How to Reduce the Risk of Radiological Dirty Bombs?

By Jacob Kamen Ph.D., DABHP, Icahn School of Medicine at Mount Sinai, New York, NY, USA


While the CBRN community including civil and military first responders are trained to respond to radiological dirty bomb, the risk of dirty bomb could be reduced by encouraging institutions who have such sources to migrate to Alternative Technologies and dispose these radioactive sources. Due to the unique characteristics of the cesium chloride (Cs-137) used in medical and research irradiators, it is especially susceptible to be used as a dirty bomb. Terror organizations have been trying hard to get their hands on high activity radioactive materials and use them as Radioactive Dispersal Device (RDD) or dirty bomb. These types of devices are considered as Weapons of Mass Disruption (WMD) and could bring the economy of a densely populated area to its knees. The recent University of Washington Research Center incident in Seattle with a minor Cs-137 leakage, and its cost (about $100 million), is an example of how expensive the total loss could be. Unfortunately, there are thousands of high radioactive irradiators still being used in Universities and Hospitals. This article describes steps to take to reduce this risk. Mount Sinai Hospital in NYC originally had four of such irradiators with cesium sources. Mount Sinai took steps to reduce the risk of Cs-137 Irradiators by using Alternative Technologies which presently exist in the market. As of January 2018, Mount Sinai in NYC successfully disposed all its Cesium-137 irradiators. The CBRN community could encourage the institutions having such sources in their campus to start using alternative technology and reduce the risk of dirty bomb. Financial incentive is available from the US government offices of DOE-NNSA-ORS under OSRP and CIRP program. History of Cobalt-60 and Cesium-137 Irradiators

The commercial use of gamma irradiators began in the late 1950s with the use of radiation to sterilize health care products. The increased experience and confidence with that technology lead naturally to the investigation of additional irradiator applications. Over time, novel irradiator designs were developed and optimized specifically for different applications, from food irradiation to materials processing1.

Additional gamma ray irradiators were built and the kinds of applications that uses gamma radiation steadily increased, from sterilization of health care products, to food irradiation, blood transfusion as well as research irradiators in universities, medical schools and national laboratories. Material processing also makes uses of irradiators where gamma radiation is used to treat polymers, like cables and tubing, for the purpose of property modification. Some of these irradiators operate for a single purpose while others are used for multiple purposes2. In recent times, the use of x-ray irradiators as a replacement for gamma irradiators has been is increasing.

Figure 1- Left, Cs-137 gamma irradiator Model GC 3000 Blood irradiator. On the right is Cs-137 research irradiators model Mark I-68. Each one contains a few thousand curies of radioactive materials.

Radioactive Cesium Chloride Irradiators and the Security Issues

Cesium-137 self-shielded irradiators have been used for many years for blood products, biomedical, and small animal irradiations. Approximately 10% of donated blood, about 3 million units per year3, is irradiated in a production mode by blood centers and medical institutions largely to prevent transfusion associated graft vs. host disease (TA-GvHD) for certain patients. Biomedical and small animal irradiations are performed mostly for research purposes at universities and hospitals.4

In 2008, the U.S. National Academies of Sciences (NAS) published a landmark report Radiation Source Use and Replacement, which examined the feasibility of replacing high-risk radioactive sources with less risky (and most likely non-isotopic) alternatives in order to forestall an act of radiological terrorism. The report expressed particular concern about the threat posed by the continued use of one isotope—cesium chloride—whose unique characteristics make it especially susceptible to being used by terrorists. The report recommended that government policies be enacted that would lead to the substitution of less hazardous technologies.5

In addition, there seems to be no liability insurance coverage provided to compensate the indirect damage from the malicious use of a cesium-137 irradiator source. The contaminated items and the cleanup cost are not covered by the insurance. This could be a significant financial burden to the institutions which possess high activity radioactive sources if these were used maliciously. Most security connections between the irradiators and security command centers as well as the Local Law Enforcement Agencies (LLEA) are connected through the internet. The breach of a security system could give the terrorists more time to take the sources out.

Experience with Radiological WMD (Goiania and University of Washington) Incidents

The Goiânia accident was a radioactive contamination accident that occurred on September 13, 1987, at Goiânia, in the Brazilian state of Goiás, after an old radiotherapy source was stolen from an abandoned hospital site in the city. It was subsequently handled by many people, resulting in four deaths. About 112,000 people were examined for radioactive contamination and 249 were found to have significant levels of radioactive material in or on their bodies.

The radiation source in the Goiânia accident was a small capsule containing about 93 grams (3.3 oz) of highly radioactive cesium chloride (Cs-137 Cs-Cl) encased in a shielding canister made of lead and steel. The source was positioned in a container of the wheel type, where the wheel turns inside the casing to move the source between the storage and irradiation positions.6 The important lesson learned was that less than 100 grams of Cs-Cl powder resulted in more than 40 tons of radioactive waste. That incident was not a dirty bomb attack, but one can imagine if that incident would have happened in 2020 in a density populated area, the result would be economically devastating.

In May 2019 there was an incident during the decommissioning of Cesium irradiator source by the DOE contractor. This incident took place at the University of Washington Research Center in Seattle where a contractor accidently cut the source, resulting to a leakage. Although this was not a terrorist attack, it was evidence of possible devastation from WMD. The irradiators were 2900 Ci of Cesium sources where the INIS, a DOE subcontractor by accident cut the capsule. The investigation took 9 months and DOE took the responsibility for the lack of defining clear roles and responsibilities. The leakage spread to the loading dock and 100 ft around the loading dock. Ventilation to the building was not isolated because no one knew there was a leakage and contaminated the first three floors. 13 people were exposed with whole body dose of 55 mrem. It did cost about $9 million to decontaminate and total cost of about $90 million up to now.

How real is the risk of a Dirty Bomb (RDD)?

There have been many attempts globally, to use radioactive materials in a dirty bomb or WMD. In Chechnya 1998, a container filled with radioactive material was attached to an explosive device found near a railway. In June 2002, Jose Padilla, a US citizen with links to Al-Qaeda was arrested in Chicago for planning to build and detonate a dirty bomb. In January 2003, based on the evidence uncovered by the British Intelligence from Afghanistan, it was concluded that Al-Qaeda had succeeded in constructing a small dirty bomb. In August 2004, Dhiren Barot was arrested for planning to blow up the New York Stock Exchange with a dirty bomb.

There have been numerous articles showing that ISIS have been trying to get their hands on high activity radioactive sources to make Radioactive Dispersal Devices (RDD). Mount Sinai realized that the dispersion of a cesium irradiator source would cause a disastrous outcome if someone were to use it maliciously against the public, especially in the densely populated area like New York City. In the last 20 years, there have been at least 12 terrorist attacks and at least 20 attempts in New York City, including 4 attacks in the last few years. No doubt that New York City is the terrorist target of choice in the United States.7

Mount Sinai’s Three Phase Action Plan

Mount Sinai as one of the largest health care institution in the US, has planned and collaborated closely with the US government agencies [Department of Energy, National Nuclear Security Administration (NNSA)] as well as the local agencies such as the New York City Department of Health and Mental Hygiene (NYCDOHMH) and the New York Police Department (NYPD to minimize the risk of malicious use of radioactive materials in quantities of concern. Mount Sinai adopted a three-phase plan to eventually remove the Cs-Cl irradiators from all the campuses.

Phase 1- Preparation to respond to possible Radiological Incident

  • Proper Radiation Equipment Mount Sinai purchased proper radiation equipment such as portal monitors, area monitors, electronic radiation dosimeters, the identifinder, and decontamination kits for possible use. The staffs were trained to use the dosimeter and respond to any abnormality detected. These radiation Alarms are checked on a regular basis for proper operation.

Figure 2- (Left) Portal monitors which can be used to survey personnel contamination monitoring and meets the FEMA standard for Emergency Response Portal Monitoring. (Middle) The electronic radiation dosimeter distributed to our security personnel to detect abnormal radiation level. (Right) IdentiFinder is used to identify unknown radioisotopes.

Phase 2- Reduce the risk: Harden Security, Limit Access, FBI background check on staff who have access and Pre-arranged Plan with LLEA

To prepare for an actual or attempted theft, sabotage, and diversion of radioactive materials in quantities of concern, Mount Sinai developed a pre-arranged plan with NY Police Department. We limit the unescorted access to the research irradiator to only one primary individual as well as a backup person. For people who seek the authorization of the unescorted access, Mount Sinai conducted a very strict background investigation. The background check includes the identification verification, the reputation review, the employee history of the last seven years, the FBI background check of criminal history, and the FBI finger printing process.

Mount Sinai collaborated with the US Department of Energy (US DOE) and National Nuclear Security Administration (NNSA) to enhance the security of irradiators through the Office of Radiological Security (ORS).

Phase 3- Remove the risk: Use Alternative Technologies and dispose all radioactive irradiators

After phase 2, the risk has already been reduced. Moreover, with the development of the non-isotopic alternative technologies, the Cs-Cl irradiators could be replaced and removed from medical and research facilities. Therefore, Mount Sinai decided to collaborate with the US DOE and NNSA to proceed with comparison studies and permanently remove the cesium-137 irradiators. All these comparison studies can be found here.

  • US government OSRP and CIRP Program The Department of Energy’s (DOE) National Nuclear Security Administration (NNSA) Office of Radiological Security (ORS) works with domestic users of cesium-137 based irradiators who are interested in converting to viable non-radio-isotopic alternatives. The Cesium Irradiator Replacement Project (CIRP)8, offered by ORS, provides qualified sites who are interested in making the switch with a financial incentive towards the purchase price of a new non-radio-isotopic device, as well as the removal and disposal of the cesium irradiator. For further information on the CIRP and to discuss whether and how CIRP could work for your site, please contact ORS at [email protected]

  • Feasible Non-Isotopic Alternative Technologies: Blood Irradiators and Biomedical Irradiators • Blood Irradiators In 2010, an interagency Task Force on Radiation Protection and Security submitted its quadrennial report to the US President and Congress. The Task Force report noted that for blood irradiation, x-ray technologies were cost competitive with radionuclide technologies on an annualized basis although concerns remained about their throughput and reliability. 6 We found out that there are two x-ray blood irradiators for human use approved by the US Food and Drug Administration (FDA) available in the market. These two x-ray blood irradiators meet the American Association of Blood Banks (AABB) recommendation that a radiation dose of 25Gy (minimum 15Gy) for treating blood in order to prevent GVHD.9 In 2011 the UK guideline by the British Committee for Standards in Hematology blood transfusion task force, concluded that blood x-ray irradiation was recommended as a suitable, safe alternative to gamma ray irradiation.10Biomedical Research Irradiators There were several options in the market for biomedical irradiators. Among the various models, the maximum energies vary from 160 kVp to 450 kVp. Other differences among the irradiators that should be considered, include the irradiation chamber size, the irradiator size, the cooling method, and the accessories of the irradiator etc. Unlike the blood irradiators which are FDA approved, there is not a criterion to determine which models of x-ray biomedical irradiators to acquire for research purposes. Mount Sinai comparison studies was done while running both irradiators (gamma ray and X-ray) side by side until all the researchers were ready to irradiate the use of gamma irradiators. The report of these comparison studies can be found here.

  • Disposal of Radioactive Irradiators Mount Sinai had 4 cesium irradiators. The first blood cesium irradiator was disposed in October 2016 and the first biomedical cesium irradiator was disposed in December 2016. The remaining blood and biomedical irradiators were disposed in January 2018. All of the irradiators were disposed through the US DOE CIRP program.

Figure 3. From left to right RS3400 blood irradiator, X-RAD 320 Biomedical irradiator installed in Mount Sinai.

Global Effort to Reduce and Remove the Risk.

France started in 2006 with a 10-year plan to remove the cesium irradiators. They had 30 irradiators and they have completely replaced them with x-ray irradiators. Whereas Norway finished replacing all 13 cesium blood irradiators with x-ray blood irradiators in 2015, and Japan started replacing the cesium blood irradiators 20 years ago with 80% of the cesium blood irradiators replaced by x-ray irradiators.11


Since the reliable alternative technologies are available now, we do believe that phasing out the cesium irradiators will reduce the risk of using the high activity radioactive sources as possible WMD. Institutions with such sources should use the US government program called “Off-site Source Recovery Program” to dispose high activity cesium sources. In the near future these sources may become commercially disposable and it may then cost about $200,000 to dispose each cesium irradiator. In this effort, we encourage the institutions which own these high activity irradiators to work US-DOE-NNSA to get financial support and replace their gamma irradiators with alternative technologies to minimize dirty bomb risk. Similar efforts are being conducted elsewhere, such as in Norway, France or Japan. The three countries must be commended for their decisions to remove such sources from their societies. For instance, France is considering not to allow addition of new radioactive sources devices and declining the renewal of applications for older ones, in an effort to phase them out.12 Perhaps this is one way we could help to fight and reduce the risk of malicious use of high activity radioactive sources.13 We all have to remember that our lives will be affected from possible dirty bomb and we all have to be proactive and encourage institutions with such sources to migrate and use alternative technologies to remove this risk from our society.


The author would like to thank the US government offices of ORS, NNSA, PNNL and OSRP of DOE for their assistance with security enhancement equipment, irradiator disposal, and the CIRP program.

Dr. Kamen is the Senior Director and the Chief Radiation Safety Officer for the Mount Sinai Health System (MSHS). He also serves as Professor of Radiology. He is board certified by the NRRPT, ABHP and BLS. He earned his doctoral degree in Nuclear Engineering at Columbia University where he served as the president of ANS University Chapter. He spent several years at Brookhaven National Laboratory (BNL), home to seven Nobel Prizes.

He was elected as the President of GNYCHP in 2004 and as the Executive Council for 2010 and 2011. He received BLS illumination award given by the Board of Laser Safety for his leadership as well as David Sliney award for laser safety excellence.

As an SME, he was invited to speak at various conferences such as ANS, HPS, and IAEA. He has chaired many sessions at both national and international meetings including the Institute for Nuclear Material Management (INMM), HPS, ANS, IAEA, etc. In 2011, he delivered the opening statement at West Point Academy for the GNYHPS meeting following the Fukushima Daiichi nuclear disaster. Subsequently, he was interviewed by Fox News TV in NY as well as the Daily News about Fukushima nuclear accident.

1 2 3 Sullivan MT, Cotten R, Read EJ, Wallace EL. Blood collection and transfusion in the United States in 2001. Transfusion 47:385–394; 2007 4 B. Dodd and R.J. Vetter. Replacement of 137Cs Irradiators with X-ray Irradiators, The Radiation Safety Journal Vol. 96, suppl 1 February 2009 5 Pomper M, Murauskaite E, Coppen T. Promoting Alternative to High-Risk Radiological Sources: The Case of Cesium Chloride in Blood Irradiation. James Martin Center for Nonproliferation Studies, 2014 Washington D.C. 6 The Radiological accident in Goiânia Vienna: International Atomic Energy Agency. 1988. ISBN 92-0-129088-8 7 Startling maps show every terrorist attack worldwide over the last 20 years, 8 9 Radiological Devices Advisory Panel, 2012. 10 Treleaven J, Gennery A, Marsh J et al. “Guidelines on the use of irradiated blood components prepared by the British Committee for Standards in Haematology blood transfusion task force”. Br J Haematol 2011;152(1):35-51. 11 Radiological Security Progress Report, NTI, March 2016 12 13 Autorité de Sureté Nucléaire, "Nuclear Safety and Radiation Protection in France in 2012," http://www.french-nuclear ASN-s-annuaI-reports/ Nuclear-safety-and-radiation-protection-in-France-in-2012.