Answer to Question #219 Submitted to "Ask the Experts"
Category: Radiation Basics — Radionuclides
The following question was answered by an expert in the appropriate field:
I recently discovered 90Sr is used for a variety of commercial purposes. Among them are for measuring
thickness of rubber and paper, medical and pharmaceutical uses, and in aircraft.
My question has three parts: (1) Are there other major uses for 90Sr? (2) How is it produced? and (3) How much of it is produced in this country
per year? Thank you for your help in this matter. Stephen Weldert
- 90Sr is one of the most useful radionuclides. The primary uses of 90Sr are:
- As a heat source for SNAP power sources (SNAP stands for "systems for nuclear
auxiliary power"), which are used to produce electricity in remote locations where
electrical power lines do not exist. SNAP devices have been used by the military
as a source of transportable power, such as power sources in the arctic, and as
power and heat sources for spacecraft. 90Sr is useful because it emits, together with its daughter product, 90Y, large amounts of beta energy as heat.
- As a source of the medical radionuclide, 90Y, which is used as the radioactive component of radiolabeled antibodies for
cell-targeted radioimmunotherapy of cancer. 90Y also has applications as the radioactive material in direct intratumoral injection
drugs for cancer therapy and in restenosis stents that are used to unblock clogged
arteries in heart disease patients. Some of these devices incorporate 90Sr, which produces 90Y in place for irradiation of arterial tissue that may reclog arteries after
balloon angioplasty. 90Y colloids have also been injected into synovial spaces (knee and finger joints)
to treat rheumatoid arthritis.
- 90Sr is a product of uranium fission. Thus, 90Sr is a major product of nuclear weapons testing fallout. 90Sr accumulates in uranium fuel as the fuel is irradiated in nuclear reactors. 90Sr (half-life = 29 years) was separated out from the nuclear waste products during
the production and recovery of plutonium at the Hanford Site (Washington State)
and at the Savannah River Plant (South Carolina) so that the nuclear waste would
not generate as much heat. Therefore, the United States has large stockpiles (millions
of curies) of 90Sr in storage. Several thousand curies of 90Sr from these stockpiles were purified as generator material for weekly production
of 90Y as a medical nuclide.
- Since the United States has large stockpiles of 90Sr and, since 90Sr has a relatively long half-life, we are not producing and recovering additional
amounts of 90Sr for commercial applications.
Darrell R. Fisher, PhD
Pacific Northwest National Laboratory
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