Conventional liquid scintillator (BC501A) and pulse shape discrimination capable plastic scintillator (EJ-299-33A) based detector of dimension; 5 inch diameter and 5 inch long, have been used to study pulse height response for quasi-monoenergetic neutrons of energy in the range 3 to 15 MeV generated using 7Li(p,n)7Be reaction. Scintillation light output of plastic scintillator having pulse shape discrimination property is found to be 75% of the liquid scintillator at neutron energy (maximum recoil proton energy) of 3 MeV which improves with the increase in energy. Functional dependence of the scintillation light output in terms of recoil protons energy has been determined for the liquid and the plastic scintillator detectors for neutron energy in the range 3 to 15 MeV. This functional dependences were used in the Geant4 simulation to calculate the pulse height responses at several neutron energies.

Positive ion accelerators have gamma and neutrons as prompt radiation. Though neutron yield is less but due to high energy and penetrability it becomes of concern for radiation protection [1]. The information however is important for radiation protection practices. In radiation therapy, the secondary particles generated during the treatment are anticipated to further interact with the surrounding tissues and is now found to be a cause for manifestation of latent cancer. The study of the secondary particle yield is thus critical in heavy ion treatment planning. Since heavy ions, (particularly carbon) are being widely used in therapy, such information becomes important. Also, the data available on neutron yield from heavy ion interaction in thick targets is limited. Organic scintillator detectors have been long recognized for their very good n- separation and are being extensively used in neutron measurements in positive ion accelerator facilities, which have mixed field where gammas are always present with neutrons. This work discusses the integrated neutron yield with its angular distribution and integrated dose from thick Al and C targets bombarded by C with kinetic energy ~ 10 MeV/A and F projectiles at ~ 7.6 MeV/A on thick Al target. The energy integrated yields from the different target projectile systems is compared and presented. Thick targets were studied as it represents any accidental or controlled beam loss situations in the accelerator component, drift tubes or beam dump. The thickness taken is such that the projectile particle loses its complete energy into the target before being completely stopped inside the target.

Arup Singha Roy, K. Banerjee, Pratap Roy, C. Bhattacharya, T.K.Rana, Arijit Sen ,T.K. Ghosh, S. Kundu, G. Mukherjee, S. Mukhopadhyay, R. Ravishankar, S. Manna, R. Pandey, D. Paul, K. Atreya, S. Basu, V. Suman, S. Saha, M. Das, Deepak Pandit, Debasish Mondal, Surajit Pal, G. Mohanto, M. S. Kulkarni, S. Bhattacharya 1Variable Energy Cyclotron centre, 1/AF Bidhan Nagar, Kolkata-700064, India 2Health Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085 3Nuclear Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai-400085 4HBNI, training School Complex, Anushaktinagar, Mumbai-400094 5Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata-700064, India 6(Ex) Variable Energy Cyclotron centre, 1/AF Bidhan Nagar, Kolkata-700064, India *email: a.singharoy@vecc.gov.in

Presently accelerator facilities emphasizes on generating charged particles with enhanced energy and flux. The radiation protection practices at these facilities are considered in civil engineering designs and strictly implemented through different administrative, access control measures (Sarkar in Radiat Meas 45:1476–1483, 2010). However, concern arises from induced activities, during maintenance and decommissioning stages, when sections of accelerator and shielding materials become highly radioactive. Major contribution of induced activity arises from stainless steel (SS-304) beam enclosures and Cu-dumps. Present work focuses on the generation of induced radioactivity profiles with delay counting of SS-304 and Cu along with instantaneous gamma and neutron dose rate measurements at various proton energies for source term estimation.

The thick target neutron yield from a O-16(6+) beam on a thick Al-27 target at 120- and 142-MeV (7.5- and 8.8-MeV/nucleon, respectively) incident energies is presented and compared with theoretical calculations. The theoretical estimates for the yield of a high-energy neutron was obtained using a preequilibrium (PEQ) heavy-ion reaction model (HION), whereas that for the low-energy part was obtained using the standard evaporation models PACE4 and EMPIRE 3.2. In the present data a significant PEQ contribution, similar to 2% to 3% of the evaporation contribution, is observed even at projectile energies below 10 MeV/nucleon. The measured energy spectrum of neutrons for E > 20 MeV (the predominant PEQ region) is in good agreement with the PEQ model code HION.

Energy distributions of neutrons emitted from the interaction of 20 MeV protons incident on a thick Be target were estimated at two angles (0 degrees and 90 degrees) with respect to the incident beam using activation foils as threshold detectors. A recently developed unfolding code GAMCD based on Genetic Algorithm and Monte Carlo methods was used to estimate the neutron spectra by unfolding the counts obtained from the activation foils. These results were compared with the unfolding codes, MAXED and GRAVEL. In the GAMCD code, a guess spectrum as a-priori information need not be provided as input unlike in MAXED and GRAVEL. Results obtained from all these codes matched each other reasonably well. Out of 30 reactions studied experimentally only the selected 15 were found sufficient to generate acceptable spectra in the case of neutrons emitted from the p+Be reaction at 20 MeV. A peak in the energy distributions around 3 MeV at both the measured angles is contributed by the three body breakup process while a broad hump between 6 MeV and 10 MeV only in the forward direction suggests contribution from the pre-equilibrium emissions from the Be-9(p, n)B-9 channel, which also contributes to the small peak observed around 15 MeV. The code GAMCD was found to perform satisfactorily for the present data set.

Neutron yield from 115 MeV 12C projectiles bombarding a thick 27Al target has been measured using the time of flight technique. Nuclear reaction model code PACE and the FLUKA Monte Carlo code are used to calculate the yield and the results are compared with the experimental data. The energy for maximum neutron emission in experimental measurement and reaction code output has a slight disagreement in the extreme forward emission angle but in all other angles it has a close match. The slope of the distribution in general shows good match between the experimental and the reaction code results as well as FLUKA calculations. The maximum energy of the emitted neutrons is observed to decrease with the increasing emission angles.

Fast neutron spectral yield from the interaction of 20 MeV protons with thick Be and C targets are measured using CR-39 detectors. An image analysing program (autoTRAK_n) dedicated for neutron spectrum generation and dose estimation is developed based on the analysis of greylevel variations within each track and is used in the present study. The most important parameters for neutron spectrometry, i.e., track depth (length) and angle of all neutron-induced recoil tracks are determined using autoTRAK_n. The methodology is tested successfully to reproduce the spectra of some standard neutron sources which was reported earlier. In this study, autoTRAK_n is applied to generate neutron spectra from the above mentioned reactions, i.e., Be-9(p, n), C-12(p, n) and the neutron yields (total number of neutrons per projectile) for both the reactions are determined by folding the track density with the detector response. The dose equivalents and H*(10)-to-fluence ratios are also estimated. All these quantities are automatically obtained from the program. The neutron yield and the dose equivalent for Be-9(p, n) reaction are found to be about 4 times higher than that for C-12(p, n) reaction. The present methodology for neutron spectrum generation is found to be simple and effective and does not involve the complex spectrum unfolding procedures. (C) 2013 Elsevier B.V. All rights reserved.

A wavelet transform based denoising methodology has been applied to detect the presence of any discernable trend in (137)Cs and (90)Sr activity levels in bore-hole water samples collected four times a year over a period of eight years, from 2002 to 2009, in the vicinity of typical nuclear facilities inside the restricted access zones. The conventional non-parametric methods viz., Mann-Kendall and Spearman rho, along with linear regression when applied for detecting the linear trend in the time series data do not yield results conclusive for trend detection with a confidence of 95% for most of the samples. The stationary wavelet based hard thresholding data pruning method with Haar as the analyzing wavelet was applied to remove the noise present in the same data. Results indicate that confidence interval of the established trend has significantly improved after pre-processing to more than 98% compared to the conventional non-parametric methods when applied to direct measurements.

In the field of nuclear technology risk assessment due to inadvertent release of radioactivity during mal-operation of a reactor is an important task from the point of risk informed decision making to implement the appropriate protective measures during a radiation emergency. Probabilistic method of risk analysis may not be appropriate due to lack of data or difficulty to specify the appropriate probability distribution because the available information is incomplete or imprecise. In Imprecise probability, input parameters of representative risk model are addressed by fuzzy set theory. Fuzzy vertex method has been used to evaluate risk due to ingestion of food items, grown around the nuclear power plant. The various food items considered are wheat, rice, maize, pulses, vegetables, fruit, milk, mutton, and fish. The radionuclides considered for the present study are Cs-137, Sr-90. Paper presents the detail of the fuzzy vertex method of uncertainty estimation in risk analysis due to ingestion pathway. Ranking of risk (fuzzy numbers) from each specific food is carried out to provide a guideline for ranking the contamination of food items.