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PHITS & DCHAIN-SP: Induced Radioactivity Time Variation Connection

This tutorial discusses connecting PHITS for initial calculations and DCHAIN-SP for time-variant induced radioactivity estimations. Learn how to assess induced radioactivity variations using both systems. Understand terminology, glossary, flowchart, and detailed data libraries for accurate results and shielding design in nuclear facilities. Execute simulations, track outputs, and calculate induced activity, decay heat, and gamma-ray spectrums. Enhance accuracy by separately calculating nuclear yields from neutrons below 20 MeV in DCHAIN-SP. Important notices and limitations of the current version are highlighted for efficient usage of the systems.

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PHITS & DCHAIN-SP: Induced Radioactivity Time Variation Connection

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  1. PHITS Multi-Purpose Particle and Heavy Ion Transport code System Evaluation of Induced Radioactivity: Connection between PHITS & DCHAIN-SP May 2016 revised Title 1

  2. Purpose • PHITS can calculate the induced radioactivity just after pulse irradiation, but cannot estimate their time variation • DCHAIN-SP can calculate the time variation of induced radioactivity as well as heat and gamma-ray spectrum due to the radioactive decays In this lecture, you will learn how to connect PHITS and DCHAIN-SP, and calculate the time variation of the induced radioactivity using these 2 codes. Purpose 2

  3. Terminology • Radioactivity： • Radioactive Isotope: • (Ionizing) Radiation: • Activity of matter to emit radiations due to decay of unstable isotopes (Unit = Bq) • Unstable isotopes that can decay and emit radiations • Particles (neutron, proton photon etc.) that travels through some matter by ionizing it • PHITS can handle the transport of only radiation Both radiation dose and radioactivity must be evaluated in the shielding design of nuclear facilities Glossary 3

  4. Table of Contents • Abstract • Parameter settings in [t-dchain] • Output files from DCHAIN-SP • Exercises • Summary Table of Contents 4

  5. Flowchart of Connection Calculation PHITS DCHAIN-SP Particle Transport Simulation Calculation Results • Induced activity（Bq) • Decay heat （W） • Emitted γ-ray spectrum Output files from [t-dchain] during and after irradiation • Basic input file for DCHAIN-SP (specified by “file=“) • Nuclear yield calculated by [t-yield]（*.dyld, nmtc_yield） • Neutron fluxes below 20 MeV calculated by [t-track]（*.dtrk, n.flux_**) • Information on the path of data library used in DCHAIN-SP(dch_link.dat) Decay chain calculation Data libraries for DCHAIN-SP • Activation cross section for neutron (1968 groups) • γ-ray spectrum and decay chain • Electron capture & ratio of β+ decay Overview 5

  6. Let’s Try! • Execute PHITS with “dchain.inp” (send to -> PHITS) (tdchain.out, .dtrk, .dyld, dch_link.dat, n.flux_**, nmtc_yieldare generated) • Execute DCHAIN-SP with “tdchain.out” (send to -> DCHAIN) （tdchain.lst, .act, .pht, .ang, .gsd, .gso, .alr, .epsare generated） tdchain.eps Time variation of induced activity in each cell Overview 6

  7. Output files from [t-dchain] • tdchain.out: Basic input file for DCHAIN-SP • 　　　　　　　　　　（File name is specified by “file=“ in [t-dchain]) • tdchain.dyld: Nuclear yields calculated by [t-yield] • nmtc_yield: Nuclear yields written in DCHAIN-SP input format • tdchain.dtrk: Neutron fluxes below 20 MeV calculated by [t-track]* • n.flux_**: Neutron fluxes below 20 MeV written in DCHAIN-SP format • dch_link.dat: Folder name containing the libraries for DCHAIN-SP • (specified by “file(21)=“ in [parameters]） *In principle, time variation of induced activity can be calculated only from the nuclear yields calculated by [t-yield]. However, the calculation accuracy can be improved when nuclear yields from neutrons below 20 MeV are separately calculated in DCHAIN-SP using specially developed activation cross sections Overview 7

  8. Output files from DCHAIN-SP • tdchain.ｌｓｔ: Basic output file (similar to “phits.out” in PHITS) • tdchain.act: Main output (Induced radioactivity, decay heat, • tdchain.pht: γ-ray spectrum written in PHITS input format • tdchain.ang: Induced radioactivity, decay heat, dose rates • tdchain.eps: Graphs generated by ANGEL using above file • tdchain.gsd: γ-ray spectrum written in MCNP input format • tdchain.yld: Nuclear yields when irradiation and cooling is finished • tdchain.gso: Origin nuclei and their contribution for emitting γ-ray • tdchain.alr: Induced radioactivity and decay heat dose rate, emitted γ-ray spectrum) written in ANGEL input format Overview 8

  9. Important Notice • Some parameters used in DCHAIN-SP can be also specified in [t-dchain] section • In general, their default values are adequately set, and need not to be changed. If you would like to change them, please read the manual of DCHAIN-SP for their meanings */phits/dchain-sp/manual/DCHAIN-SP2014-jpn.pdf Limitation of Current Version • Only one [t-dchain] is allowed in an PHITS input file • “Mesh” should be “reg” and combined cells cannot be specified in [t-dchain] Overview 9

  10. Table of Contents • Abstract • Parameter settings in [t-dchain] • Output files from DCHAIN-SP • Exercises • Summary Table of Contents 10

  11. Check Calculation Result yz-track.eps 150 MeV Proton Water Vacuum Irradiate 150 MeV protons into 3 cylindrical water tanks (10 radius x 10 cm height each) Parameter Setting 11

  12. Settings for using [T-Dchain] dchain.inp [ P a r a m e t e r s ] ... $ must option for DCHAIN jmout = 1 # (D=0) Density echo, 0:input, 1:number density e-mode = 0 # (D=0) Event generator mode … [ V o l u m e ] $ must section for DCHAIN reg vol 1 pi*c1*c2**2 $ c1&c2: height and radius of cylinder (cm) 2 pi*c1*c2**2 $ c1&c2: height and radius of cylinder (cm) 3 pi*c1*c2**2 $ c1&c2: height and radius of cylinder (cm) • [volume] section & jmout must be set because DCHAIN-SP is necessary to know the number of nuclei in each cell • Event Generator Mode should not be used （e-mode = 0)because nuclear yields from low-energy neutron interactions are separated calculated in DCHAIN-SP Parameter Setting 12

  13. Example of [T-Dchain] dchain.inp [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton into water mesh = reg reg = 1 2 3 file = tdchain.out timeevo = 2 6.0 m 1.0 50.0 m 0.0 outtime = 7 1.0 m 3.0 m 6.0 m 10.0 m 20.0 m 30.0 m 40.0 m $ beam current (nA) set:c21[100.0] amp = c21*1.0e-9/1.602e-19 # (D=1.0) Source Intensity Basic parameters 　　・ file (input file name for DCHAIN-SP) 　　・ mesh (must be “reg”） 　　・ amp、timeevo(Irradiation condition） 　　・ outtime (Output timing) Parameter Setting 13

  14. Parameters in [T-Dchain] [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = 1 2 3 file = tdchain.out timeevo = 2 6.0 m 1.0 50.0 m 0.0 outtime = 7 1.0 m 3.0 m 6.0 m 10.0 m 20.0 m 30.0 m 40.0 m $ beam current (nA) set:c21[100.0] amp = c21*1.0e-9/1.602e-19 • file：Input file name for DCHAIN-SP 　・ Following file names are not allowed because PHITS or DCHAIN-SP automatically generate them ***.dtrk, ***.dyld, ***_err.dyld, ***.dout, ***.lst, ***.yld, ***.gsd, ***.gso, ***.alr, ***.act, ***.ang, ***.pht, n.flux_01～n.flux_99, nmtc_yield, dch_link.dat Parameter Setting 14

  15. Parameters in [T-Dchain] [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = 1 2 3 file = tdchain.out timeevo = 2 6.0 m 1.0 50.0 m 0.0 outtime = 7 1.0 m 3.0 m 6.0 m 10.0 m 20.0 m 30.0 m 40.0 m $ beam current (nA) set:c21[100.0] amp = c21*1.0e-9/1.602e-19 • mesh：should be “reg” at this momentreg = specify cell ID Combined cell, e.g. (1 2), cannot be used • amp：Beam amplitude (source/sec) • timeevo：Number of irradiation and cooling time steps. After this line, time and relative amplitude must be specified Example: 6.0 m 1.0 → irradiate 6 minutes by full amplitude 50.0 m 0.0 →　cool 50 minutes • s (second), m (minute), h (hour), d (day), y (year) • You have to insert space before and after them Parameter Setting 15

  16. Parameters in [T-Dchain] [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = 1 2 3 file = tdchain.out timeevo = 2 6.0 m 1.0 50.0 m 0.0 outtime = 7 1.0 m 3.0 m 6.0 m 10.0 m 20.0 m 30.0 m 40.0 m $ beam current (nA) set:c21[100.0] amp = c21*1.0e-9/1.602e-19 • outtime：Number of output timing After this line, output timing must be specified in the same manner as timeevo • Positive value: Count from the beginning of the first irradiation • Negative value: Count from the end of the last irradiation You cannot specify time after the last time specified by timeevo; 56 m in this case Parameter Setting 16

  17. Relation between timeevo & outtime dchain.inp [ T – D c h a i n ] timeevo = 2 6.0 m 1.0 50.0 m 0.0 outtime = 7 1.0 m 3.0 m 6.0 m 10.0 m 20.0 m 30.0 m 40.0 m Irradiation time ← specified by timeevo Irradiationfor 6.0 m Cooling for 50 m （min） Output timing ← specified by outtime Cannot specify Irradiation time and output timing Parameter Setting 17

  18. Relation between timeevo & outtime - in the case of using negative outtime - Manual [ T – D c h a i n ] mesh = reg reg = 100 file = testDC.spd title = [t-dchain] test calc. amp = 1.0E12 timeevo = 4 3.0 h 1.0 2.0 h 0.0 3.5 h 1.0 15.5 h 0.0 outtime = 3 3.0 h -1.0 h -3.0 h Irradiation time ← specified by timeevo IrradiationIrradiation End of the last irradiation step 3.0 h 3.5 h 2.0 h 15.5 h Cooling Cooling 時間 3.0 h 1.0 h 3.0 h Output timing ← specified by outtime Irradiation time and output timing Parameter Setting 18

  19. Table of Contents • Abstract • Parameter settings in [t-dchain] • Output files from DCHAIN-SP • Exercises • Summary Table of Contents 19

  20. Basic Output File (*.lst) • tdchain.lst： Similar to “phits.out” in PHITS Errors messages might be given at the end of the file *** error message from main *** primary file is not found. file name = /spd-dcylib ↑ Library file is found • Solution1:Correct “file(21)” in [parameters] section & Execute PHITS again • Solution2: Correct “dch_link.dat” by yourself -> easier *** error message from s.rdinpt *** total flux of neutron irradiation was less than 0. no. of region= 1 jmode= 2 fluxs= 0.0000E+00 ↑ Neutron flux is 0 in some cells • Solution1:Restart PHITS calculation to obtain better statistics • Solution2-1: Set “jmode = 0”(if neutron fluxes for all cells are 0) • Solution2-2: Delete the cell information (if neutron fluxes only for some cells are 0) DCHAIN-SPOutput 20

  21. Main Output File (*.act) • tdchain.act:Induced activity, decay heat & dose rates Calculated results are given for each cell and output timing ← Cell ← Output timing Dose rate (uSv/h*m2) Decay Heat (W) Induced Activity (Bq) Many output files are generated from DCHAIN-SP (see its manual in more detail) DCHAIN-SPOutput 21

  22. Graphic Output File (*.eps) Decay heat Induced activity β decay heat* Dose rate** γ decay heat* α decay heat* Time variation for each cell (dot+line) & total (thick line) tdchain.eps *Decay heat due to β-ray, γ-ray, and α-ray emissions, respectively **Ambient dose equivalent H*(10) rate at 1 m away from the point source DCHAIN-SPOutput 22

  23. Table of Contents • Abstract • Parameter settings in [t-dchain] • Output files from DCHAIN-SP • Exercises • Summary Table of Contents 23

  24. Check current input & output dchain.inp [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = 1 2 3 file = tdchain.out timeevo = 2 6.0 m 1.0 50.0 m 0.0 outtime = 7 1.0 m 3.0 m 6.0 m 10.0 m 20.0 m 30.0 m 40.0 m $ beam current (nA) set:c21[100.0] amp = c21*1.0e-9/1.602e-19 tdchain.eps • Induced activity becomes the maximum at 6 minutes (360 seconds) • Activity becomes smaller with increase of depth • 　　（cell 1＞cell 2＞cell 3） Exercise 24

  25. Exercise 1 dchain.inp Change irradiation time [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = 1 2 3 file = tdchain.out timeevo = 2 6.0 m 1.0 50.0 m 0.0 outtime = 7 1.0 m 3.0 m 6.0 m 10.0 m 20.0 m 30.0 m 40.0 m $ beam current (nA) set:c21[100.0] amp = c21*1.0e-9/1.602e-19 Before • 6.0 m 1.0 → irradiate 6 minutes by full amplitude • 50.0 m 0.0 →cool 50 minutes After • Irradiate 5 minutes by full amplitude • Cool 5 minutes • Irradiate 10 minutes by a half amplitude • Cool 1 hour • timeevo：Number of irradiation and cooling time steps. After this line, time and relative amplitude must be specified • s (second), m (minute), h (hour), d (day), y (year) • You have to insert space before and after them →　Execute PHITS & DCHAIN Exercise 25

  26. Exercise １(Answer) dchain.inp [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = 1 2 3 file = tdchain.out timeevo = 4 5.0 m 1.0 5.0 m 0.0 10.0 m 0.5 1.0 h 0.0 outtime = 7 1.0 m 3.0 m 6.0 m 10.0 m 20.0 m 30.0 m 40.0 m $ beam current (nA) set:c21[100.0] amp = c21*1.0e-9/1.602e-19 tdchain.eps Induced activity becomes larger at 20 minute (1200 seconds) after the first irradiation Exercise 26

  27. Exercise 2 Change output timing tdchain.out (after 30th line) ! --- irradiation time --- itstep = 4 5.0000E+00 m 1.0000E+00 5.0000E+00 m 0.0000E+00 1.0000E+01 m 5.0000E-01 1.0000E+00 h 0.0000E+00 ! --- output time --- itout = 7 1.0000E+00 m 3.0000E+00 m 6.0000E+00 m 1.0000E+01 m 2.0000E+01 m 3.0000E+01 m 4.0000E+01 m Before 1, 3, 6, 10, 20, 30, and 40 minutes after the first irradiation After 1, 3, 5, 7, 10, 13, 16, 20, 25, 30, and 40 minutes after the first irradiation (11 points) （You can reduce the number if you use a slow computer） • itout: Number of output timings corresponding to “outtime” in [t-dchain] →Change “tdchain.out” and execute only DCHAIN-SP Exercise 27

  28. Exercise 2(Answer) tdchain.out (after 30th lines) ! --- irradiation time --- itstep = 4 5.0000E+00 m 1.0000E+00 5.0000E+00 m 0.0000E+00 1.0000E+01 m 5.0000E-01 1.0000E+00 h 0.0000E+00 ! --- output time --- itout = 11 1.0000E+00 m 3.0000E+00 m 5.0000E+00 m 7.0000E+00 m 1.0000E+01 m 1.3000E+01 m 1.6000E+01 m 2.0000E+01 m 2.5000E+01 m 3.0000E+01 m 4.0000E+01 m You do not have to execute PHITS again if you would like to change only the irradiation time and output timing Exercise 28

  29. Use γ-ray spectrum as [source] tdchain.pht： γ-ray spectrum written in the PHITS input format tdchain.pht ← Each cell ← Each output timing Normalization factor (/sec) ←rectangular source shape (s-type=5) Region for source generation You have to define a rectangle that covers the whole cell for generating source because DCHAIN does not know the source location and shape • Isotropic source (dir=all) • Energy distribution is expressed in successive type (e-type=4) Exercise 29

  30. Exercise 3 dchain.inp Execute PHITS again using γ-ray spectrum calculated by DCHAIN-SP [ S o u r c e ] off s-type = 1 … [ S o u r c e ] totfact = 2.4444E+10 s-type = 5 proj = photon reg = 1 x0 = x1 = y0 = y1 = z0 = z1 = dir = all e-type = 4 ne = 37 $ Energy Flux $ ^^^^ Energy 0.0010 3.8688E+04 0.0100 0.0000E+00 0.0200 0.0000E+00 … • Insert “off” after current [source] section • Copy the 1st [source] section in “tdchain.pht” and paste to “dchain.inp” （cell 1, output timing = 1 m) • Input appropriate rectangle size for source generation Cell 1 is covered by -10cm < x < 10 cm -10 cm < y < 10 cm 0 cm < z < 10 cm Not necessary to be the exact size, but too big size is not recommended → change “dchain.inp” and execute PHITS Exercise 30

  31. Exercise 3 (Answer) dchain.inp [ S o u r c e ] off s-type = 1 … [ S o u r c e ] totfact = 2.4444E+10 s-type = 5 proj = photon reg = 1 x0 = -10.0 x1 = 10.0 y0 = -10.0 y1 = 10.0 z0 = 0.0 z1 = 10.0 dir = all e-type = 4 ne = 37 $ Energy Flux $ ^^^^ Energy 0.0010 3.8688E+04 0.0100 0.0000E+00 0.0200 0.0000E+00 … yz-track.eps，page 3 Photons are generated from the whole region of cell 1 Exercise 31

  32. Table of Contents • Abstract • Parameter settings in [t-dchain] • Output files from DCHAIN-SP • Exercises • Summary Table of Contents 32

  33. Summary • DCHAIN-SP can calculate the time variation of induced activity, decay heat, γ-ray spectrum, and dose rates during irradiation and cooling time • PHITS automatically generate an input file of DCHAIN-SP by using [t-dchain] tally • Combination of PHITS & DCHAIN-SP enables to estimate the long-term variation of induced activity whose information is necessary for the design of nuclear and accelerator facilities Summary 33

  34. Future Plans • Allow multiple [T-Dchain] in a PHITS input file • Improve the function for using γ-ray spectrum calculated by DCHAIN-SP as [source] in PHITS e.g.) automatic normalization, use discrete spectrum • Allow xyz-mesh in [t-dchain] section • Directly implement DCHAIN-SP into PHITS Summary 34

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