# Presentation: 321581

## Opportunities and Issues for IFE Chamber Science 

**Jeff Latkowksi, Wayne Meier**
***Fusion Energy Program, LLNL***
**Per F. Peterson, Philippe Bardet, Haihua Zhao*****Department of Nuclear Engineering***
***University of California, Berkeley***

**Heavy Ion Fusion Science VNL**
** ****Program Advisory Committee**** Meeting**
**Aug. 9-10, 2006**
**Livermore, CA**

## Outline

**Thick liquid wall chambers for IFE**
**Near-term opportunities**
**Preparing for an experimental test facility**
**Connecting to NIF**

## Thick liquid wall (TLW) chambers have beenthe focus of chamber research for HIF 

**Potential advantages are well known:**
**Chamber structures experience a much lower rate of damage ******** may last for plant lifetime (>30 years)**** **
**14 MeV neutron source (~$1B) not required ******** existing or slightly modified steels can be used**
**Chambers can be much more compact ******** improves HI focusing**
**TLW also protects from short range target emission and shock due to first surface ablation**
**Most fusion energy deposited directly in the coolant ******** efficient heat transport**
**Have high tritium breeding efficiency**

## The key issues can be summarizedin three primary categories

**Issues related to ****repetitive nature of IFE****, including liquid wall response and recovery of chamber conditions between pulses (reformation of protective liquid configuration, clearing of drops and vapor that could interfere with next shot). **
**Issues related to ****shock mitigation****, including ability of multi-layer thick liquid wall configurations to attenuate shocks and thus protect the structural wall from possible damaging effects of shocks.**
**Issues related to ****use of molten salt**** (preferred liquid), including material compatibility (corrosion), target debris transport and removal, tritium recovery, heat transport and power conversion.**

## Recent past R&D has focused on fundamental understanding and key issues

**Hydrodynamic scaling**
**High quality jets needed along beam paths**
**Disruption and re-establishment of liquid protection**
**Condensation and vacuum recovery**
**Shock propagation through jet array**
**New schemes, e.g., vortex flow, that may permit higher rep-rate**
**Interface issues and integrated design studies, e.g., Robust Point Design**

## Near-term opportunities 

**Re-engage Universities for small scale experiments**
**Focus on schemes compatible with lower cost development path**
**Small effort on system integration to assure coupling of development in targets, driver, and focusing schemes**

## Scaled water experiments have demonstrated multiple liquid configurations of interest for HIF

**Re = 100,000**

**High-Re**
**Cylindrical Jets**

**Vortex Layers for**
**Beam Tubes**

**Oscillating Voided**
**Liquid Slabs**

**UCB**

## Large liquid vortices could enable thick-liquid, high-rep-rate, lower yield HIF options

**Example:**
**Chamber volume: 80m****3**
**Liquid volume: 28m****3**
**Open fraction of solid angle: 2.4%**

## UCB has performed detailed measurements of turbulence and surface topology in vortex beam tubes

## A series of scaled experiments were constructed at UCB to provide proof of principle for large vortex generation

**A first-generation test device was fabricated from a short segment of cylindrical pipe (22.5-cm diameter)**
**Eight pressurized plenums provided blowing flow**
**Perforations between injection plenums provided suction**
**A****suction**** = 2A****injection**
**End walls produced modest non-ideality**

## Liquid accumulated during startup was cleared in the first-generation device

**t = 2.0 sec**

**t = 7.0 sec**

**t = 14.0 sec**

**The first viability issue for large-vortex flows is removing excess liquid during startup**
**UCB experiments demonstrate that this can be done by providing sufficient suction area**
**After startup, flow dumps on suction drains can be closed, and pressure recovery can be achieved**
**Reduce pumping power**
**Increase layer thickness**

**stable layer established**

## A large variable recirculation flow loop was constructed 

**A large variable recirculation flow loop was constructed **

**Flow meter**

**Nozzle**

**Manifold**

**1000 liter tank**

**50 hp pump**

**Frequency controller**

** ****Pump is rated for 500-gpm at 300-ft of head**
**Thanks to the frequency controller,****the flow rate can be accurately controlled****at any flow rates up to 800-gpm**

## Larger scale facilities will be needed prior to ETF (could begin prior to ignition if funding available)

**Hydraulics Test Facility**** – Demonstrate the type of flow configurations needed for TLW chambers at ~1/4 scale. Simulant fluid (e.g., water) used to minimize costs. Facility would simulate (e.g., by using chemical detonations) flow disruption by fusion energy pulses to study chamber clearing. Also used to study/validate shock mitigation techniques.**
**Chamber Dynamics Test Facility**** – Study vaporization/condensation dynamics of molten salt. Focus on aspects unique to molten salt and cannot be simulated in the hydraulic test facility.**
**Molten Salt Test Loop(s)**** – Address issues related to use of molten salts in fusion applications: corrosion, transport & recovery of target debris, transport and recovery of tritium.**
**Heat Transfer Component Facilities**** – Develop/demonstrate compact, efficient heat exchangers and power cycle components using molten salt coolants. Applicable to IFE, MFE and fission, including hydrogen production.**

## NIF will benefit from chamber science work and spin-backs are possible

**First opportunity for test with prototypical target emissions**
**Experiments to validate chamber response models**
**First opportunity for neutron isochoric heating experiment (disassembles jets in some TLW designs)**
**IFE analyses tools will be improved and can be used for NIF experiment planning**
**X-ray and debris transport and deposition**
**Surface heating, ablation, shocks**
**Liquid motion, condensation, etc.**
**Neutron heating, neutron activation**

## Neutron isochoric heating can be an important issue for the NIF

**Neutron isochoric heating will first be experienced on NIF**
**Can drive debris and shrapnel threats to the final optics****(e.g., He-filled cryotubes was the original design)**
**Understanding of the liquid response to isochoric heating is a critical issue for TLW IFE:**
**liquid break-up**
**droplet formation**
**chamber clearing**

**Can ion beams be used as near-term surrogate and assist in these issues prior to high-yield shots on NIF?**

## Target drop experiment on the NIF?

**One could think about “dropping” a target rather than holding it on the target positioner**
**Would greatly reduce the mass sitting near the target, and thus, debris and shrapnel issues**
**Translates into reduced debris loading on diagnostics and final optics – may lead to reduced maintenance needs**
**Would benefit IFE along path of getting past the giggle factor regarding target injection & tracking**
**Can it be done?**
**Is this also too many sigmas from the norm?**

## Conclusions

**A good start has been made in TLW chamber science for HIF**
**Opportunities exist for modest cost, near-term R&D to continue progress**
**A serious IFE effort will require larger scale facilities to address key issues**
**Chamber science will benefit from experiments that can be fielded on NIF – more work is needed to define in detail**
**HIF chamber science can also benefit NIF operation**

## BACK-UP SLIDES

## An second-generation device was constructed, based on the previous experiment

**A test device was fabricated from a segment of cylindrical pipe (25.4-cm diameter, 14-cm wide)**
**Injection and suction holes were fabricated with precision**
**Eight pressurized plenums provided blowing flow**
**Perforations between injection plenums provided suction**
**A****suction**** = 2A****injection**
**End walls produced modest non-ideality**

## Different layer thicknesses have been obtained with Froude number as low as 3 in the second-generation device

** ********/R = 5%**
**Fr = U****2****/gR = 13.6**
**Re = UR/******** = 5·10****5**** **

** ****the layer is inhomogeneous, due to sharp angle of injection****   **** Polygon shape layer**

## Dye marking of injection jets revealed their behavior in the layer - further work is required

**Homogeneous Nozzle**

**Inline Nozzle**

**Dye Marking**

**Rapid prototyping nozzles**

**Free Surface**

## Based on the 2nd generation, a new area of study was commenced on concepts with modular nozzles

** ****To provide improved vortex layer control, distributed injection and suction are needed**
** ****The investigation studied injection/suction modules****    ****to study the influence of the injection and suction**** ****angles****    ****the injection is homogeneously distributed over the circumference**
** ****the modules can be built with rapid prototyping**

## Two nozzles with different injection/extraction patterns were built and tested in a ramp experiment

**Ramp experiment allows testing of a modular nozzle section   (1/8****th**** circumference).**

** ****Inline Concept**

** ****Homogeneous Concept**