Nuclear Technology User Community

Nuclear Energy

2008-06-04T02:15:00.000-07:00

Nuclear Waste

The majority of high level radioactive waste produced comes from the fuel in the core of nuclear power reactors. Irradiated fuel is the most radioactive fuel on the planet and accounts for some 95% of radioactivity generated in the last 50 years from all sources, including nuclear weapons production. Once removed from the core, irradiated fuel is stored in cooling pools on the nuclear reactor site. Each 1000 megawatt nuclear power plant produces about 500 pounds of plutonium a year and about 30 metric tons of high-level radioactive waste.

Environmental Costs

While electricity generated from nuclear power does not directly emit carbon dioxide (CO2), the nuclear fuel cycle does release CO2 during mining, fuel enrichment and plant construction. Uranium mining is one of the most CO2 intensive industrial operations and as demand for uranium grows because of new electricity generation and new plant construction, CO2 levels will also rise.

In a case study in Germany, the Oko-Institute determined that 34 grams of CO2 are emitted per generated kilowatt (kWh). Other international research studies show much higher figures (up to 60 grams of CO2 per kWh). In comparison to renewable energy, energy generated from nuclear power releases 4-5 times more CO2 per unit of energy produced, taking into account the entire nuclear fuel cycle.

US government regulations allow radioactive water to be released into the environment at "permissible" levels. Accurate accounting of all radioactive wastes released into the air, water and soil from the nuclear fuel cycle is simply not available. The Nuclear Regulatory Commission relies on self-reporting and computer modeling from reactor operators to track radioactive releases and project dispersions.

Health

It has been scientifically established that low-level radiation damages tissues, cells, DNA and other vital molecules. Effects of low-level radiation doses cause cell death, genetic mutations, cancers, leukemia, birth defects, and reproductive, immune and endocrine system disorders.

Radioactivity is measured in "curies." An average operating nuclear power reactor core has about 16 billion curies at its core, which is equivalent to the long-lived radioactivity of at least 1,000 Hiroshima bombs. In comparison, a large-sized medical center with as many as 1000 laboratories in which radioactive materials are used, has a combined inventory of about 2 curies.

Nuclear Safety

There have been repetitive problems with security, safety and environment impact in the nuclear industry. Radioactive contamination does not discriminate between national borders and nuclear power plants threaten the health and well-being of all surrounding environments.

Nuclear Sustainability

Nuclear power plants produce extremely toxic radioactive wastes that are long-lived and have no safe means of disposal. Disposal is neither scientifically credible nor is there any sustainable options for interim storage. Producing long-lived radioactive wastes with no solution for its disposal will leave serious and irreversible environmental damage and degradation for generations to come, which is contrary to the principles of sustainability.

Radiation Safety Logo

2008-05-21T22:53:00.001-07:00

The radioactive sources used in the experiments on these pages are very low level isotopes referred to as "license free" sources. This does not mean, however, that these materials represent no hazard to students. The Nucleus, PO Box T, Oak Ridge, Tennessee, 37830, has provided the following guidelines for use of low-level radioactive materials in classroom environments.

Eating, drinking, and application of cosmetics in the laboratory is not permitted.

Pipetting by mouth is never permitted. Use suction devices such as pipette fillers.

Gloves and lab coats should be worn when working with all liquid radioisotopes.

Before leaving the lab, wash your hands thoroughly then check for possible contamination with a survey instrument.

Report ALL spills, wounds, or other emergencies to your teacher.

Keep exposure time to a minimum.

All radioactive liquids wastes are to be poured into the liquid waste container, NEVER a sink.

Maintain good housekeeping at all times in the lab.

Store radioactive materials only in designated storage areas. Do not remove sources from the lab.

Efek Radiasi pada Tubuh Manusia

2008-05-14T18:53:00.000-07:00

Kerusakan sel akan mempengaruhi fungsi jaringan atau organ bila jumlah sel yang mati/rusak dalam jaringan/organ tersebut cukup banyak. Semakin banyak sel yang rusak/mati, semakin parah gangguan fungsi organ yang dapat berakhir dengan hilangnya kemampuan untuk menjalankan fungsinya dengan baik. Perubahan fungsi sel atau kematian dari sejumlah sel menghasilkan suatu efek biologi dari radiasi yang bergantung antara lain pada jenis radiasi (LET), dosis, jenis sel dan lainnya.

Pada tubuh manusia, secara umum terdapat dua jenis sel yaitu sel genetik dan sel somatik. Sel genetik adalah sel ogonium (calon sel telur) pada perempuan dan sel spermatogonium (calon sel sperma) pada laki-laki. Sedangkan sel somatik adalah sel-sel lainnya yang ada dalam tubuh. Bila dilihat dari jenis sel, maka efek radiasi dapat dibedakan atas efek genetik dan efek somatik.

Waktu yang dibutuhkan sampai terlihatnya gejala efek somatik sangat bervariasi sehingga dapat dibedakan atas efek segera dan efek tertunda. Efek segera adalah kerusakan yang secara klinik sudah dapat teramati pada individu terpapar dalam waktu singkat (harian sampai mingguan) setelah pemaparan, seperti epilasi (rontoknya rambut), eritema (memerahnya kulit), luka bakar dan penurunan jumlah sel darah. Sedangkan efek tertunda merupakan efek radiasi yang baru timbul setelah waktu yang lama (bulanan-tahunan) setelah terkena paparan radiasi, seperti katarak dan kanker. Bila ditinjau dari dosis radiasi (untuk kepentingan proteksi radiasi), efek radiasi dibedakan atas efek deterministik dan efek stokastik.

Bila sel yang mengalami perubahan ini adalah sel genetik maka sifat-sifat sel yang baru tersebut akan diwariskan kepada turunannya sehingga timbul efek genetik atau efek pewarisan. Apabila sel terubah ini adalah sel somatik maka sel-sel tersebut dalam jangka waktu yang relatif lama, ditambah dengan pengaruh dari bahan-bahan yang bersifat toksik lainnya, akan tumbuh dan berkembang menjadi jaringan ganas atau kanker.

1. Efek : Efek radiasi yang dapat dirasakan langsung oleh orang yang menerima radiasi (contoh: kanker, leukimia, luka bakar, katarak, kemandulan, kelainan kongenital)
2. Efek Genetik : Efek radiasi yang diterima oleh individu akan diwariskan kepada keturunannya (contoh: penyakit keturunan, kanker pada masa kanak-kanak)
3. Efek Teragonik: Efek pada embrio (contoh: kemunduran mental)
4. Efek Stokastik: Efek yang kebolehjadian timbulnya merupakan fungsi dosis radiasi dan diperkirakan tidak mengenal dosis ambang (contoh: leukimia, kanker, efek genetik)
5. Efek Deterministik: Efek yang kualitas keparahannya bervariasi menurut dosis dan hanya timbul bila dosis ambang dilampaui (contoh: katarak, anemia, penurunan IQ janin, pneunomitis, kemandulan, sindrom radiasi akut)

Sifat Efek Stokastik

Sifat Efek Deterministik

- Tidak mengenal dosis ambang

- Timbul setelah melalui masa tenang yang lama

- Tidak ada penyembuhan spontan

- Keparahan tidak tergantung pada dosis radiasi

- Punya dosis ambang

- Timbul beberapa saat setelah terkena radiasi

- Ada penyembuhan spontan

- Keparahan tergantung dosis radiasi

ALFABET YUNANI

2008-05-09T02:40:00.000-07:00

Kapital	Kecil	Latin	Ekuivalen	Indonesia
A	α	Alpha	a	Alfa
B	β	Beta	b	Beta
Γ	γ	Gamma	g	Gamma
Δ	δ	Delta	d	Delta
Ε	ε	Epsilon	e	Epsilon
Ζ	ζ	Zeta	z/dz	Zeta
Η	η	Eta	(e panjang)	Eta
Θ	θ	Theta	th	Theta
Ι	ι	Iota	i	Iota
Κ	κ	Kappa	k	Kappa
Λ	λ	Lambda	l	Lambda
Μ	μ	Mu	m	Mu
Ν	ν	Nu	n	Nu
Ξ	ξ	Xi	x, ks	Ksi
Ο	ο	Omicron	o	Omikron
Π	π	Pi	p	Pi
Ρ	ρ	Rho	r	Rho
Σ	σ	Sigma	s	Sigma
Τ	τ	Tau	t	Tau
Υ	υ	Upsilon	u	Upsilon
Φ	φ	Phi	f, ph	Phi
Χ	χ	Chi	kh	Khi
Ψ	ψ	Psi	ps	Psi
Ω	ω	Omega	(o panjang)	Omega

Dosimetri

2008-05-05T04:05:00.001-07:00

PERHITUNGAN DOSIS

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Dosis Ekuivalen
H =DQN

dengan  H = dosis ekuivalen (Sv)   
D = dosis serap (Gy)
Q = faktor kualitas
N = faktor modifikasi lainnya

Dosis Ekuivalen ICRP 60
H_T = W_R D_T.R

dengan  H_T   = dosis ekuivalen pada jaringan T (Sv)
W_R   = faktor bobot radiasi
D_T.R  = dosis serap rata-rata pada jaringan T akibat radiasi R (Gy)

FAKTOR BOBOT RADIASI

Jenis Radiasi	WR
Foton, semua energi	1
Elektron dan muon, semua energi	1
Netron, dengan energi
<10 keV	5
<10 - 100 keV	10
100 keV - 2 MeV	20
2 - 2 MeV	10
>20 MeV	5
Foton, selain dari proton rekoil, energi >2 Mev	5
Partikel alfa, fragmen fisi, inti berat	20

Semua harga tersebut berlaku untuk radiasi eksternal dan internal.
Untuk elektron tidak termasuk elektron Auger yang dipancarkan inti yang diikat DNA.
Harga W_R berdasarkan ICRP 60 (1990)

Dosis Efektif ICRP 60

Jumlah dosis rata-rata dalam organ atau jaringan tubuh dengan memperhitungkan nilai bobot masing-masing.

E = W_TH_T

dengan E= dosis efektif individu
W_T= faktor bobot jaringan
H_T= dosis ekuivalen dalam jaringan T

Dosis Kolektif

Digunakan apabila terjadi paparan dalam sejumlah besar populasi (penduduk). Biasanya karena kecelakaan radiasi.

S_T = pH

S_T = pE

dengan S_T = dosis ekuivalen kolektif = dosis efektif kolektif (Sv-Man)
p = populasi
H = dosis ekuivalen (Sv)
E = dosis efektif (Sv)

Dosis Terikat

Dosis terhadap organ atau jaringan tubuh yang akan diterima selama 50 tahun yang disebabkan oleh asupan satu macam atau lebih radionuklida ke dalam organ atau jaringan yang bersangkutan.

ICRP 23 Reference Man
Air masuk harian = 2,2 l/hr
Nafas rata-rata = 2E4 ml/mnt
Permukaan kulit = 18.000 cm²

Kira-kira terdapat 10E13 sel di dalam tubuh manusia. Ada 140 gram Kalium, 125 nCi (4,625 kBq) adalah K⁴⁰ yang menghasilkan 0,25 mrem/minggu atau 13 mrem/th (2,5 μSv/minggu atau 0,13 mSv/th) untuk seluruh tubuh. Akan terjadi penambahan 15 mrem/th ketika mengkonsumsi senyawa garam lainnya.

DOSIMETRI INTERNAL

Kontaminasi Internal

ALI=BMT=L/h
dengan ALI = Anually Limited Intake (Bq)

BMT = Batas Masukan Tahunan (Bq)

L = batas dosis efektif tahunan atau NBD (Sv)

h = dosis efektif terikat per Bq intake (Sv/Bq)

Tingkat Dosis Efektif Terikat

D=(C:ALI)*L

dengan ALI = Anually Limited Intake (Bq)

L = batas dosis efektif tahunan atau NBD (Sv)

D = tingkat dosis efektif terikat (Bq)

C = nilai kontaminasi permukaan (Bq)

DOSIMETRI EKSTERNAL

Menghitung Lama Penyinaran

Penghitungan lama penyinaran secara khusus digunakan untuk menentukan berapa lama seseorang dapat berada di daerah radiasi yang tinggi sampai mencapai batas dosis.

Resolusi dari Sistem Spektroskopi Gamma
R = (FWHM : Peak Energy) x 100%
dengan R = Resolusi
FWHM = Full Width Half-Max peak height (lebar dari setengah tinggi maksimum) (keV)
Peak energy = energi puncak (keV)

Laju Dosis di Udara dari Sumber Beta Berbentuk Titik
D = 3,2291A / d2

dengan D= laju dosis serap (rad/jam)

A = aktivitas sumber (Ci)

d = jarak dari sumber (m)

Laju Fluks Foton dari Sumber Titik

Φ = AY/4πr²

dengan Φ = laju fluks foton (γ/cm².jam)

A = aktivitas sumber (peluruhan/jam)

Y = medan foton (γ/peluruhan)

d = jarak dari sumber titik (cm)

Laju Paparan dari Sumber Gamma Berbentuk Titik

X = ΓA/r²
dengan X = laju paparan (R/jam)

Γ = faktor gamma spesifik (R/jam pada 1 meter/Ci)

A = aktivitas sumber (Ci)

r = jarak dari sumber titik (m)

Hukum Kuadrat Terbalik

X₁ (d₁)²= X₂ (d₂)²
dengan X₁ = laju paparan terukur (Sv/jam)

X₂= laju paparan yang akan dihitung (Sv/jam)

d₁= jarak dari sumber dengan paparan terukur (m)

d₂= jarak dari sumber yang akan dihitung (m)

Laju Dosis Ekuivalen

H = AE / 6r²

dengan H = laju dosis ekuivalen (μSv/jam)
A = aktivitas (MBq)
E = energi (MeV)

r = jarak (m)

Laju Dosis Serap Sumber β dan γ Berdimensi Besar

D = 1,07 SE
dengan D = laju dosis serap (rad/jam)

S = aktivitas jenis sumber (μCi/gram)

E = energi rerata perdisintegrasi (MeV)
untuk β,

energinya (E) adalah 1/3 dari energi maksimum spektrum β

Konstanta Peluruhan

λ_eff = λ_r + λ_b
dengan λ_eff= konstanta peluruhan efektif (dt^-1)

λ_r = konstanta peluruhan radioaktif (dt^-1)

λ_b = konstanta peluruhan biologi (dt^-1)

Oleh karena

λ = 0,693 / T
dengan T = waktu paruh (dt)

maka, 1/Teff = 1/Tr + 1/Tb

dengan T_eff = waktu paruh efektif (dt)

T_r = waktu paruh radioaktif (dt)

T_b = waktu paruh biologi (dt)

Radioisotop Pemancar Gamma Berbentuk Bola

Diasumsikan radioisotop yang terdeposit dalam organ berbentuk bola

D = C Γ g

dengan C = konsentrasi radioisotop (aktivitas per satuan volume) (Ci/l)

Γ = faktor gamma (R.m²/Ci.jam)

g = faktor geometri, diberikan harga g rata-rata

Cosmic Rays

2008-05-02T04:45:00.000-07:00

High energy electrons, protons, and complex nuclei can be produced in a number of astronomical environments. Such particles travel throughout the universe and are called cosmic rays. Some of these particles reach our Earth. As these objects hit our atmosphere, other particles called pions and muons are produced. These particles then slow down or crash into other atoms in the atmosphere. Since the atmosphere slows down these particles, the higher we travel, the more cosmic radiation we see. When you visit the mountains or take an airplane ride, you will encounter more cosmic radiation than if you stayed at sea level.

Most cosmic radiation is very energetic. It can easily pass through an inch of lead. Since cosmic radiation can cause genetic changes, some scientists believe that this radiation has been important in driving the evolution of life on our planet. While cosmic radiation can cause some damage to individuals, it also has played an important role in creating humans. Our atmosphere is naturally shielding us from harmful effects. However, if we were to leave the earth and travel to some planet, we could be subjected to very high levels of radiation. Future space travelers will have to find some way to minimize exposure to cosmic rays.

Konversi Satuan

2008-04-30T03:28:00.000-07:00

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Satuan Radiasi
Rad, Roentgen, Sievert, Rem, Curie, Gray, J/Kg, C/Kg dan lain-lain
Satuan Panjang
meter, mil, yard, kaki, amstrong, inchi, dan lain-lain
Satuan Luas
are, barn, meter kuadrat, kaki kuadrat, mil kuadrat, inchi kuadrat, dan lain-lain

Satuan Massa
gram, kilogram, pound, ton, ons, kwintal, dan lain-lain
Satuan Volume
kaki are, kaki kubik, liter, galon, yard kubik, inchi kubik, fl oz, fluid ons, cc, kuart, dan lain-lain
Satuan Kecepatan
mil/jam, m/s, ft/s, km/jam, dan lain-lain
Satuan Kerapatan
gram/cm, pound/kaki kubik, pound/galon, dan lain-lain
Satuan Panas
BTU/lb, kJ/kgC, dan lain-lain
Satuan Gaya
kip, lbf, N, dan lain-lain
Satuan Tekanan
atm, bar, Pascal, mmHg, dan lain-lain
Satuan Energi
kWh, kal, BTU, erg, joule, dan lain-lain
Satuan Waktu
jam, menit, detik, hari, tahun, dan lain-lain
Satuan Konsentrasi
Ci/lt, Bq/m3, dpm/m3

Fusion and Fissian Reaction

2008-04-24T05:30:00.000-07:00

Reactions

If nuclei come close enough together, they can interact with one another through the strong nuclear force, and reactions between the nuclei can occur. As in chemical reactions, nuclear reactions can either be exothermic (i.e. release energy) or endothermic (i.e. require energy input). Two major classes of nuclear reactions are of importance: fusion and fission.

Fusion

Fusion is a nuclear process in which two light nuclei combine to form a single heavier nucleus. An example of a fusion reaction important in thermonuclear weapons and in future nuclear reactors is the reaction between two different hydrogen isotopes to form an isotope of helium:

²H + ³H ----> ⁴He + n

This reaction liberates an amount of energy more than a million times greater than one gets from a typical chemical reaction. Such a large amount of energy is released in fusion reactions because when two light nuclei fuse, the sum of the masses of the product nuclei is less than the sum of the masses of the initial fusing nuclei. Once again, Einstein's equation, E=mc², explains that the mass that is lost it converted into energy carried away by the fusion products.
Even though fusion n is an energetically favorable reaction for light nuclei, it does not occur under standard conditions here on Earth because of the large energy investment that is required. Because the reacting nuclei are both positively charged, there is a large electrostatic repulsion between them as they come together. Only when they are squeezed very close to one another do they feel the strong nuclear force, which can overcome the electrostatic repulsion and cause them to fuse.
Fusion reactions have been going on for billions of years in our universe. In fact, nuclear fusion reactions are responsible for the energy output of most stars, including our own Sun. Scientists on Earth have been able to produce fusion reactions for only about the last sixty years. At first, there were small scale studies in which only a few fusion reactions actually occurred. However, these first experiments later lead to the development of thermonuclear fusion weapons (hydrogen bombs).
Fusion is the process that takes place in stars like our Sun. Whenever we feel the warmth of the Sun and see by its light, we are observing the products of fusion. We know that all life on Earth exists because the light generated by the Sun produces food and warms our planet. Therefore, we can say that fusion is the basis for our life.

When a star is formed, it initially consists of hydrogen and helium created in the Big Bang, the process that created our universe. Hydrogen isotopes collide in a star and fuse forming a helium nucleus. Later, the helium nuclei collide and form heavier elements. Fusion is a nuclear reaction in which nuclei combine to form a heavier nucleus. It is the basic reaction which drives the Sun. Lighter elements fuse and form heavier elements. These reactions continue until the nuclei reach iron (around mass sixty), the nucleus with the most binding energy. When a nucleus reaches mass sixty, no more fusion occurs in a star because it is energetically unfavorable to produce higher masses. Once a star has converted a large fraction of its core's mass to iron, it has almost reached the end of its life.

The fusion chain cannot continue so its fuel is reduced. Some stars keep shrinking until they become a cooling ember made up of iron. However, if a star is sufficiently massive, a tremendous, violent, brilliant explosion can happen. A star will suddenly expand and produce, in a very short time, more energy than our Sun will produce in a lifetime. When this happens, we say that a star has become a supernova.
While a star is in the supernova phase, many important reactions occur. The nuclei are accelerated to much higher velocities than can occur in a fusing star. With the added energy caused by their speed, nuclei can fuse and produce elements higher in mass than iron. The extra energy in the explosion is necessary to over come the energy barrier of a higher mass element. Elements such as lead, gold, and silver found on Earth were once the debris of a supernova explosion. The element iron that we find all through the Earth and in its center is directly derived from both super novae and dead stars.
More peaceful uses of fusion are being researched today with the hope that soon we will be able to control fusion reactions to generate clean, inexpensive power.

Fission

Fission is a nuclear process in which a heavy nucleus splits into two smaller nuclei. An example of a fission reaction that was used in the first atomic bomb and is still used in nuclear reactors is

²³⁵U + n ----> ¹³⁴Xe + ¹⁰⁰Sr + 2n

The products shown in the above equation are only one set of many possible product nuclei. Fission reactions can produce any combination of lighter nuclei so long as the number of protons and neutrons in the products sum up to those in the initial fissioning nucleus. As with fusion, a great amount of energy can be released in fission because for heavy nuclei, the summed masses of the lighter product nuclei is less than the mass of the fissioning nucleus.
Fission occurs because of the electrostatic repulsion created by the large number of positively charged protons contained in a heavy nucleus. Two smaller nuclei have less internal electrostatic repulsion than one larger nucleus. So, once the larger nucleus can overcome the strong nuclear force which holds it together, it can fission. Fission can be seen as a "tug-of-war" between the strong attractive nuclear force and the repulsive electrostatic force. In fission reactions, electrostatic repulsion wins.
Fission is a process that has been occurring in the universe for billions of years. As mentioned above, we have not only used fission to produce energy for nuclear bombs, but we also use fission peacefully everyday to produce energy in nuclear power plants. Interestingly, although the first man-made nuclear reactor was produced only about fifty years ago, the Earth operated a natural fission reactor in a uranium deposit in West Africa about two billion years ago!

Definisi PLTN

2008-04-23T03:36:00.000-07:00

Pembangkit Listrik Tenaga Nuklir adalah sebuah pembangkit daya thermal yang menggunakan satu atau beberapa reaktor nuklir sebagai sumber panasnya. Prinsip kerja sebuah PLTN hampir sama dengan sebuah Pembangkilt Listrik Tenaga Uap, menggunakan uap bertekanan tinggi untuk memutar turbin. Putaran turbin inilah yang diubah menjadi energi listrik. Perbedaannya ialah sumber panas yang digunakan untuk menghasilkan panas. Sebuah PLTN menggunakan Uranium sebagai sumber panasnya. Reaksi pembelahan (fisi) inti Uranium menghasilkan energi panas yang sangat besar.

Daya sebuah PLTN berkisar antara 40 Mwe sampai mencapai 2000 MWe, dan untuk PLTN yang dibangun pada tahun 2005 mempunyai sebaran daya dari 600 MWe sampai 1200 MWe.
PLTN dikategorikan berdasarkan jenis reaktor yang digunakan. Namun pada beberapa pembangkit yang memiliki beberapa unit reaktor yang terpisah memungkinkan untuk menggunakan jenis reaktor yang berbahan bakar seperti Uranium dan Plutonium.

PLTN yang menggunakan reaktor fisi
PLTN yang menggunakan reaktor fisi menghasilkan panas dari reaksi fisi nuklir isotop fisil seperti Uranium dan Plutonium.
Reaktor fisi ini dibagi menjadi 3 kelas yaitu:
• Reaktor thermal yang menggunakan sebuah moderator neutron untuk memperlambat atau memoderasi laju produksi neutron cepat dari reaksi fisi, dan untuk meningkatkan kemungkinan terjadinya reaksi fisi berikutnya sehingga memungkinkan terjadi reaksi fisi berantai. Jenis Reaktor Thermal:
o Reaktor Air Ringan (Light Water Reactor/LWR): reaktor Air Mendidih (Boiling Water Reactor/BWR), Reaktor Air Bertekanan (Pressurized Water Reactor/PWR)
o Bermoderator Grafit: Reaktor Magnox, Reaktor Maju Berpendingin Gas (AGR), Reaktor RBMK, reaktor Pebble Bed (PBMR)
o Bermoderator Air Berat: Reaktor CANDU
Pembangkit Listrik Tenaga Nuklir di dunia didominasi oleh penggunaan reaktor PWR untuk menghasilkan sumber panasnya. Hal ini disebabkan teknologi PWR yang memiliki efisiensi yang cukup baik dan fitur keselamatan yang telah teruji.

• Reaktor cepat yang menghasilkan reaksi fisi berantai tanpa memerlukan moderator neutron.
Meskipun reaktor generasi awal adalah reaktor cepat, namun perkembangan yang dicapai reaktor cepat tidak sebanding dengan perkembangan yang dicapai oleh reaktor thermal.
Reaktor cepat memiliki beberapa keuntungan seperti dalam siklus bahan bakarnya dapat menggunakan Uranium alam, dan reaktor cepat juga dapat mengubah radioisotop yang berumur panjang dalam limbahnya menjadi bahan yang cepat meluruh. Dengan alasan ini, reaktor cepat lebih dapat terus-menerus sebagai sumber energi daripada reaktor thermal. Karena kebanyakan reaktor cepat digunakan untuk menghasilkan plutonium, maka reaktor ini dihubungkan dengan pertimbangan proliferasi nuklir. Lebih dari dua puluh reaktor cepat telah dibangun di Amerika Serikat, Inggris, Uni Soviet, Perancis, Jerman, Jepang dan India dan pada tahun 2004 dibangun satu buah di Cina. Jenis reaktor cepat ini seperti:
o EBR-I, 0.2 MWe, USA, 1951-1964.
o Dounreay Fast Reactor, 14 MWe, UK, 1958-1977.
o Enrico Fermi Nuclear Generating Station Unit 1, 94 MWe, USA, 1963-1972.
o EBR-II, 20 MWe, USA, 1963-1994.
o Phenix, 250 MWe, France, 1973-saat ini.
o BN-350, 150M We plus desalination, USSR/Kazakhstan, 1973-2000.
o Prototype Fast Reactor, 250 MWe, UK, 1974-1994.
o BN-600, 600 MWe, USSR/Russia, 1980-saat ini.
o Superphenix, 1200 MWe, France, 1985-1996.
o FBTR, 13.2 MWe, India, 1985-saat ini.
o Monju, 300 MWe, Japan, 1994-saat ini.
o PFBR, 500 MWe, India, 1998-saat ini.

• Reaktor subkritis yang menggunakan sumber neutron luar untuk menghasilkan reaksi fisinya untuk memulai reaksi berantai.

PLTN yang menggunakan reaktor fusi
Reaksi fusi nuklir memberikan kemungkinan dapat menghasilkan energi yang sangat besar dengan limbah yang sedikit dan tingkat keselamatan yang lebih baik. Namun masih terdapat tantangan ilmiah, teknis dan ekonomi untuk menjadikan reaktor fusi sebagai pembangkit listrik komersial. PLTN yang menggunakan reaktor fusi masih belum dalam tahap pengembangan.

Identifinder

2008-04-17T06:46:00.000-07:00

Identifinder adalah salah satu dari AUR (Alat Ukur Radiasi) yang menggunakan detektor NaITl dan tabung He-3. Alat dapat digunakan untuk:
1. Mengukur laju dosis dan dosis sinar gamma
2. Mengukur laju cacah netron
3. Analisis spektrum
4. Identifikasi nuklida
5. Mencari sumber radiasi
6. Stabilisasi spektrum
Range energi dari detektor ini adalah 25 keV – 2,5 MeV, sedangkan range pengukuran adalah 10 nSv/jam – 25 mSv/jam (untuk laju dosis) dan 100 nSv – 1 Sv (untuk dosis). Karena detektor ini menggunakan detektor sintilasi, maka efisiensinya cukup baik. salah satu kelebihan dari detektor ini yaitu dapat mengidentifikasi nuklida tertentu karena di dalam memorinya sudah terdapat library dari karakteristik nuklida-nuklida tertentu, seperti Co-60, Cs-137, K-40, U-235 dan sebagainya. Detektor ini mampu mengkalibrasi dirinya sendiri, multifungsi dan portable sehingga mudah di bawah kemana-mana. Alat ukur yang sejenis dengan alat ini adalah Fieldspec dan Identifinder Ultra.

Jika anda menginginkan Juknis AUR, dapat download di sini

Kestabilan Inti Atom

2008-04-15T03:29:00.000-07:00

Jika anda menginginkan file.doc. Silahkan Download di sini

KAIDAH PARTIKEL ALFA

Partikel Alfa (α) adalah bentuk radiasi partikel yang dapat menyebabkan ionisasi dan daya tembusnya rendah. Partikel tersebut terdiri dari dua proton dan dua netron yang terikat menjadi sebuah partikel yang identik dengan inti Helium (₂He⁴).

Partikel Alfa dipancarkan oleh inti radioaktif seperti Uranium atau Radium dalam proses peluruhan alfa. Kadang-kadang proses ini membuat inti dapat tereksitasi dan memancarkan sinar gamma untuk membuang kelebihan energi.

Peluruhan alfa dominan terjadi pada inti-inti tidak stabil yang relatif berat (Z > 80). Contoh Radium yang menjadi gas Radon karena peluruhan alfa. Proses puluruhan alfa dapat dituliskan secara simbolik melalui reaksi inti sebagai berikut:

_zX^A -->_z-2X^A-4 + α

Contoh peluruhan partikel alfa yang terjadi di alam adalah:

1. ₉₂U²³⁸ --> ₉₀Th²³⁴ + α

2. ₈₈Ra²²² --> ₈₆Rn²¹⁸ + α

1. Energi partikel alfa paling rendah 7,5 MeV diperlukan untuk penetrasi lapisan pelindung nominal pada kulit

(7 mg/cm² atau 0,07 mm).

2. Jangkauan partikel alfa di udara 1 atm

R_a = 0,56 E (E <>

R_a = 1,24 E – 2,62 (E ≥ 4 MeV)

Pada kondisi STP, setiap 1 mm udara, energi partikel alfa berkurang sebesar 60 keV.

3. Ketebalan jendela detektor menyebabkan energi partikel alfa berkurang sekitar 0,8 MeV per mg/cm² ketebalan jendela. Oleh karena itu detektor yang mempunyai jendela dengan tebal 3 mg/cm² (seperti pada proposional gas untuk deteksi alfa/beta dan detektor GM) tidak akan dapat mendeteksi emisi alfa yang lebih rendah dari 3 MeV. Detektor ini mempunyai efisiensi yang sangat rendah untuk partikel alfa yang berenergi rendah atau partikel alfa teratenuasi.

4. Detektor alfa proposional udara mempunyai energi dan respon efisiensi yang lebih tinggi dari pada detektor proposional gas atau GM.

5. Transfer energi partikel alfa ke udara.

Partikel alfa 6 MeV memproduksi 40.000 pasangan ion per cm.

Partikel alfa 4 MeV memproduksi 55.000 pasangan ion per cm.

Karena ω udara 34 eV per pasangan ion. Maka:

a. Partikel alfa berenergi 6 MeV turun 1,18 MeV per cm udara

b. Partikel alfa berenergi 4 MeV turun 1,87 MeV per cm udara

6. Energi partikel alfa turun 0,8 MeV per mg/cm² ketebalan kerapatan pada material penganetuasi.

7. HVT (Half Value Thickness) = Ketebalan yang meyebabkan energi alfa tinggal setengahnya.

a. Pada permukaan kontaminasi alfa, pertama kita menentukan laju cacah netto (dikurangi latar) tanpa perisai dengan detektor.

b. Letakkan sehelai mylar antara sumber dan detektor lalu ambil pembacaan lainnya. Ketebalan mylar antara lain 0,29; 0,45; 0,85; dan 0,9 mg/cm².

c. Hitung densitas HVT dengan persamaan:

d. Tentukan energi partikel alfa dalam MeV dengan persamaan:

Sifat Radiasi Alfa

a. Daya ionisasi partikel alfa sangat besar, kurang lebih 100 kali daya ionisasi partikel beta dan 10.000 kali daya ionisasi sinar gamma.

b. Jarak tembusnya sangat pendek, hanya beberapa mm udara, tergantung energinya.

c. Partikel alfa akan dibelokkan jika melewati medan magnet atau medan listrik.

d. Kecepatan partikel alfa bervariasi antara 1/100 sampai 1/10 kecepatan cahaya.

KAIDAH PARTIKEL BETA

Partikel Beta adalah elektron atau positron yang berenergi tinggi yang dipancarkan oleh beberapa jenis inti radioaktif seperti K⁴⁰. Partikel beta yang dipancarkan merupakan bentuk radiasi yang menyebabkan ionisasi sinar beta. Produksi partikel beta disebut juga peluruhan beta.

Peluruhan beta terjadi pada inti tidak stabil yang relatif ringan. Dalam peluruhan ini akan dipancarkan partikel beta yang mungkin bermuatan negatif (ß^- atau elektron) atau bermuatan positif (ß⁺ atau positron). Pada diagram N-Z peluruhan ß^- terjadi bila inti tidak stabil berada di atas kurva kestabilan, sedangkan peluruhan ß⁺ terjadi bila intinya berada di bawah kurva kestabilan.

Kurva pita kestabilan

Proses peluruhan partikel beta adalah sebagai berikut:

_zX^A --> _z+1X^A + β^-+ υ⁺ _zX^A --> _z-1X^A + β⁺+ υ^-

Contoh: ₁₅P³²--> ₁₆S³² + β^-+ υ⁺ ₈O¹⁵ --> ₇N¹⁵ + β⁺+ υ^-

Neutrino (υ⁺) dan antineutrino (υ^-) adalah partikel yang tidak bermassa, tetapi mempunyai energi yang disertai peluruhan β.

1. Energi partikel beta paling rendah 70 keV diperlukan untuk penetrasi lapisan pelindung nominal pada kulit

(7 mg/cm² atau 0,07 mm)

2. Rata–rata energi spektrum sinar beta ±1/3 dari energi maksimum.

3. Jangkauan partikel beta di udara sekitar 12 ft (3,6 m)/MeV.

4. Jangkauan partikel beta atau elektron dalam gram/cm² (tebal dalam cm dikalikan densitas dalam g/cm³) adalah kira–kira setengah dari energi maksimum dalam MeV. Kaidah ini menaksir terlalu tinggi jangkauan energi rendah (0,5 MeV) dan nomor atom rendah, dan taksiran rendah untuk energi tinggi dan nomor atom tinggi.

5. Laju paparan (rad/jam) dalam medium infinit yang terkontaminasi oleh pengemisi beta adalah 2,12 EC / ρ

dengan E(MeV) adalah rata-rata energi beta per peluruhan,

C (μCi/cm³) adalah konsentrasi, dan

ρ (g/cm³) adalah densitas.

Laju dosis pada permukaan massa adalah setengah dari nilai yang ditunjukkan oleh persaman di atas. Untuk partikel yang mempunyai massa besar, laju dosis gamma dan beta relatif berada pada rasio energi rata-rata yang dilepaskan per peluruhan.

6. Laju dosis permukaan yang melalui 7 mg/cm² dari deposisi tipis seragam 1 μCi/cm³ adalah 9 rad/jam (90 mGy/jam) untuk energi di atas 0,6 MeV. Catatan itu untuk lapisan tipis, laju dosis beta melebihi laju dosis gamma untuk energi-energi sama yang dibebaskan dengan faktor ~100.

7. Bremsstrahlung dari 1 Ci P³² larutan encer dalam botol kaca ~3 mrad/jam (30 μGy/jam) pada jarak 1 m.

8. Jangkauan partikel beta dari 0,01 – 2,5 MeV dapat dihitung dengan persamaan:

R (mg/cm²) = 412xE^{(1,265 – 0,0954ln E)}

dengan E adalah energi beta maksimum.

9. Untuk sumber Sr⁹⁰ atau Y⁹⁰ yang diameternya lebih besar dari 10 cm, pembacaan 0,1 mR/jam oleh pencacah Geiger portabel dengan jendela terbuka sesuai untuk tingkat kontaminasi 3,5E-5 μCi/cm² (0,069 μCi total). Untuk sumber kecil dengan diameter 0,75 cm, pembacaan sama sesuai untuk 3,5E-3 μCi/cm² (1,5E-3 μCi total).

10. HVT untuk energi beta:

a. Pada permukaan kontaminasi beta, pertama, ditentukan laju cacah netto (dikurangi latar) tanpa perisai dengan alat ukur yang digunakan.

b. Diletakkan selembar kertas 20 pound antara sumber dan detektor lalu diambil pembacaan lainnya.

Selembar kertas akan menghentikan semua partikel alfa dan beberapa partikel beta yang berenergi rendah. Jika laju cacah baru adalah 0, maka kontaminasi berasal hanya dari alfa dan atau beta yang berenergi sangat rendah seperti C¹⁴.
Selembar kertas akan mengurangi laju cacah partikel beta berenergi 400 keV menjadi setengahnya.

c. Penambahan selembar kertas berikutnya di antara sumber kontaminasi dengan detektor menjadikan laju cacah nettonya di bawah setengah dari laju cacah netto tanpa perisai.

d. Jumlah lembar yang digunakan untuk perisai adalah 7,5. Ini menunjukkan nilai HVT dalam mg/cm².

e. Jika tidak dapat menurunkan laju cacah menjadi setengahnya, maka dapat menggunakan persamaan berikut untuk mencari nilai HVT:

Untuk menentukan energi partikel beta dalam keV dengan persamaan:

Sifat Radiasi Beta

a. Daya ionisasinya di udara 1/100 kali dari partikel alfa.

b. Jarak tembusnya lebih jauh dari partikel alfa, di udara dapat beberapa cm.

c. Kecepatan partikel beta antara 1/100 sampai 99/100 kecepatan cahaya.

d. Karena sangat ringan maka partikel beta mudah sekali dihamburkan jika melewati medium.

e. Partikel beta akan dibelokkan jika melewati medan magnet atau medan listrik.

KAIDAH SINAR GAMMA

Peluruhan gamma tidak menyebabkan perubahan nomor atom maupun nomor massa, karena radiasi yang dipancarkan dalam peluruhan ini berupa gelombang elektromagnetik (foton). Peluruhan ini dapat terjadi jika energi inti atom tidak dalam keadaan dasar (ground state). Peluruhan ini dapat terjadi pada inti berat maupun ringan, di atas maupun di bawah kurva kestabilan.Biasanya peluruhan gamma ini mengikuti peluruhan alfa atau beta. Peluruhan gamma dapat dituliskan sebagai berikut:

_zX^A* --> _zX^A + γ

Contoh peluruhan gamma yang mengikuti peluruhan beta

₂₇Co⁶⁰ --> ₂₈Ni^60* + β^-

₂₈Ni^{60* -->} ₂₈Ni⁶⁰ + γ

Sinar Gamma buatan

X^m + n --> X^m+1* + γ

1. 6CEN. Untuk sumber titik dengan energi antara 0,07 – 2 MeV. Laju dosis (rem/jam) pada jarak ±30 cm diberikan dalam 20% oleh 6CEN.

2,22 TBqEN adalah formula yang sama dalam Sv/jam.

2. Laju dosis 1 m di atas lempengan, bidang infinit yang terkontaminasi dengan lapisan tipis (1 Ci/m²) oleh pengemisi gamma adalah:

Energi (MeV)

Laju Dosis

rem/jam

mSv/jam

0,4

0,6

0,8

1,0

1,2

7,2

100

130

160

190

3. Laju dosis (rem/jam) dalam medium infinit secara seragam terkontaminasi oleh pengemisi gamma adalah 2,12EC/ρ, dengan C (μCi/cm²), E (MeV) adalah energi gamma rata-rata per peluruhan dan ρ adalah densitas dari medium. Pada permukaan yang besar laju dosisnya kira-kira setengah dari laju di atas. Pada tingkat dasar (1/2 dari awan infinit), laju dosis yang terkontaminasi di atmosfer secara seragam sebesar 1600 EC rem/jam per μCi/cm³_.

4. Radiasi yang terhambur di udara dari sumber Co⁶⁰ sebesar 100 Ci dengan jarak 30 cm di belakang perisai dengan tinggi 1 m adalah 100 mR/jam (1 mSv/jam) pada 15 cm di luar perisai.

Sifat Radiasi Gamma

a. Sinar gamma dipancarkan oleh nuklida tereksitasi (isomer) dengan panjang gelombang antara 0,005 – 0,5 amstrong.

b. Daya ionisasinya di dalam medium sangat kecil sehingga daya tembusnya sangat besar bila dibandingkan dengan daya tembus partikel alfa atau beta.

c. Karena tidak bermuatan maka sinar gamma tidak dibelokkan oleh medan listrik maupun medan magnet.

KAIDAH NETRON

Jumlah netron per cm² per detik pada jarak R dari sumber kecil mengemisikan Q netron per detik tanpa perisai dapat dirumuskan:

Untuk sumber netron α,n

Q (netron per sejuta partikel alfa) = 0,152E^3,65

Dengan E adalah energi partikel alfa dalam MeV.

Nilai di atas untuk target Be. Sedangkan untuk target B dikalikan 0,16 dan target F dikalikan 0,05.

Energi Netron

Netron dingin 0 - 0,025 eV

Netron thermal 0,025 eV

Netron epithermal 0,025 - 0,4 eV

Netron cadmium 0,4 - 0,6 eV

Netron epicadmium 0,6 - 1 eV

Netron lambat 1 - 10 eV

Netron resonansi 10 - 300 eV

Netron intermediate 300 eV - 1 MeV

Netron cepat 1 - 20 MeV

Netron relativistik > 20 MeV

Catatan: Netron thermal mempunyai energi dan perubahan yang sama pada kecepatan yang sama sebagai molekul gas pada suhu 20 °C. Kecepatan netron thermal adalah 2200 m/dt (± 5000 m/jam).

Using x-ray

2008-04-10T02:02:00.000-07:00

Using x-ray diffraction to solve minerals processing problems

CSIRO Minerals is using in-situ and on-line x-ray diffraction analysis to examine various aspects of minerals processing.

Of Contents

The science behind x-ray diffraction (XRD)

CSIRO Min erals is using x-ray diffraction (XRD) to examine various aspects of minerals and materials characterisation and processing. Crystals are solids that form by a regular repeated pattern of molecules connecting together. Most (95 per cent) solid materials are crystalline. This means that they have a regular three-dimensional (3D) distribution (lattice) of atoms. When an x-ray beam hits a set of planes in such a lattice it is diffracted at a particular angle. This produces a peak in the diffraction pattern.

Mineralogical changes during pressure acid leaching of nickel laterites

Researcher aligning a capillary sample for x-ray powder diffraction. In-situ x-ray diffraction (XRD) studies werze used by CSIRO scientists to examine the pressure acid-leaching process used to extract nickel from laterite ores. In-situ XRD replicates the industrial processing conditions and collects data while the process is occurring, that is at elevated temperature and pressure. This avoids potential artefacts from sample extraction and preparation affecting the results. Using this technique, scientists can observe reaction mechanisms and rates as well as transitory intermediate phases.

CSIRO's study determined the reaction mechanisms of the nickel extraction process for different temperatures and acid concentrations. This contributes to the fundamental understanding of the process which is essential for its optimisation.

On-line mineralogy via continuous x-ray diffraction

(XRD) Commercial version of an on-line powder x-ray diffraction (XRD) analyser. CSIRO Minerals worked collaboratively with Fuel and Combustion Technology Ltd to design, build and test an on-line powder x-ray diffraction (XRD) analyser to provide a direct measure of the mineralogy in an industrial processing stream. The data from the on-line XRD can be used for dynamic plant control and product quality control.

The Australian cement industry has incorporated the on-line XRD analyser to accurately measure the composition and mineralogy of finished cement in real time. As well as providing quick and accurate information for the cement industry, on-line XRD analysis has potential uses in other areas including:

mineral processing
mineral sands
slurry streams
paint and pigments
detergents and cleaners
routine quantification of sodium phosphates
polymers
pharmaceutical

Nuclear Agency

2008-04-09T03:58:00.001-07:00

IAEA

The IAEA is the world´s center of cooperation in the nuclear field. It was set up as the world´s "Atoms for Peace" organization in 1957 within the United Nations family. The Agency works with its Member States and multiple partners worldwide to promote safe, secure and peaceful nuclear technologies.

Organizational Profile

The IAEA Secretariat is headquartered at the Vienna International Centre in Vienna, Austria. Operational liaison and regional offices are located in Geneva, Switzerland; New York, USA; Toronto, Canada; and Tokyo, Japan. The IAEA runs or supports research centers and scientific laboratories in Vienna and Seibersdorf, Austria; Monaco; and Trieste, Italy. See Offices and Contacts.

The IAEA Secretariat is a team of 2200 multi-disciplinary professional and support staff from more than 90 countries. The Agency is led by Director General Mohamed ElBaradei and six Deputy Directors General who head the major departments. See IAEA Staff.

IAEA programmes and budgets are set through decisions of its policymaking bodies - the 35-member Board of Governors and the General Conference of all Member States. Reports on IAEA activities are submitted periodically or as cases warrant to the UN Security Council and UN General Assembly. See Policy Bodies.

IAEA financial resources include the regular budget and voluntary contributions. The Regular Budget for 2007 amounts to Euro 283 611 000. The target for voluntary contributions to the Technical Co-operation Fund for 2007 is $80 million.

IAEA Mission & Programmes

The IAEA´s mission is guided by the interests and needs of Member States, strategic plans and the vision embodied in the IAEA Statute. Three main pillars - or areas of work - underpin the IAEA´s mission: Safety and Security; Science and Technology; and Safeguards and Verification. See Our Work.

Relationship with United Nations

As an independent international organization related to the United Nations system, the IAEA´s relationship with the UN is regulated by special agreement [pdf]. In terms of its Statute, the IAEA reports annually to the UN General Assembly and, when appropriate, to the Security Council regarding non-compliance by States with their safeguards obligations as well as on matters relating to international peace and security.

ANSTO Australia

The Australian Nuclear Science and Technology Organisation (ANSTO) is the centre of Australia's nuclear science capabilities and expertise. ANSTO's vision is to be recognised as an international centre of excellence in nuclear science and technology for the benefit of Australia.

ANSTO produces radiopharmaceuticals to help in the diagnosis and treatment of a range of serious illnesses. We also help solve a wide range of industrial and environmental problems.

ANSTO's ability to deliver these solutions is made easier by our international reputation for undertaking outstanding, innovative scientific research including environmental work into climate change, air pollution and groundwater ageing. The new OPAL nuclear research reactor makes it possible for ANSTO to deliver an extensive range of radioisotope products and industrial services to Australian and overseas customers.

OPAL also produces neutron beams which are used in neutron scattering science which is encouraging the best researchers from around the world to collaborate with us. Applications include analysis at an atomic level of structures, fluids, foods, as well as biological processes of the human body.

A further significant activity ANSTO undertakes is providing strategic advice to government on a range of important long-term issues, including climate change, power generation and counter-terrorism.

US-NRC Amerika

he U.S. Nuclear Regulatory Commission (NRC) was created as an independent agency by Congress in 1974 to enable the nation to safely use radioactive materials for beneficial civilian purposes while ensuring that people and the environment are protected. The NRC regulates commercial nuclear power plants and other uses of nuclear materials, such as in nuclear medicine, through licensing, inspection and enforcement of its requirements.

Regulatory Activities

Outreach

Opportunities To Work With NRC

Related Information

NRC Mission

To regulate the nation's civilian use of byproduct, source, and special nuclear materials to ensure adequate protection of public health and safety, to promote the common defense and security, and to protect the environment.

The NRC's regulatory mission covers three main areas:

Reactors - Commercial reactors for generating electric power and research and test reactors used for research, testing, and training
Materials - Uses of nuclear materials in medical, industrial, and academic settings and facilities that produce nuclear fuel
Waste - Transportation, storage, and disposal of nuclear materials and waste, and decommissioning of nuclear facilities from service

ANSN Asia

The objective of the ANSN project is to pool and share existing and new technical knowledge and practical experience to further improve the safety of nuclear installations in Asia.

The ANSN computer network is operated in a coordinated yet decentralised manner with 8 ANSN National Centres in China, Indonesia, Japan, Korea, Malaysia, the Philippines, Thailand and Vietnam. The web site associated to each National Centre provides access to important nuclear safety knowledge and serves as a portal to other ANSN sites. Searching the ANSN is done either locally or through the IAEA web site.

Nuclear Technology

2008-04-07T18:28:00.004-07:00

Nuclear technology is technology that involves the reactions of atomic nuclei. It has found applications from smoke detectors to nuclear reactors, and from gun sights to nuclear weapons. There is a great deal of public concern about its possible implications, and every application of nuclear technology is reviewed with care.

Discovery

In 1896, Henri Becquerel was investigating phosphorescence in uranium salts when he discovered a new phenomenon which came to be called radioactivity.[1] He, Pierre Curie and Marie Curie began investigating the phenomenon. In the process they isolated the element radium, which is highly radioactive. They discovered that radioactive materials produce intense, penetrating rays of several distinct sorts, which they called alpha rays, beta rays and gamma rays. Some of these kinds of radiation could pass through ordinary matter, and all of them could cause damage in large amounts - all the early researchers received various radiation burns, much like sunburn, and thought little of it.

The new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine (as had the discoveries of electricity and magnetism, earlier), and any number of patent medicines and treatments involving radioactivity were put forward. Gradually it came to be realized that the radiation produced by radioactive decay was ionizing radiation, and that quantities too small to burn presented a severe long-term hazard. Many of the scientists working on radioactivity died of cancer as a result of their exposure. Radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters.

As the atom came to be better understood, the nature of radioactivity became clearer: some atomic nuclei are unstable, and they can decay, releasing energy (in the form of gamma rays, high-energy photons) and nuclear fragments (alpha particles, a pair of protons and a pair of neutrons, and beta particles, high-energy electrons).

Nuclear Fission

Radioactivity is generally a slow and difficult process to control, and is unsuited to building a weapon. However, other nuclear reactions are possible. In particular, a sufficiently unstable nucleus can undergo nuclear fission, breaking into two smaller nuclei and releasing energy and some fast neutrons. This neutron could, if captured by another nucleus, cause that nucleus to undergo fission as well. The process could then continue in a nuclear chain reaction. Such a chain reaction could release a vast amount of energy in a short amount of time. When discovered on the eve of World War II, it led multiple countries to begin programs investigating the possibility of constructing an atomic bomb—a weapon which utilized fission reactions to generate far more energy than could be created with chemical explosives. The Manhattan Project, run by the United States with the help of the United Kingdom and Canada, developed multiple fission weapons which were used against Japan in 1945. During the project, the first fission reactors were developed as well, though they were primarily for weapons manufacture and did not generate power.

Nuclear Fusion

Nuclear fusion technology was initially pursued only in theoretical stages during World War II, when scientists on the Manhattan Project (led by Edward Teller) investigated the possibility of using the great power of a fission reaction to ignite fusion reactions. It took until 1952 for the first full detonation of a hydrogen bomb to take place, so-called because it utilized reactions between deuterium and tritium, isotopes of hydrogen. Fusion reactions are much more energetic per unit mass of fusion material, but it is much more difficult to ignite a chain reaction than is fission.

Research into the possibilities of using nuclear fusion for civilian power generation was begun during the 1940s as well. Technical and theoretical difficulties have hindered the development of working civilian fusion technology, though research continues to this day around the world.

Nuclear Weapons

The design of a nuclear weapon is more complicated than it might seem; it is quite difficult to ensure that such a chain reaction consumes a significant fraction of the fuel before the device flies apart. The construction of a nuclear weapon is also more difficult than it might seem, as no naturally occurring substance is sufficiently unstable for this process to occur. One isotope of uranium, namely uranium-235, is naturally occurring and sufficiently unstable, but it is always found mixed with the more stable isotope uranium-238. Thus a complicated and difficult process of isotope separation must be performed to obtain uranium-235. Alternatively, the element plutonium possesses an isotope that is sufficiently unstable for this process to be usable. Plutonium does not occur naturally, so it must be manufactured in a nuclear reactor. Ultimately, the Manhattan Project manufactured nuclear weapons based on each of these.

The first atomic bomb was detonated in a test code-named "Trinity", near Alamogordo on July 16, 1945. After much debate on the morality of using such a horrifying weapon, two bombs were dropped on the Japanese cities Hiroshima and Nagasaki, and the Japanese surrender followed shortly.

Several nations began nuclear weapons programs, developing ever more destructive bombs in an arms race to obtain what many called a nuclear deterrent. Nuclear weapons are the most destructive weapons known - the archetypal weapons of mass destruction. Throughout the Cold War, the opposing powers had huge nuclear arsenals, sufficient to kill hundreds of millions of people. Generations of people grew up under the shadow of nuclear devastation.

However, the tremendous energy release in the detonation of a nuclear weapon also suggested the possibility of a new energy source.

Nuclear Power

Commercial nuclear power began in the early 1950's in the US, UK, and Soviet Union. The first commercial reactors were heavily based on either research reactors, or military reactors. The first commercial nuclear reactor to go online in the US was the Shippingport Atomic Power Station in Western Pennsylvania. In some countries any form of nuclear power is banned.

Types of nuclear reaction

Most natural nuclear reactions fall under the heading of radioactive decay, where a nucleus is unstable and decays after a random interval. The most common processes by which this can occur are alpha decay, beta decay, and gamma decay. Under suitable circumstances, a large unstable nucleus can break into two smaller nuclei, undergoing nuclear fission.

If these neutrons are captured by a suitable nucleus, they can trigger fission as well, leading to a chain reaction. A mass of radioactive material large enough (and in a suitable configuration) is called a critical mass. When a neutron is captured by a suitable nucleus, fission may occur immediately, or the nucleus may persist in an unstable state for a short time. If there are enough immediate decays to carry on the chain reaction, the mass is said to be prompt critical, and the energy release will grow rapidly and uncontrollably, usually leading to an explosion. However, if the mass is critical only when the delayed neutrons are included, the reaction can be controlled, for example by the introduction or removal of neutron absorbers. This is what allows nuclear reactors to be built. Fast neutrons are not easily captured by nuclei; they must be slowed (slow neutrons), generally by collision with the nuclei of a neutron moderator, before they can be easily captured.

If nuclei are forced to collide, they can undergo nuclear fusion. This process may release or absorb energy. When the resulting nucleus is lighter than that of iron, energy is normally released; when the nucleus is heavier than that of iron, energy is generally absorbed. This process of fusion occurs in stars, and results in the formation, in stellar nucleosynthesis, of the light elements, from lithium to calcium, as well as some formation of the heavy elements, beyond Iron and Nickel, which cannot be created by nuclear fusion, via neutron capture - the S-process. The remaining abundance of heavy elements - from Nickel to Uranium and beyond - is due to supernova nucleosynthesis, the R-process. Of course, these natural processes of astrophysics are not examples of nuclear technology. Because of the very strong repulsion of nuclei, fusion is difficult to achieve in a controlled fashion. Hydrogen bombs obtain their enormous destructive power from fusion, but obtaining controlled fusion power has so far proved elusive. Controlled fusion can be achieved in particle accelerators; this is how many synthetic elements were produced. The Farnsworth-Hirsch Fusor is a device which can produce controlled fusion (and which can be built as a high-school science project), albeit at a net energy loss. It is sold commercially as a neutron source.

The vast majority of everyday phenomena do not involve nuclear reactions. Most everyday phenomena only involve gravity and electromagnetism. Of the fundamental forces of nature, they are not the strongest, but the other two, the strong nuclear force and the weak nuclear force are essentially short-range forces so they do not play a role outside the atomic nucleus. Atomic nuclei are generally kept apart because they contain positive electrical charges and therefore repel each other, so in ordinary circumstances they cannot meet.

Nuclear Accidents

Three Mile island Incident (1979)

The Three Mile Island incident, which ironically occurred two weeks after the release of the disaster film The China Syndrome greatly impacted the public's perception of nuclear power. Many human factors engineering improvements were made to American power plants in the wake of Three Mile Island's partial meltdown.

Chernobyl Accident (1986)

The Chernobyl accident in 1986 further alarmed the public about nuclear power. While design differences between the RBMK reactor used at Chernobyl and most western reactors virtually eliminate the possibility of such an accident occurring outside of the former Soviet Union, it is only recently that the general public in the United States has started to embrace nuclear energy.

Nuclear Power

Nuclear power is a type of nuclear technology involving the controlled use of nuclear fission to release energy for work including propulsion, heat, and the generation of electricity. Nuclear energy is produced by a controlled nuclear chain reaction which creates heat—and which is used to boil water, produce steam, and drive a steam turbine. The turbine can be used for mechanical work and also to generate electricity.

Currently nuclear power is used to propel aircraft carriers, icebreakers and submarines; and provides approximately 15.7% of the world's electricity (in 2004). The risk of radiation and cost have prohibited use of nuclear power in transport ships.

Medical Applications

Imaging - medical and dental x-ray imagers use of Cobalt-60 or other x-ray sources. Technetium-99m is used, attached to organic molecules, as radioactive tracer in the human body, before being excreted by the kidneys. Positron emitting nulceotides are used for high resolution, short time span imaging in applications known as Positron emission tomography.

Industrial Applications

Oil and Gas Exploration- Nuclear well logging is used to help predict the commercial viability of new or existing wells. The technology involves the use of a neutron or gamma-ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography.

Road Construction - Nuclear moisture/density gauges are used to determine the density of soils, asphalt, and concrete. Typically a Cesium-137 source is used.

Commercial Applications

An ionization smoke detector includes a tiny mass of radioactive americium-241, which is a source of alpha radiation. Tritium is used with phosphor in rifle sights to increase nighttime firing accuracy. Luminescent exit signs use the same technology.

Food Processing and Agriculture

In an effort to find new markets for isotopes, the Canadian nuclear industry is promoting the use of intense radiation from cobalt-60 to kill insects and microbes in spices, fruit, poultry, grain and other foodstuffs. The purpose is to prolong shelf life. A similar technology is used to sterilize medical equipment.

The industry proposes that irradiated food be labeled inconspicuously to minimize consumer anxiety.