science and technology

With the widespread forest destruction in Central Kalimantan, a group of environmental activists is engaged in the training of primary school teachers in Katingan regency, in which environment education textbooks meant for local students are being tried out.

This program is facilitated by the Katingan regency administration in cooperation with WWF-Indonesia and relevant agencies, like the local education office, environment office and the national park management.

The training takes place in Mendawai village, Mendawai district, and Petak Bahandang village, Tasik Payawan district — both situated on the Katingan River plain bordering Sebangau National Park. Illegal logging and wildfire-causing forest damage have remained rife in the two villages. Sixty primary school teachers and principals in both districts have joined the program, which comprises class presentations, group discussions and field practice,” said Novita, 25, an activist from Lampung.

According to Novita, who graduated from Lampung University with a degree in agricultural engineering, the subjects taught concern an introduction to environmental education and various topical environmental issues such as global warming.

Nancy made it clear that the activities were designed to arouse children’s concern for and love of nature through environment education.

“This training is expected to deepen teachers’ knowledge of environment matters, which will be imparted to their students for further application in daily life,” said the WWF-Indonesia/Sebangau conservation project communication officer.

A day’s training is followed by subject presentations before class, among others in the state primary school of Tewang Kampung, which is only over a dozen meters away from the Katingan riverbank in Mendawai district. It is accessible by speedboat from the terminal of Kereng Bangkirai, Palangkaraya. The trip takes eight hours. A simple wooden stilted building, the school has about 20 students per class, mostly the children of farmers, fishermen and sawmill workers.

The new lessons given by the trainees to their first to sixth graders include water and air pollution and the importance of forests as the world’s lungs. Students are also taken to observe water springs and soil types as well as to plant trees in school yards. Dedy Mardianto, a Mekar Tani state primary school teacher, has instructed third graders to grow Galam trees to suit the generally peat covered marshy land around Katingan river.

Novita noted that this replanting practice was intended to make local children familiar with the greening activity in view of the considerable forest damage in Katingan regency due to illegal logging and wildfire. “It’s part of environment education to make them strive for improvement as soon as they notice disruption in natural conditions,” added Novi.

Local student Yanti Nurhidayanti, 12, could not help but express her delight at taking environmental studies. “I’m very happy to be taking subjects that were previously never taught in school. Outdoor instruction makes us better understand through direct observations and field trials,” said the fifth grader.

The textbook tryout and teachers’ training are also meant to improve the environment books earlier compiled by local teachers, besides gathering addition information to enrich future text content. As planned, the environment subjects will be made mandatory for the primary school curriculum in Katingan regency, Central Kalimantan.

By: Bambang Parlupi

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HSDPA improves on W-CDMA by using different techniques for modulation & coding. It creates a new channel within W-CDMA called HS-DSCH, or high-speed downlink shared channel. That channel performs differently than other channels & allows for faster downlink speeds. it is important to note that the channel is only used for downlink. That means that data is sent from the source to the phone. It isn't possible to send data from the phone to a source using HSDPA. The channel is shared between all users which lets the radio signals to be used most effectively for the fastest downloads.

HSDPA, short for High-Speed Downlink Packet Access, is a new protocol for mobile telephone data transmission. it is known as a 3.5G (G stands for generation) technology. Essentially, the standard will provide download speeds on a mobile phone equivalent to an ADSL (Asymmetric Digital Subscriber Line) line in a home, removing any limitations placed on the use of your phone by a slow connection. it is an evolution & improvement on W-CDMA, or Wideband Code Division Multiple Access, a 3G protocol. HSDPA improves the data transfer rate by a factor of at least three over W-CDMA. HSDPA can achieve theoretical data transmission speeds of 8-10 Mbps (megabits per second). Though any data can be transmitted, applications with high data demands such as video & streaming music are the focus of HSDPA.

The long-term acceptance & success of HSDPA is unclear, because it is not the only alternative for high speed data transmission. Standards like CDMA2000 1xEV-DO & WiMax are other potential high speed standards. Since HSDPA is an extension of W-CDMA, it is unlikely to succeed in locations where W-CDMA has not been deployed. Therefore, the eventual success of HSDPA as a 3.5G standard will first depend upon the success of W-CDMA as a 3G standard.

The widespread availability of HSDPA may take a while to be realized, or it may never be achieved. Most countries did not have a widespread 3G network in place as of the end of 2005. lots of mobile telecommunications providers are working quickly to deploy 3G networks which can be upgraded to 3.5G when the market demand exists. Other providers tested HSDPA through 2005 & are rolling out the service in mid to late 2006. Early deployments of the service will be at speeds much lower than the theoretically possible rates. Early service will be at 1.8 Mbps, with upgrades to 3.6Mbps as devices are made accessible that can handle that increased speed. Read more...

A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate, as opposed to a nuclear bomb, in which the chain reaction occurs in a fraction of a second and is uncontrolled causing an explosion.

The most significant use of nuclear reactors is as an energy source for the generation of electrical power (see Nuclear power) and for the power in some ships (see Nuclear marine propulsion). This is usually accomplished by methods that involve using heat from the nuclear reaction to power steam turbines. There are also other less common uses as discussed below.

Nuclear Reactor Firsts

The first artificial nuclear reactor, Chicago Pile-1, was constructed at the University of Chicago by a team led by Enrico Fermi in 1942. (Fermi and Leo Szilard have patented the nuclear reactor.) It achieved criticality on December 2, 1942 at 3:25 PM. The reactor support structure was made of wood, which supported a pile of graphite blocks, embedded in which was natural Uranium-oxide 'pseudospheres' or 'briquettes'. Inspiration for such a reactor was provided by the discovery of Lise Meitner, Fritz Strassman and Otto Hahn in 1938 that bombardment of Uranium with neutrons provided by an Alpha-on-Beryllium fusion reaction (a neutron howitzer) produced a Barium residue, which they reasoned was created by the fissioning of the Uranium nuclei. Subsequent studies revealed that several neutrons were also released during the fissioning, making available the opportunity for a chain reaction. Shortly after the discovery of fission, Hitler's Germany invaded Poland in 1939, starting World War II in Europe, and all such research became militarily classified. On August 2, 1939 Albert Einstein wrote a letter to President Franklin D. Roosevelt suggesting that the discovery of Uranium's fission could lead to the development of "extremely powerful bombs of a new type", giving impetus to the study of reactors and fission.

Soon after the Chicago Pile, the U.S. military developed nuclear reactors for the Manhattan Project starting in 1943. The primary purpose for these reactors was the mass production of plutonium (primarily at the Hanford Site) for nuclear weapons. After World War II, the U.S. military sought other uses for nuclear reactor technology. Research by the Army and the Air Force never came to fruition; however, the U.S. Navy succeeded when they steamed the USS Nautilus (SSN-571) on nuclear power January 17, 1955.

Besides the military uses of nuclear reactors, there were political reasons to pursue civilian use of atomic energy. U.S. President Dwight Eisenhower made his famous Atoms for Peace speech to the UN General Assembly on December 8, 1953. This diplomacy led to the dissemination of reactor technology to U.S. institutions and worldwide.

"World's first nuclear power plant" is the claim made by signs at the site of the EBR-I, which is now a museum near Arco, Idaho. This experimental LMFBR operated by the U.S. Atomic Energy Commission produced 0.8 kW in a test on December 20, 1951 and 100 kW (electrical) the following day, having a design output of 200 kW (electrical). The first nuclear power plant built for civil purposes was the AM-1 Obninsk Nuclear Power Plant, launched on June 27, 1954 in the Soviet Union. It produced around 5 MW (electrical).


How it works

The key components common to most types of nuclear power plants are:

* Neutron moderator
* Coolant
* Control rods
* Pressure vessel
* Emergency Core Cooling Systems (ECCS)
* Reactor Protective System (RPS)
* Steam generators (not in BWRs)
* Containment building
* Boiler feedwater pump
* Steam turbine
* Electrical generator
* Condenser

Conventional electrical power plants all have a fuel source to provide heat. Examples are natural gas, coal, and fuel oil. For a nuclear power plant, this heat is provided by nuclear fission inside the nuclear reactor. When a relatively large fissile atomic nucleus (usually uranium-235 or plutonium-239) is struck by a neutron it forms two or more smaller nuclei as fission products, releasing energy and neutrons in a process called nuclear fission. The neutrons then trigger further fission. When this nuclear chain reaction is controlled, the energy released can be used to heat water, produce steam and drive a turbine that generates electricity. It should be noted that a nuclear explosion involves an uncontrolled chain reaction, and the rate of fission in a reactor is not capable of reaching sufficient levels to trigger a nuclear explosion (even if the fission reactions increased to a point of being out of control, it would melt the reactor assembly rather than form a nuclear explosion). Enriched uranium is uranium in which the percent composition of uranium-235 has been increased from that of uranium found in nature. Natural uranium is only 0.72% uranium-235; the rest is mostly uranium-238 (99.2745%) and a tiny fraction is uranium-234 (0.0055%).


Reactor types

Classifications
Nuclear Reactors are classified by several methods; a brief outline of these classification schemes is provided.

Classification by type of nuclear reaction
* Nuclear fission. Most reactors, and all commercial ones, are based on nuclear fission. They generally use uranium as fuel, but research on using thorium is ongoing (an example is the Liquid fluoride reactor). This article assumes that the technology is nuclear fission unless otherwise stated. Fission reactors can be divided roughly into two classes, depending on the energy of the neutrons that are used to sustain the fission chain reaction:
o Thermal reactors use slow or thermal neutrons. Most power reactors are of this type. These are characterized by neutron moderator materials that slow neutrons until they approach the average kinetic energy of the surrounding particles, that is, until they are thermalized. Thermal neutrons have a far higher probability of fissioning uranium-235, and a lower probability of capture by uranium-238 than the faster neutrons that result from fission. As well as the moderator, thermal reactors have fuel (fissionable material), containments, pressure vessels, shielding, and instrumentation to monitor and control the reactor's systems.
o Neutrons of intermediate energies are less useful because plutonium-239 has a high ratio of capture cross section vs. fission cross section at these energies, impairing neutron economy. Uranium-233 has low capture/fission ratios across the neutron energy spectrum, so the thorium cycle can use intermediate neutron energies.
o Fast neutron reactors use fast neutrons to sustain the fission chain reaction. They are characterized by an absence of moderating material. Initiating the chain reaction requires enriched uranium (and/or enrichment with plutonium 239), due to the lower probability of fissioning U-235, and a higher probability of capture by U-238 (as compared to a moderated, thermal neutron). Fast reactors have the potential to produce less transuranic waste because all actinides are fissionable with fast neutrons, but they are more difficult to build and more expensive to operate. Overall, fast reactors are less common than thermal reactors in most applications. Some early power stations were fast reactors, as are some Russian naval propulsion units. Construction of prototypes is continuing (see fast breeder or generation IV reactors).
* Nuclear fusion. Fusion power is an experimental technology, generally with hydrogen as fuel. While not currently suitable for power production, Farnsworth-Hirsch fusors are used to produce neutron radiation.
* Radioactive decay. Examples include radioisotope thermoelectric generators and atomic batteries, which generate heat and power by exploiting passive radioactive decay.

Classification by moderator material
Used by thermal reactors:
* Graphite moderated reactors
* Water moderated reactors
o Heavy water reactors
o Light water moderated reactors (LWRs). Light water reactors use ordinary water to moderate and cool the reactors. When at operating temperatures if the temperature of the water increases, its density drops, and fewer neutrons passing through it are slowed enough to trigger further reactions. That negative feedback stabilizes the reaction rate. Graphite and heavy water reactors tend to be more thoroughly thermalised than light water reactors. Due to the extra thermalization, these types can use natural uranium/unenriched fuel.
* Light element moderated reactors. These reactors are moderated by lithium or beryllium.
o Molten salt reactors (MSRs) are moderated by a light elements such as lithium or beryllium, which are constituents of the coolant/fuel matrix salts LiF and BeF2.
o Liquid metal cooled reactors, such as one whose coolant in a mixture of Lead and Bismuth, may use BeO as a moderator.
* Organically moderated reactors (OMR) use biphenyl and terphenyl as moderator and coolant.

Classification by coolant
* Water cooled reactor
o Pressurized water reactor (PWR)
+ A primary characteristic of PWRs is a pressurizer, a specialized pressure vessel. Most commercial PWRs and naval reactors use pressurizers. During normal operation, a pressurizer is partially filled with water, and a steam bubble is maintained above it by heating the water with submerged heaters. During normal operation, the pressurizer is connected to the primary reactor pressure vessel (RPV) and the pressurizer "bubble" provides an expansion space for changes in water volume in the reactor. This arrangement also provides a means of pressure control for the reactor by increasing or decreasing the steam pressure in the pressurizer using the pressurizer heaters.
+ Pressurised channels. Channel-type reactors can be refueled under load.
o Boiling water reactor (BWR)
+ BWRs are characterized by boiling water around the fuel rods in the lower portion of primary reactor pressure vessel. During normal operation, pressure control is accomplished by controlling the amount of steam flowing from the reactor pressure vessel to the turbine.
o Pool-type reactor
* Liquid metal cooled reactor. Since water is a moderator, it cannot be used as a coolant in a fast reactor. Liquid metal coolants have included sodium, NaK, lead, lead-bismuth eutectic, and in early reactors, mercury.
o Sodium-cooled fast reactor
o Lead-cooled fast reactor
* Gas cooled reactors are cooled by a circulating inert gas, usually helium. Nitrogen and carbon dioxide have also been used. Utilization of the heat varies, depending on the reactor. Some reactors run hot enough that the gas can directly power a gas turbine. Older designs usually run the gas through a heat exchanger to make steam for a steam turbine.
* Molten Salt Reactors (MSRs) are cooled by circulating a molten salt, typically a eutectic mixture of fluoride salts, such as LiF and BeF2. In a typical MSR, the coolant is also used a matrix in which the fissile material is dissolved.

Classification by use
* Electricity
o Power plants
* Propulsion, see nuclear propulsion
o Nuclear marine propulsion
o Various proposed forms of rocket propulsion
* Other uses of heat
o Desalination
o Heat for domestic and industrial heating
o Hydrogen production for use in a hydrogen economy
* Production reactors for transmutation of elements
o Breeder reactors. Fast breeder reactors are capable of enriching Uranium during the fission chain reaction (by converting fertile U-238 to Pu-239) which allows an operational fast reactor to generate more fissile material than it consumes. Thus, a breeder reactor, once running, can be re-fueled with natural or even depleted uranium.
o Creating various radioactive isotopes, such as americium for use in smoke detectors, and cobalt-60, molybdenum-99 and others, used for imaging and medical treatment.
o Production of materials for nuclear weapons such as weapons-grade plutonium
* Providing a source of neutron radiation (for example with the pulsed Godiva device) and positron radiation[clarify]) (e.g. Neutron activation analysis and Potassium-argon dating[clarify])
* Research reactors : Typically reactors used for research and training, materials testing, or the production of radioisotopes for medicine and industry. These are much smaller than power reactors or those propelling ships, and many are on university campuses. There are about 280 such reactors operating, in 56 countries. Some operate with high-enriched uranium fuel, and international efforts are underway to substitute low-enriched fuel.

Advanced reactors
More than a dozen advanced reactor designs are in various stages of development.[6] Some are evolutionary from the PWR, BWR and PHWR designs above, some are more radical departures. The former include the Advanced Boiling Water Reactor (ABWR), two of which are now operating with others under construction, and the planned passively safe ESBWR and AP1000 units (see Nuclear Power 2010 Program).

* The Integral Fast Reactor was built, tested and evaluated during the 1980s and then retired under the Clinton administration in the 1990s due to nuclear non-proliferation policies of the administration. Recycling spent fuel is the core of its design and it therefore produces only a fraction of the waste of current reactors.[7]
* The Pebble Bed Reactor, a High Temperature Gas Cooled Reactor (HTGCR), is designed so high temperatures reduce power output by doppler broadening of the fuel's neutron cross-section. It uses ceramic fuels so its safe operating temperatures exceed the power-reduction temperature range. Most designs are cooled by inert helium. Helium is not subject to steam explosions, resists neutron absorption leading to radioactivity, and does not dissolve contaminants that can become radioactive. Typical designs have more layers (up to 7) of passive containment than light water reactors (usually 3). A unique feature that may aid safety is that the fuel-balls actually form the core's mechanism, and are replaced one-by-one as they age. The design of the fuel makes fuel reprocessing expensive.
* SSTAR, Small, Sealed, Transportable, Autonomous Reactor is being primarily researched and developed in the US, intended as a fast breeder reactor that is passively safe and could be remotely shut down in case the suspicion arises that it is being tampered with.
* The Clean And Environmentally Safe Advanced Reactor (CAESAR) is a nuclear reactor concept that uses steam as a moderator - this design is still in development.
* Subcritical reactors are designed to be safer and more stable, but pose a number of engineering and economic difficulties. One example is the Energy amplifier.
* Thorium based reactors. It is possible to convert Thorium-232 into U-233 in reactors specially designed for the purpose. In this way, Thorium, which is more plentiful than uranium, can be used to breed U-233 nuclear fuel. U-233 is also believed to have favourable nuclear properties as compared to traditionally used U-235, including better neutron economy and lower production of long lived transuranic waste.
o Advanced Heavy Water Reactor — A proposed heavy water moderated nuclear power reactor that will be the next generation design of the PHWR type. Under development in the Bhabha Atomic Research Centre (BARC).
o KAMINI — A unique reactor using Uranium-233 isotope for fuel. Built by BARC and IGCAR Uses thorium.
o India is also building a bigger scale FBTR or fast breeder thorium reactor to harness the power with the use of thorium.
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