Standardization News

It has been more than 70 years since the nuclear energy industry got its start following World War II. Today, nuclear energy provides about 10% of the world’s electricity and 29% of the world’s low-carbon power, according to the World Nuclear Association (WNA). Reactors are also being used to power naval vessels, serve as heat sources for industry, and in laboratory research. 

The nuclear industry is seeing increased interest as more countries look to move away from fossil fuels in favor of more sustainable solutions. The 440 nuclear power reactors in use worldwide make up the second-largest source of low-carbon power according to the WNA, and recent nuclear power plant investments in China, the Middle East, parts of Europe, and elsewhere promise to keep nuclear in the global energy mix for the foreseeable future.

Nuclear reactors require numerous safety precautions, and the industry is tightly regulated with strict standards outlining everything from the fuel used in reactors to the ways new technologies can be applied. ASTM International has two committees dedicated to the nuclear industry: the nuclear fuel cycle committee (C26) and the committee on nuclear technology and applications (E10), both of which have numerous subcommittees dedicated to specific aspects of reactor work.

READ MORE: Nuclear Roadmap 

“Most plants were designed to last 40 years when they were built, so almost all of them are licensed and operate with that timeline in mind,” says Brian Hall, chair of E10. “But now plants are applying for up to 80 years of operation, so we’re looking at the effects of embrittlement and measuring radiation at various locations in the vessel to support this longer-term operation. At the same time, small modular reactors [SMRs] are becoming more common in the industry, so we’re working to adapt some standards to address these unique SMR designs.”

To learn more about how ASTM International works with the nuclear industry and which ASTM standards have had the most impact, we recently spoke with Hall as well as Ramkumar Venkataraman, the chair of C26. 

1) Practice for Design of Surveillance Programs for Light-Water Moderated Nuclear Power Reactor Vessels (E185) 

According to Hall, over the service life of a reactor, the materials in the vessel experience great stress and wear due to radiation effects. Not all reactor vessel steels age at the same rate, however, so monitoring is required to track changes in material properties caused by long-term exposure to the neutron radiation and temperature environment of the reactor vessel. This standard outlines the criteria that need to be taken into account when creating a reactor vessel surveillance program, which in the United States is required by federal law. 

2) Guide for Predicting Radiation-Induced Transition Temperature Shift in Reactor Vessel Materials (E900)

Hall says nuclear power reactor operators must conform to pressure-temperature limits during heat up and cool down in order to prevent over-pressurization at temperatures that might cause a problem in the presence of a [Q1: vessel?] flaw. Over time, vessel materials can become embrittled and subject to sudden failure, especially as neutron damage accumulates. The standard is intended to help operators better determine potential embrittlement based on the transition temperature shift in vessel materials over the operating life of the reactor.

3) Guide for the Selection, Training, and Qualification of Nondestructive Assay (NDA) Personnel (C1490)

According to Venkataraman, at a nuclear facility, nondestructive assay refers to the measurement techniques that are used to test and monitor nuclear fuel materials, measuring the radiation that they are emitting. It’s nondestructive in that these methods don’t change the physical or chemical characteristics of the fuel. Of course, this work is staffed by people with specific technical backgrounds, making the process of selection, training, and qualification of personnel involved with NDA measurements a key part of the nuclear industry’s quality assurance efforts. This standard sets the benchmark for the educational qualifications and experience that are needed by NDA workers at different levels, starting from a technician all the way up to the NDA manager.

4) Guide for Making Quality Nondestructive Assay (NDA) Measurements (C1592/C1592M) 

Although the original version of this guide was withdrawn in 2018, the nuclear fuel cycle committee is working on an updated version that will outline best practices for performing nondestructive assay measurements on radioactive materials, says Venkataraman. Its intent is to help facilities achieve quality NDA results that satisfy their needs. The guide has long been a very important standard for U.S. facilities, where NDA is tightly regulated and is an often-quoted standard across the industry.

5) Test Method for Nondestructive Assay of Special Nuclear Material in Low-Density Scrap and Waste by Segmented Passive Gamma-Ray Scanning (C1133/C1133M)

When 55-gallon waste drums containing what might be active nuclear waste are assayed, says Venkataraman, there are several ways to determine the state of what’s inside. Using the techniques outlined in C1133, operators are able to determine the amount of nuclear material present in that waste at several different vertical segments within the drum. This is a very powerful pillar standard because segmented gamma scanning systems have been around since the late 1970s and many of them are still in operation: Facilities around the world are actively using this technique and rely on this standard.

6) Test Method for Nondestructive Assay of Plutonium in Scrap and Waste by Passive Neutron Coincidence Counting (C1207)

This neutron-based test method is useful for determining the plutonium content of scrap and waste in containers ranging from small cans to larger crates and boxes of material, says Venkataraman. It’s particularly useful as a way to distinguish neutrons that are originating from nuclear material from any that may be present in the background or coming from other sources.

7) Test Method for Nondestructive Assay of Plutonium, Tritium, and ²⁴¹Am by Calorimetric Assay (C1458)

Considered to be the most accurate NDA method to measure tritium, this standard outlines the testing method for the assay of many physical forms of plutonium, according to Venkataraman. By measuring the heat that is produced by the radioactive decay of nuclear materials, this method offers a nondestructive way to measure the presence of plutonium, making it a very popular and widely cited standard in the industry. 

Moving Forward

And the work of these committees continues.

In addition to the standards listed above, the nuclear technology and applications committee is working on a standard that is in the final stages of approval, and is related to what the industry calls a small punch test for the characterization of metallic materials. It has yet to be published, but one of the trends in the nuclear industry is toward smaller test samples, with the industry following the maxim “the smaller the better” when working with irradiated material. This small punch method works with smaller specimens and will provide useful data for the evaluation of aging, not only in terms of radiation embrittlement but also thermal aging and other changes in metallic properties over the long term.

Tim Sprinkle is a freelance writer based in Colorado Springs, Colorado. He has written for Yahoo, The Street, and other websites.