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ARIES Conference Call, 6 August 2013

Documented by M. Tillack

(Boeing) Waganer
(FIRE) -
(FNTC) Malang
(FPA) -
(GA) Turnbull
(GT) Yoda, Abdel-Khalik
(INL) Humrickhouse
(LLNL) Rognlien, Rensink
(ORNL) Rowcliffe
(PPPL) Kessel
(RPI) -
(UCSD) Tillack, Wang, Najmabadi
(UTK) -
(UW) Blanchard, El-Guebaly


Mark Tillack noted that the next project meeting will be held at the Hampton Inn Germantown on Sept 18 (a one-day meeting). A meeting room has been reserved, and everyone can make their travel arrangements. (Note: a room block is not being held; everyone is on their own for hotel reservations). Mark requested that everyone who plans to present should email him ASAP their title and required time.

ARIES-ACT1 draft articles have been posted on the web at We have only 5 so far (Tillack, Wang, Blanchard, Yoda, Kessel), expecting 4-5 more (El-Guebaly/2, Humrickhouse, Rognlien, Najmabadi). Laila asked about deadlines for submission. She plans to have one paper ready in a couple of weeks, but another may take longer. Farrokh agreed to let people know the final deadline after it is known.

Mark asked Team members to review the on-line publication list and provide any new publications before the peer review on Aug 29.

ARIES Technical Efforts

Costing - Les Waganer reported on several recent activities.
  1. Responses to Al Opdenaker's email relaying concerns from the peer review committee. Farrokh added that he recently visited GA to speak with Tony Taylor and others, including members of the fission community. The subject of fusion costs is important to GA because of their interest in FNSF, and has captured the attention of the VP (Parmentola). Interestingly, the fission community uses a very similar methodology to ours for next-generation cost estimates.
  2. Interactions related to PPPL (Neumeyer, Hawryluk) attempts to compare ITER and power plants. Les already provided substantial information and feedback to PPPL, and has not received additional requests or communications lately. Kessel added that PPPL tried to cross-compare ITER and power plants by putting ARIES-AT and ITER in the same cost categories. They tried to exclude costs of additional bureaucracy built into ITER that are inappropriate for a power plant, but the details have not been forthcoming. Standout differences exist, with the magnets ($3B for ITER, $300M for -AT) being the largest. Najmabadi added that they should also remove tooling (cost of factories to build things) from their power plant estimates to be more consistent with our methodology.
  3. Les also documented suggested fixes to errors in the code and sent those to Tillack.

Physics - Chuck Kessel described the current work emphasizing ideal MHD stability for ACT2. The system code makes a distinction between low-beta (no-wall limit) and high beta (wall stabilized) operation around betaN=3. More detailed parametric analysis is being performed, and suggests the transition occurs closer to 2.6. The current near the plasma boundary is important. Lower hybrid heating and current drive will be difficult to use, because it tends to aggravate stability problems. We may have to drop it. Neutral beam works the best, but ion cyclotron and electron cyclotron may be OK. He is planning to have a look at taking credit for structures outside the blanket.

Phil Snyder provided a pedestal height estimate for ACT2, which is different than ACT1. The pedestal temperature is hotter compared with ACT1 (~7 keV), which also makes lower hybrid heating more difficult.

Systems Analysis - Chuck Kessel recalled that the ACT2 operating point was distributed some weeks ago. Some parameters:
R = 9.75 m
same shaping as ACT1
higher Bt (~14 T at coil)
nGr = 1.3
low Pn ~1.5 MW/m2
Pf ~ 2600 MW

Tillack will distribute a link to the full details. See

Chuck noted that the EU Demo uses an inductive machine with higher Ip, which compensates in part for the low values of fGr and H98. But another reason they can make a sensible machine with conservative parameters is their low power output of only ~500 MW. Chuck and Mark ran a physics and ASC scan with reduced power and found more operating points as well, albeit with higher COE. Najmabadi recalled that a similar study of the sensitivity to Pe had been done in ARIES-AT, and promised to locate and distribute a plot.

Edge Physics - Tom Rognlien mentioned he is writing a longer standalone paper for the special issue on ACT1. More work was done recently using Ar (vs. Ne) to have a quantitative comparison. We need 10x less Ar than Ne for detached divertor operation. The energy conservation issue in the code is larger for Ar; they are trying to resolve that.

He-cooled divertor experiments - Said Abdel-Khalik described the Georgia Tech high-temperature helium loop, which is up and running. The loop runs at pressures of 10 MPa and inlet temperatures up to 400°C. They are testing a W test section that models the multiple-jet finger design (HEMJ). Heat fluxes up to 3 MW/m2 have been achieved using an oxyacetylene torch, and plan to increase this incident heat flux significantly using an induction heater on loan from INL, courtesy of M. Shimada.

Tillack asked whether heat transfer is expected to depend on heat flux. Said noted that the Japanese raised this issue in the PHENIX program (the latest incarnation of the US/Japan collaboration), suggesting that there may be localized laminarization due to acceleration of He along the heated surface at very high heat fluxes. Minami Yoda added that the KIT and Efremov experiments on HEMJ mockups at nearly prototypical conditions never reported any observations of laminarization, however. Nevertheless, the GT experiments will focus on whether this laminarization occurs, and if so, under what conditions.

Safety - Paul Humrickhouse is still working on the ACT1 paper and hopes to finish in a couple of weeks. A skeleton of an ACT2 MELCOR model has been developed. He asked if paramaters such as surface areas and volumes, flow path lengths, etc could be obtained from CAD for use in the Melcor model. Xueren agreed to send these after Paul provides a list of parameters he needs.

Power core engineering - Xueren Wang has started to define the power core based on R=9.75 m. Laila needed the surface CAD model; this was completed and passed to her for neutronics analysis

DCLL analysis has been performed. He flow paths, PbLi flow paths, grid plates, separation plates, access pipe layout and size, etc have been defined.

A parametric primary stress calculation was performed based on 8 MPa internal He pressure plus gravity loads (including PbLi). Design iteration and optimization was done to decide on blanket dimensions. Xueren is preparing for thermal stress analysis. He will focus effort on the OB-I blanket, which has the highest power (by far).

Mark Tillack wrote, debugged and ran a code to determine heat transfer in the PbLi. This is a 2D code similar to the one he wrote for ACT1. Heat transfer will be solved iteratively with the ANSYS analysis of the He-cooled steel structures in order to find a self-consistent solution.

Neutronics - Laila El-Guebaly noted that their activation code has been modified for activation analysis in 3D. First results have been obtained for ACT1. She plans to generate activation data for all components using this new 3D approach.

Laila reviewed volumes from the system code and CAD and found significant differences, which were relayed to Tillack.

Using the ACT2 systems results and the new CAD skeleton, the neutron wall load distribution was obtained for ACT2. Laila will start to develop a 3D neutronics model, but needs more details of the blanket for TBR analysis.

Laila is concerned that we may have a breeding problem in ACT2, so we should minimize structure volume. PbLi was included behind the divertor, but that adds 2-3% only to the TBR. She recommends a conformal blanket (minimizing the effect of the divertor slot).

Another important factor is the depth of the OB-I module (in front of the W shells). She would like to make the OB segments more like 50 cm / 50 cm rather than the current 40/60. This would move the W shells out a bit. Farrokh mentioned that the requirement is based on b/a, and so we should be able to move the shells to a larger distance from the plasma with the present machine at R=9.75 m. Someone needs to look at b/a requirement and find the location where the W shell needs to be - probably ~80 cm from the plasma boundary. Chuck added that we should assume no kink shell, or locate it behind the blanket.

Laila is waiting for Xueren to send full details on the compositions. Xueren sent a table with several options: which will we choose? She needs to generate neutronics results this month, before the student leaves. Laila will review Xueren's options and make a recommendation.

Chuck recommended that we use the same fraction of holes for heating and current drive as we did for ACT1.

EM analysis - Jake Blanchard presented disruption calculations at the last meeting, but the geometry at that time was not the latest. He redid all the analysis using the latest ACT1 parameters. He still plans to incorporate TF coils in the calculation of forces

All analysis was done for ACT1. We don't plan to redo for ACT2. Generally we can scale the results. The steel blanket in ACT2 is significantly different than ACT1. But modeling of the ACT2 steel blanket for EM analysis would be difficult. Jake will check on the difficulty of modeling one box and do it if he can.

Farrokh asked for a recommendation on how to convert from pressure to body force. This should be a simple matter of dividing the force by the volume and distributing it uniformly.

Materials - Arthur Rowcliffe is working on the materials contributions to the ACT1 paper. He is planning to visit ORNL and will try to get more content for the paper. Arthur will write paragraphs on ODS and bainitic steel himself, but SiC and W will be done by others. We don't think we need anything on ordinary RAFS, which has been documented adequately already.

Arthur requested more info on the structural ring: doses, helium production, operating temperature range. He is looking for materials that can be fabricated by more conventional means, like powder metallurgy. We've talked about ODS or nano-steel, but there's a big issue with large-scale fabrication. He wants to explore other alloys, such as those being developed for the fossile fuel industry and ultra super critical cycles. 650°C steels have been qualified already. They are not low activation, but the same alloying principles could possibly be employed using solutes with low activation characteristics.

Tillack will send Arthur the exact numbers on temperature. Dose and He information can be found in Laila's presentation from the previous project meeting.