Lithium Blanket Module Research Articles

Determination of flow distribution in a HCLL blanket mock-up through electric potential measurements

Magnetohydrodynamic experiments in a scaled mock-up of a helium-cooled lead lithium blanket module have been performed with the aim of determining the liquid–metal flow distribution inside breeder units and between sub-channels formed by the cooling plates. It has been observed that, even for strong magnetic fields, the distribution of the flow among these sub-channels is not completely uniform, i.e. inertial entrance and exit conditions still affect the flow partitioning in the breeder units. Moreover, depending on the balance between inertia, viscous and electromagnetic forces namely on Reynolds and Hartmann numbers, regions with almost stagnant or reversed flow can be observed. Since, in closed recirculation loops the accumulated tritium could represent a safety issue, their occurrence is investigated by a detailed parametric study.

Results from Recent Experiments at the LOTUS Facility

Under the ongoing experimental program of fusion neutronics at the LOTUS facility, a number of activation and tritium breeding measurements were recently completed. The presence of Lithium Blanket Module (LBM) made a number of measurements also possible in it alone and in a number of more complex assemblies, incorporating it as one of the components. Both axial and off-axis measurements were made. All the experiments have been analyzed using the two dimensional discrete ordinates code DOT3.5 coupled to the first collision source evaluator GRTUNCL. The agreement between the measured and computed reaction rates is better than 10% for ThO/sub 2/; it is not so good for others.

Evaluation of the7Li(n, n’t)4He Cross Section for ENDF/B-VI and Application to Uncertainty Analysis

A new covariance analysis of n+7Li cross section data has been completed for Version VI of ENDF/B. The analysis updates our 1981 work for ENDF/B-V.2 to include new data that has become available since that time and to incorporate cross correlations between different experiments. The bulk of the new measured data consists of some 10 new (or newly revised) tritium-production measurements involving about 70 new data points. The new analysis results in only small changes in the previous evaluation of the tritium-production cross section but significantly reduces the magnitudes of uncertainties due to the more extensive and accurate data base that was used. A two-dimensional sensitivity and uncertainty analysis of the Lithium Blanket Module experiments at the LOTUS facility was performed in order to assess the effects of the new 7Li cross sections on tritium breeding uncertainty in a realistic system.

Lithium Test Module on Iter/Tiber: Engineering Design of the Tritium Recovery System

The design presented is an overview of the tritium recovery system for a lithium module on an ITER type reactor. The design of a tritium recovery system for larger blanket units, sectors, etc. could use the information developed in this report. A goal of this design was to ensure that a reliable, integrated performance of the tritium recovery system could be demonstrated. An equally important goal was to measure and account for the tritium in the liquid lithium blanket module and its recovery system in order to validate the operation of the blanket module.

Overview of the TFTR Lithium Blanket Module Program

The LBM (Lithium Blanket Module) is an approximately cubic module, about 80 cm on each side, with construction representative of a helium-cooled lithium oxide fusion reactor blanket module. Measurements of neutron transport and tritium breeding in the LBM will be made in irradiation programs first with a point-neutron source, and subsequently with the D-D and D-T fusion-neutron sources of the TFTR. This paper summarizes the objectives of the LBM program, the design, development and construction of the LBM, and progress in the experimental tests.

Tritium Assay of Li2O in the LBM/LOTUS Experiments

The Lithium Blanket Module (LBM) is an assembly of over 20,000 cylindrical lithium oxide pellets in an array representative of a limited-coverage breeding zone for a toroidal fusion device. A principal objective of the LBM program is to test the ability of advanced neutronics coding to model the tritium breeding characteristics of a fusion device blanket. The LBM has been irradiated at the Ecole Polytechnique Federale de Lausanne (EPFL) LOTUS facility with a 14 MeV point-neutron source. Princeton Plasma Physics Laboratory (PPPL) and EPFL assayed the tritium bred in lithium oxide diagnostic samples placed at various positions in the LBM. PPPL employed a thermal extraction technique while EPFL used a dissolution method. The results form the assay are reported and compared to MCNP Monte Carlo neutronics calculations for the LBM/LOTUS system.

The LBM Program at the EPFL/LOTUS Facility

An experimental program of neutron transport studies of the Lithium Blanket Module (LBM) is being carried out with the LOTUS point-neutron source facility at École Polytechnique Fédérale de Lausanne (EPFL), Switzerland. Preliminary experiments use passive neutron dosimetry within the fuel rods in the LBM central zone, as well as, both thermal extraction and dissolution methods to assay tritium bred in Li2O diagnostic wafers and LBM pellets. These measurements are being compared and reconciled with each other and with the predictions of two-dimensional discrete-ordinates and continuous-energy Monte-Carlo analyses of the LOTUS/LBM system.

Neutron Dosimetry Qualification Experiments for the Tokamak Fusion Test Reactor Lithium Blanket Module Program

The Tokamak Fusion Test Reactor (TFTR) Lithium Blanket module (LBM) program is a first-of-kind neutronics experiment involving a toroidal fusion neutron source. Qualification experiments have been conducted to develop primary measurement techniques and verify dosimetry materials that will be used to characterize the neutron environment inside and on the surfaces of the LBM. The deuterium-tritium simulation experiments utilizing a 14-MeV neutron generator and a fusion blanket mockup facility at the Idaho National Engineering Laboratory are described. Results and discussions are presented that identify the quality and limitations of the measured integral reaction data, including the minimum fluence requirement for the TFTR experiment and the use of such data in neutron spectrum adjustment and in predicting integral performance parameters, e.g., tritium production.

Lithium Blanket Module (LBM) Dosimetry Measurements at the Lotus 14-MeV Neutron Source Facility

This paper describes the measurements and results of the dosimeter material reaction rates inside the Lithium Blanket Module (LBM) after irradiation by the LOTUS 14-MeV neutron source at the Ecole Polytechnique Federale de Lausanne. The measurement program has been designed to utilize sets of passive dosimeter materials in the form of foils and wires. The dosimetry materials reaction thresholds and interaction response ranges chosen for this series of measurements encompass the entire neutron spectra along the full length of the LBM fuel rods.

New Monte Carlo Results for the TFTR/Lithium Blanket Module System

Neutronics analysis results from Phase II of the TFTR Lithium Blanket Module (LBM) program are reported. Principal activities were analyses of new coverplate and protective plate designs; updating of the MCNP Monte Carlo model of TFTR/LBM; and performing new reference calculations for D-D and D-T plasmas. The new protective plate was found to reduce LBM responses by 20%. Updating the model included a new tally structure in which the LBM is divided into 92 volume elements corresponding to foil locations. A new version of the MCNP surface-source routine was used, along with the latest pointwise cross sections. All flux, tritium and foil responses are stored at NMFECC and are available for comparison with measurements, when the experimental program gets underway.

TFTR Lithium Blanket Module Component Development, Testing and Fabrication

A lithium blanket module (LBM), representative of a fusion reactor blanket module has been fabricated by GA Technologies Inc. via sub contract from Princeton Plasma Physics Lab under the sponsorship of the Electric Power Research Institute. The LBM consists of a cubical array of 92 cylindrical breeder rods, 2.54 cm in diameter. Each rod consists of an ∼59 cm long section of lithium oxide pellets clad in 0.03 cm wall Type 316 stainless steel tube followed by a 20 cm long stainless steel reflector rod. Reusable test rods in the 20 cm diameter central region incorporate activation foils for neutron dosimetry and aluminum clad pellets for tritium dosimetry. The breeder rods are contained in an enclosure structure which has provisions for insertion and removal of test rods and dosimeter wires. Procedures developed for fabrication and assembly of the rods and enclosure structure proved to be satisfactory and reliable and the work was done on schedule and within budget.

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The TFTR Lithium Blanket Module program

The Lithium Blanket Module (LBM) is an approximately 80×80×80 cm cubic module, representative of a helium-cooled lithium oxide fusion reactor blanket module, that will be installed on the TFTR (Tokamak Fusion Test Reactor) in late 1986. The principal objective of the LBM Program is to perform a series of neutron transport and tritium-breeding measurements throughout the LBM when it is exposed to the TFTR toroidal fusion neutron source, and to compare these data with the predictions of Monte Carlo (MCNP) neutronics codes. The LBM consists of 920 2.5-cm diameter breeder rods constructed of lithium oxide (Li2O) pellets housed in thin-walled stainless steel tubes. Procedures for mass-producing 25,000 Li2O pellets with satisfactory reproducibility were developed using purified Li2O powder, and fabrication of all the breeder rods was completed in early 1985. Tritium assay methods were investigated experimentally using both small lithium metal samples and LBM-type pellets. This work demonstrated that the thermal extraction method will be satisfactory for accurate evaluation of the minute concentrations of tritium expected in the LBM pellets (0.1–1 nCi/g).

Tritium recovery from lithium oxide pellets

The TFTR Lithium Blanket Module is an assembly containing 650 kg of lithium oxide that will be used to test the ability of neutronics codes to model the tritium breeding characteristics of limited-coverage breeding zones in a tokamak. It is required that tritium concentrations as low as 0.1 nCi/g bred in both metallic lithium samples and lithium oxide pellets be measured with an uncertainty not exceeding ±6%. A tritium assay technique for the metallic samples which meets this criterion has been developed. Two assay techniques for the lithium oxide pellets are being investigated. In one, the pellets are heated in a flowing stream of hydrogen, while in the other, the pellets are dissolved in 12 M hydrochloric acid.

The TFTR Lithium Blanket Module Final Design and Materials Development

A Lithium Blanket Module (LBM) representative of a fusion reactor blanket module has been designed and will be tested using the toroidal neutron source of the Tokamak Fusion Test Reactor (TFTR) beginning in 1985. A rugged design consisting of 921 2.54 cm diameter breeder rods in an 80 cm cubic box has been developed, and the techniques and equipment necessary for mass production of the Li/sub 2/O breeder pellets have been demonstrated. Analysis using a coupled Monte Carlo neutronics model has shown that tritium production is uniform across the module to within 8 cm of the edge, and that the front face fusion fluence and central region tritium production can be calculated to acceptable accuracies for eventual comparison with measurements on the LBM installed on the TFTR.

Monte Carlo Neutronic Analysis for the TFTR Lithium Blanket Module

Neutronics analysis for the TFTR Lithium Blanket Module (LBM) design included 1-D, 2-D, and 3-D exploratory calculations culminating in reference noncoupled and coupled Monte Carlo calculations of fluxes, tritium production, and foil responses throughout the module for both D-T and D-D plasmas., Neutron flux and tritium production were shown to be quite flat across the module, validating the choice of a 10-cm-radius central test region. A Monte Carlo perturbation routine was extensively used for modeling studies. The front-face fusion fluence and central region tritium production can be calculated to better than ±15% uncertainty overall.