P HI T S Evaluation of Induced Radioactivity: Connection between PHITS & DCHAIN-SP Multi-Purpose Particle and Heavy Ion Transport code System Title1 Last update 2015/06

Purpose2 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

Glossary3 Terminology Radioactivity ： Radiative 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

Table of Contents4 1.Abstract 2.Parameter settings in [t- dchain] 3.Output files from DCHAIN-SP 4.Exercises 5.Summary Table of Contents

Overview5 Flowchart of Connection Calculation PHITS Particle Transport Simulation 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) Output files from [t-dchain] DCHAIN-SP 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 Calculation Results Induced activity （ Bq) Decay heat （ W ） Emitted γ-ray spectrum during and after irradiation

6 Let’s Try! Execute PHITS with “dchain.inp” (send to -> PHITS) (150pH2O.out,.dtrk,.dyld, dch_link.dat, n.flux_**, nmtc_yield are generated) （ 150pH2O.lst,.act,.pht,.ang,.gsd,.gso,.alr,.eps are generated ） Time variation of induced activity in each cell 150pH2O.eps Overview Execute DCHAIN-SP with “150pH2O.out” (send to -> DCHAIN)

7 Output files from [t-dchain] 150pH2O.out: Basic input file for DCHAIN-SP （ File name is specified by “file=“ in [t-dchain]) 150pH2O.dyld: Nuclear yields calculated by [t-yield] nmtc_yield: Nuclear yields written in DCHAIN-SP input format 150pH2O.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

8 Output files from DCHAIN-SP 150pH2O. ｌｓｔ : Basic output file (similar to “phits.out” in PHITS) 150pH2O.act: Main output (Induced radioactivity, decay heat, 150pH2O.pht: γ -ray spectrum written in PHITS input format 150pH2O.ang: Induced radioactivity, decay heat, dose rates 150pH2O.eps: Graphs generated by ANGEL using above file 150pH2O.gsd: γ -ray spectrum written in MCNP input format 150pH2O.yld: Nuclear yields when irradiation and cooling is finished 150pH2O.gso: Origin nuclei and their contribution for emitting γ - ray 150pH2O.alr: Induced radioactivity and decay heat Overview dose rate, emitted γ -ray spectrum) written in ANGEL input format

9 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 Overview Important Notice Only one [t-dchain] is allowed in an PHITS input file “Mesh” should be “reg” and combined cells cannot be specified in [t- dchain] Limitation of Current Version

Table of Contents10 1. 使用方法の概要 2.[t-dchain] のパラメータ設定 3.DCHAIN-SP の出力ファイル 4. 演習 5. まとめ 実習内容

Parameter Setting11 Check Calculation Result 150 MeV Proton Water Vacuum Irradiate 150 MeV protons into 3 cylindrical water tanks (10 radius x 10 cm height each) yz-track.eps

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 file(21) = c:/phits/dchain-sp/data # dchain data folder name 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 Folder name for DCHAIN-SP libraries must be specified by file(21) Parameter Setting

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 = file = 150pH2O.out timeevo = m m 0.0 outtime = 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

file ： Input file name for DCHAIN-SP ・ Following file names are not allowed because PHITS or DCHAIN-SP automatically generate them 14 Parameters in [T-Dchain] [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = file = 150pH2O.out timeevo = m m 0.0 outtime = 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 ***.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

mesh ： should be “reg” at this moment reg = 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 15 [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = file = 150pH2O.out timeevo = m m 0.0 outtime = 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 Example: 6.0 m 1.0 → irradiate 6 minutes by full amplitude 50.0 m 0.0 → cool 50 minutes Parameter Setting Parameters in [T-Dchain] s (second), m (minute), h (hour), d (day), y (year) You have to insert space before and after them

outtime ： Number of output timing 16 Parameters in [T-Dchain] [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = file = 150pH2O.out timeevo = m m 0.0 outtime = 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 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

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

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

Table of Contents19 1. 使用方法の概要 2.[t-dchain] のパラメータ設定 3.DCHAIN-SP の出力ファイル 4. 演習 5. まとめ 実習内容

20 Basic Output File (*.lst) *** error message from s.rdinpt *** total flux of neutron irradiation was less than 0. no. of region= 1 jmode= 2 fluxs= E+00 *** error message from main *** primary file is not found. file name = /spd-dcylib ↑ Neutron flux is 0 in some cells ↑ Library file is found DCHAIN-SP Output 150pH2O.lst ： Similar to “phits.out” in PHITS Errors messages might be given at the end of the file 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) Solution1: Correct “file(21)” in [parameters] section & Execute PHITS again Solution2: Correct “dch_link.dat” by yourself -> easier

150pH2O.act: Induced activity, decay heat & dose rates 21 Main Output File (*.act) Calculated results are given for each cell and output timing ← Output timing Induced Activity (Bq) Dose rate (uSv/h*m 2 ) Decay Heat (W) ← Cell Many output files are generated from DCHAIN-SP (see its manual in more detail) DCHAIN-SP Output

22 Graphic Output File (*.eps) 150pH2O.eps Time variation for each cell (dot+line) & total (thick line) Induced activity Decay heat β decay heat * γ decay heat * α decay heat * Dose rate ** ** Ambient dose equivalent H*(10) rate at 1 m away from the point source * Decay heat due to β-ray, γ-ray, and α-ray emissions, respectively DCHAIN-SP Output

Table of Contents23 1. 使用方法の概要 2.[t-dchain] のパラメータ設定 3.DCHAIN-SP の出力ファイル 4. 演習 5. まとめ 実習内容

24 Check current input & output Induced activity becomes the maximum at 6 minutes (360 seconds) [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = file = 150pH2O.out timeevo = m m 0.0 outtime = 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 pH2O.eps Activity becomes smaller with increase of depth （ cell 1 ＞ cell 2 ＞ cell 3 ） Exercise dchain.inp

Exercise25 Exercise 1 Change irradiation time [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = file = 150pH2O.out timeevo = m m 0.0 outtime = 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 5 minutes by a half amplitude Cool 1 hour → Execute PHITS & DCHAIN dchain.inp 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

26 Exercise １ (Answer) Induced activity becomes larger at 20 minute (1200 seconds) after the first irradiation [ T - D C H A I N ] $ must section for DCHAIN title = 150MeV proton mesh = reg reg = file = 150pH2O.out timeevo = m m m h 0.0 outtime = 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 pH2O.eps Exercise dchain.inp

27 Exercise 2 Change output timing (after 30 th line) ! --- irradiation time --- itstep = E+00 m E E+00 m E E+01 m E E+00 h E+00 ! --- output time --- itout = E+00 m E+00 m E+00 m E+01 m E+01 m E+01 m E+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) itout: Number of output timings 150pH2O.out corresponding to “outtime” in [t- dchain] →Change “150pH2O.out” and execute only DCHAIN- SP （ You can reduce the number if you use a slow computer ） Exercise

28 Exercise 2 (Answer) You do not have to execute PHITS again if you would like to change only the irradiation time and output timing (after 30 th lines) ! --- irradiation time --- itstep = E+00 m E E+00 m E E+01 m E E+00 h E+00 ! --- output time --- itout = E+00 m E+00 m E+00 m E+00 m E+01 m E+01 m E+01 m E+01 m E+01 m E+01 m E+01 m 150pH2O.out Exercise

150pH2O.pht ： γ -ray spectrum written in the PHITS input format 29 Use γ -ray spectrum as [source] ← Each cell ← Each output timing Region for source generation 150pH2O.pht 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 ←rectangular source shape (s-type=5)

30 Exercise 3 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 ] s-type = 5 proj = photon reg = 1 x0 = x1 = y0 = y1 = z0 = z1 = dir = all e-type = 4 ne = E E E+00 … 1. Insert “off” after current [source] section 2. Copy the 1 st [source] section in “150pH2O.pht” and paste to “dchain.inp” （ cell 1, output timing = 1 m) 3. Input appropriate rectangle size for source generation dchain.inp → change “dchain.inp” and execute PHITS Cell 1 is covered by -10 cm < 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 Exercise

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

Table of Contents32 1. 使用方法の概要 2.[t-dchain] のパラメータ設定 3.DCHAIN-SP の出力ファイル 4. 演習 5. まとめ 実習内容

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 Summary33 Summary

34 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 Future Plans