Ruthenium is a transition metal element with the chemical symbol Ru and an atomic number of 44.
Naturally occurring ruthenium has 7 stable isotopes: 96Ru, 98Ru, 99Ru, 100Ru, 101Ru, 102Ru, and, 104Ru. The abundance of each isotope in naturally occurring ruthenium is given in the table below:
| isotope | abundance % |
|---|---|
| ruthenium-96 | 5.54 |
| ruthenium-98 | 1.87 |
| ruthenium-99 | 12.76 |
| ruthenium-100 | 12.60 |
| ruthenium-101 | 17.06 |
| ruthenium-102 | 31.55 |
| ruthenium-104 | 18.62 |
In addition to these naturally occurring stable isotopes, about 30 unstable, or radioactive, isotopes have also been identified. The most stable of these radioisotopes is ruthenium-106 which has a half-life of 359 73.days. It decays by emitting a beta particle to produce rhodium-106:
| 106 | Ru | → | 0 | e | + | 106 | Rh |
| 44 | -1 | 45 |
Ruthenium-106 is produced in a nuclear reactor as a product of the nuclear fission of uranium-235. Ruthenium-106 can be extracted from spent nuclear fuel and then it can be used in medicine to treat eye tumors.
The radioactive cloud wafting across Europe is most likely to be due to a spill of ruthenium-106 rather than a nuclear reactor accident since this would have released other radioisotopes which would have been detected in the cloud. France's nuclear safety agency has estimated the amount of radiation released at the source as between 100 and 300 billion becquerels.
A becquerel (Bq) is the SI unit for measuring radioactivity. It is equivalent to the radioactive decay of 1 nucleus in 1 second.
We can use this to estimate the mass of ruthenium-106 spilled:
| ABq | = | mass atomic weight | x NA x | ln(2) t½ |
ABq = activity in becquerels = 200 x 109 Bq (averaged)
mass = ? grams
atomic weight = 106 g/mol (from the Periodic Table)
NA = 6 x 1023 mol-1 (Avogadro's number)
t½ = 373.59 days = 373.59 days x 24 hours/day x 60 minutes/hour x 60 seconds/minute = 3.22 x 107 seconds
| 200 x 109 | = | mass 106 | x 6 x 1023 x | 0.6931 3.22 x 107 |
| 200 x 109 | = | mass 106 | x 6 x 1023 x | 2.15 x 10-8 |
| 200 x 109 | = | mass 106 | x 1.29 x 1016 | |
| mass | = | 200 x 109 x 106 1.29 x 1016 | ||
| mass | = | 1.64 x 10-3 g | ||
If the source of this ruthenium-106 was an accident involving spent fuel rods, then we can calculate the mass of spent fuel involved since 1.9 kg of ruthenium-106 can be extracted from 1 ton (or 1000 kg) of used fuel.
1.9 kg = 1.9 kg x 1000 g/kg = 1900 g
1900 g of ruthenium-106 can be extracted from 1000 kg (1 000 000 g) of spent nuclear fuel.
1 g of ruthenium-106 can be extracted from 1 000 000 g/1900 g = 526 g of spent fuel
1.64 x 10-3 g ruthenium-106 would be produced from 1.64 x 10-3 x 526 = 0.86 g of spent fuel
A typical nuclear power plant produces 20 tons (2 x 107 g) of used nuclear fuel per year, about 0.6 grams per second!
Reference:
http://www.smh.com.au/world/with-a-radiation-cloud-comes-a-mystery-from-russia-20171123-gzrvtf.html
Further Reading:
Isotopes
Atomic Number (number of protons)
Mass Number (number of nucleons)
Calculating Relative Atomic Mass (atomic weight)
Nuclear Half-life
Suggested Study Questions
- What does the term "isotope" mean?
- Give the atomic number of each of the following species:
- ruthenium-96
- ruthenium-98
- ruthenium-100
- ruthenium-102
- ruthenium-104
- ruthenium-106
- Give the mass number (or nuclear number) of each of the following species:
- ruthenium-96
- ruthenium-98
- ruthenium-100
- ruthenium-102
- ruthenium-104
- ruthenium-106
- Determine the number of protons in the nucleus of an atom of each of the following:
- ruthenium-96
- ruthenium-98
- ruthenium-100
- ruthenium-102
- ruthenium-104
- ruthenium-106
- Determine the number of neutrons in the nucleus of an atom of each of the following:
- ruthenium-96
- ruthenium-98
- ruthenium-100
- ruthenium-102
- ruthenium-104
- ruthenium-106
- Use the information in the article to calculate the relative atomic mass (atomic weight) of ruthenium.
- Explain what is meant by the term "unstable isotope".
- Explain what is meant by the term "beta decay".
- A number of unstable isotopes of ruthenium undergo beta decay. Write balanced nuclear decay equations for the beta decay of the following ruthenium isotopes:
- ruthenium-103
- ruthenium-105
- ruthenium-106
- ruthenium-107
- ruthenium-108
- ruthenium-109
- Explain what is meant by nuclear "half-life"?
- Ruthenium-106 has a half-life of of 359 73.days. Calculate the percentage of ruthenium-106 remaining after:
- 359.73 days
- 719.46 days
- 1079.19 days
- 3597.3 days
- If the mass of ruthenium-106 in the cloud over Europe is currently 1.64 x 10-3 g, calculate the mass of ruthenium-106 remaining in the cloud after:
- 1 year
- 2 years
- 10 years
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