aries project meeting, l. m. waganer, 3-4 april 2007 page 1 how to achieve high reliability,...
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ARIES Project Meeting, L. M. Waganer, 3-4 April 2007Page 1
How to Achieve High Reliability, Availability, and Maintainability
L. Waganer
14-15 June 2007ARIES Project Meeting at GA
ARIES Project Meeting, L. M. Waganer, 3-4 April 2007Page 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
ARIES Project Meeting, L. M. Waganer, 3-4 April 2007Page 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.
ARIES Project Meeting, L. M. Waganer, 3-4 April 2007Page 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
ARIES Project Meeting, L. M. Waganer, 3-4 April 2007Page 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 based on 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
ARIES Project Meeting, L. M. Waganer, 3-4 April 2007Page 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 based on 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
ARIES Project Meeting, L. M. Waganer, 3-4 April 2007Page 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.