Investigation of long lived activity produced due to neutron emitting reactions (original) (raw)
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Study for the long-lived gamma background due to neutron emitting calibration reactions
EPJ Web of Conferences
In this article, a detailed theoretical investigation has been done on the long-lived gamma background due to neutron emitting reactions. It mainly focused on the experiments that will be used to calibrate energy with the terminal voltage of an upcoming Facility for Research in Experimental Nuclear Astrophysics (FRENA). Many reactions like (p, n), (p, γ) have been utilized in various accelerator facilities around the globe for energy calibration purposes. Neutron emitting reactions like 7Li(p, n), 13C(p, n), 19F(p, n), 27Al(p, n), etc. have been very commonly used. For such reactions, a significant number of neutrons produced from such experiments can interact with surrounding elements like copper, tantalum, stainless steel (SS304 and SS316), concrete materials,etc. These interactions may create long-lived gamma activity in the vicinity of the accelerator and detection area. Background gammas from these radioactive isotopes can interfere with gamma measurements in future experiments...
Radiation Protection Dosimetry, 2007
A good knowledge of the radiation field present outside the shielding of high-energy particle accelerators is very important to be able to select the type of detectors (active and/or passive) to be employed for area monitoring and the type of personal dosemeter required for estimating the doses received by individuals. Around high-energy electron and proton accelerators the radiation field is usually dominated by neutrons and photons, with minor contributions from other charged particles. Under certain circumstances, muon radiation in the forward beam direction may also be present. Neutron dosimetry and spectrometry are of primary importance to characterise the radiation field and thus to correctly evaluate personnel exposure. Starting from the beam parameters important for radiation monitoring, the paper first briefly reviews the stray radiation fields encountered around high-energy accelerators and then addresses the relevant techniques employed for their monitoring. Recent developments to increase the response of neutron measuring devices beyond 10-20 MeV are illustrated. Instruments should be correctly calibrated either in reference monoenergetic radiation fields or in a field similar to the field in which they are used (workplace calibration). The importance of the instrument calibration is discussed and available neutron calibration facilities are briefly reviewed.
Neutron dosimetry in the particle accelerator environment
Radiation Measurements, 2010
Radiological safety aspects in general and neutron dosimetry in particular, around medium and highenergy particle accelerators pose some unique challenges to the practitioners of radiation protection. This is mainly because the source of radiations are directional, dynamic, pulsed and a mixture of different types. In conventional dosimetry, measurements are done in the units of the quantities in which the radiological protection limits are expressed. In the accelerator environment, measurement of energy and angular distribution of radiations is preferred instead. Research activities being carried out (particularly in India) in the field of neutron dosimetry are discussed. Measurements of neutron ambient dose equivalent directly using conventional rem-meters as well as neutron energy distributions using the time-of-flight technique employing proton recoil scintillators have been done at different directions with respect to light and heavy ion projectiles incident on various thick elemental targets. The observations and conclusions are summarized. Finally, a discussion on the concept of dose and radiological protection and operational quantities is done along with the recommendation of using Evidence theory instead of Bayesian probability in assessing radiological risk.
Use of Gamma Radiation Techniques in Peaceful Applications [Working Title]
Gamma rays are high frequency electromagnetic radiation and therefore carry a lot of energy. They pass through most types of materials. Only an absorber such as a lead block or a thick concrete block can stop their transmission. In many alpha and beta transitions, the residual nucleus is formed in an excited state. The nucleus can lose its excitation energy and move to a "fundamental level" in several ways. (a) The most common transition is the emission of electromagnetic radiation, called gamma radiation. Very often the de-excitation occurs not directly between the highest level of the nucleus and its basic level, but by "cascades" corresponding to intermediate energies. (b) The gamma emission can be accompanied or replaced by the electron emission so-called "internal conversion", where the energy excess is transmitted to an electron in the K, L or M shell. (c) Finally, if the available energy is greater than 2m e c 2 = 1022 keV, the excited nucleus can create a pair (e + ,e À). The excess energy appears as a kinetic form. This internal materialization process is very rare. In this chapter we are presenting two applications of gamma rays: On the one hand, TL dosimeters and field gamma dosimetry are studied, a careful study of the correcting factors linked to the environmental and experimental conditions is performed. On the other hand, we are presenting a calculation method for controlling neutron activation analysis (NAA) experiments. This method consists of simulating the process of interaction of gamma rays induced by irradiation of various samples.
Radiation Measurements, 2010
Recent developments in accelerator physics have led to new challenges for radiation protection dosimetry. Doses have to be determined for workplace fields which are characterized by high-energy radiation, a dominant contribution from neutrons, high intensities and pulsed time structure This may present problems for active measuring devices. As is well known, the ambient dose equivalent is often underestimated by area monitors operating in high-energy neutron fields behind shielding. Therefore, it is desirable to calibrate survey monitors in a characterized neutron field with the type of spectral fluence distribution that is expected behind shielding, i.e. where the main dose from neutrons arises from two peaks with mean energies of about 1 MeV and 100 MeV, respectively. Such a neutron fluence distribution is produced by the irradiation of a Fe-target with 200 MeV/u 12 C-ions. Measurements with the extended range Bonner sphere spectrometer NEMUS of PTB were performed at two positions inside the experimental area Cave A of the heavy-ion synchrotron SIS at GSI. The measured neutron spectra show different fluence contributions for the two peaks at the two positions. The results were compared to Monte Carlo Simulations with MCNPX and FLUKA.
Measurement of Parameters of Neutron Radiation on the Accelerator-Based Epithermal Neutron Source
27th Russian Particle Accelerator Conference (RuPAC'21), Alushta, Russia, 27 September-01 October 2021, 2021
Treatment of oncological diseases using Boron Neutron Capture Therapy (BNCT) is an important issue of our time. Cancer cells accumulate a boron-containing drug, after which they are irradiated with a beam of epithermal neutrons, a nuclear reaction 10 B(n,α) 7 Li occurs, and the products of a nuclear reaction destroy these cells. In BNCT, it is generally accepted that the total dose of ionizing radiation consists of four components: boron dose, dose from fast neutrons, dose from thermal neutrons, and dose of gamma radiation. Dose values and their ratio strongly depend on the neutron flux; therefore, the measurement of the neutron flux (yield) is an urgent task. In this work, the neutron yield was measured by the activation of the target with the radioactive isotope beryllium-7, which is formed in the reaction of neutron generation 7 Li(p,n) 7 Be. It was found that the neutron yield from a specifically manufactured lithium target is in good agreement with the calculated one, which is important for planning therapy.
The neutron field inside high energy and high intensity proton accelerators can produce activation of air. The neutrons backscattered by the concrete walls contribute largely to production of argon-41 and carbon-14 concentration. Detailed knowledge on the neutron spectrum is necessary for the accurate estimation as the neutrons lying above thermal energy up to around 1.5 MeV, can also produce the 41 Ar considerably large amount in addition to the thermal neutrons. Hence, the reflection of neutrons in a typical proton accelerator facility for proton energies in the range 100-500 MeV by concrete walls and the concentration of 41 Ar and 14 C has been studied in detail in using FLUKA Monte Carlo code. The neutron spectra inside the facility clearly indicate the dominance of the neutrons of energies within 1.5 MeV. The estimated neutron albedo/backscatter factors for the secondary generated by the 100 MeV proton beam falling on the copper target have been estimated around 11%. The build up of 41 Ar and 14 C concentration for a 24 hr proton beam irradiation and the decay of the activity for the next 24 hours after the beam shut down are estimated. The Monte Carlo computed saturated 41 Ar concentration values are 2.5 times higher than that of the estimations based on analytical calculations, which assume the activation only by thermal neutrons.
ipenInstituto de Pesquisas Energéticas e Nucleares
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DEPARTAMENTO DE FftlCA E QUÍMICA NUCLEARES CNEN/SP INSTITUTO DE PESQUISAS ENERGÉTICAS E NUCLEARES SAO PAULO-BRASIL Série PUBLICAÇÃO IPEN IN IS Categories and Descriptors A34.10 CAPTURE NEUTRON REACTIONS NICKEL 58 TARGET IPEN -Doc -3052 Publicsçfo aprovada pala CNEN am 09/11187 Nota: A radaçfo, ortografia, eoocalto» a rtvttio final ifo da rsiponiabilldada doll* autortatl.