# NJOY Automation¶

The purpose of this module is to enable simple generation of cross section libraries and avoiding the need to write NJOY input files by hand. A complete processing of an evaluated datafile is done by invoking methods of the Njoy99 class. This class contains the various instance variables and methods required to use NJOY in the simplest possible way.

For a complete specification for the classes in the njoy module, please refer to the Library Reference entry for NJOY Automation – pyne.njoy.

## Njoy99 Attributes¶

The generation of cross section libraries is controlled by a number of attributes of the Njoy99 class. These attributes are passed as input parameters to NJOY for setting options, temperatures, tolerances, etc.

self.evaluationName

Path of directory where you want to store the pendf, gendf, draglib and acelib files. The path can be prefixed by /tmp/ to force the files to be created locally on the /tmp directory.

self.legendre

Order of Legendre polynomials for neutrons (= 1 for linear anisotropy in LAB - default)

self.legendregg

Order of Legendre polynomials for gamma particles (default: = 6)

self.nstr

Option for a particular neutron group structure (= 22 for the XMAS 172–group structure)

self.gstr

Option for a particular gamma group structure, for producing neutron–gamma coupled sets (equal to zero by default)

self.iwt

Type of flux weighting in groupr (= 1 for user-defined spectra; = 3 for 1/E weighting; = 4 recommended/default)

self.wght

User-defined weighting spectra to be used if self.iwt = 1. Given as “””–delimited string.

self.autolib

Three-component tuple containing the energy limits of the autolibs (must correspond to energy-group limits) and the elementary lethargy width of the autolibs

self.temperatures

Value of temperatures at which the cross sections are generated

self.hmat

Material name that is included in the DRAGLIB – User dependent

self.mat

mat number of nuclide under consideration

self.hmatgg

Photo-atomic element name that is included in the DRAGLIB – User dependent

self.matgg

Photo-atomic mat number of element under consideration

self.za

ZA number, mainly required for generation of S(α, β) cross section in acer

self.scatName

Name of S(α, β) cross section identifier for inclusion in xsdir

self.suff

The suffix to be attached to nuclide in ACELIB - User dependent

self.evaluationFile

Path of the evaluated datafile.

self.scatteringLaw

Path of file having thermal scattering data (default = None)

self.scatteringMat

mat number in scattering data file

self.fission

Choice for including delayed neutron fission data in groupr module

self.ss

Two-component tuple containing energy limits in eV for the self-shielding domain

self.potential

Value of the potential cross section used in the flux calculator of groupr

self.dilutions

Tuple containing the dilution values that need to be considered for calculation of resonance integrals and probability tables

self.dirName

Directory name to store data for independent verification of ACELIB.

self.tempace

Temperature at which ACELIB needs to be generated.

self.eFiss

Fission energy in MeV. Used in cases where this value is not available in the evaluation.

self.branchingNG

Radiative capture isomeric branching ratio (default = None). If you use this value, don’t forget to reset it to None after the isotope is completed.

self.branchingN2N

N2N isomeric branching ratio (default = None). If you use this value, don’t forget to reset it to None after the isotope is completed.

self.purr

Set to 1 to use purr module. By default, use unresr.

self.oldlib

Name of an existing DRAGLIB file that is modified by self.draglib().

## DRAGLIB Generation¶

The modules that will be used in the generation of DRAGLIB are MODER, RECONR, BROADR, PURR (if dilutions present), THERMR, GROUPR and DRAGR. Figure 3 gives the flow chart for generation of DRAGLIB formatted library. It is important to identify the nuclides that are needed to be included as part of library and corresponding evaluated datafiles from respective data centers need to be compiled in a particular directory. This will help in cross verification and assessment at any stage of library generation. In this section specific examples of elements will be provided to understand the nuances of DRAGLIB library generation. The examples will be such that all the reactor type materials will be chosen. They are scattering material (heavy water), structural material (Zirconium), fission product (Xe-135), Actinide (U-235). A special example for burnup dependent data will also be provided. For isotopes that have resonances and whose presence in fuel can alter the flux in the energy region between 2.76792 eV and 1.66156e4 eV, cross sections are generated at specific dilution values. The choice of dilution values is shown in Table-1 and shown in Figure 4. The value for potential scattering cross section is obtained using the Fortran code getmf2.f which is provided by IAEA. Using this code, and the evaluated datafile for the particular element, one can obtain the value for self.potential. In general we cannot provide more than ten temperature values and ten dilution values. If one has to generate cross sections for more than ten dilution values, it has to be split, as shown in example for U-235. After each “self.dragr()” run, one will obtain a file “out draglib elementname”. Energy information is recovered from this ascii file by method self.burnup() and is collected in a file named ‘chain’ + self.evaluationName (stored on directory self.evaluationName). Sometimes, it is likely that fission energy is not provided in the tape. In that case one obtains “????????” in the “out draglib elementname” file. In that case, one has to obtain the energy value from some other source (typically, from another evaluation) and provide it using the self.eFiss instance variable, even if one does not use the tape for generation of multigroup data.

File 8 of ENDF evaluation contains half-lives, decay modes, decay energies, and radiation spectra for most isotopes. Information concerning the decay of the reaction products is also given in this file. In addition, fission product yield data (MT=454 and 459) for fissionable materials and spontaneous radioactive decay data (MT=457) for the nucleus are included.

File 8 information is processed by module DRAGR. A large number of fission products are included in the evaluated file for each element capable of undergoing fission. For example, in the fission product yield data file included in ENDF/B-VI rel. 8, one can notice that there are information of 1232 fission products for 0.0253 eV fission of 233 U, 1247 fission products for 0.0253 eV fission of 235 U etc. But the evaluations are not available for all the nuclides, as most of them have very short half-lives and in the reactor context, can be considered insignificant. They are subsequently lumped by a procedure that is built in DRAGR. If there are nuclides with long half lives, but are not available as evaluated files, a warning is provided before lumping the corresponding element. The DRAGR user has the complete control over the lumping process. DRAGR currently has no capability to produce pseudo fission product, i.e., custom library isotopes made from the combination of many minor ENDF fission products. All the isotopes missing in the ’chain’ + self.evaluationName file are tested against a lumping criterion and are lumped. The criterion for lumping a depleting isotope is a half life less than thirty days and a fission yield less than 0.01%. If this criterion is not met, this isotope is lumped and a warning message is issued.

Information on energies for various reaction types like (n, $$\gamma$$), (n, f), (n, 2n), (n, 3n), (n, 4n), (n, $$\alpha$$), (n, p), (n, 2 $$\alpha$$), (n, np), (n, d), (n, t) are recovered from earlier DRAGR single-isotope calculations and used for inclusion in relevant depletion data in DRAGLIB format. The fission energy (n, f) is obtained from MF1 MT458 and the energy from delayed betas and gammas are subtracted from it. Information regarding energies for other reactions are derived by DRAGR from MF3. The corresponding MT numbers for the above mentioned reactions (other than (n, f)) are 102, 16, 17, 37, 107, 103, 108, 28, 104, 105 respectively. The complete information required to do the depletion calculations is provided in ten specific records of the DRAGLIB file.

### Heavy Water¶

Heavy water is used in CANDU reactors as moderator and coolant. So it is important to generate consistent data for efficient analysis of CANDU lattices. The instance variables and methods that will be used are

candu.hmat = "H2_D2O"
candu.temperatures = (293.6, 323.6, 573.6)
candu.mat = 128
candu.evaluationFile = "/home/user/Tripoli4/JEF2/eval/jef2.neutron.H2.bcd"
candu.scatteringLaw = "/home/user/Tripoli4/JEF2/eval/jef2.neutron.D_D2O.bcd.therm"
candu.scatteringMat = 11
candu.fission = None
candu.dilutions = None
candu.pendf()
candu.gendf()
candu.draglib()


### Zirconium¶

Zirconium is used in CANDU reactors as cladding material and also for pressure tube and calandria tube. Zirconium has some resonances and as a result of this it is important to generate the cross sections of Zirconium for certain dilution values. The instance variables and methods that will be used are

candu.hmat = "Zr0"
candu.temperatures = (293.6, 323.6, 573.6)
candu.mat = 4000
candu.evaluationFile = "/home/user/Njoy99/evaluations/database/jendl306.asc"
candu.fission = None
candu.ss = (2.76792, 1.66156e4)
candu.potential = 6.5144
candu.dilutions = (1.e10, 10000.0, 3549.18335, 1259.67004, 447.079956, 158.676849, \
56.3173141, 19.9880447, 7.09412289, 2.51783395)
candu.pendf()
candu.gendf()
candu.draglib()


### Xenon-135¶

Xenon is a very important fission product in nuclear reactors. It is very important to estimate the number density of this nuclide as a function of burnup. This will help in estimating reactivity variations due to change in concentration of the nuclide. By using makeFp option, we avoid generating scattering matrices in (NG x NG) format, where NG is number of groups. We instead generate only the scattering matrices along the diagonal.

candu.hmat = "Xe135"
candu.temperatures = (293.6, 323.6, 573.6)
candu.scatteringLaw = None
candu.legendre = 0
candu.fission = None
candu.dilutions = None
candu.mat = 5458
candu.evaluationFile = "/home/user/Njoy99/evaluations/database/jendl310.asc"
candu.makeFp()


### Uranium-235¶

U-235 is one of the most prevalently used fissile material for energy production. In case of CANDU reactors, natural uranium is used as fuel, where weight (%) of U-235 is 0.711.

candu.hmat = "U235"
candu.temperatures = ( 293.6, 323.6, 573.6, )
candu.mat = 9228
candu.evaluationFile = "/home/user/Njoy99/evaluations/database/U-235"
candu.fission = 2
candu.ss = (2.76792, 1.22773e5)
candu.potential = 11.6070
candu.dilutions = (1.e10, 94.5317612, 56.3173141, 33.5510521, 19.9880447, \
11.9078817, 7.09412289, 4.22632504, 2.51783395, 1.5)
candu.pendf()
candu.gendf()
candu.draglib()
candu.dilutions = (1.e10, 10000.0, 5957.50244, 3549.18335, 2114.42676, 1259.67004, \
750.448669, 447.079956, 266.347961, 158.676849)
candu.pendf()
candu.gendf()
candu.draglib()


### Process Burnup¶

It is important to identify the tapes provided by evaluators which contains information on fission yields and decay chains. These files are provided as mentioned below, along with the chain(self) file mentioned already.

candu.fissionFile = "/home/user/Njoy99/evaluations/database/TAPE.107"
candu.decayFile = "/home/user/Njoy99/evaluations/database/TAPE.106"
candu.burnup()


## ACELIB Library Generation¶

The modules that will be used in the generation of ACELIB are MODER, RECONR, BROADR, PURR (if dilutions present), THERMR, and ACER. Figure 3 gives the flow chart for generation of ACE formatted library. In this section specific examples of elements will be provided to understand the nuances of ACELIB library generation. The examples will be along the same lines as that for DRAGLIB library generation, i.e scattering material (heavy water), structural material (Zirconium), fission product (Xe135), Actinide (U-235). The prsent script is such that the ACELIBs are appended in a single file named “acecandu” and is available in the same directory as the draglib file. The other important file that is generated is the “acexsdir”, which contains the information about the nuclides for which the cross sections are generated and the temperature at which the ACELIB is generated. A small code has been written-“append.f”, which will read the file acecandu and acexsdir and create the file “myxsdir”. This file has to be appended to existing xsdir file provided with MCNP5 data. It is important to provide suffix values “self.suff” for different temperatures. This will be automatically appended to the ZA value and written in main ACELIB and xsdir file. Care should be taken not to repeat the “.suff” value already used in xsdir file for other evaluations. For each temperature provide different “self.dirName” so that all the required data for comparison with PENDF tape generated using PREPRO code is made possible. The “self.comp()” does the task of verifying the ACELIBs generated, and is described in the next section. The example provided here helps in generating ACELIB alone. In case a DRAGLIB file also is to be generated, please refer to Figure 2.

### Heavy Water¶

candu.hmat = "H2_D2O"
candu.temperatures = (293.6, 323.6, 573.6)
candu.mat = 128
candu.za = 1002
candu.scatName = "hwtr"
candu.evaluationFile = "/home/user/Tripoli4/JEF2/eval/jef2.neutron.H2.bcd"
candu.scatteringLaw = "/home/user/Tripoli4/JEF2/eval/jef2.neutron.D_D2O.bcd.therm"
candu.scatteringMat = 11
candu.fission = None
candu.dilutions = None
candu.pendf()
candu.dirName = "D2O-1"
candu.tempace = (293.6,)
candu.suff = 0.20
candu.acer()
candu.comp()
candu.dirName = "D2O-2"
candu.tempace = (323.6,)
candu.suff = 0.21
candu.acer()
candu.comp()
candu.dirName = "D2O-3"
candu.tempace = (573.6,)
candu.suff = 0.22
candu.acer()
candu.comp()


### Zirconium¶

candu.hmat = "Zr0"
candu.temperatures = (293.6, 323.6, 573.6)
candu.mat = 4000
candu.za = 40000
candu.evaluationFile = "/home/user/Njoy99/evaluations/database/jendl306.asc"
candu.fission = None
candu.dilutions = (1.e10, 10000.0, 3549.18335, 1259.67004, 447.079956, \
158.676849, 56.3173141, 19.9880447, 7.09412289, 2.51783395)
candu.pendf()
candu.dirName = "Zr-1"
candu.tempace = (293.6,)
candu.suff = 0.20
candu.acer()
candu.comp()
candu.dirName = "Zr-2"
candu.tempace = (323.6,)
candu.suff = 0.21
candu.acer()
candu.comp()
candu.dirName = "Zr-3"
candu.tempace = (573.6,)
candu.suff = 0.22
candu.acer()
candu.comp()


### Xenon-135¶

candu.hmat = "Xe135"
candu.temperatures = ( 293.6, 323.6, 573.6, )
candu.scatteringLaw = None
candu.legendre = 0
candu.fission = None
candu.dilutions = None
candu.mat = 5458
candu.za = 54135
candu.evaluationFile = "/home/user/Njoy99/evaluations/database/jendl310.asc"
candu.makeFp()
candu.dirName = "Xe135-1"
candu.tempace = (293.6,)
candu.suff = 0.20
candu.acer()
candu.comp()
candu.dirName = "Xe135-2"
candu.tempace = (323.6,)
candu.suff = 0.21
candu.acer()
candu.comp()
candu.dirName = "Xe135-3"
candu.tempace = (573.6,)
candu.suff = 0.22
candu.acer()
candu.comp()


### Uranium-235¶

candu.hmat = "U235"
candu.temperatures = (293.6, 323.6, 573.6)
candu.mat = 9228
candu.za = 92235
candu.scatteringLaw = None
candu.legendre = 0
candu.evaluationFile = "/home/user/Njoy99/evaluations/database/U-235"
candu.fission = 2
candu.dilutions = (1.e10, 10000.0, 5957.50244, 3549.18335, 2114.42676, \
1259.67004, 750.448669, 447.079956, 266.347961, 158.676849)
candu.dirName = "U235-1"
candu.tempace = (293.6,)
candu.suff = 0.20
candu.acer()
candu.comp()
candu.dirName = "U235-2"
candu.tempace = (323.6,)
candu.suff = 0.21
candu.acer()
candu.comp()
candu.dirName = "U235-3"
candu.tempace = (573.6,)
candu.suff = 0.22
candu.acer()
candu.comp()