Nuclear Reactor Basics

I had a conversation this morning with my two good friends. We're discussing Japan nuclear crisis following the 9.0 earthquake and tsunami. Radioactive materials are released into ocean and atmosphere, and I was left wondering how many kilograms of uranium material needed to power a typical nuclear reactor. Below are my estimates.

A nuclear power plant is powered by the nuclear splitting process (fission) of either natural or enriched uranium. Natural uranium has largely U-238, about 0.7% U-235 isotope, and a tiny amount of U-234. Enriched uranium has 3-5% U-235. Either natural or enriched uranium can act as nuclear fuel. The amount of heat liberated by one fissile U-235 atom is 202.5 MeV. Since 1 eV = 1.602 × 10^-19 J, 202.5 MeV = 3.2 × 10^-11 J. The atomic weight of uranium is 238 amu = 238 g/mol due to the overwhelming fractional amount of U-238. Since 1 mole = 6.02 × 10²³, the amount of energy liberated per kg of natural uranium due to U-235 fission is 134 is 566.6 GJ/kg.

A large power plant typically produces about 1 GW electrical power. Per year, this means an energy production of 31,536 TJ. Hence, the natural uranium needed to produce this much energy is 55.7 metric ton. But, this much uranium is for a 100% heat-to-electricity energy conversion efficiency. A more realistic efficiency number is 40% – as I expect the nuclear power plant will use high temperature steam to drive turbine blades – so that a more realistic estimate of natural uranium required per year for the 1 GW power is 139.3 metric ton.

The estimate amount for the enriched uranium will be 4-7 times less due to its higher U-235 composition, but the numbers of U-235 atoms required in either fuel types are the same.

Neutrons produced by the U-235 fission are also captured by the more abundant U-238 leading to the production of fissile Pu-239 (plutonium). The amount of heat released by fission of one Pu-239 atom is 207.1 MeV, which is comparable to the heat produced by fissile U-235, and is used as well for power generation. The Economist (31 March 2011) reported that Pu-239 was detected in soil samples taken from the surrounding area of Fukushima Daiichi nuclear power plant.

The Fukushima Daiichi nuclear power plant has 6 units with a combined electrical power output of 4.6 GW. They are boiling water reactor (BWR) type, where cooling water passes through the hot fuel and the steam is directly produced from the water.

Solar Thermal Heater: Molten Salt & Synthetic Oil

I came across a useful article on solar thermal power plants by MIT's Technology Review. It summarizes efforts of large energy companies to harness solar energy by capturing the energy through evaporation of a suitable working fluid in a Rankine cycle. The resulting steam from the evaporation is used to drive turbine blades, which then converts the steam's energy into electricity.

Siemens wants to use a mixture of molten potassium & sodium nitrate (molten salt) for the solar thermal power plant it designs and manufactures. The problem is that this molten salt freezes at around 220 °C. Kilometer long pipes used for this large scale power plant can be clogged by solid chunks since it is also difficult to control the pipe temperature to be always above the freezing point 24/7. Heat loss - radiative and convective - can be significant and freezing risk is real. A large scale power plant would require a heat storage to regulate the molten salt temperature.

This limitation also means that molten salt is not a good material for small scale power plant. The daily fluctuations of solar intensity makes molten salt unattractive as a result.

Solar thermal energy conversion method is more promising than solar photovoltaic since photovoltaic researchers still muse about 14 cents/kWh price, while solar thermal technology already has 13-20 cents/kWh pricing.

Another material used for solar thermal power plant is synthetic oil. The problem here is the temperature cannot exceed 390 °C since the oil will break down.

If I Won't Quit I Can't Win

My friend gave me $40 to gamble in a casino after his win from a jackpot terminal. I spent the first $20 and won. I have never played at casino before and have to say it can get addictive. There are those bright lights. There is also my feeling that maybe the next turn will make me win more.

The bright lights symbolize a lure any casino lays on anyone to visit and spend money. The lights never go off and daylight seems to go on forever. The buffet restaurant inside it offers cheap, good food. People - I think - figure why not go to casino and have a meal there. The money saved from the meal can be spent for gambling. Who knows maybe the saving can turn to a jackpot. I bet the reasoning is like that, pun intended.

The feeling that a win is just a game away is what keeps people coming back. I tasted my first ever win and wanted to get more. I know how easy it is, and it is exciting. The taste of winning makes me want play more. I get to know the odds, so I think.

I figure the odds are about 50-50 on a mechanical terminal game. Putting a $20 on a $5 game allows me to play 4 times. And the odds of winning once from the four games are very slim to even break even. I therefore decided to spread the risk by having at least 10 games. You see I thought I knew the odds could be tilted in my favor, if I was just smart enough. This feeling can become a reason to come back.

My friend, who gave me $40, has won a lot more several times before. It is possible to win more than once. He said he knew people who made a living from gambling, especially in Las Vegas. These guys are professional and they learn how to assess risks without emotion even when they play. They bet a lot and know when to quit by accepting losses. Some people can do this, but I suspect a lot more people cannot.

The question is thus whether I can control the urge to win a lot more than what I have. When I played the second $20, I lost. I concluded I had to quit if I wanted to win. Even with this knowledge, I kept playing until I lost $100. I still came out on top by a slim margin because I finally told myself to quit.

Harga Tak Berbanding

Aku kaget diberitahu kalau harga beras di Indonesia sekitar Rp. 8000/kg, atau sekitar US 90 sen/kg. Pendapatan rata-rata per orang di Indonesia US$4380 per tahun, atau sekitar Rp. 39 juta/tahun, yang bisa dipakai untuk beli 4870 kg beras.

Pendapatan rata-rata per orang di Canada US$39033, sementara tadi aku beli beras 9 kg seharga US$25. Jadi pendapatan rata-rata per orang di Canada bisa dipakai untuk beli 15613 kg beras.

Kekuatan beli orang Canada rata-rata 4 kali lipat lebih kuat dari orang Indonesia. Atau dengan kata lain, semestinya harga beras di Indonesia Rp. 2000/kg agar daya beli rakyat Indonesia setara dengan daya beli rakyat Canada.

Ketimpangan harga Indonesia-Canada seperti ini aku temui sehari-hari sewaktu di Indonesia tahun lalu. Harga secangkir kopi di Starbucks di Jakarta sekitar Rp. 20000, dan ini sama persis dengan harga secangkir kopi di Canada, yang sekitar CD$2. Herannya, kok banyak di Jakarta yang beli kopi di Starbucks?

Aku gak menyalahkan perilaku konsumen yang keliru karena aku melihat ada keuntungan ngopi di Starbucks. Duduk lebih enak dan tenang, ruangan lebih asri dan dingin, mau baca buku dan cangkruk gak diusir.

Harga-harga di Canada menurutku lebih mendekati ekuilibrium karena laju inflasi sangat rendah (1-2% per tahun). Masuk akal jadinya berpendapat masih ada banyak peluang bisnis di Indonesia untuk mengisi celah beda harga agar sampai ke titik ekuilibrium harga.

Making Sense of Heating Cost

Body heat is retained when using sleeping bag: A self-heating technology.

Living in Canada means surviving in very cold winter, unless you live in Vancouver or surrounding areas abutting Pacific Ocean. Canadian winter is harsh; temperature can dip to below -20°C regularly and it's been said to make Canadians strong quiet type. In the province of Ontario, it is slightly milder, about -10°C but the wind is fiercer. In Alberta, we get chinook ("snow eater") wind every 2-3 weeks, so the temperature can change from -20° to 5°C in a day and a week later it will drop to -20°C again.

At a household level, the winter means Canadian families need to spend money to heat their houses. Typically, a house is kept at about 21°C to make everyone feel comfortable (i.e., not wearing sweater at home), so there could be a 50°C temperature difference between inside and outside the house. The monthly heating cost can range from $90 in summer to $200 in winter. What is interesting is that most of this heating cost comes from administrative (30%) and delivery (30%) charges.

It is also interesting to notice that the retail natural gas price in Canada remains low, at about $4/GJ. (GJ = Gigajoule = 10⁹ Joule; Joule is a unit of energy, named after James Prescott Joule). How can I say $4/GJ price cheap? An old, energy-hungry fridge typically needs 639 kWh per year = 2.3 GJ per year. This means natural gas priced at $4/GJ could power this fridge for one month for less than $1. Another benchmark I can compare to is the electricity price in Canada, which is 8 ¢/kWh. The natural gas price of $4/GJ is equal to 1.4 ¢/kWh. It is not surprising Canadians are not that interested in energy-saving measures. It's the economy, stupid.

Note: A more familiar unit of energy is Watt (named after James Watt). 1 Watt = 1 Joule per second, so that 1 kWh = 10³ W × 3600 seconds = 3.6 × 10⁶ J = 3.6 MJ. (MJ = Megajoule.)

When the administrative and delivery charges are included, the natural gas price becomes roughly $8/GJ. The energy needed to heat an average-sized house per month is roughly 24 GJ in winter; thus the cost is about $200/month in the winter. Okay, so the numbers add up and we now understand our monthly natural gas bill.

The household 24 GJ/month heating budget is to compensate mostly for thermal radiation and convection heat loss from the house to outside. Thermal radiation loss from a house is proportional to the surface area of the house in contact with the outside. The larger the house, the larger the area becomes. A typical house in Canada has a surface area of 300 m². Using the Stefan-Boltzmann law,

ΔP = 4 ε σ A T³ ΔT,

we can figure out the amount of thermal radiation loss ΔP which depends on emissivity ε and outside temperature T (say, -23°C = 250 K). ΔT is the temperature difference which is about 7°C (roughly the difference between the exterior wall's and the outside's), while σ is the Stefan-Boltzmann constant. (Emissivity ε of the house exterior wall can be assumed to be 1, so we don't need to worry about it.) The numbers work out to be ΔP = 7.0 kW, or 18.1 GJ/month.

In addition to heating the house, we need to heat water for shower as well. The heat capacity of water is 4200 J/kg per degree Celcius. A person can use water up to 160 litre = 160 kg per shower. Considering a more environmentally committed family, a family of four might use about 450 litre for shower, cooking, and washing dishes. Canadians shower once a day, so the amount of energy needed to heat the water from 10°C to 60°C is about 95 MJ. In a month, it will be 4 GJ when factoring furnace efficiency. The water heating energy budget is about 17% of the total 24 GJ/month

The remaining 1.9 GJ/month could be attributed to convection loss and thermal contact loss with the ground.

The 7 kW heat emitted by a typical house is a waste heat. Your house is a light bulb, LOL. Your carbon footprint. This heat can be tapped and converted into electricity, but thermoelectric technology is not cheap.

Budaya Cangkruk

Aku anak kampung Surabaya. Waktu SD aku sering main di jalan: main petak umpet, gundu, baca komik. Bapak-bapak duduk merokok di emper jalan sambil cerita ini-itu. Tidak jarang ibu-ibu ikut nimbrung. Aku masih ingat karakter tetangga kiri-kanan rumah. Aku ingat pernah main sepatu roda jam 8 malam dengan teman-teman sekampung. Saking ramainya, kita diteriaki satu ibu tetangga yang memang tukang labrak dan disiram air got. Untung saja pakai sepatu roda jadi bisa kabur cepat.

Budaya cangkruk (nongkrong pinggir jalan) ini oleh sebagian orang dianggap kampungan. Kalau maksudnya: hanya orang kampung yang melakukan ini, ya benar juga.

Orang Canada berarti juga orang kampung. Orang Canada - terutama yang muda - suka sekali cangkruk. Mereka cangkruk di pub untuk minum bir, makan sayap ayam atau nachos, sambil ngomong ngalor ngidul. O ya, jangan lupa pub ini juga dipakai untuk memprospek cewek/cowok yang ingin mereka dekati. 

Jadi jangan disangka cangkruk gak ada di Canada. Cangkruk terpaksa dilakukan di pub karena cuaca Canada dinginnya minta ampun. Di Calgary musim dingin dari November sampai Mei (6 bulan cak!) dan suhu udara bisa turun sampai -30°C. Lha siapa yang mau ngobrol ngalor ngidul di emper jalan?! Bisa mati kedinginan dalam 5 menit.

Jadi tolong deh, jangan dihubungkan budaya cangkruk dengan sebagian orang yang bilang kurang produktifnya orang Indonesia. This is bullshit.

Satu budaya lain yang berhubungan dengan cangkruk adalah kenduri. Saat 17 Agustusan, gang di depan rumah ditutup dan tikar digelar berlembar-lembar. Kita duduk bersama dan menikmati makanan yang disiapkan ibu-ibu yang tinggal di gang. Satu kenangan manis yang tidak ada gantinya.

Di Canada, suasana kampung masih bisa dirasakan kalau tinggal di apartemen. Kita masih kenal tetangga karena lorong lantai menggantikan gang dan kita saling sapa. Suara anak kecil terdengar dari balik dinding. Kita masih ketemu waktu cuci pakaian. Apalagi di apartemen mahasiswa: ada tetangga yang bisa dititipin anak kecil, ada yang jualan makanan. Seperti kampung di Indonesia.

Saat aku pindah ke kompleks perumahan waktu SMP di Surabaya, aku tidak pernah lagi temui budaya cangkruk. Yang cangkruk cuma satpam dan tukang becak di pos ronda. Rasanya kurang hidup dan tiap-tiap keluarga sepertinya hidup sendiri-sendiri. Ini yang terjadi di hampir semua perumahan di Canada. Kita hidup sendiri-sendiri. Ada sih seperti balai RW - namanya community association centre - tapi kurang akrab karena tidak ada spontanitas. Semua pakai format rapat, jadi kalau ngomong harus hati-hati.

Hiburan cerita tetangga yang sering segar lucu jadi hilang karena spontanitas hilang. Cangkruk hilang dan diganti acara melototin teve. Payahnya banyak acara teve yang membosankan. Ada sih yang asyik; waktu di Indonesia aku suka lihat Take A Celebrity Out-nya Choky Sihotang atau Bukan Empat Mata-nya Tukul Arwana. Selebihnya bikin angop (ngantuk). Di Canada juga ada acara teve yang bagus: Seinfeld (rerun euy), House, Criminal Minds. Budaya cangkruk diganti budaya melototin teve.

Aku sih lebih senang cangkruk. Cerita lebih nyata dan aku mengenal karakter orang yang beragam.

What to Study at University?

My teenage son and I regularly discuss what he'll study at university. He plans to apply next year and I remember when I was his age I didn't know what to study. I knew what I liked but I never asked harder than that.

I tried to not repeat my mistake. I suggest him to apply to a program that suits his natural talent. We also discuss job paths. To ask how and why people become professors, businessmen, designers, engineers, and others. He gets bored sometimes when I want to discuss this issue, but he knows it's important.

I learn that parents - me included - are very invested in their children's higher education. It is difficult to separate what I want for him from what he wants for himself. If I am not willing to admit this, I am likely to repeat my mistake since my son and I share similar personal traits.

Undergraduate programs we consider in our discussion are

1. Engineering. He'll learn to memorize and use math equations, but he won't know how to get them. He'll have to study with his friends to survive grueling homework & exam schedule. Going into a program means specializing in a specific area of engineering. Mechanical engineering is the broadest and safest. Working as an engineer in the first 5-10 years means doing routine maintenance, design, or sales. Above average math and physics skills are needed, but it is not necessary to be creative. Experience matters since engineers learn by induction.

2. Mathematics. He'll learn abstract problem solving by pure reasoning and without specific area of specialization. He'll have to study alone most of the time. There is no team effort; if he doesn't get it, he will not understand it. Studying math often means also taking a minor in business or something else to make job prospect better. Above average math skills are a must and creativity is required. Experience does not matter since mathematicians learn by deduction. Engineer makes money by specialization and experience, while mathematician by generalization and quick mind.

3. Physics. He'll learn how to use math to solve science and engineering problems. Unlike engineering though, physics offers little specialization. But most what we know in engineering come from physics. He can think independently and analyze all sorts of real-world problems. Experience matters but deduction matters more. In the long run, knowing physics is more useful than engineering even in engineering companies. Taking math, however, is more general than physics since business problems do not follow mechanics axioms.

4. Business. He'll learn how to draw up a business plan when starting a company, to raise capital, to read financial statements, to understand tax and business laws. He'll learn how to run a business, the ins and outs of money. He and I agree that these skills are best studied by practice. I personally see little point of taking business courses if I am not going to use them now. He does not want to specialize in tourism, accounting, or others; they seem too narrow for him.

5. Design. I don't know any undergraduate program on design. I took a design course when in undergrad and I have to say it was not that useful unless I know physics well so that my design can be functional. Design is also part arts. If he does not draw and sketch, then he has no talent in design.

6. Economics. If the study route is mathematical economics, then studying math seems to give a better foundation for economics study. If the route is economics and one of social sciences - political, history, geography - then he'll have to read a lot. He seems more a thinker than a reader. He would waste his math talent as well.