Physics Department Lancaster University Physics Department Lancaster University Reliability Rebecca Seviour Cockcroft Institute Dept Physics Lancaster University

Physics Department Lancaster University Reliability is: estimating, controlling and managing, the probability of failures in complex systems. Technical complexity of systems mean it is not enough to specify and allocate the reliability of components to predict the reliability of the system.

Physics Department Lancaster University Identification of possible failure modes of each component Listing of all the envisaged faults Effects of the component fault on the performance of system Identification of preventive and corrective actions Severity ranking of the faults Relative frequency of faults Failure Mode and Effects Analysis (FMEA) The purpose of the FMEA is to take actions to eliminate or reduce failures, starting with the highest-priority ones. Failures are prioritized according to how serious their consequences are, how frequently they occur and how easily they can be detected. Component data has only a limited role on system reliability, nature of connection is important!

Physics Department Lancaster University - Availability : Fraction time system meets its specification. - Reliability : probability system performs intended function for a specified time interval - Mean Time Between Failure (MTBF): mean time system performs to spec, during a given time interval. - Mean Down Time (MDT): Mean time system is unavailable due to a failure. Repair time plus all delays associated with the repair (finding the spare part, etc). - Mean Time To Repair (MTTR): sum of corrective maintenance time divided by the total number of failures during a given time interval.

Physics Department Lancaster University

Physics Department Lancaster University Accelerator Spallation Target ~25 N < 20MeV Per P Proton Beam Core 10 MW, 10 mA, 1 GeV (14MeV) ADSR block diagram As providing a service to national grid, need to ensure >95% availability with only one long shutdown per year for maintenance. Linac Cyclotron FFAG

Physics Department Lancaster University Akio Yamamoto Annals of Nuclear Energy 30 (2003) What is the effect of Loss N flux ? How long before fuel cools o stops power generation 1 Second before fuel cools ! Could be 1-3 secs Or even 10’s

Physics Department Lancaster University Accelerator Spallation Target ~25 N < 20MeV Per P Proton Beam Core 10 MW, 10 mA, 1 GeV (14MeV) ADSR block diagram As providing a service to national grid, need to ensure >95% availability with only one long shutdown per year for maintenance. Linac Cyclotron FFAG

Physics Department Lancaster University Given components, MTBF and MTTR, Monte-Carlo can be used. Analyses for RIA – 400 KW SC Linac, availability: 0.96 Contribution to down time (>0.4%) E. S. Lessner and P. N. Ostroumov (2005) LINAC (1 Sec rule)

Physics Department Lancaster University Using RIA availability 0.96 With 8 hr weekly and one 4 week maintenance per year. Over 42 weeks cts running  ~12 days down time But using complete 3 fold (hot) redundancy, derated (Bauer) Complete system down ~ 1 Hr per year Or..... Run 2 Linacs hot, one down for maintenance 1 day system down per year LINAC (1 Sec rule)

Physics Department Lancaster University “….The problem of the few long beam trips per year that are expected can be solved with equipment redundancy.” Accelerator-driven Systems (ADS) and Fast Reactors (FR) in Advanced Nuclear Fuel Cycles NUCLEAR ENERGY AGENCY ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENT “The super-conducting linac design is derived from the experience gained at CERN, TJLab, and DESY, …. …strong proof that the expectations of improved reliability, and reduced capital and operational cost have to be considered as fully realistic.” “…trips caused by sparking and similar (non-failure) events can be reduced to a time scale <100 milliseconds, and would have practically zero impact….” LINAC

Physics Department Lancaster University L Hardy, P. K. Sigg + ~10000 < 1 min a year ~ 2 per Hr (not included in stats) 90 % of Beam trips due to sparking at injection/extraction devices ~ 1 per day > 1 sec ~70 % < 1 Sec Availability: (Heyck & Wagner) 60 % of failures RF related 1.8 mA P, 590 MeV ~1 MW (been considered for ADS) Cyclotron - SINQ Sparking increases with beam current, 1.8 mA  ~ 1 trip a week over 3 sec ADSR needs to go from 1.8 mA – 10 mA 10 mA  1 ? trip a day over 3 sec

Physics Department Lancaster University Very little in way of FFAG design, don’t have components spec, Source: 5 MeV, availability FFAG: 4 Cavities and 12 Magnets ? FFAG compared to linac availability: ~ (vacuum, power, control, diagnostics) RIA contribution to down time E. S. Lessner and P. N. Ostroumov (2005) Sub-availability: ~ 0.94 Over 42 weeks cts running  ~18 days down time using triple(hot) redundancy, Complete system down ~ 2 Hr per year FFAG

Physics Department Lancaster University RF structures & systems very different to Linac and Cyclotron few RF systems Normal conducting Q ~1 Frequency hop/sweep scheme 240 KV Sparking may occur rarely/never ? Some sparking at Injection/extraction, but lower than SINQ With triple redundancy should reduce risk of trip FFAG

Physics Department Lancaster University Circular machines: beam trip real problem Cyclotron (SINQ based) Sparking increases with beam current, 1.8 mA  ~ 1 trip a day over 1 sec ADSR needs to go from 1.8 mA – 10 mA 10 mA  ?3? trip a day over 1 sec FFAG derate cavities to 240 KV (lower voltage lower spark rate) Cavities very different from SINQ 10 mA  ? trip a day over 1 sec

Physics Department Lancaster University beam E B Beam Induction Acceleration

Physics Department Lancaster University prototype devices generate a 250nsec flat-top voltage at a repetition rate of 1 MHz, Acceleration 500MeV -> 8GeV

Physics Department Lancaster University en In the limit that E i « E f then ~longitudinal gradient.  B volume-averaged flux change in core Take t p = 100 ns pulse, Metglas core  B = 2.5 T, Ri = 0.1 m and Ro = 0.5 m. Vacuum ports, power feeds, insulators cores   = 0.5. Assuming cavity section 0.3m  Max gradient ~ 1 MV. L1 = 133 μH. damping resistance of R1 = 30  and min cavity voltage of 100 kV, the modulator supplies a current greater than 5.3 kA

Physics Department Lancaster University non-resonant and if designed properly stores neither the drive fields nor Wakefields. Can define unique accelerating field Broadband switching characteristics, repetition ratio, duty factor. super-bunch acceleration pulse modulator has to be kept far from the induction cavity as solid-state switching elements can’t radiation dose. Jitter The limitations of available ferromagnetic materials must be understood

Physics Department Lancaster University Seviour – Owen Compact Neutron Source Fusor based System MeV neutrons per sec 20 m 2 footprint High-reliability, low maintenance Approx £ 3 M per system