IMPEP — Evaluating the NRC’s Radioactive Materials Program

David Spackman
Health Physicist

For the NRC and each of the 37 states that regulate radioactive materials under agreements with us, a time comes every few years when we start talking about “IMPEP.” The acronym is spoken about as frequently as the top 10 new words added to Webster’s Dictionary every year – that is to say a lot.

IMPEP may be very easy to say, but understanding its true value requires a closer look.

IMPEP stands for the Integrated Materials Performance Evaluation Program. Think of it like an audit. It is the NRC’s primary tool for assessing how well radioactive materials programs are agreementstatenesperforming. Every Agreement State and NRC program is evaluated under IMPEP every four to five years. A rotating team of experts from the Agreement States and the NRC do the reviews. The teams focus on specific areas of a radioactive materials program that have the potential to affect public health and safety. The reviews are very detailed, typically lasting a full week.

Once an IMPEP review team has looked at everything they need to see on-site, they document their findings. They write a report and recommend a “grade” on the program’s performance to the Management Review Board, which is comprised of senior NRC managers and a state program manager who keeps in touch with the other Agreement States. The board holds a public meeting to talk about what the team saw and assigns the overall program rating: “Satisfactory,” “Satisfactory but Needs Improvement,” or “Unsatisfactory.”

Recently it was the NRC’s turn to undergo an IMPEP review. From Dec. 8-11, a team of experts from Ohio, Tennessee, and the NRC reviewed the NRC’s Sealed Source and Device (SS&D) Evaluation Program. This program performs engineering and radiation safety evaluations of sealed radioactive sources and the devices that use them.

Sealed sources are just what the name says—radioactive sources sealed in a capsule to prevent leakage or escape of the material. The devices are used for many things, but generally they measure something, such as soil density, fluid levels, the thickness of a pipe, and whether metal and welds are sound. They can also help to map geologic formations from inside a gas or oil well. The NRC needs to do adequate technical evaluations of SS&D designs to ensure they’ll maintain their integrity and their designs are adequate to protect public health and safety.

During the four-day IMPEP review at NRC Headquarters, the team looked at the NRC program’s technical quality, staffing and training, and any defects or incidents involving SS&Ds. Most of the work was done through in-depth staff interviews and targeted document reviews. S

Since finishing the evaluation in mid-December, the team has drafted their report. They expect to recommend to the board that the NRC’s SS&D program be rated Satisfactory – the highest possible rating. Furthermore the review team commended NRC staff for performing very competent technical SS&D reviews. Although this is an excellent result so far, there is still one more important step to complete the IMPEP review process – the public meeting.

This meeting allows the review team to present its findings and formally recommend the overall program rating. While the structure of these meetings is simple, it is very common to see a spirited discussion of the strengths, weaknesses, innovations and shortcomings of the program under review.

This is where the true value of IMPEP is laid bare. If all goes right, the end result is improving a program’s ability to protect public health and safety and the environment – even if the program gets the highest rating.

The MRB’s public meeting to discuss NRC’s SS&D program will be held at NRC Headquarters in Rockville, Md., on March 5, 2015. The meeting details are available on the NRC website at http://meetings.nrc.gov/pmns/mtg. We encourage members of the public to come or listen in by phone.

Hitting the Road – How the NRC Makes Sure Radioactive Material Is Shipped Safely

Bernard White
Senior Project Manager

LWT in Air 2
The NAC LWT transport package Photo courtesy of NAC International

In September 2013, we talked about transportation of spent nuclear fuel and how we know it is safe. This month, we want to discuss the safety basis for transporting other types of radioactive material.

The NRC recently approved a package to transport high enriched uranyl nitrate. This material is left over from the production of medical isotopes used in millions of diagnostic procedures every year. This package is to be used to bring material currently stored in Canada, where the isotopes were made, to the Savannah River site in South Carolina. The shipments are part of a DOE program to take back high enriched uranium from countries to which the U.S. supplied it.

Our review did not address whether the shipment should be made. Nor is it specific to any route. It just looked at whether the proposed shipping package design meets our requirements for safe transport. We rigorously reviewed the information submitted by the cask designer, NAC International. We asked four sets of detailed questions and thoroughly reviewed the applicant’s responses. After two years of review and two face-to-face meetings, we have answers to all our questions and we’re satisfied that the package design meets all NRC requirements for safe transport.

The high enriched uranyl nitrate, which is a liquid, will be transported using special containers that were designed to prevent leakage. To ensure they do not leak, the containers are leak tested after fabrication and prior to transport, each time the container is filled. These containers must also be replaced once they have been in use for 15 months. Together, these requirements give the NRC confidence that the containers will not leak.

These leak-tight containers will be placed into specially-designed packages for transport. This package design has been used for 25 years to safely transport a wide variety of radioactive materials. The inner containers and the outer packaging together make up the transport package.

Our review of this transport package design gives us confidence that, even if there were to be a transport accident, radioactive material will not leak from the package; dose rates will not be high enough to cause harm to anyone; and a nuclear chain reaction will not occur. Packages are evaluated for conditions that mirror normal transportation as well as the forces the package may experience in a severe accident.

The conditions assessed for routine transport include rain, hot and cold temperatures, a drop that may occur during handling, and the vibration that we all feel in a car or riding on a train.

For accident conditions, the package must be shown to be able to withstand forces that are more severe than in a real-world accident. This is done by testing or evaluating the package in a sequence of stringent tests. We discussed these tests in detail in our September 2013 blog.

This package has been shown to be able to safely transport contents that are much heavier and more radioactive than the high enriched uranyl nitrate, including spent nuclear fuel. The dose rates from the package containing liquid uranyl nitrate will be much lower than when the package is loaded with spent fuel.

For all these reasons, the NRC Is confident the package design meets all our requirements for safe transport. We follow the same review process for every transport package design we receive. In every case, we make sure we thoroughly understand the design and all the analyses in the application. We ask questions, if necessary, and often perform our own analysis. In some cases, including this one, we impose special conditions to give added assurance of safety. Only when we are satisfied a design meets every NRC requirement will we issue an approval.