Daniela Kiselev, Ryan Bergmann, Polina Otiougova, Vadim Talanov, Michael Wohlmuther : Paul Scherrer Institut Total radioactive waste of decommissioning the high intensity proton accelerator (HIPA) facility at PSI SATIF13, Dresden, Germany, 10.10.-12.10.2016

Motivation Authority (NAGRA) requires an estimate of the amount of the radioactive waste after the final shutdown of the proton accelerator facility (HIPA)  input for the planning of the final repository Exemption limits in Switzerland will change (~ 2018) Switzerland will follow Euratom Basic Safety Standards Directive (BSS)  New cost estimate for the decommisioning required Side remark: Nowadays an estimate of total rad. waste volume is required for the operational approval of a facility in Switzerland.

New and old exemption values in Switzerland Nuclide LE present regulation [Bq/g] LL future regulation [Bq/g] LE/LL H-3 200 100 2 Co-60 1 0.1 10 Ni-63 70 0.7 Eu-152 7 Eu-154 5 50 Most of the limits for important isotopes (steel, concrete) are considerably reduced Nuclide LE [Bq/kg] artificial LL [Bq/kg] natural K-40 2000 1000 10000 Ra-228 10 100 Th-232 50 6 U-238 200 400

Applied technique for waste estimate Monte Carlo particle transport program : n,p,g,a,p,d,3H.... Input: dedicated geometry, material compositions, cross sections: for n<20MeV ENDF-B, otherwise Bertini-Dresner Output: n-fluxes (E<20 MeV), residual nuclei production rates with rnucs-card (former active htape) in *.o file - avoids huge histp file (can be several GB) - developed by F. Gallmeier & M. Wohlmuther - patch in the Cinder2008 release on RSICC MCNPX2.7.0 activation script M. Wohlmuther et al., Proc. AccApp 2007, Pocatello, p. 226. F.X. Gallmeier, dito, p. 207 Cinder or SP-Fispact + EAF2010 or Orihet3 + c.s. library + irradiation history  nuclide inventory clearance index for each cell in script sum_nuclides, summing up volumes

Clearance index Clearance index: LE = limit de exemption LL= limite de libération CI > 1 (after 30 y cooling time)  radioactive waste Influence of U, Th and daughters Ra-228 on the CI for concrete is non-negligible (depending on geometry and activation) for longer storage times of 75 y, 100 y But: Natural and artificial isotopes have different exemption limits!

Material definition(s) Some trace elements are particular important due to large neutron capture cross section For cooling times > 30 years in concrete and steel: Eu-152 (T1/2 = 13.5 years), Eu-154 (T1/2 =8.6 years) ,Co-60 (T1/2 = 5.3 years) Values as used for the calculation of the nuclide inventory of operational waste (PWWMBS), mainly conservative. Element Steel Concrete Co 170 ppm 1 ppm Eu 3 ppm Material analyses @Radiochemie Munich initiated by NAGRA Element Steel (St52.3) Steel (St37) Concrete Co 140 ppm 110 ppm 4 ppm Eu - <0.007 ppm (?) 0.5 ppm Amount of concrete waste volume is sensitive on Eu content  analyses on more samples needed

NAA @ SINQ (Spallation source at PSI) 3 capsules irradiated at the same time: MCNPX simulation: D2O PNA Fly ash from NIST for calibration: Eu: 4.67 ppm +/- 0.07% 2. Sample 3. Sample NAA 20% agreement between measured and calculated Eu-152n (T1/2 = 9.3h)

Samples and Results Sample Eu (ppm) shielding block exp. hall #1 0.40 +/- 7.0% roof Ring machine bunker 0.52 +/- 20.3% p-channel around MHC5 #4 0.39 +/- 13.4 % Ring bunker @ EEC 0.25 +/- 11.8 % Ring bunker @AHA 0.27 +/- 6.7 % shielding block exp. hall #1, 3 stones 0.53 +/- 4.8 % shielding block exp. hall #1, milled 0.26 +/- 7.4 % p-channel around MHC5 #4, milled 0.40 +/- 5.4 % Weighted mean 0.34 +/- 2.6 % shielding block exp. hall #1: the same as measured by NAGRA Eu: 0.549 +/- 6.2%  0.5 ppm Eu was assumed in the material definition of concrete

PSI Proton Accelerator Facilities SINQ OPTIS Injector 1 Target E Gantry 3 Injector 2 OPTIS 2 Ring cyclotron 590 MeV Target M Gantry 2 at present: Nominal 2.2 mA (approval for 2.4 mA) Max. integral charge/year: 10 Ah UCN Gantry 1 PROSCAN Comet: 250 MeV Length scale: Target M to beam dump = 35.5 m

Main Loss points in the 590 MeV areal Accelerator: 72 MeV Injector2 + transfer line 590 MeV Ring cyclotron @EEC and AHA 0.005-0.01% (100-200 nA) - p-channel: 590 MeV beam line: Target M rebuild in 1985 1 % Target E rebuild in 1991 10 % KHE2/3 rebuild in 1991 20 % Beam dump rebuild in 1991 <=1996 70 % >=1997 5% * 70 % - Spallation neutron production targets: SINQ: thermal neutrons (~ 25 meV) cold neutrons (< 5 meV) >= 1997 70 % UCN: ultra cold neutrons (~ meV) pulsed operation with 1 % duty cycle >= 2011 1 % Page 10

The geometry: From CAD to MCNPX Conversion process: CATIA-V model  step file SuperMC/MCAM developed by Institute of Nuclear Energy Safety Technology (INEST), China Post-editing: simplification, removing of gaps, double lines of step file usually necessary  ANSYS SpaceClaim is a good tool (also for modification of existing geometry) Restriction in MCAM, McCAD: 1000 cells  combination of several parts possible Loss of information about the material def. in CATIA  solved by an additional material list + Python script

Example: Tg M region CAD (SpaceClaim) Model in MCNPX modeled in SpaceClaim CAD (SpaceClaim) in CATIA-V modeled region Model in MCNPX also done (partly) for TgE-Region Page 12

The need for biasing methods Built-in methods in MCNPX: importances: - based on cells  fine structure needed! - have to be adjusted by hand  tedious work in large regions weight windows: (ww ~ 1/importances) - meshed (or cell) based - energy dependend - semi-automatic, optimization on 1 direction (= tally, detector) For activation calculations: Biasing in every cell, not only 1 direction  global variance reduction Otherwise 6 different runs for one geometry (done for UCN) Applied technique: convert neutron flux to weight windows weight windows(E) ~ neutron flux(E) ~ 1/importances UCN geoemtry: 6 different runs for each direction one

Target M to Target E region Loss points with and without magnetic field in the tripletts: TgM C1 C2 C3 C4 C5 C6 TgE Losses from 1.1% 1.0% 0.0 2.9 10-5 5.7 10-6 8 10-6 1.3 10-4 10% beam dynamics Losses (no magnetic field) 1.5% 0.45% 0.0 1.7% 2.7% 4.5% 18% 1.7 10-4 2.6 10-1 Total losses are 1000 times smaller with magnetic field  1000 times smaller activity

FLUKA simulation for estimating the effect of the magnetic field in the Triplett after Target M: horizontal plane vertical plane Beam losses evaluated in FLUKA in MCNPX: After triplett: neutron/proton fluxes are scaled down according to FLUKA & TURTLE results

Results for Target M to Target E region colored:  radiactive waste LE-values: steel LL-values: concrete Vadim Talanov

Target E to Beam dump The geometrical model: set to «void» to speed up the calculation The geometrical model: concrete steel/cast iron GC009 GC007 heavy concrete Conditioned Container filled with accelerator waste Polina Otiougova

The Ring Cyclotron 8 sector magnets, each more than 400 t Injection: 72 MeV Extraction: 590 MeV

The Ring: a special case Approach: Measurement of the neutron dose rates on Ring bunker roof LB6411: 0 -20 MeV Wendi-II: 0 – 5 GeV Relative distribution: Adjustment of the relative strength of the sources in the MCNPX model Remark: Implementing the response function of LB6411 and Wendi-II into MCNPX compared to applying actual neutron dose conversion factors has negligible effect

Dose rate measurements on bunker roof 0.7 6.6/11.3 2.0 1.4 3.9 5.7 3.8/6.2 3.2/5.5 5.1 0.4 Results in mSv/h: LB6411/Wendi-II Extraction Injection Measurements on the roof!  Source of loss point is few meters shifted

Distribution of the sources adjusted to match the measured dose rate distribution AHA Kav1 EEC Kav4 Kav5 Kav3 ZS2 Kav2 Quelle Stärke in MCNPX AHA 0.5 EEC 0.14 Kav1 0.74 Kav2 0.1 ZS2 0.05 Kav3 Kav5 Kav4 main losses

Relative dose rate distribution on bunker roof Energy range: 0 – max. (~ Wendi-II) Distribution up to 20 MeV looks similar (~LB6411) Measured DR(Wendi-II) DR(LB6411) ~ 1.7 Calculated DR(0-max.) DR(0-20MeV) ~ 2.5 Reduction of H-content (0.1% to 0.05%)  DR(0-max.) DR(0-20MeV) ~ 2.0

Proton and Neutron distribution at beam plane Protons Neutrons Sample2 EEC Sample1 AHA Sources: Protons scattering on metal piece Effective Thickness of the piece determines the neutrons per proton Adjustment by absolute total loss, measured dose rates & measured activity from 3 samples

Comparison to samples   Sample 1 AHA Sample 2 EEC Sample 3 roof (AHA+EEC) Bq/g Data MCNPX Meas/Calc Be7 1.22 2.61 0.47 0.88 1.52 0.58 0.32 Na22 2.46 1.17 2.11 1.09 0.76 1.43 0.19 Na24 8.21 5.08 1.62 3.13 4.48 0.70 3.46 Sc46 0.05 9.29 0.49 0.03 14.70 0.01 Sc47 0.07 0.38 0.16 0.06 Cr51 0.34 0.43 0.79 0.21 Mn54 0.31 0.92 0.29 0.30 0.95 0.11 Fe59 0.20 0.17 1.21 0.26 0.14 1.84 Co60 0.72 0.48 1.50 1.14 0.41 2.79 0.82 2.60 Cs134 0.35 0.09 3.87 6.55 Eu152 1.63 0.78 2.09 3.08 0.69 0.57 0.55 1.03 Eu154 0.25 2.89 5.18 Measured activities in sample is factor 2-3 larger than calculated

Beam losses in Ring .Likely explanation: In year 2015, where the dose rates were measured, total losses were small (100 nA). In previous years much larger losses (200-300 nA) in ring. 2013 600 400 200 loss current [nA] Nominal operation Test-operation: 2.4 mA 2015 600 400 200 loss current [nA] 2014 600 400 200 loss current [nA] Problems with Kav.5 We hope that the losses will stay small in the future (needed for increasing beam current)

Wir schaffen Wissen – heute für morgen Monte Carlo based estimate for the expected radioactive waste for the final repository after the shutdown of the HIPA facility including SINQ and UCN.