Thanks to a tip from a friend, I spent Friday morning on a tour of the MIT Nuclear Reactor, which has intrigued me every time I walked by it on Massachusetts Avenue for almost 10 years. No cameras are permitted in the secure zone around the reactor building, so I can’t show you what’s inside the mysterious robin’s egg blue dome. It’s just as well, as the reactor core (less than a cubic meter) is utterly dwarfed by the shielding that surrounds it. Of course, I didn’t expect to get a direct look into the nuclear fire, and I was pretty well satisfied with the photograph in the very nice opening presentation, showing the 400 core plates lit by their own ńĆerenkov glow (a light, as the speaker carefully noted, produced by the beta emissions, as gamma and neutrons are not charged).

The reactor was built in 1958, and has been upgraded frequently since then, leading to a facility that is virtually a study in contrasts. The reactor building is built tough the old fashioned way, with two battleship steel shells and 4 meters of concrete between them. The only way in or out is through two manually operated airlocks. The catwalks and “polar crane” overhead all look far from modern. In the control room, about half the controls look like they could be six decades old.

The other half have been transferred to flat-panel displays shoehorned into the old switchboard racks. They track neutron flux and core temperature, as well as the flow of ultra-high-purity silicon ingots along a conveyor belt near the core for Neutron Transmutation Doping, which provides some of the income to support the reactor.

The MIT reactor is not widely known in Cambridge and Boston, and only makes the news when someone declares that they find it a worrying security threat. In fact, it’s a Highly Enriched Uranium reactor, meaning it contains the right kind of fuel to build an atomic bomb. In fact, this threat is very remote. Once a fuel rod has spent some time in the core, it contains an increasing level of fission byproducts that interfere with the chain reaction. These are called nuclear poisons, because they poison the chain reaction required for a nuclear explosion, rendering the fuel useless for bombs. The reactor only replaces a few fuel rods at a time, so there is never more than a very small amount of pure “HEU” on site, a tiny fraction of what would be needed for a bomb. Nonetheless, the reactor is switching to Low Enriched Uranium next year.

A greater worry is the spent fuel, after it is removed from the reactor. Uranium 235 has a half-life of 700 million years, and such great stability produces very little radiation. The fission byproducts have half-lives spanning days, months and years, so they are too radioactive to handle. Some people worry that such spent fuel might be used in a “dirty bomb”, dispersed as carcinogenic shrapnel by a conventional explosive. The reactor team is very cautious about spent fuel, to the point that our tour guide declined to tell us where it is stored.

I was very impressed to learn that the reactor can be staffed by a total of two people … and those people are often both MIT undergraduates. Talk about empowering students!

EDIT: Argh. Looks like WordPress can’t handle Unicode, and instead decided to truncate my post. Had to recreate it from memory.


I walked home from VoiceLab’s first rehearsal of the year amidst the falling snow. The streets were empty save for plows and buses. The sidewalks showed clear footprints from the small number of pedestrians.

I passed a pub, from which musical instruments could be heard as a few patrons stepped out into the weather, and thought about the timelessness of the scene.

I passed Cambridge City Hall, preceded by electrified trees and silhouetted by the sodium-vapor-orange midnight sky. It was far from timeless, but no less beautiful.

Direct Mail

I get a lot of junk mail from Sunsail, a charter boat company that my family used once for a (very pleasant) vacation. I hardly even glance at their brightly colored oversize postcards anymore, but before I tossed the latest one I was struck by their latest tagline:

Sunsail: Have Your Way With Us!

I have almost convinced myself that this is an accident.

I suppose they could just be really desperate for business. That would also explain why they’re trying to sell yacht charters in the Caribbean to a grad student.


I resolved to dig out my car today, and walked over to my parking space with my shovel. Here’s what my car looks like:
My snowbank... I mean car.
I visualized the packed ice under the snow, surrendered, and retreated to my apartment for the House marathon.

Oh, and we’re expected to get more snow before the temperature is ever above freezing. Argh.

EDIT: Pretty much ran out of food yesterday, and my bike has a flat tire, so I bit the bullet and actually dug out today. Actually, more like chipped out. As expected, the snow was only a light dusting over rock-hard ice. The excavation took over two hours, much of which I spent using the shovel’s handle as a truncheon.

Up and running

My laptop came back from Dell yesterday. Today I disassembled it to swap back in my actual hard drive. The repair sheet that came with it only says they wiped the hard drive (glad I didn’t ship them my real disk!) and “Other”. After looking at the motherboard, “Other” appears to amount to a piece of masking tape to hold a particular ribbon cable in place. Oh well.

Now I’ve got it back together with the right disk in it, and so far, so good. We now return to your regularly scheduled programming.


We won the hunt. I think I can say this in public now that 3:17 PM has passed, and the hunt is officially closed. We found the “coin” at about 6 AM this morning, hidden above a light fixture in an obscure lecture hall on the MIT campus. I have a replica of it here on my desk, in the form of a gorgeously laser-engraved wooden companion cube whose six faces commemorate the six worlds of the hunt: Mario, Megaman, Civilization, Zelda, Katamari, and Portal.

I can’t take any real credit for the team’s success. I can hardly name a puzzle I touched that was solved at all, never mind solved with any help from me. Computed this way, my success rate this year was lower than the last two, and far lower than you would expect from chance alone. I had fun brute-forcing Picross images and sketching convex hulls of point clouds, but my real contributions to the team were sparse, if not outright negative, overall.

Nonetheless, I’m filled with nervous excitement about next year’s Hunt. You see, the team that wins each year is obligated to create the next year’s challenge.

Thankfully the team has plenty of people who, unlike me, have the skill and creativity needed to create the next incarnation of this great tradition.


A friend threw a party tonight (theme: mass produced junk food). I brought a Slim Jim, which might have deserved third place behind the Twinkies and Easy Cheese. I biked there, on the theory that it was faster and safer than trudging a bit over a mile each way through the iceslush that covers the sidewalks. The streets were far from clear, but the sidewalks were worse.

This plan was working pretty well right up until the sudden flat tire near One Kendall Square. I considered trying to patch the tube there, in the dark alley. I considered dragging my bike, flat tire and all, through the snow back to my apartment. I considered walking back, getting my car, and driving back to pick up the bicycle, but my car is presently indistinguishable from a snowdrift so this was not a very good option.

In the end I left the bike there, locked to a signpost atop an icebank. I walked back wearing my helmet, taking some comfort that if I fell on the slippery sidewalks I would be well protected. I’ll have to pick up the bicycle soon, but I sure don’t know when. The next 36 hours are pretty much booked by the Mystery Hunt.

On the plus side, the party was a lot of fun, with all the best in terrible snacks, math talk, computer talk, and firsthand gossip about the rich and famous.

Snow Day

I’m not sure what exactly the definition of a blizzard is, but the city of Boston is pretty much taking the day off. That’s a lucky break for me, since I just ran out of clean socks and the laundromat downstairs is the one thing that’s open.

Somehow a snow day still manages to make me feel like I’m in elementary school. Too bad there’s no real chance of sledding, given the local topography.

Caveat Emptor

I eat a lot of tomato sauce, and so I’ve had a chance to figure out what I like in a sauce. One thing I find really unappetizing is excessive sweetness. (Francesco Rinaldi might be the worst offender.) I love the strong flavor of an unsweetened sauce, but they’re hard to buy. That’s why I was excited to find a can of Hunt’s sauce labeled “No Sugar Added” in my local Shaw’s.

I didn’t check the ingredients until I got home. Last ingredient: sucralose.

Today I found that Trader Joe’s sells a marinara that’s actually unsweetened. I bought it immediately.


A friend threw a low-key birthday party on Wednesday evening. We met up in the oak-paneled library of one of the Harvard houses, enjoying its parquet floor, high vaulted ceiling, and classic leather-bound volumes, dutifully dusted but never opened. We chatted about graduate studently things while toasting an occasional marshmallow in the marble fireplace. It was a really nice evening.

On the way out I borrowed an Asus EeeBox EB1007 to use while my Dell Latitude 13 is in the shop (for this problem). It claimed to ship with “Red Flag Linux”, the semi-official distro of the Chinese Communist Party*, so I was kind of excited to get a taste of bootable propaganda. Unfortunately the actual OS turned out to be “ASUS Express Cloud Gate”, a.k.a. Splashtop, a craptacular locked-down kiosk system without a terminal. On a system with no CD drive, this makes installing a real operating system a bit of a challenge.

*: Every political party should have a distro!