Securing -99 supply

The molybdenum molybdenum-99 and its decay cousin -99m are extremely helpful and widely used in medical procedures, for example in the diagnosis of cancer. Current production methods for 99Mo are in question because of aging reactors and the use of weapons-grade . Fortunately, some new methods for producing 99Mo are under development and show great promise. If they are successful, molybdenum can continue to play its life-saving role.

Recent articles in MolyReview discussed 99mTc can be chemically bound to different uranium (LEU) in the reactor. Unlike HEU, the basic components of the molybdenum pharmacological agents that concentrate LEU cannot be used to make nuclear atom (January 2012 issue) and the the isotope in different parts of the body, weapons. The SAFARI-1 reactor in South extreme importance of the 99Mo isotope for example the heart, brain, and kidneys, Africa, for example, has operated using for medical use (July 2010 issue). Atoms among others. The gamma rays from the LEU fuel since June 2009 and other are composed of a nucleus, made of decaying 99mTc atoms produce a picture operators have followed suit, or are positively charged protons and uncharged of the target area, which is vital for the working on similar ways to reduce the use neutrons, surrounded by negatively diagnosis of different medical conditions. of HEU in the world. charged electrons. In a neutral atom, the 99m Tc is the most widely used medical number of electrons and protons is the isotope with over 55,000 procedures Two of the newer processes under same, and this number is called the performed every day in the US alone. development do not use a reactor or atomic number of the element, which for at all. These methods molybdenum is 42. However, atoms of The problem is that a few aging reactors use a particle accelerator. For one pro - the same element can have different are producing nearly all the world’s cess, the Government of Canada awarded numbers of neutrons in their nuclei. These supply of 99Mo, and they use highly $15 million in 2011 to the Canadian are called of the element. There enriched (weapons-grade) uranium (HEU) Light Source, a 2.9 GeV electron are 33 known isotopes of molybdenum, in the process. So there is an intense accelerator facility. They are investigating but only six are stable – the others effort by governments and private the production of 99Mo by bombarding decaying radioactively. companies to find alternative methods of another molybdenum isotope, 100Mo, producing 99Mo to secure its supply, and with high-energy gamma rays. In a similar The 99Mo isotope, with 42 protons and to reduce the use of HEU and the risk effort, the US Government has awarded 57 neutrons, is uniquely suited for use in of proliferation. a $22.2 million matching grant to medical diagnostic procedures. It is Northstar Medical Radioisotopes to build radio-active with a half-life of about 2.75 One of the newer methods is similar to a multiple linear accelerator complex to days, meaning that half the atoms, on the traditional, but uses low enriched make 99Mo, also from 100Mo. Northstar average, decay in that time. It decays to believes it could be producing 50% of the technetium-99m (99mTc), the metastable US need for 99Mo by the end of 2014. isotope of technetium, the element to the right of Mo in the periodic table. The short For the second process, the University half-life of 99Mo is ideal, as it is sufficiently of Wisconsin received a $20 million grant stable to be transported to its place of for the design of an accelerator-based use, while its radioactivity is short lived. neutron generator. In this route, the neu- trons would strike a sub-critical solution The 99mTc isotope is the one used in of uranium, producing the desired 99Mo medical procedures. It decays with a half- isotope. life of only six hours, emitting a 140 keV , similar in energy to that It is hoped that one or both of these from X-ray machines. The radiation is methods will provide a reliable source of thus detectable using standard “gamma the much needed molybdenum isotope in cameras”. This short half-life means that Technetium-99m is used as tracer in diagnostic the near future. This would maintain our the medical procedure can happen procedures to visualize organs. Here blood was vital supplies of 99 Mo without the use of labelled with 99mTc. The scans are showing blood rapidly and the radioactivity will leave uptake by the heart muscle (red-adequate, blue- weapons-grade uranium. the patient quickly. inadequate). © Zephyr/SPL (Tom Ferguson)

Excerpt from MolyReview 1/2013 1