放射源倒装的防护管理与监测

放射源倒装的防护管理与监测郁惠莲，冯平恩（陕西省卫生防疫站，西安）随着我国核技术的发展，射线辐照在农业育种、医疗器械及药品辐射灭菌、食品保鲜、辐射杀虫、工业橡胶、塑料辐射改性等领域的应用日益广泛。建立辐照装置，倒装源是项重要的工作。在倒装源过程中，除...

On-Line Monitoring of Grinding Status Based on Rough Set Theory

This paper focuses on the new approach of on line monitoring of grinding burn and wheel wear based on the rough set theory. This method adopts the grinding chip flow thermal signal, and acquires identification rules by establishing sensitive characteristic parameters and constructing the knowledge system through continuum attribute discretization, attribute reduction and knowledge acquisition, and then monitors grinding burn and wheel wear in accordance with the acquired rules. The experiment results show that the new method is effective.

Energy dissipation of coal and rock during damage and failure process based on EMR

The physical and mechanical change processes of coal and rock are closely related to energy transformation,and the destruction and failure of coal and rock is an instability phenomena driven by energy change.However,the energy change of large-scale coal rock in the mine site is hardly calculated accurately,making it difficult to monitor coal-rock systematic failure and collapse from the perspective of energy.By the energy dissipation EMR monitoring system,we studied the damage and failure of coal and rock with bursting liability from the energy dissipation point using the geophysical method-EMR,and explored the energy dissipation characteristics during uniaxial compression and their main influencing factors.The results show that under displacement-control loading mode,there are 2 types of energy dissipation trends for both coal and rock with bursting liability.The type Ⅰ trend is a steady increase one during the whole process,therein,the energy dissipation of rock samples is accelerated at the peak load.The type Ⅱ trend energy is a W-shaped fluctuating one containing 6 stages.Under load-control loading mode,there is one energy dissipation trend of shock downward-steady rise.Besides that,rock samples also present a trend of 4 stages.The energy dissipation characteristics of coal and rockduring loading failure process can be used as effective criteria to assess whether they are in a stable or destructive stage.The factors influencing energy dissipation in the loading failure process of coal and rock mainly include strength,homogeneity,and energy input efficiency.

Daily Variability of Radon Gas in Brazilian Tropics Near Ground Level Surface

By monitoring the ionizing radiation from minute to minute in S^o Jos6 dos Campos, SP, Brazil （230 S, 450 W） using Geiger counter, during January to August 2015, it has confirmed the presence of radon gas in these measures. The observation confirms the existence of a periodicity of 24 hours through the technique （Fast Fourier Transform） applied to the data set, and this cycle can be better visible in longer dry periods. On rainy days or with heavy fog in the region, this periodicity is modified or even disappears. As Geiger do not detect alpha particles due to absorption in the walls of the sensor tube, it measured X and gamma rays coming from the radon gas progeny. Radon gas （222Rn） has a half-life of 19.7 minutes to decays in 214Bi emitting gamma ray energy （45%） with 0.609 MeV which is monitored daily by Geiger. Also 222Rn decays in 26.8 minutes in 214pb giving （37%） with 0.35 MeV and others with less energy. It is confirmed the good performance ofa Geiger tube with LND 712 working with about 500 VDC rated voltage.

Monitoring of Ionizing Radiation Using Geiger Instrument during February to April 2015 in Sao Jose Dos Campos, SP, Brazil

Measures of ionizing radiation were observed in a tower which is 20 meters above the ground relative height. They show a distinct period of 24 hours oscillation during this Februaryl 1 to April 11, 2015. It is suggested that these oscillations originate from radon gas （222Rn） vented from the ground floor. One Russian specific Geiger tube with associated electronics developed at ITA was used, Monitoring of ionizing radiation from 30 keV to l0 MeV shows that the X and gamma rays up to 3.0 MeV is prevalent in the region comes from the Radon gas 222Rn that decay in 214Bi and 214pb in the energies of the gamma rays 0.269, 0.609 and 1.05 MeV respectively. Then, with this simple, portable instrument was possible to monitoring the dynamics of radon gas in the region every interval minutes.

Monitoring of Ionizing Radiation and Rain Intensity during May to October 2015 in S^o Jos~ dos Campos, Brazil

Radiation affects the environment and local human activity in any location of the earth＇s surface. Due to this fact, the aim of this study was to monitor the ionizing radiation and rain intensity using portable devices. During May 23 to October 2, 2015, it was made measures the intensity of gamma radiation from 30 keV to 10.0 MeV at a height of 25 meters in Sao Jos6 dos Campos city, SP, Brazil. It was used a crystal of sodium iodide scintillator 3 - 3 inches coupled to a photomultiplier and associated electronic. The measurements were made continually with minute＇s interval throughout the period and it was monitored rain intensity every minute at the same height of the tower. In this job, it was possible to correlate rain-radiation and it was observed which gamma radiation has a directly proportional relationship with rain and visible frequency of 1 day.

Radiation Dose Monitoring and Analysis for the Construction of the Upgraded Beijing Electron-Positron Collider(BEPCⅡ) During Its Storage Ring Operation

In this paper,the average dose level is introduced in an environment and area when BEPCⅡis debugged. The typical dose graphs are offered when the electronic storage ring is debugged and works in the synchrotron radiation mode.At the same time,some suggestions about radiation protection are presented.All the data indicate that the main and local part shielding satisfy the need and attain the design target.

Minimum detectable activity for NaI(Tl) airborne γ-ray spectrometry based on Monte Carlo simulation

The determination of the effective minimum detectable activity （MDA） of radionuclides by a detection system plays an im- portant role in environmental radiation monitoring. In this study, the responses of an NaI（TI） airborne γ ray spectrometry （AGRS） system to different radionuclides （137Cs and 131I） were investigated using the Monte Carlo technique. The MDA values were determined under different conditions according to the counting spectra obtained from the Monte Carlo simulation. The equivalent mass thickness method was applied to the Monte Carlo modeling for monitoring ground radiation to reduce sta- tistical uncertainty. The secondary source method was used to monitor both air and ground radiation. A quadratic relationship was found between the MDA and activity concentration. An exponential relationship was found between the MDA and altitude The MDA of a specific radionuclide from external detectors was found to be superior to that obtained from internal detectors under the same conditions. The MDA values in an NaI（Tl） AGRS system under different conditions can be estimated based on the results of this study.

Variations of the relativistic electron flux after a magnetospheric compression event

On January 21, 2015, a sharp increase of the solar wind dynamic pressure impacted the magnetosphere. The magnetopause moved inward to the region L< 8 without causing a geomagnetic storm. The flux of the relativistic electrons in the outer radiation belt decreased by half during this event based on the observations of the particle radiation monitor(PRM) of the fourth of the China-Brazil Earth Resource Satellites(CBERS-4). The flux remained low for approximately 11 d; it did not recover after a small magnetic storm on January 26 but after a small magnetic storm on February 2. The loss and recovery of the relativistic electrons during this event are investigated using the PRM data, medium-and high-energy electron observations of NOAA-15 and the Van Allen Probes, medium-energy electron observations of GOES-13, and wave observations of the Van Allen Probes. This study shows that the loss of energetic electrons in this event is related to magnetospheric compression. The chorus waves accelerate the medium-energy electrons, which causes the recovery of relativistic electrons. The Van Allen Probes detected strong chorus waves in the region L =3–6 from January 21 to February 2. However, the flux of medium-energy electrons was low in the region. This implies that the long-lasting lack of recovery of the relativistic electrons after this event is due to the lack of the medium-energy"seed" electrons. The medium-energy electrons in the outer radiation belt may be a clue to predict the recovery of relativistic electrons.

Application of wavelet transform in-ray spectra analysis

The frequency distribution of different ingredients in-ray spectra,e.g.,photo-peak,fluctuations of counts and Compton region,is separately analyzed.After wavelet transform of-ray spectra,the wavelet coefficients of a photo-peak increase with transforming scales and these coefficients show direct proportion with intensity of peak at determinate scale.A novel algorithm based on wavelet transform is proposed and studied.The results indicate that most of the photo-peaks in multi-spectra can be determined accurately,the-rays energy and intensity of the peak can also be determined.This method has the prospect of being applied in on-line multi-spectra analysis in such fields as radioprotection and nuclear safety monitoring.

Optical transient waveform monitoring based on cross-gain modulation in semiconductor optical amplifier

An all-optical transient waveform equivalent time sampling system based on cross-gain modulation （XGM） in semiconductor optical amplifier （SOA） is presented. Anoisy SOA dynamic model and PIN equyalent circuit function are employed for system evaluating. The results show this SOA-XGM sampler with subtracting postprocessing can achieve picosecond sampling window. The shape of sampling window can be adjusted by SOA bias current and amplitude of control pulse. Compared with amplified spontaneous emission （ASE） noise of SOA and thermal noise in PIN, the jitter of sampling control pulse causes most sampling error. Simulations show that this SOA-XGM sampler can be a capable candidate for transient waveform sampling.