18 OCTOBER CLASS SUMMARY. HARRY POTTER VS TWILIGHT STYLE.

Bella, Edward and Jacob were strolling around the park minding their own business. Though the feud isn’t over, they’ve agreed over a truce for a while less Bella decides to go Mr. Bean again. Out of nowhere, the wind starts to blow rather wildly and the ghosts of Harry, Hermione, Ron and Lord Voldemort appear.

Harry: What the ... where am I?

Ron: What happened?

Hermione: Arghh! We’re dead! It was that damn Beaver!

LV: Haha! You guys are ghosts now!

Bella: Whoa! Vampires, werewolves and now ghosts!

Edward: Easy Bella, don’t go Mr. Bean again on me. It was hideous!

Jacob: Cool! I’ve always wanted to see a ghost, now I’ve got four!

‘Five actually’ says a voice and the ghost of Professor Dumbledore appears.

LV: Dumby!

HRH: Professor!

Jacob: Now who’s this old geezer?

PD: Hallo Jacob. My name is Dumbledore and I was the one who brought these ghosts here.

Hermione: You did? But why?

LV: Yeah Dumby, why?

PD: I’m not really sure though. Seems like the author wants me to teach you guys what he learned during his nuclear class the other day.

LV: Ooohh goody, nuclear!

Edward: Funny, we were talking about nuclear reactor safety just then.

PD: Well it seems we share the same author.

Hermione: Ooohh, hi Edward...

Bella and Ron: Hey!

PD: Back to the topic, some of the things he learned were already posted in previous entries so I’m going to touch on certain selected topics only. First off, the interim (temporary) storage of spent fuel.

Harry: OMG!

Everyone else: ...

Harry: Sorry, old habit...

PD: As I was saying, an irradiated (exposed to radiation) fuel has three properties namely heat generating, highly radioactive and fissile which is why we need to provide cooling, provide shielding and prevent criticality respectively. All irradiated fuel requires a period of at least 90 days for short-lived radioisotopes to decay which is why all reactors are designed with short-term storage facilities.

Hermione: Oohh really? What kind of storage?

PD: Well, storage facilities ‘at reactor’ (AR) can be either wet (ponds) or dry. In both cases they must

·        Shield against intense radiation from freshly discharged fuel

·        Have a method of decay heat removal

·        Ensure physical integrity of fuel.

·        Guard against criticality.

·        Allow easy and accurate fuel identification

·        Allow for easy fuel manoeuvrability

·        Withstand external hazards (earthquake, plane crash etc.)

For wet storage ... hold on let me magically summon a picture... Imagi-rumba Appear-oohlala!

Well now, you see:

·        Most spent fuel stores are formed from stainless steel-lined, reinforced concrete ponds filled with water, typically 2-3 metres above the top of fuel.

·        Water provides both heat removal and radiation shielding.

·        Cooling ponds are normally enclosed, incorporating heat exchangers and ventilation systems.

·        Ponds are designed with import/export facilities which allow fuel to be transferred into / out of transport flasks while underwater.

Ron: Oohh, it’s like watching Avatar in 3D.

PD: Next, I’ll talk about spent-fuel recycling. For additional energy production, uranium and plutonium recovered from spent fuel is introduced back into the reactor. This is called mixed oxide fuel (MOX) which is made from the mixture of uranium (UO2) and recycled plutonium (PuO2) where they follow separate routes in the fuel cycle:

·        Uranium is converted, re-enriched and fabricated

·        Plutonium is ‘diluted’ with depleted uranium (for example) then fabricated

Bella: Err, professor Dumbledore, why do we need to recycle the spent-fuel?

PD: A good question Bella and there are many answers to that namely:

·        Cost

·        Resource conservation

·        Political

·        Proliferation resistance

·        Ex-military material

·        Reducing environmental impact

Jacob: Uh-huh. What’s the catch?

PD: Aren’t you a sharp one. Here, have a dog biscuit. Plutonium recycling introduces problems in terms of its isotopes where:

·        The main problem from Pu is the increased activities of all the isotopes involved and the change in time of the isotopic composition.

·        Production of higher Pu isotopes by neutron absorption leads (by beta decay) to higher actinides of Am, Cm, etc.

·        Over time, stored241Pu β-decays to 241Am which means that the fuel loses its fissile potential and the activity is too high for practical fabrication.

However, to every problem there’s always a solution. True that about 1 nanogram of Pu ingested is enough to give an exposure equal to the annual limit (5000 milirem per year) which is why high levels of containment are required. In process containment, hold on ... Imagi-rumba Appear-oohlala!

Gloveboxes held at sub-atmospheric pressure achieve this whilst in process shielding, Pu gamma and neutron shielding will be required so steel/lead composite is used for gamma and polythene impregnated wood for neutrons respectively. Oh, and criticality control is also important. Again, Imagi-rumba Appear-oohlala.

Harry: That’s one funny-sounding spell.

Ron: Agree, sounds like a Lady Gaga’s song.

PD: Ahem. Moving on, next is nuclear transport. Did you know that every year, almost 38 million nuclear materials are transported worldwide? By road, rail, sea, air, usually in purpose-built transport vehicles. The IAEA has developed advisory regulations and standard tests for nuclear material containers and FYI, there have NEVER been any significant accidental releases of nuclear material during the transportation procedure.

 

Edward: Really? Are they as fast as me?

PD: Err no. There are different type of packages for these transportation and are chosen depending on the nature of the material (i.e. solid or liquid) and how radioactive it is. The higher the potential hazard presented by the material the more robust the package. Ahem, Imagi-rumba Appear-oohlala.

The type B package is for transportation of highly radioactive material and

is required to maintain integrity during routine, normal and severe accident conditions. After an accident the integrity must be such that there is no breach of containment, no increase in radiation to a level which would endanger the public or those involved in rescue and clean-up operations.

Type B –Test Requirements. Cumulative effects of:

·        free drop of 9m in most vulnerable orientation

·        penetration: 9m drop onto spike.

·        thermal test (fire of 800^oC for 30mins)

·        immersion in water (15m for 8hrs). Enhanced immersion test for packages carrying spent nuclear fuel –200m for 1hr

The type C Packages was added in 1996 and is used for small volume/ highly radioactive material being transported by air –including Pu. The tests carried out are:

·        Type B test plus

·        Dynamic crush test (drop 500kg mass from 9m onto specimen)

·        Enhanced thermal test (fire of 800oC for 1hr)

·        Impact test (not less than 90ms-1)

·        Enhanced immersion test (200m for 1hr)

LV: OIC. I hate to admit this, but that was pretty good Dumby.

PD: Why thank you Tom.

Again like Lady Gaga and Justin Bieber, they all heard another horrifying sound.

You’ve got the best of both worlds! And Miley Cyrus makes an appearance.

Everyone: Arghh!!! Make it stop!

PD: It’s okay. I’ll handle this. Disaster-movie-spoof spell!

Miley: Arghh! Buy Hannah Montana underwear and bra and tuuuuuttt...

The End