ADS reliability requirements Dirk Vandeplassche Eucard-2 — Reliability for ADS Workshop, CERN June 22-23, 2015

ADS reliability workshop, CERN, 22-23/06/2015 Overview fundamental accelerator needs for ADS the availability goal GUINEVERE operational experience the beam trip spectrum pathways towards availability ADS reliability workshop, CERN, 22-23/06/2015

the accelerator for ADS Accelerator driving a subcritical fission core: external neutron source  spallation reaction subcritical core acts as a neutron amplifier ADS proton beam power, rule of thumb, order of magnitude: core power k beam power MYRRHA 100 MWth .975 2.4 MW industrial transmuter 1 GWth .99 10–15 MW nothing shocking ... up to now ADS reliability workshop, CERN, 22-23/06/2015

the accelerator for ADS Hence accelerator = HPPA-class fission core = DC device  CW beam yes, but with holes for n-monitoring beam energy: efficient neutron production, core geometry MYRRHA choice: Ebeam = 600 MeV transmuter: Ebeam = 1000–1500 MeV Ibeam MYRRHA: Ibeam ≈ 4 mA transmuter: Ibeam ≈ 10–12 mA the acceptable time structure of the beam is determined by the "target" ADS reliability workshop, CERN, 22-23/06/2015

ADS reliability workshop, CERN, 22-23/06/2015 the ADS target MYRRHA reactor rev. 1.6 ADS reliability workshop, CERN, 22-23/06/2015

ADS reliability workshop, CERN, 22-23/06/2015 the ADS target ADS reliability workshop, CERN, 22-23/06/2015

ADS reliability workshop, CERN, 22-23/06/2015 the availability goal effect of a beam trip in a fast core prompt neutron population drops down to zero in tens of µs small fraction of delayed neutrons may subsist, depending on the fuel power delivered by core becomes instantaneously very low — its heat capacity is fairly low  temperature drops very fast ADS reliability workshop, CERN, 22-23/06/2015

ADS reliability workshop, CERN, 22-23/06/2015 the availability goal problems thermal stresses  fatigue structural materials, e.g. core support structures fuel pins' cladding material loss of integrity of oxide layer Pb-Bi environment  corrosion, embrittlement tolerances to fast and unexpected drops fast reactor experience (PHENIX)  min. fast reactor design (PHENIX)  typical ? thermal stress modeling of structural mat.  max. ADS reliability workshop, CERN, 22-23/06/2015

ADS reliability workshop, CERN, 22-23/06/2015 the availability goal numbers for 1 MYRRHA cycle = 3 months: PHENIX experience: 10 trips PHENIX design: 30 trips (for 20y lifetime) structural modeling: t < 10s : 1000 10s < t < 5m : 100 t > 5m : 10 τmax ? t < τmax : thermally "transparent" immediate restart is allowed τmax = 3s ADS reliability workshop, CERN, 22-23/06/2015

ADS reliability workshop, CERN, 22-23/06/2015 the availability goal ADS reliability workshop, CERN, 22-23/06/2015

ADS reliability workshop, CERN, 22-23/06/2015 GUINEVERE ADS reliability workshop, CERN, 22-23/06/2015

ADS reliability workshop, CERN, 22-23/06/2015 GUINEVERE GUINEVERE is : zero power ADS @ SCK•CEN electrostatic d-accelerator 230 keV (GENEPI-3C), 3H target coupled to VENUS-F fast core critical or subcritical operation GUINEVERE has : operational experience with beam trips without bothering about structural integrity ADS reliability workshop, CERN, 22-23/06/2015

ADS reliability workshop, CERN, 22-23/06/2015 GUINEVERE operational limits given in official licence document "core certificate" one main safety parameter = reactor period — GUINEVERE: 10s this limit prevents restarting (SCRAM !) if t > few s "almost every accidental beam trip causes a scram" recovering from a scram : 30 minutes (zero power !) comparison PHENIX (600 MWth) : scram recovery time = 22 hours ! ADS reliability workshop, CERN, 22-23/06/2015

the practical beam trip spectrum assume a conservative SCRAM recovery time of 24 hours (first of a kind !) accept a 10% availability loss due to SCRAMs (OK for research, not for industry !) hence, for MYRRHA: may accept 10 SCRAMs per period of 3 months equiv.: not more than 10 accidental beam interruptions > 3s per 3 months equiv.: beam-MTBF > 250 hours, failure = beam trip > 3s important: purely operational argument which luckily coincides with the "PHENIX experience" ADS reliability workshop, CERN, 22-23/06/2015

the practical beam trip spectrum ADS reliability workshop, CERN, 22-23/06/2015

pathways to availability 2 questions : wishful thinking ? how to reach ? startpoint = gut feeling : no fundamental show stopper recipe : main ingredient = build in fault tolerance, hence redundancy implementation : modularity goes well with redundancy ADS reliability workshop, CERN, 22-23/06/2015

pathways to availability ADS reliability workshop, CERN, 22-23/06/2015

pathways to availability initial modeling beam dynamics : seems OK FMEA studies : fault tolerance seems effective for gaining, say, 1 order of magnitude today : recipe basically unchanged advanced beam dynamics, start-to-end simulations, including errors working reliability model several experimental results International Design Review : they tasted, evaluated positively and gave many recommendations R&D program : focus on availability ADS reliability workshop, CERN, 22-23/06/2015

pathways to availability ADS reliability workshop, CERN, 22-23/06/2015

pathways to availability today's confidence : " much more than wishful thinking" but the 2nd question remains : " how to get there ?" some thoughts, besides trivial issues of reliability 3s is short for doing all that has to be done a decision taking control system is new to us innovative functionalities overlooked R&D item ? ADS reliability workshop, CERN, 22-23/06/2015

pathways to availability commissioning and its uncertainties the benefits of a phased approach : a hold point at intermediate energy evaluation application with strongly reduced constraints flexibility at reactor side is a must constraints should not be magic numbers refer to PHENIX : allowable # scrams seems to be a design parameter unavailability in a demo context should be allowable ADS reliability workshop, CERN, 22-23/06/2015