How to Achieve High Reliability, Availability, and Maintainability

1. How to Achieve High Reliability, Availability, and Maintainability L. Waganer 14-15 June 2007 ARIES Project Meeting at GA

2. ARIES Design Approach for High RAM • ARIES-AT (and other tokamak predecessors) concentrated on faster maintainability to achieve higher availability • Power core design featured independent sectors that can be quickly removed • Individual vacuum ports allow access to individual sectors • Remove half or all core sectors during same maintenance action • Immediately replace used sector with refurbished sector • Refurbish sectors off line during operation

3. ARIES Approach for High Reliability • System Reliability is based on several concepts • Use high reliability components • Have an aggressive testing program to validate component reliability • Increase design margin to extend life and decrease likelihood of failure • Employ sophisticated modeling and simulation to uncover potential life-limiting conditions and failure modes • Implement failure mode and effects (and criticality) analysis • Institute an initiative (program) to identify life-limiting or failure predictors • Fusion has a very limited component reliability database • Initial database can be constructed from some experimental machines, but component applicability to larger machines may be questionable • Need to start a standard component procurement with extensive testing and reliability enhancement program.

4. ARIES Approach for High Maintainability • ARIES has developed an approach to achieve a high degree of maintainability • All components including life of plant elements are removable remotely • All internal plumbing removed with sector • Removal sequences designed for fast removal • Unplanned failures can be isolated to a single sector that can be quickly replaced • Maximize standardization of parts, components, and subsystems • Maximize interchangeability of components • Implement a Reactor Health Management System to monitor reactor health and predict maintenance actions • Include Built In Test capabilities into critical components All replaceable power core components have equivalent full power lifetimes that allow all components to be replaced at the same time, thus minimizing maintenance times (maximizing availability) High degree of automation is utilized to reduce radiation exposure, high motion repeatability/precision (accuracy?), and faster operation

5. ARIES Approach for High Availability Availability is a combination of reliability and maintainability Avail = Operational Time (at full power)/Total Time Avail = (Total Time – Down Time)/Total Time Avail = (Total Time – Scheduled Down Time – Unscheduled Down Time)/Total Time Avail = (Total Time – Scheduled Down Time – (MTBF x MTTR) ) / Total Time • Scheduled maintenance is basedon component wear-out and lifetime and preventative maintenance actions • Blanket and Divertor lifetimes are matched to be replaced at same interval • Scheduled Blanket and Divertor replacement schedule optimized for availability and capital cost of replacement sectors and maintenance equipment • Remainder of scheduled Plant and BOP maintenance (including Turbine maintenance) are scheduled to coincide with FWBD replacement • FWBD/BOP maintenance dominates scheduled maintenance as other maintenance can be done off line and redundancy of key components and systems keeps plant operational

6. ARIES Approach for High Availability Availability is a combination of reliability and maintainability Avail = Operational Time (at full power)/Total Time Avail = (Total Time – Down Time)/Total Time Avail = (Total Time – Scheduled Down Time – Unscheduled Down Time)/Total Time Avail = (Total Time – Scheduled Down Time – (MTBF x MTTR))/Total Time • Unscheduled maintenance is basedon the Sum of Mean Time Between Failures times Mean Times To Repair • These failures apply only to components that are necessary for operation • Time to repair includes shutdown and startup • Redundancy mitigates consequence of failure • Ready supply of spares reduces consequence of failure • IHMS can mitigate potential failure by scheduling replacement

7. Plan to Achieve HIGH RAM • High reliability systems have been done before; space, electronics, and automobiles, but low quantity, high complexity applications require more high quality components and testing programs. • Fully or highly automated maintenance has only been accomplished in a few instances, fission refueling, deep sea exploration, space, medical, and high cleanliness manufacturing. Modeling and simulation are the likely technologies, supplemented with large scale testing facilities. • Achieving high and verifiable availability data will require both analytical simulation and physical testing in integrated prototypical maintenance facilities.