10 differences of the RBMK and a PWR

Since it was 30 years since the Chernobyl accident on Tuesday, I was thinking it would be a good idea with 10 facts related to that as a little "comeback" of Friday Facts (so sorry that I don't manage to make these facts every week, it's just that lately I've either been travelling, or really busy with my PhD, which I sort of have to prioritize sometimes ;) ). Or, not just ten facts, but ten differences between the Chernobyl type RBMK reactor ("reaktor bolshoy moshchnosty kanalny", meaning high-power channel reactor), and the standard pressurized water reactor (PWR). 

Ready? 

Let's go!

1. PWR is the most common type of reactor in the world operated in countries like USA,  Belgium, Brazil, China, Finland, France, Germany, India, Japan (the Fuksuhima reactor was not a PWR, though), Russia, Spain, and Sweden, and several more. The RBMK was a Soviet develloped design - only built in the former Soviet Union.
2. the PWR uses water as both moderator (for slowing down all the neutrons from really high energies, to really low energy - which is what we want <3 ) and as cooling medium, but the RBMK uses graphite as moderator, and water as cooling medium. Normally we say that the PWR is light water (light water is what we normally just call "water", instead of heavy water) moderated and cooled, and the RBMK is graphite moderated and light water cooled.
3. the RBMK was designed with a positive void coefficient; I'll don't go in detail on that now (if you want me to, I can make a separate blogpost about what this means), but in short it is the reason why the RBMK is unstable under certain conditions
4. the tip of the control rods of the RBMK actually didn't control the reactor/absorb the neutrons -it was made out of graphite that speeds up the fission process, instead of a material that actually shuts it down
5. the control rods of the RBMK could be withdrawn completely from the reactor - even if it wasn't allowed (no one should EVER be able to overrun safety systems, like it was done the night of the accident)
6. it took almost half a minute to insert the control rods into the RBMK reactor; on a PWR it takes around a second or so
7. a PWR needs fuel which is enriched to 5% uranium-235, but the RBMK only needed 2% - so it was economical with the fuel
8. the RBMK could have its fuel changed while it was running. This, together with the low enrichment (no 7) made it ideal as a producer of weapons plutonium 
9. a PWR is passively safe, but the RBMK definitely wasn't
10. the Chernobyl reactor didn't have any outer barrier; meaning the reactor was placed more or less in a warehouse rather than a full containment building. Therefore, when the reactor actually exploded, the radioactive inside of it could get out, and fresh air (oxygen...!) could get in, making a strong fire that lasted for days

These are just the first ten big differences I could think of, but there are even more. 

When I, or other nuclear scientists, say that Chernobyl could never happen in a modern, Western reactor, it's not because we just don't want to see reality or something silly like that, but it's because of these facts listet above - which makes that accident physically impossible in, for example a PWR...!

testing of reactor grade concrete - the concrete stays intact, as the plane is just disintegrated (plane vs concrete: plane 0, concrete 1)

PS: There are still some RBMKs operating in the world today, but major modifications have been made to these reactors.

Not a good night...

the experiment is behind this thick, blue door (just before the migraine)

I had such plans for last night! I had the evening shift at the cyclotron, and in addition to baby sit the experiment, I was planning to answer a lot of e-mails, prepare for my teaching today, work on my  gammas from fission results, and I had planned to make a long blogpost about Chernobyl.

Then I got a migraine, and could just barely be at the lab, and didn't get to do anything at all! Luckily the cyclotron was behaving, so it was an easy shift, and I could even get an hour sleep - the only thing that helps.

The annoying thing is that now, even though the pain is gone, I'm really exhausted - wish I could just stay here in bed and sleep for a couple of hours, but I'm teaching the nuclear physics students about thorium and nuclear energy in a couple of hours, and I din't at all get to prepare my teaching yesterday. Meaning I have to do it now. 

Well well, hoping I'll feel better very soon (*poof* away with exhaustion...!), and hope you all will have a productive and good day!

If all goes as planned, I guess my todo list look something like this:

1. prepare teaching
2. answer e-mails
3. teach
4. work with TALYS - where to go next...?
5. make figures of gammas, gather them and send them to supervisor Jon
6. (start preparing for PhD day???)
7. work out (which I'm not particularly fond of, but I want my body to last for 70 more years, and then there's no getting around going to the gym)

"Chernobyl equals 100 Hiroshima bombs..." (foredrag)

"Radiation and reason" by Wade Allison

So tonight I'm preparing for a talk I'm going to give at Kongsberg Library tomorrow, which is the day that marks the 30 years anniversary for the tragic accident in the nuclear power plant in Chernobyl, and I feel like I need to address some of the myths and misconceptions about the accident and its consequences. The statement in the title of this blogpost is one of these myths, and it's of course NOT true. 

CHERNOBYL DID NOT EQUAL 100 HIROSHIMA BOMBS!

The thing is that this statement comes from someone (only) looking at the release of one isotope of caesium, and then comparing how much of this isotope was released in the Hiroshima atomic bomb explosion, and how much was released in Chernobyl. It is true that the release of one particular isotope was 100 times bigger from Chernobyl than from the Hiroshima bomb, but that tells us more or less zero... 

The reason why there was a bigger release of caesium from Chernobyl was that even tough the source of energy is fission in both a nuclear power plant and an atomic bomb, the fission process isn't exactly the same: the atomic nucleus is divided in different ways in those two, and you don't get the same fission products (caesium isotopes are some of them) from a nuclear power plant versus a bomb. (Remember, there was no nuclear explosion in the Chernobyl reactor - the radioactive release came from the normal operation.)

You do get caesium in both fission processes, but the amount of the different isotopes is different, and there's no problem finding certain isotopes that were released in much higher quanta in the Chernobyl accident than the Hiroshima bombing (like caesium).

What does this tell us?

Nothing, really.

The only thing it might tell us something about is that caesium is produced in different quanta in an explosion versus a power plant.

What does this saying makes us feel or think?
It makes us scared.

It makes us instantly think that Chernobyl was 100 times worse that the Hiroshima bomb. The accident was bad, but it doesn't even come close to dropping an atomic bomb on a city...!

What really kills in a nuclear explosion/atomic bomb is the extreme release of force, and not the radioactivity - believe it or not. The release of one specific caesium isotope from Hiroshima actually isn't particularly interesting. And the fact that there was a release of one certain type of caesium that was 100 times greater in the Chernobyl accident than the Hiroshima bombing does not tell us that Chernobyl was like 100 Hirsohima bombs!

Quote from this interesting article with five facts about nuclear power plants:

There's no getting around it: Chernobyl was awful. The design of the reactor was terrible, its purpose for being was terrible, its operation was terrible, the test they were performing when it blew up was terrible. The reactor was designed to primarily produce plutonium for nuclear weapons. The reactor was housed in a warehouse rather than a full containment building. It was designed so overheating sped up the reaction until the whole thing burst like an overinflated balloon. But we don't have to fear nuclear energy just because the Soviets did it the dumb way. That would be like banning cars because some drunk guy crashed one while trying to steer with his penis.

PS: I'm going to be a guest on Tidenes Morgen on P13 tomorrow morning around 8 AM, it will not be about the Chernobyl accident, but maybe it'll be fun to listen to :)

Grandmothers of Chernobyl

On Tuesday it's 30 years since the tragic accident at the Chernobyl nuclear power plant, and I see all kinds of articles and films and talks about the accident popping up on Facebook (and basically all over the internet) these days. Not so strange, really.

A friend of mine posted this video of "The Moonshine Grandmothers of Chernobyl", about old women living inside the exclusion zone in Chernobyl, that I really think you should watch :) (Click on the link just below the picture.)

https://www.facebook.com/AJWitness/videos/10156797667900557/?pnref=story

It's soon time for bed here in Rose-castle - we have a busy week in front of us, where I'm giving a talk about the Chernobyl accident at the library in Kongsberg, being a guest on "Tidenes Morgen" (P13), going to a funeral (unfortunately), and of course trying to work hard on my research - time flies, and by the end of this year there is no more money coming my way from the University anymore... 

Plan for tomorrow: get up super early, get Alexandra to kindergarden, work on Tuesday's talk, go to funeral, more preparation of talk, get home, work out, sleep...

Hope you all have had a great weekend!

See you tomorrow :)

One last "natural" post

So I was on the radio this morning (Kulturnytt - you can hear it here), and one thing that Berit made a point of was "natural carrots" versus "un-natural beta-carotene": In a study someone had isolated beta-carotene (that you find in carrots), and seen that it actually may increase the risk of getting some types of cancer (I haven't read the study, so don't take this as a warning - I have no idea of how big this risk increase is supposed to be, or how much you actually had to eat to see this increase, or if the study was even done on people, or what), but eating carrots seems to be healthy...

Well, if you isolate one substance (beta-carotene) from carrots, and this turns out to potentially cause cancer, then the only thing you've shown is that this particular substance cause cancer. And that there is an element in carrots that may be bad for you.

You have not shown that carrots are healthy because they're natural, and you have NOT shown that beta-carotene is bad because it was made in a lab! 

Maybe carrots are made of other substances than just beta-carotene...? 

These other substances may either neutralisze the negative effects of beta-carotene in some way, or the positive effects from the other substances may turn out to be so much better than the negative effects from the beta-carotene, so that all in all the effect is positive. But it's NOT because carrots are natural!

Someone critized me for my first blogpost about this subject, since no-one is talking about eating uranium. Ok, here are two other examples of something that people actually may eat: 

European destroying angel mushroom (Hvit fluesopp in Norwegian) and Cowbane (Selsnepe in Norwegian). Both of these are deadly poisonous!

Even potatoes may be dangerous to eat - if you eat potatoes that have become green you may have diarrhea, cramps, or you can even die (rare!)...

So again; please just stop using "natural" as a justification of why something is good, or that stuff that's made in a lab is bad!

2 years since we met...and happy birthday!

Yesterday it was two years since I was sitting alone in my office at Science Library; it was the middle of Easter, and was making my last preparations for the talk I was going to give later that day, in Hamar, at "The Gathering (TG) 2014".

As aI often do, I shared a couple of pictures on Instagram and Facebook...

...and suddenly I got a message from a guy…

I had never really talked to him before, but since I didn’t know anyone in Hamar, I was just happy to have someone to meet for a coffee, maybe eat something, maybe have a beer with.

In the middle of my talk I saw a new person in the audience, and I guessed it was Anders, and after I had finished on stage we started talking. And we talked. Ate pizza, drank beer. Shared a bottle of wine. And we talked, and we talked. And shared another bottle of wine.

There were never any coffee, but we talked for 12 hours straight  (a lot about physics, obviously, and especially about torque…:P), and somewhere between the beginning of the first bottle of wine and the end of the second, he kissed me.

I didn’t at all think that Anders was going to be the man of my dreams (it took me several months to realise); I thought he was too young, too much of a student, and too geeky. There were ups and downs from that first meeting in April until the end of December that year. First Anders was more into me than I was into him, and then it was the other way around, and then it was all a big mess!

For a long time I thought we would never happen…

it was the best of times, it was the worst of times

For some reason, something happened in January 2015, and finally we were at the same place at the same time. The emotional roller coaster ended, and we became a couple. We went on our first vacation...

...and just after we came back home from Barcelona, Anders moved in with me in Rosecastle <3

It’s so weird to think about how I’ve only known him for 2 years, because it really feels so much longer.

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So yesterday we were out celebrating the two years we've known each other, and today it's your 29th birthday, Anders. I am so grateful you sent those messages, and I am so happy we both figured out we were great for each other! Happy Birthday, I love you <3

after drinking a bottle of bubbles at Champagneria, we decided we were just tipsy enough to go bowling before we went home - perfect evening!

"Natural" (rant) on the radio

Remember this blogpost/rant, about how I hate the word "natural"?

Well, tomorrow I'm going to be on the radio (Kulturnytt), to rant a little bit more about why I think it's silly to use naturality as an argument for anything. Of course, a lot of things that people like to think about as natural are good, but that's not because they are "natural" - like I said in the other blogposts: a lot of things that are 100% "natural" are not at all good for us...

Judging by the first pictures you get from a "natural" google search, water is one of the things that's very "natural". Well, what if I go to the lab and make water from oxygen gas and hydrogen gas? Is there a difference on the water made in the lab or the water you get from nature?

Of course not!

(If you think there's a difference here, you're just missing basic knowledge of chemistry - you should educate yourself, and not go on and on about how "natural" is better.)

What does it even mean? What is "natural", and what is "un-natural"?

Abstract accepted! (#phdlife)

The week after Easter, just before we went on vacation, I got a very nice email. It read as follows:

Subject: ND 2016 - Decision on your abstract

Dear Mrs. Rose,

The organizers are pleased to note that your abstract ND/793 was accepted as a regular contribution to the conference. The slot allocated to your contribution is 20 minutes: 15 minutes for your presentation and 5 minutes for questions.

To confirm your attendance please complete at your earliest possible convenience your full registration for the conference at www.nd2016.eu (General Information, drop-down menu: Registration). You will be entitled to submit a regular paper for the proceedings.

Yours sincerely,

Arjan Plompen,

On behalf of the Organizing Committee

I have quite some work to do before this, but now I just definitely have to do it; so it's a good thing :) The abstract I submitted for the International Conference on NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY is this:

Prompt fission gamma ray emission from the (d,p)-induced fission of 233U

Prompt fission gamma-ray spectra have been measured in an experiment at the Oslo Cyclotron Laboratory (OCL), using a 12.5 MeV deuteron beam on a 233U target.Charged particles were recorded with the SiRi particle telescope, in coincidence with γ-radiation in the CACTUS γ-detector system,  and fission fragments were recorded with the NIFF PPAC-detectors .  CACTUS consists of 28 5”5” NaI(Tl) crystals,  mounted on a spherical frame;  with a total efficiency of 15%.

The (d,pf) reaction has been used as a “surrogate” reaction for the (n, f) reaction, and characteristics such as the prompt fission gamma ray spectra, and the γ multiplicity have been studied. Both characteristics have been extracted as functions of excitation energy, in the energy range 5-10 MeV, in the fissioning nucleus. The results are compared to a similar experiment from the OCL on the 239Pu isotope.

The setup enables us to study the nuclear level density and the gamma ray strength function, and these properties have also been extracted for the 234U isotope, from the same experiment. These results will also be presented.​

It will be a nice experience where I'll be presenting basically half of the results from my PhD - which is a good exercise for the thesis defence that will (hopefully) be a couple of months after this conference...

Writing this blogpost actually reminded me that I haven't registered to the conference yet - on the TODO-list! Brussels, here I come! (Ok, not yet, but in September, I'll be there :) )

En gavepakke til sjalu og kontrollerende kjæreste?

Hei alle fine, håper dere har hatt en fin torsdag :) Snart er det plutselig helg igjen - det går sykt fort (hjelp hjelp, hver dag som går er det samme som én dag kortere igjen av doktorgradsarbeidet mitt)!

Nok om det, og over til noe helt annet (og viktigere enn at det snart er helg igjen?):

Har du hørt om iPhones "Share my location"? Det hadde ikke jeg, før Anders for noen uker siden fortalte meg om det, og vips skrudde det på på telefonen min slik at vi kunne teste det ut. 

"Share my location" går rett og slett ut på at du kan dele hvor du er til enhver tid med en eller flere. Feks kan jeg dele min posisjon med Anders, slik at han kan ha full oversikt over hvor jeg befinner meg. 

Da jeg kom fra Cannes for et par uker siden, og Anders skulle hente meg på Gardermoen, kunne han fint se at jeg var i Taxfree-området og ved bagasjen, før jeg beveget meg ut til ankomstområdet der han ventet på meg. Det ser altså ut til å vise posisjonen med en nøyaktighet på kanskje ca 20 meter. 

Så langt, så godt - intet problem at man kan velge å dele posisjonen sin med noen dersom man ønsker det, og i tilfellet med at han sto og ventet på at jeg skulle komme gjennom tollen var det jo også riktig nyttig :)

sånn så det ut på Anders sin mobil mens han tracket meg på vei fra stranden og hjem til hotellet på Tenerife; han kunne til og med be om en "notification" når jeg kom til hotellet der han var - jeg visste ingenting om det som skjedde (det er altså ikke jeg som får tilbud om "notify me", men Anders...)

Problemet kommer hvis kjæresten din skrur dette på uten at at du vet det, for man får nemlig INGEN BESKJED om at noen til enhver tid kan spore deg (eller, det vil jo si telefonen din, da). Den du deler posisjon med, kan også be om å få notification når du forlater et sted, eller ankommer et sted. Anders kan feks be om å få beksjed om at jeg forlater hjemmet.

Hva om du har en sjalu og kontrollerende kjæreste som skrur på dette uten at du en gang vet om det - er ikke det ganske ugreit?

Jeg syns ikke dette er bra nok! 

Det er helt ok å kunne dele denne informasjonen, men telefonen burde være veldig tydelig på at man faktisk driver på og deler posisjonen sin (slik som når man deler internett fra telefonen står det øverst hvor mange datamaskiner som er koblet til, slik at man har oversikt over hvem som bruker datatrafikk fra telefonen din, feks). Om ikke med jevne mellomrom, så burde det i alle fall komme en beksjed feks et døgn etter at du har satt på share my location: “hei, du deler location med Anders, er du sikker på at du vil fortsette med dette?”, og kanskje til og med samme beskjed etter en uke. Nå er det sånn at har man først skrudd det på, så er det på, og sånn er det. Har du en som kan koden til mobilen din, som kjærester ofte kan, så har han eller hun muligheten til å bare skru dette på uten at du vet om det en gang.

For å sjekke om du deler posisjonen din kan du gå inn på: 

Innstillinger (Settings) -> 1. Personvern (Privacy) -> 2. Stedstjenester (Location services) -> 3. Del plasseringen min (Share my location). Der står det hvem du deler med (4.), og der kan du skru av (5.)

Mitt "problem" med dette er altså ikke det at jeg kan velge å dele posisjonen min med noen, feks Anders; men det at jeg ikke får noen beskjed om det.

Hva syns du? Er ikke dette litt slapt av Apple?

I hate the word "natural" (rant)

Yes, this really annoys me; how people argue that since it's natural it's better/good for you, and of course un-natural is bad for you...

Well, here are a couple of things that are natural, and some things that are un-natural:

• the sun, that for example can give you a serious sunburn - not very good for you, but completely natural
• sunscreen - not natural, but good for you if you're going to spend time in the sun
• water - natural; and good for you if you drink it (just not too much - it's always about doses), but deadly if you inhale it. (Think about water next time someone argues that if it's dangerous to breathe it has to be dangerous to eat...)
• glasses - not natural, but I think they're a really good idea
• radon gas - 100% natural, radioactive gas that comes from the ground. In the "right" doses it may cause lung cancer
• uranium - also very natural, and a heavy metal, and radioactive. I wouldn't eat it...
• flying - extremely un-natural, but many of us do it quite often
• chlorine - natural, and deadly

I could go on; even rape is probably natural if you look at how most mammals have sex (biologists: please feel free to correct me on this one!)

When I was pregnant I saw this all the time, people actually arguing that it can't be bad for you or the baby since it's natural - this is just plain stupid, and it's a dangerous way of thinking.

Why do so many have this idea that "natural" is better?

Whether something is natural or not tells us exactly ZERO about the dangerousness/healthiness of the product!

Ok, back to being happy figure making science girl again (or at least pretending to be: honestly it takes forever to make these figures, and I'm kind of starting to be really sick and tired of it :P ), I just had to get this off my chest :)

Science doesn't know everything...

...that's why we are still doing science! 

If we knew (or thought we knew) everything, we would've stopped - and I'm pretty sure the government wouldn't have used any money on universities or anything.

For example: where does uranium come from? 

We don't know!

I work with uranium (uranium-233 and -234 in particular), and we know it exist here on Earth, but how was it created in the first place? Actually there are MANY elements we don't know how got here - like silver and gold. But we know they exist, and we get better and better models and theories for how it happened <3 (One theory is that the heaviest elements here on Earth are created when two neutron stars collide - really cool and amazing!)

I work mostly with understanding everything about what goes on with my precious uranium in a fuel that's based on thorium (thorium is turned into uranium in a nuclear reactor; therefore I care about the uranium, even though the overall topic of my research is sort of thorium fuels), not really how it was created out there in Space, but the cool thing is that a deeper understanding of the uranium nucleus may also let us know a little bit more about how uranium has been created. 

The bigger picture is how thorium fuels behave, and how uranium is created - which my work will give no real answer to; but hopefully my PhD will eventually give us one more tiny mini piece in the total, gigantic science puzzle. You, know - baby steps. No giant leaps here ;)

Today I've been reading about gamma radiation and stuff for several hours, before I went to a great talk about nuclear astrophysics (by one of my PhD colleagues - Jørgen), before I went back to my office to punch numbers into a table, and look for a specific plotting program I haven't worked on for a couple of weeks (I eventually found it, so tomorrow will be plotting day), and suddenly it's almost 7'clock.

I realised I actually think of gamma radiation a little bit like sweat. Since when you heat a nucleus, it gets rid of that extra energy by sending off gamma rays - the nucleus sweats :D And we study the nucleus by studying its sweat; it's a little bit like we're trying to figure out how it was heated by looking carefully at the sweat. And eventually this may tell us more about the Universe...

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PS: I'm glad I spend more time wondering about how uranium and other heavy elements were created, than when it became "acceptable" for women not to wear a bra - like some bloggers do. Guess we're different...

Aldri mer ByTaxi

I dag må jeg nesten komme med et "antitips":

Da vi kom hjem fra Tenerife i går nærmet det seg kvelden. Vi var alle slitne etter flyturen og så frem til vår egen seng. Flyturen gikk overraskende bra og Alexandra satt rolig hele turen (bortsett fra litt virrevandring på slutten, men det er jo lov). For å komme oss hjem fra Gardermoen tenkte vi å ta taxi (vi hadde ikke spart veldig mye på å ta flytoget uansett).

Vi gikk bort til taxikøen på Gardermoen og litt smånaive (slitne!) tar den første taxien som kommer. Vi har flere ganger tatt taxi fra Gardermoen tidligere og fått den normale fastprisen som blant annet OsloTaxi har (759 på hverdager på dagen og 959 i helgene). Men denne gangen ble det ByTaxi.

Før vi i det hele tatt rekker å ta på setebeltet (også på Alexandra...) begynner han å kjøre mens Anders holder kaffekoppen min (pluss hans egen). Vi hadde ikke sagt hvor vi skulle eller noen ting. Han blir så smått irritert fordi Anders enda ikke har tatt på setebeltet (bilen piper jo og klager på det) og sier "kan du ta på deg beltet?". Anders holder jo her to kaffekopper og det er vel strengt tatt han som burde vente med å kjøre til alle har fått på seg beltene og at han vet hvor vi skal. Det virket som han med overlegg ville få turen raskt i gang ut på den enveiskjørte veien ut fra ankomstterminalen.

Etter at Anders da fikk på seg beltet sitt sa han hvor vi skulle og spurte han om hva fastprisen er. Sjåføren kunne da fortelle at det har de ikke. Han anslo at prisen ville være 1400-1500 kroner - altså 500 kroner mer enn fastprisen til OsloTaxi! Det er jo ikke ukjent for sjåføren at mange selskaper har nettopp fastpris og at kundene forventer dette. Det er noe han burde nevne. 

Sånne ting setter vi ikke spesielt pris på. Anders sa til ham at han umiddelbart skulle snu bilen og dra tilbake til flyplassen slik at vi kunne ta en taxi fra et annet selskap. Sjåføren ble smått irritert og sa "kunne dere ikke spurt om fastpris på forhånd?" - jo, det kunne vi - og det kommer vi til å gjøre fremover - men vi forventet vel egentlig at priskonkurranse burde virke som normalt. 

Anders ga taxisjåføren muligheten til å matche OsloTaxi sin pris, og vi endte med å få 1090 som fastpris - 130 kroner mer enn hva vi kunne fått hos f. eks. OsloTaxi. Det ville tross alt kostet mer å returnere til Gardermoen for å bytte taxi...

Da vi kom hjem Googlet vi "ByTaxi fastpris" og fikk denne linken som treff nummer 2: http://www.bt.no/reise/Du-blir-fladd-fra-Gardermoen-28013.html. Dette er tydeligvis strategien til ByTaxi. Jeg misliker sterkt selskaper som har som forretningsmodell å håpe på at kunden ikke legger merke til at de har blitt lurt før det er for sent...jeg vil ikke kalle det svindel, men hvor går egentlig grensen?

Jeg liker best å komme med hyggelige tips, men dette antitipset måtte jeg også dele :)

Ten facts about depleted uranium

As we were approaching the Tenerife airport yesterday, I suddenly remembered something... 

The thing is, I have this weird fascination for accidents and catastrophes (Titanic, bombings of Hiroshima and Nagasaki, the Chernobyl accident, and more or less all accidents from "air crash investigation ") - which is probably one of the main reasons I was interested in nuclear physics in the first place. If you're like me, you might know which thing, or accident, I came to think about as we were approaching the airport? It was of course the Tenerife accident of March 1977, involving two Boeing-747, that crashed at the runway, killing close to 600 people. If you're weird like me, you probably don't think I'm completely crazy for googling the accident. (If you're not like me, you might think I'm insane for reading all I could find about the deadliest air crash ever, just before I'm about to go on a six hours flight :v )

First I found a very interesting and well written article, but after I had read this, and still wanted more, I kept scrolling, and suddenly I saw the two words depleted uranium. I don't think it was from the most serious web page ever, but I was inspired by it to make ten facts about this mysterious material - check fact number 10 for why the Tenerife air crash and depleted uranium have anything to do with each other:

1. depleted uranium is what you get when you take natural uranium, and you enrich it to get enriched uranium for nuclear fuel - the "waste" from this process is the depleted uranium (natural uranium minus enriched uranium equals depleted uranium, to sort of make into an equation <3) reason why it's called "depleted" is that it's depleted in the fissile uranium-235 
2. natural uranium is made by uranium-238, uranium-235, and uranium-234. The uranium-238 isotope makes up 99.275%, uranium-235 is 0.72%, and uranium-234 is just 0.0054%. Depleted uranium is made up by typically 99.799% uranium-238, 0.2% uranium-235, and 0.001% uranium-234
3. depleted uranium is often called just DU
4. it's the least radioactive kind of uranium: depleted uranium is less radioactive than natural uranium - meaning it's close to not radioactive at all. Uranium-238 has an activity of 12 445 Bequerels per gram, uranium-235: 80 011 Bequerels per gram, and uranium-234: 231 million Bequerels per gram. The total activity of natural uranium is therefore: 25 280 Bequerel from 1 gram (meaning that 25 280 atoms of the uranium - either 234, 235, or 238 is changed into another atom every second :D), and the activity of depleted uranium is about half the activity: typically 14 600 Bequerels per second. (Don't be fooled by long halflifes - the longer the halflife, the less radioactivity... Activity/radioactivity sort of tells us how fast a material is turning into something stable: if the radioactivity is very high, the halflife is short. If it's very very low, the halflife is long. Uranium-238 has a halflife of 4.5 billion years, and is not at all very radioactive.)  
5. the gamma dose rate from a 30 mm DU-bullet (of 271 grams) at a distance of 1 m is 7 nano sieverts per hours, which is almost not distinguishable from the normal background radiation of typically 100 nano sieverts per hour. If you take 10 kg of DU and disperse it over 1000 m² the result is a gamma dose rate of 4 micro sieverts per year (the average background radiation from gamma in Norway is 0.5 milli sieverts)
6. DU is extremely dense, and therefore very heavy. Natural uranium is already a metal of high density, with 18.9 g/cm³, and DU is even more dense: 19.1 g/cm³ - making it almost 70% denser than lead 
7. because of the extreme density, it's used as ammunition; since a projectile made from DU has a bigger kinetic energy than if it were made by lead, and therefore it will penetrate or destroy almost anything. Also, if a DU bullet hits a tank, all the energy that it's carrying will turn it into dust, and the heat generated will make it burn. If you're in a tank that's hit by a DU projectile - it's not exactly the radioactivity you should fear...
8. DU is actually the best kind of shielding you can make to protect yourself against gamma- or X-rays. It's even better than lead, since uranium has 92 protons in the nucleus, compared to only 82 in lead. (You could also shield with natural uranium, but since natural uranium has more of the uranium-235 isotope than depleted uranium, and 235 is more radioactive than 238 and DU, you would rather use DU than natural uranium)
9. uranium (thus also depleted uranium) is a heavy metal, like lead, and this fact is the main reason it's not very healthy - not the radioactivity. You take natural uranium, and make into something that's about half as radioactive as it already was. It's not like you make a new radioactive material. 
10. depleted uranium is also used as counterweight in airplanes like the Boeing-747; that carries around 250 kg of DU. I didn't know this until I started reading all I could find about the 1977 Tenerifie aircrash. I definitely learned something new, and now I want to learn more about counterweights :)

Luckily we got home safely after a great week of vacation, and I think I'm ready for a couple of very busy months. I've made a nice plan for this week, that includes talking about cold fusion on the radio tomorrow. Sorry I haven't been "here" last week, but I needed the vacation, and Alexandra needed her mother to be there, on vacation with her, and not on the cell or the computer all the time...:)

Friday FACTS: cosmic radiation

Friday Facts on a Sunday again - I'm starting to think I should just call it "facts"... Well, I'll try a little bit more, and see if I manage to get back on track with actually having FRIDAY facts on FRIDAYS again :P

Anyway: this day started super super early; the alarm rung at 3:15, and at 7 we took off from Gardermoen airport, with Tenerife as our destination. I feel almost silly to have one week of vacation now, just after Easter, but it just had to be this way this time. Since we've been flying today, I thought the perfect theme for facts is cosmic radiation...:

1. 1. cosmic radiation is a mixture of particles, like protons, neutrons, alphas, and electrons, and gamma- and X-rays. Most of it comes from outside our solar system, and a small part comes from the sun 
   2. when the solar activity is high, there is more radiation coming towards the earth (since the small part that comes from the sun becomes larger :) )
   3. our atmosphere works as a radiation shield for us; the cosmic rays come into it and interact, so that the rays/particles are either stopped completely, or at least lose their energy - which is a good thing for us here on Earth :)
   4. the intensity of the cosmic radiation changes with altitude - which is sort of logic, since you move “closer to space” if you climb up on a high mountain, or you get on a plane, so that there’s less atmosphere to stop whatever rays that are coming towards us from outer space. When you go from sea level to around 1600 meters above sea level, the intensity of the cosmic radiation doubles. If you go to 5000 meters, the radiation is 8 to 10 times more intense than at sea level, and if you’re on a plane, at 8500 meters above sea level,  the level of radiation is 40 times higher than at the ground 
   5. pilots and air attendants are actually classified as radiation workers; even though I work in a nuclear physics lab, with the cyclotron (that produces ionizing radiation), and with actual radioactive substances, they receive a higher dose each year than I have ever received 
   6. there are four factors that decides how big of a dose you will receive: solar activity (more activity from the sun means more particles bombarding Earth), time (if you spend a lot of time in a plane, 10 000 meters above sea level, you will of course receive a larger dose than if you spend little time at these altitudes), altitude (the higher you go, the more radiation - see point number 4), latitude (the shielding is better around equator that towards the poles - at typical flight altitudes, the difference between the cosmic ray dose rates at the equator and high latitudes is about a factor of two to three) 
   7. normal, average annul dose from cosmic radiation is 0.35 milli Sievert (this is not much - in Norway, we receive around 2 milli Sivert from radon gas, 0.6 from medical use, 0.55 from external gamma radiation, 0.35 from internal gamma radiation, and then just 0.35 from cosmic ;) )
   8. the annual dose for pilots and air attendants is somewhere between 2 and 3 milli Sivert per year; which means that if you work on a plane, your dose is well below the normal annual limit for radiation workers that is 20 milli Sievert, but more than the general public is allowed to receive (still not much - it just means that the dose limits for “members of the public” is really really strict ;) )
   9. the dose you receive on a long distance flight (like Oslo-Tokyo back and forth) is four times bigger than the total dose the average Norwegian receives from fallout from the Chernobyl accident in April 1986, from that year and 50 years into the future. (This does NOT mean that you receive a big dose from being on a plane, but that the dose we get from Chernobyl in Norway is small.)
   10. flying to the Mediterranean will get you an extra dose from cosmic radiation, equal to one meal of reindeer meat with a radioactivity of 10 000 Bq/kg. A pilot receives something equal to 100 such meals every year. If you have been scared into believing it's dangerous to eat Norwegian reindeer meat because of the radioactive downfall from Chernobyl 30 years ago, then you definitely shouldn't fly… (hint: fly as much as you want to, and eat the reindeer you want to - it's not doses that are dangerous to you; they might even be positive :) )
   
   
   
   
   
   
   Back and forth to Tenerife is about 13 hours on a plane, in roughly 10 000 meters altitude. This means that when we get back to Oslo, we've all received an extra dose of radiation of 0.065 milli Sieverts (this is just a very rough average estimate, since I haven’t really taken into account where we are flying, or where in it 11-year cycle the sun is just now - I actually have no idea of that , but maybe some of you guys know? :P ).
   
   
   PS: I didn't manage all my goals, but at least I did "finish" my article draft, and I sent it off to supervisor Jon on Friday. Also, I'm planning on plotting some stuff while I'm here - not exactly working, but sort of maintenance ;)