ARIES Program
Public Information Site


ARIES-Pathways Project Planning Meeting Minutes

14-15 June 2007

General Atomics, La Jolla, CA

Documented by L. Waganer

Organization ARIES Pathways Project
Boeing Waganer
General Atomics Schultz, Turnbull
Georgia Tech Abdel-Khalik
INL Sharp
MIT Bromberg
PPPL Kessel (Phone), Zarnstorff (phone)
RPI Steiner
UCSD Dragojlovic, Mau, Najmabadi, Raffray, Tillack, Wang
UW-Mad El-Guebaly

Ref: Agenda and Presentation Links: Meeting Agenda

Administrative (Commencing Afternoon of June 3)

Welcome – Ken Schultz welcomed the ARIES team to GA. Ken hosted the ARIES Pathways Advisory Committee the prior day and the morning of June 14. Les Waganer summarized the agenda for the ARIES Pathways project that covers advisory committee results and the status/results of the action items from the prior meeting.

Plans and General Scope (of ARIES Pathways Study)

Farrokh Najmabadi briefly described the scope of the Pathways study to identify R&D needs in addition to ITER results to minimize the risks of implementing the US Demo program. The formation of the Pathways Industrial Advisory committee will help formulate the necessary R&D needs and expected attributes for the Demo program.

Summary of the first meeting of the ARIES-Pathways Industrial Advisory Committee

Ken Schultz formed an advisory committee consisting of utilities, vendors, architect/engineers, and regulators. Not all the committee members were able to attend, but the attendees represented the spectrum of the committee expertise. The ARIES team presented the history of fusion (primarily MFE), some details of ITER as the assumed physics and engineering stepping stone, and the description of ARIES-AT as the starting baseline for the Demo and commercial plant. Ken queried the committee to determine if the prior EPRI "Criteria for Practical Fusion Power Systems" were still valid. There was some carry over of criteria from the prior criteria, but the committee recommended prioritizing those criteria. R. W. Kuhr provided some insight into the EPRI criteria, critical flaws, technology development, and major risks. Reliability and availability was a critical demonstration to be accomplished prior to starting DEMO (elevated criteria). The minutes of the advisory meeting have been recorded by Ken Schultz.

ARIES-TNS Systems Code Development (Commencing Afternoon of June 14)

Progress on Systems Code Development - Zoran Dragojlovic summarized his prior work along with his new modeling efforts and described how well the present code compared to the prior published data. Zoran also showed the scoping results using the matrix of feasible plasma and engineering solutions from Chuck Kessel. As the group examined the results, it was evident that additional modeling effects need to be implemented. Zoran also incorporated new costing algorithms from Les Waganer (for Accounts 20 and 21) and compared these costs against the prior costing results.

Updated Costing Accounts 20 and 21, Land and Structures - Les Waganer examined prior relevant MFE and IFE commercial plant cost account results and algorithms for applicability to the ARIES Pathways project. He explained the cost basis he utilized and recommended cost data and algorithms for the Land and Structures cost accounts. The group acknowledged that the costing basis should be somewhat more detailed than prior ARIES studies and should be revised to reflect new design approaches and current costing basis. The systems code will be modified in the future to reflect system and subsystem quantities and learning curves. This would increase the code capability to estimate on one-of-a-kind facilities as well as 10th-of-a-kind commercial plants. Les had action items to redo the turbine plant building, check on LSA guidelines, add dry cooling option, and consider ITER cost basis.

Progress on Systems Code Development - Chuck Kessel described his current approach of compiling a vast set of viable physics results that are filtered with engineering constraints. This smaller, yet considerable, set of solutions is input into the systems code to parametrically evaluate performance and cost. The group suggested that eventually, all the engineering filters and modeling be accomplished within the systems code, rather than separately in two codes. In the near term, Chuck would like to increase the fidelity of his engineering filters.

ARIES-TNS Technical Working Groups

Integrated Issue Resolution and R&D Needs - Mark Tillack described the approach to constitute three working groups to address significant issues that have broad implications throughout the plant systems. Mark stressed that these groups need to organize to address the R&D gaps and plans to satisfy those needs. He also outlined how the technical working groups would interact with the remainder of the study team.

Power Handling TWG - Mark (Mark and Rene are co-leaders) presented the mission statement for power handling TWG and scope of influence. The basic tasks include documentation of current capabilities and R&D to advance the capabilities. To address the remaining R&D needs, plans will be developed. Mark presented a schedule that emphasized the need to quickly develop the needs and plans (within a year).

Tritium Fuel Management TWG - Phil Sharp emphasized that the ITER tritium fuel management is a good technical baseline for the DEMO as the quantities, flow rates, and containment requirements are very similar to DEMO. However, ITER is a consumer of tritium and not a producer, which is a new capability to be demonstrated. Specific issues to be addressed are blanket and other systems tritium inventory and recovery, additional cleanup needs, and regulatory burden of proof.

Plant Operations TWG - Les Waganer described the range of operations for a spectrum of test and validation facilities. He outlined the purpose, scope, members and plan for the Plant Operations TWG.

ARIES-TNS Technical Task Results

Trade Studies and Engineering Inputs - Rene Raffray focused his discussions on the engineering modeling inputs into the ARIES systems code along with the related trade studies to refine and tailor the fusion plant parameters to optimize the performance, cost, and operations of the plant. Rene reviewed the engineering action items from the April 07 meeting, namely blanket, coil, waste treatment, RAM (reliability, availability, maintainability), and tritium breeding and recovery. He illustrated the design options and cycle efficiencies for the heat extraction. The Brayton cycle efficiency and pumping power are dependent on the heat flux because of the higher cooling demands at higher heat fluxes. Tritium breeding needs to be closely controlled to assure adequate tritium for fuel and supply for other startup plants (assuming saturated T-inventory in the power core components), yet not over breed and unnecessarily increase the inventory. Thus the LiPb blanket must have an active control system for online adjustment of Li enrichment.

Material, Design, and Cost Modeling for High Performance Coils- Leslie Bromberg is motivated to minimize the developmental and capital cost of the coils via either optimizing the conventional low temperature superconductors or using the evolving high temperature superconductor. The conventional low temperature superconductor (LTS) approach relies on improved development of traditional cable-in-conduit conductor and related winding approaches to improve protection and stability. In contrast, high temperature superconductors (HTS) will operate at higher fields and temperatures, have reduced ramping limitations, decreased sensitivity to heating, and more compact designs. MgB2 magnets may also be considered.

Leslie suggested the use of JK2LB as opposed to Incoloy as the coil structural material. The JK2LB is cheaper than Incoloy and has sufficient strength and fracture limits to serve as the coil structure. A preliminary set of design parameters and cost at $50/kg were provided. A curve of current density vs. peak field was shown for four candidate superconducting materials. Leslie said the position of the outer TF coil legs are determined by either field ripple or maintenance access (more likely). Structural analysis of the coils will be accomplished using beams and shells modeling. Modeling equations and codes were provided for the code. An out-of-plane force model was provided. These models and algorithms allow improved code analysis for the TF and PF coils with a choice of superconducting materials.

ITER Tritium Plant Overview and Design Status - The ITER Tritium Plant is very similar in size and capability to that required for a demonstration plant. The only difference is that the Demo will generate its own tritium versus ITER will obtain its tritium from an external source. ITER will be the first equimolar DT fusion machine. It is fueled with gas puffing and pellet injection.

The tritium system is responsible for handling incoming, storage and outgoing tritium, vacuum pumping and transfer of tritiated gases, processing of fluid streams, separation of hydrogen species, detritiation of water streams and atmospheres, and extraction of tritium from test blankets.

Phil examined the general fueling requirements for ITER (concentrations, flow rates and pulse lengths). Many different mixtures of D and T will be generated and stored for pellet injection, fueling, and neutral beam injection. Phil further explained the detailed requirements for the Tritium System subsystems to convey the level of detail required for ITER. Phil discussed the Test Blanket Module tritium extraction systems. Tritium confinement is a critical safety and accountability issue.

Phil showed the 7-floor tritium plant building envisioned for ITER. The tritium plant is really a chemical plant for tritium with much higher throughputs than have been demonstrated to date. However, the ITER fuel cycle subsystems are reasonably state-of-the-art and applicable to Demo. ITER must complete definition and procurement of the HVAC and atmospheric detritiation systems. Les Waganer offered to send Phil a copy of a Technical Risk Assessment of a Fusion System Fuel System study completed in the early 80's that projected capabilities into the future.

Tritium Breeding Ratio Requirements - Laila El-Guebaly emphasized that large future fusion machines must generate their own tritium fuel sufficient for their needs but no more. The net TBR must be close to 1.01 with sufficient positive margin to account for presently known deficiencies in nuclear data, 3-D neutronics modeling inaccuracies, and unknown uncertainties in the design (and performance) of the fuel system elements. This margin will become smaller in the future as the fidelity of the designs and databases increase. Laila described several sources of data and design uncertainty. Two experiments on LiPb tritium production rates at ENEA and TUD will be providing additional test data in 2008.

There was considerable discussion within the team on how to quantify and describe the TBR design margin and the quantification of the uncertainty band of TBR. It was agreed that there needs to be an active control mechanism to tailor the operational TBR to a value slightly above 1.00. Moreover, the uncertainty variation needs to be less than the control limits to assure positive control is maintained under all conditions. Stated another way, the control limits have to be greater than the uncertainty variation. Tailoring the enrichment of Li-6 is the likely means of controlling the net TBR of the LiPb system.

Making Sense of Fusion Radwaste: Recycling and Clearance, Avoiding Disposal - Laila El-Guebaly emphasized that one of the key advantages of fusion energy is the ability to not generate high level radioactive waste. Additionally, it is highly desirable for fusion to minimize the quantity of low level waste as this type of waste will become increasingly difficult to store or dispose. This minimization of low level radioactive waste can be accomplished by reducing the volume of active materials by design, recycling materials, clearing slightly radioactive materials, and burning more radioactive byproducts, if needed. All the choices entail some cost penalty and technology advances.

How To Achieve High Reliability, Availability, and Maintainability (in a fusion reactor)- Les Waganer summarized how ARIES-AT is designed specifically to achieve high levels availability. It built upon lessons learned from prior US fusion studies, particularly the most recent ARIES designs. Large complete sectors with all plumbing, shielding, and structural features will be withdrawn through vacuum ports. Half or all the sectors will be scheduled for simultaneous replacement with immediate replacement of previously refurbished sectors to minimize scheduled replacement downtime. Les then examined the factors contributing to higher reliability, maintainability and availability, which are related to both scheduled and unscheduled maintenance downtime. Les recommended a testing and predictive approach to achieve high reliability. Extensive use of automation will enable more precise and quicker removal and replacement of sectors. Redundancy will provide higher availability on exo-power core components.

How to Save Big Bucks with Modeling and Simulation - Les Waganer described some likely fusion energy R&D scenario plans that identified several multi-billion dollar facilities that are designed, built, and operated in series, resulting in a very costly and time-consuming process to minimize the risk for Demo. He suggested it might be possible in the near future with continuing advances in modeling and simulation to leverage results from physical experimental devices to create analytical models or simulations that would be cheaper to construct and provide faster results to achieve a similar level of risk (fast track approach).

Action Items and Next Meeting/Telecons

Action Items:

Zoran Dragojlovic - Continue to develop the systems code and examine areas that seemed inconsistent.

Les Waganer - Redo the turbine plant building, check on LSA guidelines, add dry cooling option, and consider ITER cost basis.

Chuck Kessel - Increase the fidelity of his engineering filters

Rene Raffray - Define an approach and suitable wording to describe the Tritium Breeding Ratio (TBR) nominal operating point with variability bands with design margins to account for data uncertainty and hardware performance variations.

Laila El-Guebaly and Siegfried Malang - Document the TBR requirements, TBR margin, and elements defining Net TBR

Laila El-Guebaly - Consult with US neutronics experts to define uncertainties in the 9% TBR margin for LiPb breeder

Laila El-Guebaly - Determine how many cycles the FW/blanket can take before reaching 10,000 Sv/h

Future Meetings:

The best time for next meeting will be in the week of September 10-14 with the second best as the prior week, Sept 3-7. Les Waganer will query the Team for their preferences and conflicts.

Future Telecons:

Because Farrokh Najmabadi and Rene Raffray will be out of the office during July, an early August telecon is suggested. Les Waganer will finalize the dates and times.