U.S. NRC Blog

Transparent, Participate, and Collaborate

Keeping the NRC’s Rules Up to Date

Anthony de Jesus
Regulations Specialist

NRC’s regulations (found in 10 CFR, Code of Federal Regulations) are very important. They are how we do our job of protecting people and the environment.

10cfrtwopartjpgOur rules cover these three main areas:

  • Commercial reactors for generating electric power and research and test reactors used for research, testing, and training.
  • Materials – Uses of nuclear materials in medical, industrial, and academic settings and facilities that produce nuclear fuel.
  • Waste – Transportation, storage, and disposal of nuclear materials and waste, and decommissioning of nuclear facilities from service.

To keep all these rules, on all these topics, up-to-date, we use a single process, called the Common Prioritization of Rulemaking, to prioritize our rulemaking activities.

Each year we identify the rules already under development and any new rules that need to be written. Using the same criteria, we rank by priority, every rule, regardless of the regulatory area. This way we ensure that we are focusing our resources on the high priority rules that most contribute to the NRC’s key strategic goals of safety and security. Through this annual review we also monitor the progress of our rulemaking activities and develop budget estimates for preparing new rules.

rulemaking web 1Because the NRC is committed to transparency, participation, and collaboration in our regulatory activities, we created a new “Rulemaking Priorities” Web page. This page allows us to provide periodic updates concerning rulemaking developments, which responds to a recommendation proposed by the Administrative Conference of the United States.

Our new page provides the rulemaking activities identified and prioritized through our Common Prioritization of Rulemaking process. From this page you can access the methodology that NRC staff uses to prioritize our rulemaking activities.

Each rulemaking activity listed on this new Web page is linked to further information on that rulemaking, including:

  • an abstract that describes the rule
  • a prioritization score
  • a justification describing how the rule was prioritized
  • estimated target dates for completion of the rule

We plan to update the web page regularly so this information remains up to date. We hope this new page will help you understand how the NRC prioritizes its rulemaking activities. After all, our regulations are at the heart of what the NRC does for a living.

Throwback Thursday – The Commission Briefing

tbtjune25This grim 1970s NRC Commission Briefing includes (from left to right): John Ahearne, Richard T. Kennedy, Joseph M. Hendrie, Victor Gilinsky and Peter A. Bradford. What is your guess for the topic of the briefing?

Shedding Some Light On Tritium Illumination Devices

Shirley Xu
Health Physicist

Some radioactive materials are used to produce light. This is done by bombarding a special material known as a phosphor with the radiation (typically beta radiation) emitted by the radioactive material. Phosphor gets its name from the Greek words for “light” and “to bring.” The phenomenon is called “radioluminescence.”

Radioluminescence can be used to provide a low level light source to allow instruments or signs to be visible at night or for other situations where light is needed for long periods without electricity, such as emergency exit signs.

watchfacePaint with radium was the first radioluminescent product. Today, tritium is most commonly used, primarily on wristwatch faces and gun sights. Small tritium lights can be made by sealing tritium and a phosphor layer in small glass tubes. Such a tube is known as a “gaseous tritium light source” (GTLS), or more commonly, a beta light (since the tritium undergoes beta decay).

Tritium is a radioactive isotope with a half-life of about 12 years, which means the glass tube loses half its energy and some of its brightness in that period. So the types of GTLS used in watches generally have a useful life of 10 to 20 years. They give off a small amount of light: not enough to be seen in daylight, but enough to be visible in the dark. The more tritium that is initially placed in the tube, the brighter it is to begin with and the longer its useful life.

The NRC regulates devices that contain small amounts of tritium. Manufacturers and initial distributors of these devices need to have a distribution license issued by the NRC. They also need to have a separate license to possess and use the material. This license can be issued either by the NRC or the state. [There are 37 states that have agreements with us to regulate these types of radioactive materials. They are called Agreement States.] Anyone who initially buys one of these products from someone who has the proper licenses and subsequent owners of the product are exempt from the requirements for an NRC license.

Approval of these types of products would require extremely low risk of radiation exposures to members of the public from normal use, misuse or accidents. The NRC would also need to see the usefulness or benefits of the product. For example, items that could be mishandled, especially by children, will be approved only if they combine an unusual degree of utility and safety. Other countries have different regulatory requirements. That is why some tritium products available for sale internationally are not sold in the U.S.

These regulations can be found in 10 CFR Part 30 and Part 32.

Testing Spent Fuel Transport Casks Using Scale Models

Bernard White
Senior Project Manager
Division of Spent Fuel Storage and Transportation

Before casks can be used to transport the most radioactive cargo—including spent nuclear fuel—the NRC requires them to undergo a thorough safety evaluation. Casks are evaluated for their ability to withstand vibration, water spray, free fall, stacking, penetration and fire. A cask must be able to contain and shield the spent fuel and keep it in a safe configuration under both normal and accident conditions. Typically, spent fuel casks are certified through a combination of engineering analyses and scale model or component testing.

People often ask why the NRC allows designers to test scale models instead of requiring tests on full-sized casks. The bottom line is scale-model testing provides the necessary information for the NRC staff to know that a cask loaded with spent fuel can be transported safely, even in the event of an accident.

scalemodel2First, it is important to understand what information comes out of these tests. Test casks are fitted with sensors to measure acceleration. These accelerometers are similar to the ones used in smart phones, video game remotes and pedometers to respond to the movements of the user. Knowing the cask’s acceleration allows designers and the NRC to understand the forces different parts of the cask will experience in different types of impacts. The design engineer generally calculates these impact forces first by hand or by computer. Tests on a scale model can be used to check the accuracy of these analyses.

Engineers follow a similar process to safety-test airplanes, ships, bridges, buildings and other large structures. Scale-model testing is a proven and accepted practice across engineering disciplines, and may be one of the oldest engineering design tools. (Ancient Egyptian, Greek, and Roman builders are known to have built small models to assist in planning structures.) Today, models allow oversized structures to be examined in wind tunnels, under different weight loads and on shake tables to provide key inputs into design and safety reviews.

Cost savings is a factor, but not the most important one. The biggest reason for using scale models is practicality. Transport casks for spent nuclear fuel are typically in the 25-ton to 125-ton range. There are very few testing facilities in the world that can put a 125-ton cask through the required tests.

For example, during 30-foot drop test, the test cask must strike the surface in the position that would cause the most severe damage. Cask designers often perform several drops to ensure they identify the correct position. After the 30-foot drop, the cask is dropped 40 inches onto a cylindrical puncture bar, then placed in a fully-engulfing fire for 30 minutes. Casks are also immersed in water to ensure they don’t leak. Measurements from these tests are plugged into computer programs that analyze the cask structure in great detail.

This analysis can determine the stresses placed on cask closure bolts, canisters and baskets that hold the spent fuel in place, and the spent fuel assemblies themselves. Computer simulations can be run for different scenarios, providing maximum flexibility to designers in understanding how best to design different parts of a cask’s structure.

In addition, NRC regulations specify that in the 30-foot drop test, the cask must hit an “unyielding” surface. This means the cask itself, which may be fitted with “impact limiters,” has to absorb all the damage. The impact limiters work much like the bumper that protects a car in a collision. The target surface cannot dent, crack or break in any way. In a real-world accident, a 125-ton cask would damage any surface significantly. It requires considerably more engineering work to achieve an unyielding surface for a full-sized cask than for a scale model, with no measurable advantage. The rule-of-thumb for testing is the impact target should be 10 times the mass of the object that will strike it. So a 125-ton cask would need to hit a 1,250 ton surface. A 30-ton cask would only need a 300-ton target.

Scale models are easier to handle and can be used efficiently for many drop orientations to meet the multiple test requirements. If a test needs to be run again, it can be done much more easily with a scale model. Design changes are also more easily tested on models. Together with extensive analyses of a cask’s ability to meet our regulatory requirements, the information from these tests allows the NRC to decide whether a cask can safely transport the radioactive contents.

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