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Strontium-90 is a silver-grey metal which is produced by nuclear fission. It decays by beta particle emission.

CHEMICAL, PHYSICAL, AND RADIOLOGICAL PROPERTIES

Important Compounds

Strontium oxide (SrO) Strontia	23321-87-1 (1314-11-0)	white solid (m.p. 2430°)	exothermic reaction with water to produce hydroxide
Strontium oxide is the compound most likely to be formed from detonation of a strontium metal radiological dispersion device
Strontium carbonate (SrCO3)	15098-86-9  (1633-05-2)	white solid (decomposes at 1100°)	soluble in dilute acids, slightly soluble in water
Strontium chloride (SrCl2)	24359-35-1 (10476-85-4)	colorless to white crystals	hygroscopic soluble in water
Strontium hydroxide (Sr(OH)2)	NA (18480-07-4)	deliquescent crystal or colorless to white powder	soluble in water forms carbonate on standing in air
Strontium nitrate (Sr(NO3)2)	69519-58-0 (10042-76-9)	white solid (m.p. 570°)	soluble in water
Strontium-90 may be shipped as strontium nitrate in 1N nitric acid. Nonradioactive strontium nitrate is commonly used to add red color to pyrotechnic signals.
Strontium peroxide (SrO2)	NA  (1314-18-7)	white solid	largely insoluble in water, but decomposes to form monoxide
Strontium sulfide (SrS)	NA  (1314-96-1)	grey solid	slightly soluble in water
Strontium titanate (SrTiO3)	12184-00-8 (12060-59-2)	solid (m.p. 2060°)	insoluble in water
CAS Registry Numbers in parentheses are for the compound without the radioisotope. These nonradioactive compound registry numbers are useful for searches for general information on the compounds.

DETECTION

Radiation detectors will detect the beta emission (0.20 MeV); the yttrium-90 daughter also emits a beta particle (at 0.94 MeV) (yttrium-90 has a half-life of 64 hours).

Because of the low penetration of beta particles, the classic symptoms of radiation sickness in exposed individuals are unlikely to be a prompt indicator of strontium-90 release. However, beta burns may appear within a few days of a release.

SYMPTOMS AND EFFECTS

Strontium-90 will be detectable in urine after exposure, and urine monitoring is the recommended bioassay technique; direct in-vivo measurement is also possible with specialized equipment.

Strontium-90 metal is not a significant chemical toxin; however, the metal is dangerous because it may ignite, producing thermal injuries. Some strontium compounds are slightly toxic.

Primary hazards due to strontium-90 are prompt radiation injuries from exposures to large quantities (likely to be rare) and radiation-induced cancers due to long term exposure.

"Beta burns" may result from direct skin exposure to strontium-90. For large exposures, burning or itching, sometimes accompanied by a transient erythema, may be noted within the first forty-eight hours of exposure. This is followed by a latent period which may last up to two weeks, after which the affected area will take on the appearance of a mild thermal burn or sunburn. This is followed by epilation (usually spotty) and the formation of skin lesions, which may be superficial and dry or deep and wet depending on the degree of damage.

High inhaled doses may produce radiation pulmonitis, which manifests as an increasingly severe shortness of breath with pulmonary crepitus detectable on auscultation. This may proceed to hypoxic coma.

Classic radiation sickness is not likely with a release of strontium-90 alone unless a victim is exposed to extremely large amounts. However, strontium-90 may be released in combination with other radioisotopes which may induce radiation sickness.

Initial symptoms of radiation sickness may include:

• weakness
• anorexia
• vomiting
• diarrhea

These symptoms are followed after a latent period by the symptoms of the major radiation sickness syndromes, which are discussed in greater detail in the Radiation Sickness document.

Strontium-90 will deposit in bone.

MEDICAL COUNTERMEASURES

Useful Drugs	Aluminum phosphate	Sodium alginate

Treatment for exposure is based on mechanical removal of all possible agent, prevention of absorption and competitive inhibition of uptake.

Decontamination (removing clothing and showering) should be accomplished as soon after exposure as possible to minimize uptake of the material. In addition, nasal passages should be irrigated gently using saline or water.

If exposure was by ingestion, immediate administration of aluminum phosphate or sodium alginate may improve excretion.

Enemas and laxatives may also be useful in speeding passage of the material through the gastrointestinal tract.

In general, regardless of the route of exposure, absorption may be inhibited and excretion improved by:

• Administration of calcium supplements
• Administration of stable strontium
• Acidification of the urine (e.g., using ammonium chloride)

Beta burns should be examined using appropriate radiation detectors to determine if any radioactive material remains at the injury site; any materials detected should be removed. Otherwise, beta burns should be treated in the same manner as thermal burns, with the specific treatment depending on the depth of injury.

Treatment of radiation pulmonitis is limited to supportive care.

PHYSICAL COUNTERMEASURES

Initial evacuation distance should be at least 100 meters (330 feet).

Protective equipment (self-contained breathing equipment or mask suitable for prevention of particculate inhalation, barrier suit) must be used by those entering the contaminated area.

Also refer to 2000 Emergency Response Guidebook (ERG2000) Guide 161.

Because of the poor penetrating power of beta radiation, prompt decontamination of exposed individuals can prevent most injury. Decontamination is accomplished by removing clothing (which may be bagged for subsequent evaluation and possible return to victims) and washing of victims (wash water will be contaminated, and should be collected for disposal).

Medical personnel treating casualties should wear at least masks and barrier clothing appropriate for Universal Precautions cases; medical personnel using this level of protection will usually also need to undergo decontamination on completion of their patient treatment tasks.

More elaborate anticontamination suits may eliminate the need for individual decontamination of medical personnel.

Procedures for decontamination of physical facilities and equipment will depend on the physical and chemical form of the agent disseminated but will be based on the collection of the agent and contaminated materials and their disposal in appropriate areas. In general, the best method of decontamination will be collection of dry materials (e.g., by sweeping, grading, or vacuuming) into sealed containers. This may be followed by the use of water or appropriate cleaning solutions to dissolve residual contamination followed by collection of the solution. However, be aware that the use of wet methods for decontamination may result in the agent becoming incorporated into porous surfaces.

COMMENTS

Sources

Strontium-90 is a fission product which does not occur in large amounts in nature. The major environmental source of strontium-90 is fallout from atmospheric nuclear testing.

Strontium-90 is associated with nuclear power sources as a decay product.

Strontium-90 is used as a beta source in systems for radiation therapy and other applications

Strontium-90 is used in a type of nuclear battery known as a radiosotope thermoelectric generator, or RTG, in which the heat generated by the decay of the isotope is converted by thermocouples into electricity. When used in these devices, the strontium-90 is usually incorporated into a compound such as strontium-90 titanate.

History

Strontium was discovered in 1787 by William Cruikshank in mineral samples taken from near the Scottish town of Strontian. It was not isolated until 1808, when Sir Humphrey Davy produced a sample by electrolytic means. Strontium-90 does not occur in nature in any significant quantities; that seen today is essentially completely the result of introduction from artificaial sources (e.g., nuclear testing, etc.), and the isotope was thus not observed until fission studies produced it in the 1940's.

In 1943, consideration was given to using strontium-90 as one of the agents to be used in radiological attacks on food and water supplies. This was outlined broadly in the 1943 Compton Report ("Radiation as a War Weapon") and a report from Dr. Joseph Hamilton titled "Review of Possible Applications of Fission Products in Offensive Warfare." in May, 1943.

However, the idea of radiological warfare seems not to have been entertained too seriously, and may have been intended to provide an indication that all the money being spent on the development of atomic bombs would not be wasted even if the bombs couldn't be made to work. Subsequent research seems to have been intended to gather information related to defense against the use of radiological weapons, and used primarily radioisotopes other than strontium-90.

Accidental Exposures

On December 2, 2001, three woodcutters found two small (4 inch diameter by 6 inch length) heat-emitting containers in the woods near the town of Lja in the Abkhazia region of Georgia. The woodcutters took the containers to their camp to use to warm themselves, where exposure produced symptoms of radiation sickness and beta burns. The cylinders are believed to be the isotope containers for strontium-90 RTGs which use 40,000 curie sources. Efforts at recovery, spurred by fears that the containers might be seized by Moslem rebels in the region, were successful in early February, 2002, and the materials were transferred to a secure storage location in Tbilisi.

Terrorists and Strontium-90

The al Qaeda terrorist group is believed to have attempted to obtain radioactive materials including strontium-90 on several occasions. This group is believed to have been the intended receipients of a shipment of 10 lead-lined containers of this material stopped by Uzbek customs officials at the Uzbekistan-Kazakhstan border on March 30, 2000. The containers were releasing high levels (over 100 times the permitted level) of radiation. Other suggestive features associated with the shipment included:

• The stated destination of the material was the Ahmadjan Haji Mohammed company in Quetta, Pakistan (approximately a six hour drive from Kandahar, Afghanistan), which had no use for the material.
• The transport documents described the cargo as (nonradioactive) stainless steel.