Based On The Quality Attributes Of Plutonium Metal 10 </ Sup> B <sup> Target

Metal plutonium is an important nuclear material that used to make nuclear bomb, and the verification technologies of metal plutonium are developing and reaching maturity. Some BF₃ or ³He detectors or fission chambers are used to verifying of the mass of metal plutonium by measuring the counting rate of neutrons and iterative correction. This paper is aimed at discussing a new method of measuring neutrons: indirect gathering neutrons information by detectingγphotons from fissile neutrons which are converted through a ¹⁰B target.This paper is concerned with using spontaneous fissile neutrons form metal plutonium to bombard a ¹⁰B target. 478keVγrays are concomitant with the nuclear reaction ¹⁰B (n,α) ⁷Li from excited ⁷Li* nuclei's deexcitation. The mass of metal plutonium that is being verified can be calculated due to the spectrum and enumerative information that are detected.After investigating related literature at home and abroad, the reports of measuring the mass of metal plutonium by a ¹⁰B target converted method and analogues are undiscovered.This paper employs the Monte Carlo program MCNP in simulating the converting and transporting process of neutrons-photons after modeling, such as selecting materials, adjusting the parameters of target, including thickness, composition, shape, size and position. Various of factors which affect the product ratio of 478keVγrays are investigated to obtain a optimized combination of all parameters which can bring a higher converted efficiency. Then, reflecter and combined target are applied to optimize system further. At the same time, energy and flux of source neutrons are analysed to heighten utilization ratio of source neutrons and reduce wastage ratio of 478keVγrays. Ulteriorly, some corrections such as thermal neutron S(a,P) treatment, body source correction and fissile spectrum correction are done to the simulant system to improve reliability of computing result. The result of simulation of optimizing model accomplishes a gamma production ratio above 10^-5, sufficing the detection of kilogram grade metal plutonium.This paper aslo carrys out a series of experiments about measuring the mass of metal plutonium by a ¹⁰B target converted method. The experiments consistit of three parts: Firstly, setting up experiment systems, including plutonium components, boracic target and spectrograph. Secondly, measuring 478keVγrays counting rate under every target parameters and detect conditions respectively to confirm reasonable parameters and conditions and validate the correctness of prophase theoretical calculation results. Thirdly, reckoning mass of metal plutonium by system calibration.Reckoning mass of metal plutonium by system calibration under these systems and conditions can supply an overall uncertainty of mass of metal plutonium of about 10%, for a common verification scene that detect time is about 10～20min and mass of metal plutonium is about kilogram-grade.