a surprise gift to Genoa / radioactive container could be Cobalt-60 dirty bomb
by Felicity Landon
Experts try to work out how to deal with 'security and ecological disaster' at Genoa
'Dirty bomb' fears are increasing at the Italian port of Genoa as the authorities try to establish the contents of a highly radioactive container, and work out how to deal with it.
The container has been at the port's Voltri Terminal since last July, but the situation, described by container scanning expert Joe Alioto as "an ecological nightmare," is reaching crisis point with fears that the box could be a terrorist weapon and opening it could trigger an explosive device.
The authorities are deciding whether to open the container by remote-controlled robot, or remove it from the port by barge.
The container is believed to have originated from Sun Metal Casting in Adjman in the UAE, and was supposed to be carrying 18 tonnes of copper for a customer north of Genoa.
It was exported through the Red Sea port of Jeddah and transhipped via Gioia Tauro to Genoa -- where it sat on the dock for several days before a technical check found it to be highly radioactive.
Since then it has been isolated by other containers filled with stones and water. It is understood that further tests this week concluded that the box contained a small but powerful source of radiation.
Joe Alioto, VP of Sales at VeriTainer, which manufactures container scanning systems, said it was likely that the container had been tampered with between Adjman and Jeddah.
"This is a security and ecological disaster," he said.
"The container is very nearly glowing with Cobalt-60; its contents are unknown and there is no game plan for its disposal. I wouldn’t go near it."
The situation has again highlighted the ongoing debate over container scanning. The box could just as easily have been transhipped to New York or any other major city port, said Alioto.
"In fact, 97% of containers arriving in the US are unscanned, then they remain on our docks, exposing 67 million Americans to the threat of a nuclear-radiation event until they are finally scanned when they leave the port.
"Many ports are surrounded by heavily populated areas, and detonating a nuclear or dirty bomb at a container terminal would be devastating."
Name, symbol Cobalt-60,60Co
Natural abundance 0 (artificial element)
Half-life 1925.1 d ± 0.1 d
Isotope mass 59.9338222 u
Decay mode Decay energy
Beta 2.824  MeV
γ-ray spectrum of cobalt-60
27Co, is a synthetic radioactive isotope of cobalt. Due to its short half life of 5.27 years, 60
27Co is not found in nature. It is produced artificially by neutron activation of 59
27Co decays by beta decay to the stable isotope nickel-60 (60
28Ni). The activated nickel nucleus emits two gamma rays with energies of 1.17 and 1.33 MeV, hence the overall nuclear equation of the reaction is
27Co + n → 60
27Co → 60
28Ni + e− + gamma rays.
Corresponding to its half life the radioactive activity of one gram of 60
27Co is 44 TBq (about 1100 curies). The absorbed dose constant is related to the decay energy and time. For 60
27Co it is equal to 0.35 mSv/(GBq h). This allows calculation of the equivalent dose, which depends on distance and activity.
Example: a 60
27Co source with an activity of 2.8 GBq, which is equivalent to 60 µg of pure 60
27Co, generates a dose of 1 mSv in one meter distance within one hour. The swallowing of 60
27Co reduces the distance to a few millimeters, and the same dose is achieved within seconds.
Test sources, such as those used for school experiments, have an activity <100 kBq. Devices for nondestructive material testing uses sources with activities of 1 TBq and more.
The high γ-energies result in a significant mass difference between 60
28Ni and 60
27Co of 0.003 u. The short lifetime contributes further to the high decay energy. This amounts to nearly 20 watts per gram, nearly 30 times larger than that of 238
The diagram shows a (simplified) decay scheme of 60
27Co and 60mCo. The main β-decay transitions are shown. The probability for population of the middle energy level of 2.1 MeV by β-decay is 0.0022%, with a maximum energy of 665.26 keV. Energy transfers between the three levels generate six different gamma-ray frequencies. In the diagram the two important ones are marked. Internal conversion energies are well below the main energy levels.
60mCo is a nuclear isomer of 60
27Co. After a half-life of 10.467 minutes and emission of 58.59 keV gamma rays it transforms into 60
With a low probability 60mCo also β-decays and populates the two "2+" levels of 60
Car scanning using Co-60 gamma-ray device.
The β-decay energy is low and easily shielded. Both strong gamma-ray frequencies are about the same magnitude, therefore 60
27Co is used as a gamma-ray source with energies around 1.3 MeV.
A container containing a small amount of cobalt-60.
Main uses for 60
* As a tracer for cobalt in chemical reactions,
* Sterilization of medical equipment,
* Radiation source for medical radiotherapy,
* Radiation source for industrial radiography,
* Radioactive source for leveling devices and thickness gauges,
* As a radioactive source for food irradiation and blood irradiation, and
* As a radioactive source for laboratory use.
27Co might be an efficient heater for a radioisotope thermoelectric generator. However, in contrast to the commonly-used 238
94Pu, its power is nearly exhausted after 10 years. It is also more difficult to absorb the γ-ray power of 60
27Co than the power of α-particles emitted by plutonium-238.
27Co could be used to "salt" a cobalt bomb. This a hypothetically-feasible but extremely "dirty" form of nuclear weapon that has never been produced. Hypothetically, a nuclear bomb with a tamper of 59
27Co would irradiate the cobalt with excess neutrons from the nuclear fission and transmute it into 60
The creation of 60
27Co is an important step in nucleosynthesis. Without the step through 60
27Co, no elements with atomic numbers from 27 through 83 could be created in supernovas.
Due to its the quite short half-life, there is no natural 60
27Co in existence. Synthetic 60
27Co is created by bombarding a 59
27Co target with a slow neutron source, usually californium-252 moderated through water to slow the neutrons down, or in a nuclear reactor such as a CANDU reactor, where the control rods usually made of steel are instead made of 59
27Co + n → 60
After entering a living mammal (such as a human being), most of the 60
27Co gets excreted in feces. A small amount is absorbed by the liver, the kidneys, and the bones, where the prolonged exposure to gamma radiation can cause cancer.
Cobalt is an element of steel alloys. Uncontrolled disposal of 60
27Co in scrap metal is responsible for the radioactivity found in several iron-based products.
Labels: Genoa Cobalt 60