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Taking Measure

Just a Standard Blog

Defending Against Nuclear and Radioactive Threats: A Q&A with NIST's Leticia Pibida

Woman standing in a lab holds a rectangular radiation detector near a metal globe that has been painted with a radiation symbol

Physicist Leticia Pibida uses a handheld radiation detector like those officers use at ports of entry to the U.S. to scan a radiological test source. 

Credit: M. Esser/NIST

Leticia Pibida, a physicist in the Radiation Physics Division at the National Institute of Standards and Technology (NIST), has been chosen as a finalist for a Samuel J. Heyman Service to America Medal, an award for federal employees given by the nonprofit Partnership for Public Service. The honor recognizes her work to strengthen “our nation’s defenses against nuclear and radioactive threats by developing performance standards and tests for detection systems that screen nearly 7 million cargo containers entering U.S. seaports every year.”

We sat down with her to discuss her work.

How did you get into science?

Since I was young I liked reading about astronomy, understanding how things worked and the origin of the universe. When I was reading these books, I found that I could get many answers to my questions through science. And as I always had many questions and I found math to be a fun thing to do, I decided to go into science.

How did you get involved in this area?

After the terrorist attacks of 9/11, many in the U.S. were greatly concerned about being potentially vulnerable to radiological, nuclear, chemical and biological threats. To protect the country more fully, we needed new technologies, in particular, instruments for detecting nuclear and radiation-based threats. The radiation detection instrumentation that was available at that time was not built for this purpose, so we needed to develop standards to support the development of new instruments with the required capabilities.

How did you come to realize that the country lacked the equipment and measurement standards to accurately detect radiological materials at U.S. seaports?

When we started to develop the first documents with these kinds of standards in 2002, we needed to validate their requirements by making lots of measurements of radiation instruments before publication. To do this, we needed to purchase many instruments from various manufacturers. In reviewing the different types of radiation instruments that were available in the market, two things became clear: First, there were no instruments that met the users’ requirements. Second, the technical specifications provided by the manufacturers were incomplete and not expressed in a uniform way that would enable users to easily make comparisons between the different brands and models. These conditions prevented critical users, such as emergency first responders and officials at the Department of Homeland Security, from selecting appropriate instruments to be deployed at seaports.

What are the challenges to detecting these radiological and nuclear materials?

The biggest challenge to detecting radiological and nuclear threats is the presence of background radiation from both the natural environment and many commercial commodities such as tiles, fertilizers, granite and sand. These things all produce radiation signals that the instruments can detect, and must be distinguished from signals originating from the radiological and nuclear materials we are guarding against. In addition to background radiation, a variety of radioactive isotopes and sources are used in many medical diagnostic procedures and treatments. People who have undergone these treatments carry levels of radiation that can also be detected by these instruments, which further complicates the problem. These additional sources of radiation also need to be weeded out during the detection process.

What’s NIST’s role specifically in ensuring accurate inspection of cargo containers?

NIST worked with the U.S. Department of Homeland Security Countering Weapons of Mass Destruction Office and U.S. Customs and Border Protection to develop standards to test radiation monitors and radioisotope identification devices that are used for scanning cargo containers. In addition, we also carried out test campaigns to evaluate their operation and performance.


semi truck driving through a pair of upright pillars in the Nevada desert
A truck driving through the Department of Homeland Security, Portal Monitor Test Area at the Radiological Nuclear Countermeasures Test and Evaluation Complex at the Nevada National Security Site.
Credit: National Nuclear Security Administration/Nevada Site Office

Describe some of the standards you and your team have developed. What do they do?

Since we started in 2002, we have developed and published approximately 20 national and international standards for homeland security applications. These standards define the performance requirements and test procedures for a host of radiation detection systems and data format standards for all types of radiation detectors.

Describe some of the tests you have developed.

I lead campaigns for testing all types of radiation instruments covered by the standards. As an example, radiation portal monitors are devices used to detect and identify potential radiation sources inside cargo containers. To test the monitors, we determined suitable sources to be used in the test, the number of trials, the speed at which the containers should move past the portal monitors, and the location of the sources within the containers. Other tests that I developed were for validating standards’ requirements and the evaluation of the performance of radiation detection instruments. Around 2010, I became involved in the Illicit Trafficking Radiation Assessment Program, a testing program initiated by the European Union and the United States to evaluate the performance of available commercial radiation detection equipment against consensus standards. As part of this program, I developed the test procedure, supervised the test team, analyzed the data and wrote the report for the spectroscopic radiation portal monitors tested in the U.S.

What were some of the ways that your work improved scanning at seaports? What’s been the impact?

Standards, in general, affect all areas of our lives as they provide a method for users to assess the performance of any device to which the standard applies and give users the confidence that the instruments are suitable for the purpose and perform as advertised. In this way, users can rely on these instruments to do their job. In the particular case of U.S. Customs and Border Protection, they use the standards we developed to evaluate portal monitors before deployment at seaports, thereby permitting the accurate and reliable detection of illicit nuclear and radiological materials that might be trafficked.

Looking to the future, what is your hope on what NIST can contribute to solving this problem?

As with everything, both technology and user needs change over time, so standards must be kept current to ensure that these evolving needs are continually addressed. The role of NIST in standards development is extremely important, and it is actually mandated by federal law in the Security and Accountability for Every Port Act of 2006 (or SAFE Port Act). My hope is to continue our involvement in developing standards as we play a crucial role in ensuring reproducible and accurate test results when evaluating instrument performance.

What does being a career civil servant mean to you?

The most rewarding part of my work as a civil servant is that the results of my work are reflected in tangible things that can make people’s lives better, and that in this way I can provide a service to the people in our country.

What is it like to be a finalist for the Sammies Awards?

It feels overwhelming and flattering. I always did my job thinking that I need to do my best, and my work in standards feels like I am making a difference in society and effecting change, but I never imagined that I was going to be nominated for such an important award. I really feel honored to be a finalist.

About the author

Leticia Pibida

Leticia Pibida has a Ph.D. in Physics from the University of Tennessee, Knoxville. She joined the National Institute of Standards and Technology (NIST) in 1998. She is the project leader for the development of a broad range of American and International standards for homeland security applications and detection of illicit trafficking of radioactive materials for radiation detection instruments. She is heavily involved in the testing of commercially available radiation detection instruments. She is currently the lead scientist for gamma-ray spectrometry measurements using high purity germanium detectors. 

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