MC 2005 Avignon September 12 15 2005 MCNPX

M&C 2005 Avignon September 12 -15, 2005 MCNPX STUDIES OF SPALLATION NEUTRON PRODUCTION ON A THICK LEAD TARGET Mitja Majerle NPI CAS Řež, The Czech Republic M&C 2005, Avignon, September 12 -15, 2005

Introduction l Generally : ¡ ¡ l Experiments with high-energy protons on heavy targets (~ADS), spallation neutrons, direct beam We measure transmutation possibilities, neutron fields, we compare data with model simulations Focus – The PHASOTRON experiment : Protons, neutron field (threshold detectors) ¡. . . and the simulations ¡ What and how we calculate ¡ Comparison with the experiment ¡ The influence of the setup parts ¡ M&C 2005, Avignon, September 12 -15, 2005

• Neutrons and protons react with detectors: (n, g), (n, 2 n), (n, xn), (n, a), (p, n), (p, a), . . . • Yields of produced elements are detectable in g-detectors M&C 2005, Avignon, September 12 -15, 2005

Experimental results B=Number of produced nuclei in 1 g of material per one incident proton M&C 2005, Avignon, September 12 -15, 2005

Simulations, how/what we calculate MCNPX code v. 2. 4. 0 (on Linux, parallel computing) l Input : l ¡ ¡ l setup geometry starting conditions Output 1: ¡ neutron distribution l Cross-section libraries l Output 2: (Au, Al - ENDF; Bi experimental; Iodine - ? ) ¡ masses of produced elements or B-values M&C 2005, Avignon, September 12 -15, 2005

Neutron spectra + cross-sections • We can convolute the calculated neutron spectrum with the cross-section for a given reaction (SSW+HTAPE 3 X+convolution). 197 Au(n, 2 n)196 Au 27 Al(n, a)24 Na 197 Au(n, g)198 Au • Computer can convolute the spectrum with cross-sections and outputs B (F 4+FM tally). M&C 2005, Avignon, September 12 -15, 2005

Calculations vs. experiment Calculated values in comparison with the experiment for 27 Al(n, a)24 Na Ratios between calculated and experimental values for 24 Na, 196 Au, 194 Au M&C 2005, Avignon, September 12 -15, 2005

Influence of the setup parts l Concrete walls : ¡ Neutrons are moderated and reflected back M&C 2005, Avignon, September 12 -15, 2005

Influence of other simplifications l Extensive calculation tests on PHASOTRON and EPT setup revealed that : ¡ ¡ ¡ HTAPE 3 X and F 4 methods results do not always agree. Beam profile and displacement influence the neutron field (3 mm ~ 5%). The use of different models (BERTINI, CEM, ISABEL) ~ 10%. Detectors minimally influence the neutron field. Metal holders, tables, . . . have minimal influence. . M&C 2005, Avignon, September 12 -15, 2005

Parallel processing l The use of parallel processing (PVM) speeds up our calculations significantly. M&C 2005, Avignon, September 12 -15, 2005

Conclusion l We try to imitate an ADS systems with the setup l We can describe new, similar systems with the computer with the accuracy (50%) Thank you. M&C 2005, Avignon, September 12 -15, 2005