Δευτέρα, 29 Νοεμβρίου 2010

'Israel behind hit on Iran N-scientist' - Dr. Majid Shahriyari

(Reuters) - Two car bomb blasts killed an Iranian nuclear scientist and wounded another in Tehran on Monday in what Iranian officials called an Israeli or U.S.-sponsored attack on its atomic program. The bombings, rare attacks in the Iranian capital, occurred ahead of a possible meeting between Iran and major powers next month to discuss its nuclear activity, which Western officials suspect is aimed at developing atom bombs. Iran denies this.In the past few months, the Islamic Republic has arrested a number of alleged "nuclear spies," warning citizens against leaking information to foreign secret services. Majid Shahriyari was martyred and his wife was injured ... Fereydoun Abbasi-Davani and his wife were both wounded," state radio said, referring to the two scientists. "The attackers planted a bomb on each of the teachers' vehicles."Abbas-Davani has been personally subjected to U.N. sanctions because of what Western officials said was his involvement in suspected nuclear weapons research. He was "not seriously injured in the blast," the semi-official Mehr news agency said.Iran's atomic energy agency chief Ali Akbar Salehi said Shahriyari had a role in one of its biggest nuclear projects, but did not elaborate, the official news agency IRNA reported.Salehi warned enemies not to "play with fire" by carrying out such attacks. "Our nation's patience has a limit ... When it is over our enemies will face a tedious fate," Salehi said, as quoted by IRNA."Dr Shahriyari was my student for many years and he had good cooperation with the Atomic Energy Organization."

Iranian television showed police and plainclothes security agents examining a silver-colored Peugeot 206 car with what looked like shrapnel holes in its bonnet. Another car was shown with its windows smashed and a door blown off.There was no immediate claim of responsibility. Iranian officials and media blamed Israel, which Tehran calls "the Zionist regime," and the United States for Shahriyari's death."The sinister Americans and Zionists thought they could derail our nation from its scientific path and stop our elites from progressing in science by killing our scientists," Mohammad-Reza Naqdi, head of the pro-government Islamic Basij militia, was quoted as saying by the semi-official Fars news agency."We will certainly avenge these crimes of the Americans and Zionists and soon the gallows will be earmarked for the retribution of the blood of Shahriyari. "Another nuclear scientist, Massoud Ali-Mohammadi, was killed by a remote-controlled bomb in Tehran in January. Some opposition websites said he had backed moderate candidate Mirhossein Mousavi in the 2009 disputed presidential election that secured President Mahmoud Ahmadinejad's return to power.Western security sources said in January that Mohammadi had worked closely with Abbassi-Davani.
The Zionists have once again targeted Iran's scientific progress by shedding the blood of a university professor, a statement by the office of President Mahmoud Ahmadinejad said on Monday. Unknown terrorists detonated bombs in the vehicles of Dr. Majid Shahriari and Professor Fereydoun Abbasi in separate locations on Monday morning between 7-8 a.m. local time. Shahriari was killed immediately, but professor Abbasi and his wife sustained injuries and were transferred to hospital.

Both men were professors at Shahid Beheshti University in Tehran. Resolution 1747 adopted by the United Nations Security Council in March 2007 against the Islamic Republic cited the name of Abbasi as a "nuclear scientist," thus suggesting that perpetrators behind the assassination could be traced through those who included the professor's name in the UN resolution. Tehran Police Chief Brigadier General Hossein Sajedinia said a motorcycle approached Shahriari's car and attached a magnetic bomb to the driver's door of the car which exploded a few seconds later. He added that terrorists separately attached another bomb to Abbasi's car and escaped, saying while the professor and his wife were wounded in the attack they are now in good health. "Political and security analysts are wondering about the connection between these inhumane incidents and the recent remarks of the head of the British intelligence agency (MI6)…," the statement said.

On October 28 John Sawers accused Iran of pursuing clandestine nuclear activities and said spying is crucial to stop Tehran's nuclear program. "Stopping nuclear proliferation cannot be addressed purely by conventional diplomacy. We need intelligence-led operations to make it more difficult for countries like Iran to develop nuclear weapons," Sawers said. The presidential office statement also referred to the "European Parliament's new stance about the necessity of removing anti-Iran terrorist groups from the US black list" and its link to the recent terrorist attack in Tehran. Last week, the European Parliament issued a declaration, urging Washington to remove the Mujahedin-e Khalq Organization (MKO) from its list of Foreign Terrorist Organizations. The European Union took the MKO off its blacklist in 2009. The terrorist group has been on the US terror list since 1997. The MKO is listed as a terrorist organization by much of the international community and is responsible for numerous acts of terror and violence against Iranian civilians and government officials. The organization is also known to have cooperated with Iraq's former dictator Saddam Hussein in suppressing the 1991 uprisings in southern Iraq and the massacre of Iraqi Kurds. 
Here is the last article of Dr. Majid Shahriyari, a prominent nuclear scientist that was killed on Monday Nov  9th
“Design of a Nuclear Level Switch using MCNP code, and Comparison with Experimental Result “
was the last article of Dr, Shahriyari. The research was done by his university student’s, Mitra Ansari, cooperation. Dr. Shahriari was a member of the nuclear engineering department of Shahid Beheshti University in northern Tehran. 

[..IEEE NPSS (Toronto), UOIT, Oshawa, ON, 25 & 26 June, 2010
International Workshop on Real Time Measurement, Instrumentation & Control [RTMIC]

Mitra Ansari, Majid Shahriari
Department of Radiation Application, Shahid Beheshti University
Tehran, Iran, P.O.Box:1983963113

Nuclear level switches have found widespread use in industry, as they allow rapid and reliable on-line measurement and control of material level in the tanks and vessels. The nuclear level switch is based on the detection of radiations emitted by a radioactive source. When radiation transmit through material it will be absorbed, scattered or transmitted without any reaction. In view of the complexity associated with these interactions, the Monte Carlo simulation can be used for evaluation of radiation interactions with matter. In this work, the simulations were performed using the MCNP4C code. The system includes a 137Cs gamma source, a water tank and a gamma detector. The count rate versus material level was obtained in the different positions of source and detector and the optimal conditions were determined for having the best sensitivity of gauge. An experimental work was also carried out to test the simulation predictions and a good agreement was found between experimental and simulation results.
Level height is an important feature in several pieces of technological apparatus, in material storing transportation systems, both from process control, either automatic or manual, and from quantity monitoring considerations. For monitoring the material level in a given system, level height indicators are used. The level indicator is suitable for sensing and remotely indicating a specified extreme value (minimum, maximum, etc.). It can be used as control elements, typically as process sensors [1].
There are several methods for detecting level material in tanks like: float, thermal level sensor, capacitance level detection, optical level devices, vibrating level switches, microwave level switches, radar sensors, ultrasonic level detectors, and radiation level sensors [2].
Unlike most other level technologies, the nuclear level switch can be considered as the most universal one because nuclear gauges avoid contact with process conditions. Processes with extreme temperature, pressure, or corrosive properties have no adverse effects on nuclear gauges. Nuclear level switch can be applied in closed and open systems. They can detect level of material in different states (solid, liquid, particulate, etc).
Nuclear level switch can be applied in virtually any industries such as: petrochemical, water and wastewater, pulp and paper, plastics, food, cement, asphalt, chemical and mining [3].
Material and Methods
A nuclear level switch contains a shielded radioactive source as a signal source and a detector converting radioactive radiation to electrical pulses. It can work based on absorption or reflection  of radiations. Absorption gauge is designed to measure the level of process material by directing a beam of gamma radiation energy from source, through the process material to a detector assembly on the other side. Some of this energy is absorbed during the passage through the material. This absorption is proportional to the mass of the material which it passes. The amount of radiation energy which reaches the detector is measured.
In reflection gauges, both source and detector are installed one side of the tank. If no material appears in sensing zone of probes, the reflection is low, due to interaction restricted to protective cover of the probe or the tank wall. With rising material level, the reflection increases significantly.
The sensitivity of gauge depends on radioisotope type as radiation source and its activity, detector type and the positions of source and detector. In this work, the proper position of source and detector was determined by simulation of nuclear level switch [4].
A proper location of source and detector should be determined in a way that to have high level indication accuracy for the level switch. More sensitivity can be achieved if the slope of the radiation count versus the level of material curve is higher. It means the detector should have a noticeable change in radiation count when the level of material is slightly changed. The MCNP transport code based on the Monte Carlo method has been used to simulate the nuclear level switch.
MCNP simulation
MCNP is a general purpose Monte Carlo code for calculating the time dependent continuous energy, transport of neutrons, photons and electrons in three dimensional geometries [5]. A number of benchmark studies using the Monte Carlo transport code, MCNP, and comparison with experimental results have been done [6,7].
The calculation model included a polyethylene tank of 80 cm diameter filled with water, a 137Cs gamma ray source with lead shield and a gamma-ray detector. Fig .1 shows four different positions of source and detector that were simulated.

IEEE NPSS (Toronto), UOIT, Oshawa, ON, 25 & 26 June, 2010
International Workshop on Real Time Measurement, Instrumentation & Control [RTMIC]
Fig. 1. The position of source and detector in four different situations
The count rate of the detector versus water level variations was determined. The numbers of histories were 5 million photons.
A 100 mCi 137Cs gamma source with lead shield is placed at level of 60 cm from tank bottom in situation (a) and (c), and at level of 35 cm in situation (b) and (d). A ZP1201Geiger-Muller tube is used to count transmitted photons and a polyethylene tank of 80 cm diameter and 120 cm height have been utilized [8]. Water has been used as the material in the tank.
The set up of electronic unit’s configuration for this experiment is shown in Fig. 2.
Fig.2 Configuration of electronics used in the experiments

Source and detector were mounted in the four positions. With raising the water level, in each level, the count rate in the detector has been counted 25 times in 5 seconds time intervals, and then averaged among the counts.
The simulation and experimental results
The following figures show the simulated count rate in the detector and the experimental results as function of water level in four positions.

The comparison of the results of Fig. 2 with the others shows the absorption method has more sensitivity than reflection method and absorption gauges can determine and control the material level in the tank accurately.
However when we are not able to access two sides of the tank for the operational conditions or there is small amount of transmission radiation due to the large diameter of the tank, the use of reflection method appears to be inventible.
As can be seen in Fig. 4, the slope of the curve is higher than others and it is better the source and detector are mounted opposite each other in the specified height.
Also in situations (c) and (d) the gauge can determine material level continuously and it is possible to determine material level in the range of 35 to 55 cm with measuring count rate. In comparison, situation (c) is more suitable.
Furthermore, the agreement between experimental and simulated results is excellent; a small
difference between the two curves may also be partially resulting from the impossibility of the
exact simulation of the detector, background count rate variations and also environmental
conditions. However based on the above conclusion, MCNP code is an effective tool for
simulation of nuclear gauging instruments.
[1] G.Foldiak, “Industrial Application of Radioisotope,” Academy Kiado Publishing, Budapest, pp.91-101 , (1986).
[2] Bela G.Liptak, “Industrial engineer’s handbook Process Measurement and analysis,” CRC Press, London, pp 405-411 ,(2003)
[3] OMEGA Complete Flow and Level Measurement Handbook and Encyclopedia, OMEGA Press,pp 93-98, (1995)
[4] OHMART VEGA corporation, level switch technical reference manual, models GM-16
[5] J.F.Briesmeister “MCNP Monte Calrlo N-Particle Transport Code System” Los Alamos, National Laboratory,(2002)
[6] M. Sohrabpour, M. Hassanzadeh, M. Shahriari, M. Sharifzadeh, Applied Radiation and Isotopes 57, 537–542, (2002)
[7] M. Sohrabpour, M. Shahriari, V. Zarifan, K.K. Moghadam, Applied Radiation and Isotopes 50, 805±810, (1999)
[8] Uhttp://www.centronic.co.uk/gamma_detectors.htmU ]

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