Neutronics Issues to be Resolved in ITER Test Blanket Module (TBM)

1. Neutronics Issues to be Resolved in ITER Test Blanket Module (TBM) • Verification of the adequacy of current transport codes and nuclear data bases in predicting key neutronics parameters (e.g. Spectra, tritium production and heating rates) • Verification of adequate radiation protection of machine components and personnel.

2. Testing Tritium Self-sufficiency in ITER • This does not appear to be possible in ITER (e.g. basic shielding blanket does not produce tritium, no interface with tritium processing system in the TBM’, partial coverage vs.. full coverage in DEMO, etc. ) • Direct demonstration of tritium self-sufficiency requires a fully integrated reactor system, including the plasma and all reactor prototypic nuclear components.

3. Testing Tritium Self-sufficiency in ITER (cont’d) • We should rely on indirect demonstration by utilizing the information obtained from local and zonal tritium production rate in the TBM and the associated uncertainties in their prediction, in addition to information on tritium extraction and flow in TBM, and extrapolate this information to DEMO and power-producing reactor conditions. This seems to be a difficult task

4. Classification of Neutronics Tests (A) Dedicated Neutronics Test Aim at examining the present state-of-the-art neutron cross-section data, various methodologies implemented in transport codes, and system geometrical modeling as to the accuracy in predicting key neutronics parameters (TBM of “Look-Alike” type) (B) Supplementary Neutronics Tests Intended to be performed in TBM (or submodulesof “Act-alike” type) used for non-neutronics tests (e.g. thermo-mechanics test, etc).

5. (A) Dedicated Neutronics Tests • Unlike the case of using engineering scaling to reproduce demo-relevant parameters in an “Act-alike” test module, dedicated neutronics tests require a “Look-alike” test module for a given blanket concept. This is due to the desire to quantify a realistic error bars associated with various neutronics parameters when predictions with various codes/nuclear data are compared to measured data. An obvious example is verifying the potential for satisfying tritium self-sufficiency conditions.

6. (A) Dedicated Neutronics Tests (con’d) • It is strongly desired to perform neutronics tests on as “cold” module as possible to minimize problems associated with elevated breeding temperature (e.g. tritium permeation). • It is therefore recommended to perform these tests as early as possible during the DD operation phase (year 4) or in low duties cycle DT operation phase (year 5&6)

7. (A) Dedicated Neutronics Tests (con’d) (A) Dedicated Neutronics Tests (con’d) • Each blanket concept (e.g. HCPB or DCLL) should have its own tritium fuel cycle that is isolated from ITER basic machine. Tests for tritium production rates, tritium permeation, transport and isotope separation will only demonstrate the potential of each blanket concept to generate and control tritium flow. It is by no means meant to confirm tritium self-sufficiency.

8. (A) Dedicated Neutronics Tests (con’d) (A) Dedicated Neutronics Tests (con’d) • Tests for tritium production and comparison to measured data will only quantitatively assign error bars (uncertainties) in TPR prediction that will be useful in demonstrating the feasibility of meeting tritium self-sufficiency in a Demo where blanket full coverage and closed tritium cycle (tritium burn up rate in the plasma) are realized

9. (A) Dedicated Neutronics Tests (cont’d) • Measurements to be performed • In-Pile Measurements • 1st Measuring Campaign: • Neutron and gamma Spectra, Neutron fluence (use of multi-foil activation methods) 2nd Measuring Campaign • Local (and if possible zonal) tritium production rates and profile. • 3rd Measuring Campaign • Neutron and gamma heating rates

10. (A) Dedicated Neutronics Tests (cont’d) • In-Pile Measurements (con’d) • Multi foil activation measurements (MFA) : • Reaction measurements sensitive to different energy range of interest: • Au-197(n,g)Au-198: thermal neutrons • In-115(n,n’)In-115m: Fast neutrons. • Ni-58(n,p)Co-58: and Ni-58(n,2n)Ni-57: En>2.9 and 13.4 MeV, respectively • Al-27(n,a)Na-24: En>8.5 MeV • Nb-93(n,2n)Nb-92: En>10.8 MeV • Out-of-pile measurements: • Dose behind test module and at cryostat, neutron yield from plasma and source characterization (part of plasma diagnostics)

11. Example of Performing MFA measurements with inserted in measuring tubes. They can be retrieved mechanically

12. Dedicated Neutronics Tests and Fluence Requirements/conditions Fluence 1 W s/m2 to 1 MW s/m2 ~ 1 MW s/m2 <1 MW y/m2 Any linear combination of wall load and operating time which has this rage of fluence is acceptable. e.g,. 400 s (1 ITER pulse) @ 2.5 x 1011 n/cm2 s is adequate. Can be performed in year 4 (DD operation) or during low duty cycle operation in DT operation (year 5&6) Out-of-module parameters H, He, dpa rates, activation In-module parametersOut-of-module parameters Neutron and Gamma Specta, Fluence Plasma neutron source Tritium production rates characterization Heating rates Dose behind shield and at cryostat. Test Module Conditions (Material, Geometry, Test Module Size) (Look-alike TBM is preferable to preserve as closely as possible Demo-relevant conditions. Measurements to be carried out at the inner most locations in the module to minimize influence of boundary conditions from ITER shielding blanket (SS/H2O). Measurements are generic in nature for all blanket concepts. Operating Scenario Pulsed operation or Steady-state Higher fluence is required to accumulate reasonable limits. Dedicated test facility other than ITER (i.e. IFMIF) may be necessary

13. Fluence Requirements for Some Measuring Techniques (To be confirmed by Experimentalists’ Group) 1 mW s/m2 1 W s/m2 ~ 1 kW s/m2 1 MW y/m2 Integral Parameters Neutron yield NE-213, fission chamber Multifoil Activation (MFA) Liquid scintillators Tritium production rate Lithium glass detectors Gas counters Mass spectroscopy Proportional counters Thermoluminescent dosimeter (TLD) Nuclear heating Gas filled counter TLD Calorimeter Nuclear Reaction rate Fission chamber Activation foil Mass spectrometry Neutron and Gamma spectrum NE-213, proton recoil MFA

14. (B) Supplementary Neutronics Tests • Intended to be performed in TBM of “Act-alike” type) used for non-neutronics tests (e.g. thermo-mechanics test, etc). • Objectives • Provide additional supporting information to the dedicated tests in quantifying the uncertainties in prediction that could be used as safety factors in Demo blanket design