Maitreyee Nandy

P K Saran

P K Sarkar

Sneh Lata Goyal

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Proceedings of the DAE Symp. on Nucl. Phys. 57 (2012) 462
Available online at www.sympnp.org/proceedings
 
Production of radio-isotopes 
197
Hg and 
198
Au from 
198
Hg 
P. K. Saran
1
, Maitreyee Nandy
2
, P. K. Sarkar
3 
and Sneh Lata Goyal
1,*
 
1
Deptt. of Applied Physics, Guru Jambheshwar University of Sci. & Tech., Hisar-125001, Haryana, INDIA 
2 
Saha Institute of Nuclear Physics, Kolkata – 700064, INDIA 
3
 Health Physics Division, Bhabha Atomic Research Centre, Mumbai - 400085, INDIA  
 
* Email: goyalsneh@yahoo.com 
 
Introduction 
 
Studies on excitation functions of neutron 
induced reactions are of considerable importance 
for testing nuclear models as well as for practical 
applications. Mercury can be a suitable material 
for spallation neutron source in an accelerator 
driven system (ADS) if corrosion, due to 
chemical wetting, gradient mass transfer, and 
high density heat generation are taken care of. In 
order to design the target system, estimation of 
induced activity in the target is important among 
other factors. In an ADS this radioactivity is 
induced by neutrons along with that by the 
primary projectile. An ADS is operated at a few 
GeV beam energy, but often logistic studies are 
carried out at much lower energies. Quantitative 
knowledge of the induced activity at such 
operating parameters is important for proper 
planning of the experiments [1].  
  The aim of the present work is to determine 
the excitation functions of 198Hg (n,  2n) 197Hg 
and 198Hg (n,  p) 198Au reactions for 1-50 MeV 
energy using statistical and pre-equilibrium 
nuclear reaction model codes. This will help us 
to determine the total yield and induced activities 
due to these radio nuclides. The computed 
excitation functions are compared with and the 
reported measured data and cross sections from 
ENDF database [2]. 
  
Model codes calculations 
 We have used ALICE-91, TALYS and 
EMPIRE 3.1 for our study. 
 
ALICE-91 
 ALICE-91 is a well known code [3] that 
calculates pre-equilibrium (PEQ) cross-sections 
using hybrid or  geometry dependent hybrid 
( G D H )  model and evaporation or compound 
nuclear (E Q) through Weisskopf–Ewing (WE) 
formalism. GDH model is the modified version  
 
of hybrid model to include the effect of diffuse 
nuclear  surface. In the present work we have 
used optical model inverse cross-section and 
Fermi gas level density options in ALICE.  
 
TALYS-1.2 
 In TALYS-1.2 [4] code direct (DIR) 
reactions are calculated using rotational optical 
model. Two component exciton model estimates 
the PEQ particle emission and the angular 
distribution of these PEQ particles is determined 
using Kalbach systematics. EQ emission is 
calculated in the framework of Hauser-Feshbach 
formalism in competition to fission. In this work 
we have used numerical transition rates with 
energy dependent matrix element for exciton 
model (preeqmode=2), Fu’s pairing energy [5] 
correction (pairmodel=1) and constant 
temperature + Fermi gas level density 
(ldmodel=1).  
 
EMPIRE-3.1 
 Nuclear reaction code EMPIRE-3.1 code 
[6], accounts for three major nuclear reaction 
mechanism, i.e., direct (DIR), pre-equilibrium 
(PEQ) and compound nuclear reactions. Binding 
energies are determined using masses 
recommended by Audi et al. [7], or using 
theoretical predictions of Moller and Nix [8]. 
The code uses several PEQ models like 
PCROSS, multistep direct (MSD), multistep 
compound (MSC) and Hybrid Monte-Carlo 
Simulation (HMS). Statistical Hauser–Feshbach 
theory with different level density options is 
used to describe the EQ emissions. We have 
used the following input options of the code: 
(a) EMPIRE1: Empire specific level densities, 
HMS and PCROSS PEQ models. 
(b) EMPIRE2: Generalized super fluid model 
level densities, HMS and PCROSS PEQ models. 
Proceedings of the DAE Symp. on Nucl. Phys. 57 (2012) 463
Available online at www.sympnp.org/proceedings
 
 
Results and Discussion 
 
 
Fig1: Excitation function of 197Hg from n+ 198Hg 
 
 
 
 
Fig2: Excitation function of 198Au from n+ 198Hg 
 
We have shown in figures 1 and 2, the 
excitation functions of 197Hg and 198Au produced 
in neutron induced reactions on 198Hg. In fig. 1 
the calculated excitation functions for 197Hg are 
compared with experimental data available 
between 13 – 16 MeV. Here the measured cross 
sections are fairly reproduced by TALYS and 
EMPIRE calculations, but they are overpredicted 
by ALICE-91. This is due to multiple PEQ 
emission and overprediction of EQ cross section 
by WE formalism considered in ALICE. Both 
for TALYS and EMPIRE results, the peak of the 
excitation function is shifted towards right, 
which is attributed to the Fermi gas level density 
formalism adopted. Beyond 15 MeV EMPIRE1 
and EMPIRE2 results vary significantly which 
shows that EQ emission, which is strongly 
influenced by level density of residual nucleus, 
plays an important role in this reaction. In the 
case of 198Au, our analysis showed that below 20 
MeV, TALYS and EMPIRE calculations agree 
well with ENDF and TENDL results. Beyond 20 
MeV the TENDL cross section are better 
reproduced by TALYS whereas EMPIRE 
produces an oscillation in the calculated 
excitation function.    
                                                                   
Conclusion 
This work on estimation of excitation 
function of 197Hg and 198Au showed that TALYS 
and EMPIRE calculations reproduce the 
measured cross sections for 197Hg. ALICE 
largely over predicts the measured cross sections. 
It has also been observed that though the 
excitation functions calculated by the different 
models vary from one another, the total cross 
sections integrated over the entire energy range 
agree fairly with one another. Thus these 
reaction model codes can be used for estimation 
of total induced activity in a system. 
 
Acknowledgement: 
 Financial support from DAE-BRNS, 
BARC, Mumbai   by   giving   major research 
project (Sanction No. 2011/36/10-BRNS/0494) is 
thankfully acknowledged. 
 
References 
[1] H Hayashi, et al,  Annals of Nuclear 
Energy 38  637  (2011). 
[2] www.nds.iaea.org/exfor/endf.htm Exptl. & 
Evaluated  Nuclear Reaction Datafiles 
(ENDF) Database  version of September 
05, (2011). 
[3]  M Blann Code ALICE/85/300, LLNL Report 
 NO.  UCID-20169 (1985). 
[4]    A J Koning S Hilaire and M C Duijvestjjn, 
“TALYS: Comprehensive nuclear reaction  
modeling”, Proc. Int. Conf. on Nuclear 
Data for Sci. and Tech.—ND2004 AIP vol. 
769 (eds) R C Haight, et al, 1154–1159 
(2005). 
[5]   C.Y. Fu, Nucl. Sci. Eng. 86, 344 (1984). 
[6] M Herman, et al, “EMPIRE: nuclear 
reaction model code system for data 
evaluation”, Nucl. Data Sheets 108, 2655 
(2007) 
[7] G Audi, A H Wapstra Nucl. Phys. A595 
409 (1995). 
[8] P Moller, J R Nix At. Data Nucl. Data 
 Tables 26 165 (1981). 


Production of radio-isotopes 197 Hg and 198 Au from 198 Hg

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Production of radio-isotopes 197 Hg and 198 Au from 198 Hg

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