILITY THEORY
• Not formally used before World War I
• During and after World War I, reliability was just a measure of the number of accidents the planes had per hour of flight time.
• 1920-1930: telephones and electron vacuum tubes grew in demand  need to make them more economically and improve their reliability. These two new technologies spurred early reliability studies.
• 1926: Walter Shewhart, Harold F. Dodge, and Harry G. Romig laid down the theoretical basis for using statistical methods in quality control of industrial products, founding the trial and error approach to reliability study
• Again, no formal use before World War II
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 5

FIRST RELIABILITY MODELS REALLY START WITH WORLD WAR II
The V-1 rocket: reliability of 1 success out of 11 attempts
 reliability of 9.1%
The mathematician Robert Lusser analysed the missile system and quickly derived the product probability of series components making the first step into the development of the Reliability Theory for a series system:
Rs = R
1
* R
2
* * R n where R i is the probability of survival for 1 element
Robert Lusser
 A system with a large number of components like the V-1 will reach a low reliability level even with very reliable components
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 6

FIRST RELIABILITY MODELS REALLY START WITH WORLD WAR II
For a series system: Rs = R
1
1 element
* R
2
* * R n where R i is the probability of survival for
Lusser’s studies resulted in Werner Von Braun’s redesign leading to the V-2 rocket.
The V-2 rocket used the principles of redundancy to enhance the rocket’s reliability.
As a result, the reliability of V2 rockets increased from 30 % from the first launch (8 september 1944) to 70 % (end of the war).
SUMMARY I:
• We are in 1944
•
Reliability theory and first reliability principles emerge with rockets technology
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 7

A BRIEF HISTORY OF ACCELERATOR NON -RELIABILITY
1924: Ising: the first Linac model
1928: Wideröe: a model based on
RF voltage
March 1936: the first external cyclotron beam:
5.8 MeV deuterons
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 8

A BRIEF HISTORY OF ACCELERATOR NON -RELIABILITY
1941: 184-inch cyclotron
(>100 MeV) for U235 /
U238 separation (Berkeley)
1947: proton Linac built under supervision of Alvarez
1959: CERN 24 GeV PS is the highest energy accelerator in the world
PS inauguration (1960)
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 9

A BRIEF HISTORY OF ACCELERATOR NON -RELIABILITY
SUMMARY II:
•
1950’s : Particle accelerator technology is already well advanced
• Emergence of basic principles of reliability
•
Until 50-60’s , reliability is not at all a concern for accelerator technology
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 10

A BRIEF HISTORY OF ACCELERATOR RELIABILITY…
1968: First dedicated X-ray source (bench test): Tantalus
(Wisconsin - USA)
1970: First beam line (Nina) with Users on an X-ray source: SRS Daresbury (UK)
( + PSI, TRIUMF)
1972: meson factories.
E.g.: Los Alamos
(LAMPF): 800-MeV beam
LAMP aerial view
One mention of ‘reliability’ in 17 pages (Particle Accelerators ©
Rosen: « we need more particles per unit time
Gordon and Breach,
1973, Vol. 4, pp. 211-227) rather than more energy per particle ! »
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 11

1956
A BRIEF HISTORY OF ACCELERATOR RELIABILITY…
MEDICAL APPLICATIONS
 USERS NEED RELIABILITY AND AVAILABILITY !!
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 12

ACCELERATOR RELIABILITY NOWADAYS
With some examples, let’s get an idea of what we can reach today:
Institute
KEK storage Ring
2008
Scheduled
User time
[hours]
Delivered time
[hours]
4344 4302
Storage Ring availability
[%]
99.0 %
Fault/year MTBF
[Hours]
40 109
Mean Time to recover
[hours]
1.0
Advanced Photon
Source (APS) 2010
5000.1
4924.8
98.5 % 48 104 1.57
ESRF
(X-ray Light source)
2010
Australian
Light Source 2010
5606 5538 98.8 % 83 67.5
0.8
4859 4784 98.5 % 82 59.25
0.9
Swiss Light Source
2009
5007 4941.9
98.7 % 69 72.6
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group
1
13

ACCELERATOR RELIABILITY NOWADAYS
From the previous graph, we can conclude that nowadays, with lot of efforts to obtain high reliability, typical particle accelerators (running 208 days – 5000 hours / year) have :
98 % < Availability < 99%
40 < Faults / year < 100
60 hours (2.5 days) < MTBF < 109 hours (4.5 days)
0.8 hour < Mean Time to Recover < 1.6 hours i.e., on average, a typical X-ray source stops
Is it sufficient for the requirements of future accelerators?
DEFINITELY :
NO
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 14

Example: Accelerator Driven System (ADS) requirements
Reminder: What is an ADS ?
This is a sub-critical reactor driven by a proton accelerator.
The accelerator bombards a target with high-energy protons which produces a very intense neutron source through the spallation process.
Basic accelerator requirements: protons,
~ 1 GeV, ~ 10 mA
Cyclotron ? Linac ?
1 proton on the spallation target will release about 20 neutrons
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 15

Example: Accelerator Driven System (ADS) requirements
What is it used for ?
• Destroy heavy isotopes contained in the used fuel from a conventional nuclear reactor, while at the same time producing electricity.
Why ? Because the long-lived transuranic elements in nuclear waste can be fissioned, releasing energy in the process and leaving behind the fission products which are shorter-lived.
This would shorten considerably the time for disposal of radioactive waste.
Why is this a promising technology ?
• Enhanced safety of ADS: once the accelerator is turned off, the system shuts down.
• If the margin to critical is sufficiently large, reactivity-induced transients can never result in a super-critical accident with potentially severe consequences
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 16

Example: Accelerator Driven System (ADS) requirements
Why an ADS must be extremely reliable ?
A Nuclear Power Plant has a hard limit on the number of thermal cycles during its lifetime, mainly due to thermal fatigue in the vessel and main instrumentation

The beam trip requirements follow from thermomechanical considerations of the spallation target and subcritical assembly and, for power production applications, reliable electrical power delivery to the grid

Thermal shocks (i.e., on / off cycles, i.e., unexpected trips) must be avoided on critical parts (beam window, reactor vessel, inner barrel and turbine system)
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 17

Example: Accelerator Driven System (ADS) requirements
Until now, the reliability goal of the accelerators was ‘we do the best we can’.
With ADS, the reliability is for the first time a CONSTRAINT (technical and economical).
September 2010, following Monte Carlo simulations, there was a consensus about ADS reliability requirements Accelerator and Target Technology for Accelerator Driven Transmutation and Energy Production
H. Aït Abderrahimh, J. Galambosd, Y. Gohara, S. Hendersonc*, G. Lawrencee, T. McManamyd, A. C. Muellerg, S.
Nagaitsevc, J. Nolena, E. Pitchere*, R. Rimmerf, R. Sheffielde, M. Todosowb
Reminder: the best statistics (KEK) are 40 faults / year but … 1 hour to recover, not 5 minutes !
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 18

Example: Accelerator Driven System (ADS) requirements
SUMMARY III:
• Nowadays accelerator reliability figures : 1-hour failure every 3 days (70/80 faults/year)
• First ADS prototypes could tolerate 50 failures / year, only stopping for a few minutes!
• Industrial ADS can NOT tolerate more than 2/3 failures (> 5 mins) / year !
When preparing this talk, I read many papers about ADS and realised that :
• ADS community performs fascinating work to explore all ways to improve accelerator reliability.
• Many references for ADS papers come from … Accelerator Reliability Workshops !
• ADS community is, like us …, dreaming of a centralised database about reliability of accelerator equipment / components (topic for Friday !)
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 19

A CHAIN IS AS STRONG AS ITS WEAKEST LINK
Before the failure FAILURE
After the failure: minimise time to repair
- Design optimization (margin, materials, modelling, )
- Preventive Maintenance
- Fault Diagnostics !
- Rigorous Spare part Policy
- Experts on standby 24 hours/day ready to intervene - Experience from other Institutes
- Realistic Operation Schedule
- Redundance
- Avoid human mistakes with automation when necessary
- Avoid unnecessary interlocks (passive sensors are sometimes sufficient)
- Operator training
- Fast interchangeability of components (<design …)
- Repair procedures
The optimization of ALL the above points (and many more) is thoroughly considered by the ADS community (as well as by others …).
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 20

250
ACCELERATOR RELIABILITY NOWADAYS : one example at the ESRF
795.5 hours (33.1 days) of delivery without a single failure
200
150
107 refills !
100
50
7/8+1
0
7/8+1 Uniform 7/8+1 16 Bunch 16 Bunch
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 21

CONCLUSIONS
• Accelerator reliability is no longer a wish but has become a constraint (ADS)
• Reliability is now considered at all stages of the accelerator’s life (from design to maintenance in routine operation)
• A requirement of 2-3 trips > 5 mins per year is a goal for the next generation
• Exchanges and workshops are essential to explore all possibilities and take the best from everyone: ARWs have an active role to play !
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 22

HOMEWORK FOR FRIDAY !

• Centralized information about accelerator reliability is missing and should be discussed at this ARW (Friday)!
• Centralized database (what should it
: https://sites.google.com/site/particleacceleratorreliability/Home contain ?)
• Accelerator reliability papers
• Statistics and records of present accelerators
• etc http://reliability.forumotion.com/
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 23

I have some questions …
• In your lab (or company), was the rate of faults / year simulated and taken into account for the design ?
• (For the Industrialists here: are you subject to penalties if you exceed a certain number of failures / year ?)
• Homework for Friday  :
• Any ideas on how to build a centralized failure database for accelerator sub-equipment / components ?
• How would it be organised ?
• To which level of equipment should it extend ?
•
• Where should it be hosted ?
Accelerator Reliability Workshop – Cape Town 2011 L. Hardy – ESRF Operation Group 24