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The use of Cf-252 Neutron source Jordan Shafiq Y.Hourani Technical manager City Corporation For Medical And Lab Supply During the past two days you heard many details about two issues. First the aspects of the Peaceful Nuclear program of Jordan. Second the various aspects of nuclear technology namely the nuclear reactor Fuel cycle and radiation Safety . Thisis the out side picture of the nuclear technology. Which every body knows namely a reactor loaded with nuclear fuel which burns (fission ), producing energy, radioisotopes and neutrons. Introduction We are establishing a laboratory for neutron physics as part of postgraduate program in nuclear physics at the Jordan University. It comprises two units: 1- A 107 n\c Cf-252 neutron source, a He-3 neutron detector , irradiation facility and ten types of thin metal foils to be used a threshold detectors for thermal and fast flux determination. 2- A gamma spectrometer, based on NaI (TI) scintillation detector, PCI MCA board with built in signal processing electronics and acquisition software type Genie 2000. this unit is intended for quantitative and analysis of both prompt and delayed gamma spectra produced during and after activation of different samples. The reason of the choice of this particular neutron source, because it produces fission neutrons similar to those of nuclear reactor. So this will provide trained man power, capable of handling various jobs related to nuclear reactor. It is worthy to mention here that this is the first neutron lab in Jordan. Objectives of the lab. The objective of of this laboratory is to qualify graduates and post graduates to carry on the jobs associated with execution of the nuclear program through under standing the processes taking place inside the reactor components during operation . During the past two days You heard many details about two issues, first the aspects of the Peaceful Nuclear program of Jordan Second the various of nuclear technology Namely the nuclear reactor Fuel cycle and radiation Safety . This is the out side picture of the nuclear technology. Which every body knows namely A reactor loaded with nuclear fuel which burns (fission ), producing energy, Radioisotopes and Neutrons. My talk will concentrate on the processes and events taking place inside the reactor and fuel. Main parameters of neutron source 1) Neutron energy spectrum (E) 2) Neutron yield N n/sec source strength. 3) Neutron flux n/sec.cm2 neutron field. Fission Neutron Energy Spectrom Neutron parameters from interaction point of view Neutron energy En MeV→ fast or thermal Cross section σ (En) cm2 strong energy dependent Elastic, inelastic and reaction modes. Specification of the Cf-252 source It is one of the isotopic neutron sources It produces via spontaneous fission (SF) fast neutrons: *spontanous fission constitute about 3% of the total decay of Cf-252 Heavy fission products Promot fission γ activity of the fission products β and γ activity of the fission products. Cf-252 Neutron Source Parameters Neutron Emission Rate 2.34x10 12 n/sec gm 4.4 x109 n/sec Ci 2.2 x x106 n/sec Ci for Am-Be Neutron per fission 3.76 2.5 for induced fission in the reactor Average neutron energy 2.35 MeV Capsule size < 1cc Effective half life 2.68 years Total heating 38.5 w/gr γ Dose at 1 meter 160 RAD / h-gm N Dose at 1 meter 2200 rem / h- gm Nuclear fission of Cf-252 & U-235 The Behavior of neutrons in matter Neutrons interact only with atomic Nuclei The behavior depends on En We will discuss three modes of interaction and their application in actual cases: 1) Elastic scattering. 2) Neutron capture. 3) Inelastic scattering and reaction. The Elastic Scattering It is used in: Neutron Moderation Neutron Protection and Safety The fission of the nuclear fuel take place by thermal neutrons En = 0.025 eV. So we have to reduce En from 2 MeV to 0.025 in order to ensure Sustain chain Reaction Neutron thermalization ( moderation ) is performed via neutron elastic scattering from nuclei. this is efficient in case of light elements such as H, D, C in the form of light ,heavy water and graphite respecttivly. The main Parameter in this process is the LETHARGY ξ = Ln ( E0 / E) Neutron Moderators Nucleus ξ N Average No of events from 2 MeV - 0.025 eV H 1 18 D 0.728 25 Be 0.208 85 C 0.159 115 Absorption cross section is 330,0.46 & 3.3 mb for H,D,C respictively. The neutron Capture Prompt gamma The nucleus capture slow neutron and is put in an excited state which decays in a very short time (<pico second) to its ground state emitting gamma rays of characteristic energy. Inelastic scattering Dominates for fast neutrons X (n ,ńγ) X Nuclear Reactions It needs a threshold energy for the incident neutron. Charged particles and neutrons can be produced.
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