Memo: Starlite-4

Date: 28 Feb 1995

Subject: Starlite Meeting Minutes, 13-15 Feb 1995 @ UCSD

To: Starlite Team

CC: R. Conn, J. Coyle, J. Davis, R. Krieger

From: L. Waganer

Ref: Starlite Schedules (posted on WWW Home Page)

Top Level Requirements (distributed by fax to organizational leaders)

Attch: Near Term Tasks and Actions

List of Attendees

L. Waganer welcomed the team and reviewed the meeting agenda. F. Najmabadi explained the envisioned process to develop the U.S. Demo including the role of the Starlite program. The Starlite program is the initial step toward defining the Demo mission, adding the necessary technical requirements, and then developing one or more conceptual designs to satisfy the mission technical requirements. Outcome of these activities will influence the DOE R&D program to enable Demo. Furthermore, elements of these requirements and designs will lay the foundation for the preliminary design phase of the Demo. The internal Starlite process of requirements, trade studies, design development, and assessment of design needs is iterative with requirements and goals being adjusted to accommodate non-attainable requirements and reach satisfactory approaches. The project schedule was discussed with the near term activities of defining plant and system requirements and conducting trade studies to select system (and plasma operating) approaches. Two Demo designs are planned with the Demo I being a more conventional physics approach such as ARIES I. The Demo II would likely represent a more advanced physics concept such as ARIES IV, Reversed Shear, or Low Aspect Ratio (LAR) machine. This would enable the Physics and Engineering Groups to apply more effort to those later concepts and thus deliver a more self-consistent concept for the advanced design development.

Mark Tillack presented an overview of the Engineering Group activities and their expected outputs. The Ferritic Steel (FS) Assessment is the initial assessment to determine if FS is suitable for Demo when judged against the Demo requirements. In addition to FS Assessment, a second activity is to characterize and assess critical engineering issues which will be used to develop the R&D needs. The engineering requirements will be documented at the next meeting.

Report on the Ferritic Steel Assessment

Mike Billone summarized the history, performance properties, and progress in developing and qualifying ferritic steel (FS) alloys for fusion structural material application in U. S., Japan, and Europe. The focus is now to develop low activation 9Cr-2WVTa class of alloys, typified by modified F82H, with better low temperature ductility, fracture toughness, and high temperature strength.

From a design standpoint, it is necessary to have the ductile-to-brittle transition temperature (DBTT) less than the minimum operating temperature and desirable to less than room temperature. The 12Cr-1Mo and 9Cr-1Mo classes of FS alloys have rather high DBTT values when irradiated at <=400deg.C and <40 dpa, especially when tested in thermal and mixed-spectrum reactors with He/dpa ratios of 1 to 10 (10 is typical for first-wall applications). Preliminary results on the 9Cr-2WVTa alloys have shown excellent DBTT values (< 0deg.C) for irradiation in fast reactors up to 13 dpa and <1 appm He. Necessary confirmatory data (50 dpa, ~400deg.C, and < 5 appm He) are expected from fast-reactor irradiation within several months.

In terms of the upper temperature limits for ferritic steels, decreasing tensile and creep strength with increasing temperature generally limit the upper design temperature to 550-600deg.C, depending on the operating loads. Compatibility with He is good and presents no additional constraint on the upper temperature limit. While compatibility with water coolant is good, water is not considered to be an attractive option for advanced DEMO-type designs. Compatibility issues with Li and Li-Pb would limit the upper temperature limit to 550deg.C and 430deg.C +/-20deg.C, respectively. Thus, of the four coolants generally considered with FS, FS/He is the most attractive combination with FS/Li second . FS/Li-Pb would only be practical with a separate coolant (e.g., He) and Li-Pb acting only as a breeder and not in contact with FS.

Clement Wong presented data on the thermal performance capability of FS. The upper temperature limit for FS is 550deg.C. The earlier BCSS study extensively studied the HT-9 material in several blanket configurations and coolant options. Dai-Kai Sze prepared several design window charts illustrating the constraining parameters of maximum material temperature, primary stress, pinch point, and thermodynamic efficiencies. For the BCSS FS designs, the thermodynamic gross efficiency was 39% for helium and 36% for water. Lithium-cooled approaches had no design window. An ARIES advanced Rankine cycle raised the efficiency values slightly. For comparison, use of vanadium or SiC structural materials allowed cycle efficiency improvements of roughly 5% (ie, net efficiencies ~ 40% (pumping power only)). It was recommended for Demo that the FS options use a He coolant, Li2O breeder with an expected 44% gross efficiency and a 34% net cycle efficiency.

Jake Blanchard reviewed magnetic effects in ferromagnetic steels in a tokamak environment. These data were documented in two papers published some time ago. The results were small effects (1-3 %) field ripple reached at ambient fields of 2 Tesla. Some of the data are suspect as these older codes have been found to contain errors. If work continues on FS, these analyses will have to be redone including disruption loads and stored energy considerations.

Laila El-Guebaly presented Hesham Khater's results on assessing the activation concerns for three candidate ferritic steels (HT-9, modified HT-9, and IEA-modified F82H steel). The analysis was done for three full power years at 1 MW/m2.

The IEA-modified F82H, the modified HT-9, the low activation LA12TaLC, and V-5Cr-5Ti alloy all qualify for class C LLW (low level waste) according to the NCR limits. In addition, the LA12TaLC and the V-5Cr-5Ti alloys could qualify for class C LLW according to the Fetter limits. [H. Khater wished to add to the minutes that the IEA-modified F82H alloy would also qualify for class C LLW according to Fetter limits if its silver impurity is limited to < 200 wppm.] Laila and Ron Miller should investigate waste disposal and recycle cost modeling for all materials. Lifetime is critical for these materials - a one-year lifetime is not acceptable.

Mark Tillack summarized the reported FS assessment results. Ferritic steel, as a class, has a good database. One alloy shows promising early results with intermediate data results expected within two months. There remain difficult problems such as the inability to effectively transfer the required heat flux. Lithium, LiPb and H20 coolants are not compatible. The upper temperature limit is 550deg.C which limits the gross thermodynamic conversion efficiency to approximately 35%. In light of these considerations, it was felt a decision on FS should be tabled until the interim testing results of the 9Cr-2WVTa alloy has been reported.

Top Level Requirements

Lester Waganer presented the list of top level requirements to the team for discussion and adoption. There was a great deal of discussion whether the COE value should be used as a unquantified goal, a quantified target goal, or as a firm requirement. The main objection seemed to be the concern that a firm requirement might not be achievable. The final compromise was to adopt both a goal value and a less-challenging requirement. Hands-on maintenance was eliminated in lieu of robotic maintenance. Demonstration of capability to load-follow was judged to be not a necessary requirement, rather a desirable goal. The requirement for no public evacuation plan (ie, one rem total dose at the site boundary) was adopted as a necessary project requirement. The desirability of a shorter construction time period was downgraded to a second-tier requirement. The use of the net efficiency was discussed but the tracking of the separate elements was judged to be of more value with the retention of the gross efficiency and the recirculating power requirements. The Demo should retain a requirement to use equipment and operating modes planned for the commercial plant. The requirements list should be reordered to show the unique requirements first and COE last. The current version of the top level requirements was distributed by fax on 2/20/95.

Dai-Kai Sze reviewed the impact of the top level requirements onto the first wall and blanket systems. The tracking to the total rejected thermal power was considered as a possible requirement to be added at a future date.

Laila El-Guebaly reviewed her work on assessing the impact to upgrade the ARIES and PULSAR design from the remote handling criteria to hands-on maintenance criteria. These criteria apply in the volume between the vacuum vessel (VV) and the bulk biological shielding and during the time period 24 hours after shutdown and before the VV ports are opened. Starfire (circa 1980) had a thicker and more efficient (and costly) shield to allow hands-on maintenance. The PULSAR contact dose showed a knee in the curve at one day after shutdown with the current calculated dose being 4 rem/h. An often quoted remote maintenance limit of 1 rem/h can be achieved with 10 cm of additional shielding. Laila is to investigate the validity and origin to the 1 rem/h limit. A total shielding increase of sixty cm of additional shielding would be required to meet the hands-on limit of 2.5 mrem/h. The group agreed that achieving the hands-on limit was not technically required as only a minimal benefit is derived from upgrading to hands-on maintenance rather robotic maintenance. Finalization of the robotic maintenance radiation level was held pending finding the origin of the 1 rem/h value.

Xueren Wang told us of his results of the 1-D thermal mechanical analysis of the PFC systems. He assumed the allowable stress, Sm to be the minimum of 1/3 of the ultimate stress or 2/3 of the yield stress. Furthermore, he assumed the primary stress was not included (assumed to be zero) and therefore the secondary thermal stress should be <= 3 Sm. A range of maximum surface heat fluxes were given for the typical tube wall thicknesses for different constraint conditions.

Glenn Sager reviewed the PFC design requirements but did not include not specific quantifying values. Leslie Bromberg discussed the magnet design requirements. One decision will involve the use a single enclosing cryostat surrounding all the TF coils or individual dewars around each TF coil pack. Ice (at cryogenic temperatures) was considered as a structural element but it was rejected because of its strength capabilities. Leslie also showed a design which had two TF coils joined on the inner legs but with separate outer legs. Data was presented on the stress of coupling the inner legs of the toroidal field coils. The primary stresses decreased from 600 MPa for the case of single coils to 540 MPa in the case of coupled coils. He is also pursuing the case of the coupling the outer legs of the toroidal field coil.

Bob Schleicher stated that the thermal conversion efficiency is the most important parameter in the plant design. The efficiency should be as high as practically possible. In the next decade, combined cycle combustion turbine efficiencies will exceed 60%. He concluded the competitive power costs in 2025 would be in the range of 60-65 mill/kWh. To achieve this value, the Demo efficiency should be in the range of 50%. A FS blanket would not be competitive. Vanadium with a lithium coolant would be close with 46% or so but still would be low. SiC with helium coolant and a direct Brayton cycle could get close to 50% but would require development of a qualified high temperature structural material. He will begin to investigate dissociating fluid cycles that do not produce activated products.

L. Waganer discussed the maintenance and confinement requirements involving remote maintenance of the power core, high plant availability, low maintenance costs, and demonstration of modular factory construction techniques.

Ron Miller described the factors affecting the plant economic operating window, namely thermal efficiency, plant capacity factor, and shorter plant construction times. Ron should define the process and the factors to relate the commercial COE value back to the Demo COE value including financing, learning curve factors, specific R&D costs, et al. He was also asked to determine the effective cost savings of having no evacuation plan. G. Hofer estimated the time savings might be approximately two years.

T.K. Mau introduced his initial, unquantified list of plasma and heating & current drive design requirements. A conference call for the Physics Group is planned to begin to quantify the requirements. He was concerned about achieving the requirement to have no disruption.

Tuesday Morning

Mark Tillack summarized the FS assessment results for the full project group, noting that all effort would be stopped pending an affirmative answer on the validity of the most promising FS option (9Cr-2WVTa). The team is to translate the mission goals and requirements into design requirements. To assist in allocating the high level requirements into subsystems requirements, Mark and Les will adapt the reactor parameter list and distribute to the team.

Don Steiner presented an overview of the project Safety and Licensing efforts. There was a lot of discussion about how to meet the requirement of no public evacuation plan (ala, 1 rem total dose at the site boundary). The toxic material regulatory limit is less severe by 2 orders of magnitude. The project agreed to lower the toxic (design) requirement to be equivalent to the radiological criterion.

Tom Dunn of GA explained the technique of analyzing plants to achieve that "no evacuation" criteria. He has been conducting that type of analyses for the MHTGR. He encouraged our project to do a preliminary analysis to assess the ability of our present design to meet the envisioned "no evacuation" criteria. GA (Tom Dunn?) will be asked to help the project to structure and conduct the preliminary analyses.

Critical Issues

C. Wong presented the rationale for surveying and collecting the critical issues to enable the formulation of a Demo R&D plan. He also reviewed the inputs received to date. L. Waganer highlighted two new maintenance issues derived from recent ITER efforts. The Demo demand of high availability requires reliable and rapid removal and reinstallation of replaceable power core components. A key element is to develop an integrated maintenance concept to enable the high availability with equally high component reliability. Another element is the use of replaceable connectors that are remotely deployable, are radiation-resistant, and have true zero leakage.

System Studies

C. Bathke presented his zero-th order systems code results based upon the initial Low Aspect Ratio (LAR) equilibrium results and minimal engineering support with informed assumptions. Based on the first results, the physics data should be reiterated with C. Kessel. Many engineering questions emerged in the areas of physical layout, size and location of components, magnet power consumption and overall power balance, cost of power supplies, and lifetime of expendable components. In the light of the evolving stringent Demo requirements, and the limited manpower that can be applied to any one concept, it was recommended that the project select the advice and counsel of Martin Peng to help address these issues.

Tom Flynn addressed the trend toward increased plant availability factors. He reiterated the general RAMI requirements of 90% availability (Commercial), demonstrate load following (now a goal), complete removal of all components, and no unanticipated forced outages. Tom presented supporting logic to achieve these goals. He also presented a sector-maintenance design concept to enhance the time to replace a major portion of the fusion power core.

Greg Hofer reported that all three of his reports he had been preparing are now ready for printing and distribution. He has been working on the tritium handling and regulation of tritium systems.

Steve Herring reviewed the status of the evolving Fusion Safety Standard. It was recommended we do not compare fusion with the other technologies with more adverse hazards. [more?]

Physics

Davis Ehst remarked that the quarterly report is nearly done. He is working to structure trade-off curves (parametric comparisons) to help analyze and select optimal operating regions. These are largely included in the systems code. He also presented results on the Reverse Shear equilibrium with bootstrap current and Fast Wave Current Drive. He modeled data from C. Kessel but he could not reproduce a value of q >=2.0. The dataset did not prove to be robust either. His next efforts are to determine why he cannot reach or exceed q=2 and work with Kessel to modify density profile to obtain a more robust case (with low current power ~ 40 MW). A stabilizing shell will be required.

T.K. Mau is working on current drive modeling on the LAR concepts for which he has developed an EQDSK file. As an example, he used a smaller machine size to verify the modeling technique and was satisfied with the modeling results. His next step is to model the Lower Hybrid Current Drive and Radio Frequency Current Drive on the low aspect ratio version of Demo. TK will be the physics point of contact between the Engineering and the Physics groups.

B. J. Lee presented the results of optimum q_min respect to (ideal) wall distance from a plasma for a reversed shear tokamak. The pressure profile has a finite edge pressure gradient to be consistent with experiments (VH-mode at DIII-D). The optimum can be understood in terms of a trade-off between the stabilizing in the safety factor and the destabilizing effect of additional rational surfaces. This work may be applicable to toroidally spinned plasma with resistive wall for reactor.

Wrapup

The project reviewed the tasks and specific actions to be accomplished over the next few months. These are summarized in the following attachment. The next conference call is scheduled for 9:30 PST on Friday, March 3. The next project meeting will be held at the Chicago AT&T Convention Center, Hickory Hill, May 1-3. [ Note: Dai-Kai just mentioned a change in the date of the ANL Liquid Metal Insulstor Workshop from May 4-5 to May 8-9. He suggests holding our Materals Townmeeting on May 10 and the Starlite Project meeting on May 11-12. Lets discuss this on the next CC on Mar 3.] There will be a materials town meeting for part or all of Monday, May 1 (Mike Billone will plan and coordinate the town meeting). A liquid metal insulator workshop will be held at ANL on May 4-5. Ron Miller will be collecting a list of papers to be submitted to the IEEE fall meeting (abstracts are due 1 May). Lets try to send Ron the tentative title of your talk before the next conference call so we can coordinate subjects to be presented.

Near Term Starlite Tasks and Actions To Be Accomplished

Mark & Les -- Assemble list or matrix of significant requirement parameters and define methodology to allocate and validate requirements

Engr Group -- Convert requirements and goals into design requirements

Bill Dove -- Contact Ron Blanken to obtain Martin Peng's support [Done]

Farrokh -- Contact Martin Peng to elicit his support on the LAR designassessment

Mark -- Assemble list of LAR topics that need clarification or work

Leslie, Laila, DK -- Provide as-needed support to Chuck Bathke on LAR effort

Chuck B -- Work with Chuck Kessel on revised LAR equib

Coordinate with Mark on LAR engr issues and assumptions

Ehst, Jardin -- Complete quarterly report, send to Farrokh

Farrokh, Mark -- Complete and distribute quarterly report

Laila, Ron -- Assess waste disposal cost values or parametrics

Ron -- Refine fission, coal, solar projections to set COE goals on a time line basis; unfold financial and economic Demo COE assumptions

Mark -- Set up a Ferritic Steel Assessment Table of Contents

Mark -- Assemble and compile FS Assessment document

Laila -- Verify basis for 1 rem/h remote maintenance limit

GA (Dunn?) -- Conduct "Preliminary" hazard risk assessment to scope the need for a fusion power plant public evacuation plan.

Tom -- Provide a preliminary allocation of reliability (MTBF) and

maintainability (MTTR) for major subsystems

Proponents -- Develop alternate design concepts to be evaluated

Leslie, Tom -- Investigate Magnet maintenance requirements and solutions

Clement, Glenn -- Assess HHFC and prepare Demo 1 selection

Laila -- Explore design improvements to SiC/He shield design

Khater -- Determine wall load limits to meet class C for V, SiC, FS, W, Cu

Chuck B&K -- Continue assessment of LAR equilibrium conditions in sys code

Chuck B -- Refine power balance, cost models, and CAD driver in sys code

TK, CK, CB -- Continue to investigate RFCD and BTST in the LAR concept

Dave E -- Work new density profiles to obtain attractive reverse shear case

CB, BJL -- Compare GATO/PEST to obtain wall position with TPX type data

DE,BJL,CB -- Use DIII-D density profiles to determine current drive and boot strap current data

BJL and Mandrekas -- Pursue validation of data on radiating mantle

Hofer -- Issue three completed reports

Hofer -- Draft document on tritium policies and regulations

Starlite Project Meeting Attendance List - February 13-15, 1995

Name -- Affiliation

Bathke, Charles -- LANL
Billone, Michael C. -- ANL
Blanchard, Jake -- UW
Bromberg, Leslie -- MIT
Cerbone, Ralph J. -- TSI
Dove, William -- DOE/OFE
Dunn, Tom -- GA
Ehst, David -- ANL
El-Guebaly -- UW
Flynn, Tom -- Raytheon
Grossman, Arthur A. -- UCSD
Herring, Steve -- INEL
Hofer, Gregory G. -- Raytheon
Mau, T. K. -- UCSD
Merriman, Barry -- UCSD
Miller, Ronald -- UCSD
Najmabadi, Farrokh -- UCSD
Sager, Glenn T. -- GA
Schleicher, Bob -- GA
Sheng, Guangzhau -- SWIP, China
Steiner, David -- RPI
Sze, Dai-Kai -- ANL
Tillack, Mark -- UCSD
Waganer, Lester -- MDA
Wang, Xueren -- UCSD
Wong, Clement -- GA