[en] An efficient space-time kinetic method, the Improved Quasi-Static Synthetic Nodal Green's Function Method (IQSYN/NGFM), is presented here. In this method, the multidimensional transient equations are changed into two coupled equations by factorizing the neutron flux into shape function and amplitude function. The theory of NGFM is used to solve the time-and space-dependent shape function equations; the PpqM method, which is very effective for stiff equations, is adopted to obtain the solutions of time-dependent amplitude function equations. To enlarge the time step further, the shape function is expanded again, and the undetermined coefficients are obtained by weighted residual approximation

[en] According to dose calculation formalism recommended by AAPM TG43U1, dose rate constant, radial dose function and anisotropy function of Model 6711(3M) ¹²⁵I brachytherapy source are calculated by Monte-Carlo method. Comparisons with the relative data recommended by AAPM are performed. Dose rate constant, 0.986 cGy·h^-1·U^-1, is in agreement within 2.31% compared to recommended value of TG43U1; values of radial dose function are in good agreement with TG43 and TG43U1; the agreement of anisotropy function with TG43 and TG43U1 is improved with increase of angle and distance. Empiric equations are obtained for radial dose function and anisotropy function by curve and surface fitting. (authors)

[en] To solve the multi-dimensional transient neutron diffusion equations, improved quasi-static Green's function method (IQS/NGFM) is adopted to deal with the temporal problem, which will increase the time step as long as possible so as to decrease the number of times of spatial calculation. The time step of IQS/NGFM can be increased to 5∼10 times longer than that of full implicit differential method. In spatial calculation, the theory of NGFM is used to get the distribution of shape function, with coarse meshes which can be nearly 20 times larger than that of traditional finite differential method. So the IQS/NGFM is considered as an efficient kinetic method

[en] Radiological protection is an important development basis for nuclear science and technology and many others related disciplines, as well as the crucial problem to promote the wider use of ionizing radiation technology. And relevant international organizations and the countries across the world have always adopted the International Commission on Radiological Protection (ICRP) proposals as the fundamental basis to develop guidelines on the radiological protection regulations and standards. The basic recommendations for radiological protection of ICRP always elaborate the general guidelines and principles on radiological protection management, so far have gone through four stages in its history of eighty years. At the end of 2007, ICRP 103 Publication 'The 2007 Recommendations of the International Commission on Radiological Protection' was published to replace ICRP 60 Publication. Review and discussion about the evolvement and enlightenment for the basic recommendations of radiological protection will be of great significance to promote the radiological protection level and the application of nuclear science and technology. (authors)

[en] The medical application of ionizing radiation has the longest history, the most extensive uses and the strongest effect among the multiple applications of ionizing radiation technology. With the development of diagnostic radiology and radiotherapy, for instances, the radiology, the interventional radiology, the nuclear medicine, and the radiation oncology; the infrastructures and teambuilding of medical physics in China has been becoming more and more important and urgent. Fortunately, people in relevant fields have already recognized this situation and made lots of progresses in the recent years, for example, the 221^st Xiangshan Science Conference took 'The Development of Medical Physics' as its main topic in 2004; in recent years, a series of regulations and national standards regarding to the quality assurance and radiological protection of medical exposure and the teambuilding of the relevant departments in hospital have been successively issued; the subject of Medical Physics was opened as both undergraduate and graduated courses in more and more universities (Tsinghua University, Peking University etc); the Committee on Medical Physics was enrolled as a new member of the Chinese Physical Society. Modern medical physics should include 4 parts, medical imaging physics, nuclear medicine physics, radiation oncology physics, and health physics. Protection against ionizing radiation needs to fully cover the development of medical physics, which includes the protection against ianizing radiation in medical uses. This article emphasizes the improvement of the ionizing radiation protection in medical uses, for marking of 30th anniversary of the Journal of Radiation Protection. (authors)

[en] A group of Monte Carlo simulations has been performed for external neutron dosimetry calculation based on a whole-body mathematical model. The Chinese mathematical phantom (CMP) is a mathematical human body model developed based on methods of ORNL (Oak ridge National Laboratory) mathematical phantom series (OMPS), and data from Chinese reference man and reference Asian man. Fluence-to-absorbed dose conversion coefficients of 24 organs and tissues for monoenergetic neutron beams ranging from 10^-9 to 10² MeV were calculated using the Monte Carlo code MCNPX. Irradiation conditions include anterior-posterior, posterior-anterior, right lateral, left lateral, rotational, and isotropic geometries. Results for the different organs are compared with those recommended in International Commission of Radiological Protection (ICRP) publication 74 and results obtained based on the visible Chinese human (VCH) phantom. Overall the consistency among the three sets of data was observed, but significant deviations up to 30-50% were also found in the anterior-posterior (AP), posterior-anterior (PA) and lateral irradiation conditions. Since CMP represents the Chinese population, this work is helpful as a reference to investigate the difference of the neutron induced organ doses due to the anatomical variation between the Chinese and the Caucasians, and that between the average population and an individual. (author)

[en] Nuclear electromagnetic pulse will do harm to the communication and navigation systems. In this paper, the response of antennas on a submarine to nuclear electromagnetic pulse is analyzed, and the induced current in antennas and energy collected by antennas are calculated, which are very important to the protection systems design. (authors)

[en] In this paper, a mixed algorithm based on genetic algorithm (GA) and Gauss-Newton algorithm was presented and applied in analysis of biokinetic data of radiopharmaceuticals through an example. A special software was programmed for data fitting. The results showed that the practically mixed algorithm was better than simple GA or Gauss-Newton algorithm. (authors)

[en] In the case of a small size detector lying inside a bulk of medium, there are two problems in the correction factors calculation of the detectors. One is that the detector is too small for the particles to arrive at and collide in; the other is that the ratio of two quantities is not accurate enough. The method discussed in this paper, which combines correlated sampling with modified particle collision auto-importance sampling, and has been realized on the MCNP-4C platform, can solve these two problems. Besides, other 3 variance reduction techniques are also combined with correlated sampling respectively to calculate a simple calculating model of the correction factors of detectors. The results prove that, although all the variance reduction techniques combined with correlated sampling can improve the calculating efficiency, the method combining the modified particle collision auto-importance sampling with the correlated sampling is the most efficient one. (authors)

[en] To simulate the shielding of mail irradiation system, Monte Carlo method is used to investigate. EGSWIN system, developed by Department of Physics Engineering in Tsinghua University, is adopted to simulate the source. The distribution of energy, angle and intensity of the bremsstrahlung from impingement of electron beam on an Al plate is calculated and a point photon source is defined as a substitute. The calculation and comparison validate the exactness and high efficiency of EGSWIN. (authors)