Rutherford to Terabecquerel

The rutherford was proposed in the 1940s when the curie was the only game in town and was inconveniently large for many lab measurements. At 10⁶ dps (1 MBq), the rutherford sat in a useful range. But the 1975 SI reform chose the becquerel (1 dps) as the base unit with standard SI prefixes — kBq, MBq, GBq — which covered every scale. Having both the rutherford and the megabecquerel for the same quantity was redundant. The scientific community picked one, and the rutherford quietly disappeared from everything except unit conversion tables and physics trivia.

Rutherford discovered the atomic nucleus by firing alpha particles at gold foil (1911), identified alpha and beta radiation as distinct particle types, and performed the first artificial nuclear transmutation — turning nitrogen into oxygen — in 1917. He won the Nobel Prize in Chemistry in 1908, which famously annoyed him because he considered himself a physicist. His students went on to split the atom (Cockcroft and Walton) and discover the neutron (Chadwick). Nearly every branch of nuclear science traces back to his Manchester and Cambridge laboratories.

Several. The stat (1 disintegration per second, identical to the becquerel but proposed earlier), the eman (used for radon concentration in water, equal to 10⁻¹⁰ Ci/L), and the mache unit (another radon measure used in Austrian and German spa water literature) are all effectively extinct. The curie itself is technically obsolete under SI but persists through sheer institutional momentum in the US. The pattern is typical of measurement science: every era invents its own units, and standardisation eventually consolidates them.

Unlikely in practice because the rutherford disappeared from active use by the 1970s, before the megabecquerel entered common parlance in the 1980s. You would only encounter the rutherford in papers from roughly 1946–1970, primarily in European nuclear physics journals. If you see "Rd" in a modern unit conversion tool, it is there for completeness and historical interest, not because anyone is publishing in rutherfords. The real risk of confusion in old literature is between the curie and the becquerel, where a missing prefix can mean a billionfold error.

The "sunshine unit" — officially the strontium unit — was coined by the US Atomic Energy Commission in the 1950s to describe strontium-90 concentration in bones and milk during nuclear weapons testing. One sunshine unit equalled 1 picocurie of Sr-90 per gram of calcium. The name was a deliberate PR choice to make fallout contamination sound cheerful and harmless. It backfired spectacularly when journalists mocked it as Orwellian doublespeak, and the term was quietly dropped in favor of pCi/g Ca. It remains a cautionary tale about naming units for political rather than scientific reasons.

The total release from Chernobyl Unit 4 is estimated at 5,200 petabecquerels (5.2 × 10⁶ TBq), though figures vary by source and isotope accounting. Of that, about 1,760 TBq was iodine-131 and 85 TBq was caesium-137. For perspective, the entire global nuclear weapons testing era released roughly 2.6 × 10⁸ TBq — so Chernobyl was devastating but still a fraction of Cold War fallout. Fukushima released about 520 TBq of Cs-137, roughly one-sixth of Chernobyl.

To sterilise food, you need to deliver 1–10 kilograys of absorbed dose in minutes across conveyor belts of product. That requires an enormous photon flux, which only a multi-hundred-TBq cobalt-60 source can provide. A typical facility starts with 500–1,000 TBq and replenishes as the Co-60 decays (5.27-year half-life). The food never becomes radioactive — gamma photons do not induce radioactivity in stable atoms at these energies. Over 60 countries have approved food irradiation for spices, meat, and produce.

Nuclear medicine staff literally call it a "moly cow." A generator arrives with ~150 TBq of Mo-99 adsorbed onto an alumina column. Mo-99 decays (66-hour half-life) into Tc-99m, which is washed off the column with saline — "milking" the generator. Fresh Tc-99m accumulates between milkings, reaching peak yield about every 23 hours. A single generator supplies a hospital for about a week before the parent Mo-99 activity drops too low. It is one of the cleverest supply chains in medicine.

Fresh spent fuel is extraordinarily active — a single assembly registers in the petabecquerel range, dominated by short-lived fission products like I-131, Xe-133, and Ba-140. Within a year, activity drops by about 99% as these burn out. After 10 years it drops another 90%, leaving mainly Cs-137 and Sr-90 (both ~30-year half-lives). After 300 years those are gone too, and the remaining activity comes from transuranics like plutonium — far less active per gram but with half-lives of thousands to millions of years.

Permanently, no — radioactivity decays by definition. Practically, it depends on the isotopes deposited and the cleanup threshold. Chernobyl's exclusion zone still restricts habitation 40 years later because Cs-137 (30-year half-life) contaminated the soil at levels above 1,480 TBq/km² in the worst spots. Parts of Fukushima were decontaminated and reopened within years because the deposition was lower. The real question is not whether an area recovers, but whether society is willing to wait — or pay for aggressive decontamination.