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Watts Bar – Making History In Yet Another Century

Jeanne Dion
Project Manager
Watts Bar Special Projects Branch
 

Unit 1 at the Watts Bar Nuclear Plant in Spring City, Tenn., has a claim to fame as the last U.S. commercial nuclear reactor to come online in the 20th century. Now, the Tennessee Valley Authority aspires to have its sister reactor (Watts Bar Unit 2) make its own historic claim.

Numerous cranes helped complete construction of the Watts Bar Nuclear Plant Unit 1 containment building in front of the plant’s cooling towers in 1977.

Numerous cranes helped complete construction of the Watts Bar Nuclear Plant Unit 1 containment building in front of the plant’s cooling towers in 1977.

If the NRC concludes that the reactor is safe to operate and approves its operating license next year, Watts Bar Unit 2 could become the first new commercial nuclear reactor to come online in the U.S. in the 21st century.

To understand a little of the history of Watts Bar Nuclear Plant, let’s rewind to a time when Schoolhouse Rock premiered and the first mobile phone call was made in New York City — a time predating the NRC. In 1973, the Atomic Energy Commission greenlighted construction of Watts Bar Units 1 and 2 under the “two-step licensing process,” where construction permits and operating licenses were issued separately.

In 1985, construction quality issues at its plants caused TVA to stop work at both Watts Bar Units. Eventually, TVA resolved the issues and completed construction of Unit 1, and the NRC issued its operating license in 1996.

Fast-forward to more recent activities. TVA decided in 2007 to reboot the Watts Bar Unit 2 construction and licensing process. They submitted an update to their original license application to the NRC in 2009.

Other recent applicants have elected to use the combined license application process, where we issue a single license to both construct and operate a nuclear power plant at a specific site. However, because of the unique history of Watts Bar Unit 2, TVA chose to continue under the two-step licensing process. So, NRC staff developed a regulatory framework and established a licensing approach tailored specifically to the project.

We updated our construction inspection program associated with the two-step licensing process to provide guidance that reflects current NRC practices. For example, the NRC staff identified areas for further inspection at Unit 2 by screening applicable communications, allegations and other open items in the review.

The NRC staff also developed inspection guidance specific to TVA’s refurbishment program, which replaces or refurbishes systems and components at Watts Bar Unit 2. TVA’s resolution of key safety issues and the continued progress of construction inspection activities drive our review schedule.

If the operating license is issued next year, the NRC’s job doesn’t just end. We’d continue to inspect start-up testing required for power ascension and to oversee that Unit 2 transitions into the NRC’s Reactor Oversight Process before it can begin producing commercial power.

And, of course, the Resident Inspectors, the agency’s eyes and ears at the plant, would continue to carry out day-to-day inspection work to ensure safety and security is monitored and inspected during licensing and throughout the transition to commercial operation.

For more information about the Watts Bar Unit 2 project, visit the NRC’s website. There will be a Commission briefing Oct. 30 at 9 a.m. on the license application review. You get details about the briefing from the meeting notice. We’ll also do a live webcast.

Making Sure SAFER Resources Are Ready To Go

Jack Davis
Director, Japan Lessons Learned Division
 

mitigation_strategies_infographic_r4Part of the U.S. nuclear power industry’s response to the NRC’s post-Fukushima Mitigation Strategies Order involves emergency equipment centers in Memphis, Tenn., and Phoenix, Ariz. The centers have multiple sets of generators, pumps and other equipment. The centers would send needed equipment to a U.S. nuclear plant to maintain safety functions indefinitely if an event disabled that plant’s installed safety systems.

The NRC’s been reviewing how an industry group, the Strategic Alliance for FLEX Emergency Response (SAFER), can move equipment from the response centers to plants. We observed two demonstrations SAFER ran in July and reviewed SAFER’s equipment, procedures, and deployment strategy. Overall, the NRC staff concludes that having the response centers and the group’s plans and procedures in place will enable plants to comply with the final phase of the Order.

The group has contracted with Federal Express (for both truck and aircraft shipment) to get supplies to a plant within 24 hours of a request. SAFER’s documentation of FedEx’s capabilities included a proven ability to work with the Federal Aviation Administration to get proper access to otherwise restricted airspace in the event that equipment must be flown to a nuclear power plant site. 

One SAFER demonstration sent equipment by road from Memphis to the Three Mile Island plant in Pennsylvania. The NRC staff noted some areas for improvement, such as clarifying who’s responsible for unloading equipment at a site or where the equipment’s first tank of fuel will come from. SAFER responded by adding details to its plans and beefing up its training program.

The other demonstration simulated airlift of equipment from Phoenix to the Surry plant in Virginia. After the NRC shared its observations, SAFER gave our staff additional details on how it would obtain helicopters to bring supplies to a plant if area roads are impassable.

 We also reviewed a report on the Memphis center’s test of packing the equipment to efficiently load and fit onto FedEx’s planes. Although the test generated a delivery schedule a few minutes longer than the industry expected, the NRC is satisfied that SAFER has applied lessons learned to streamline its approach and ensure SAFER can meet its own deadlines.

 Our website’s Japan Lessons Learned section can give you more information about the mitigation strategy requirements and related guidance.

Science 101: How a Chain Reaction Works in a U.S. Nuclear Reactor

Paul Rebstock
Senior Instrumentation and Control Systems Engineer

 

science_101_squeakychalkThe primary active ingredient in nuclear reactor fuel is a particular variety, or “isotope,” of uranium, called U235. U235 is relatively rare — only about 0.7% of uranium as it exists in nature is U235. Uranium must be enriched to contain about 5% U235 to function properly as fuel for a U.S. commercial nuclear power plant.

U235 has 92 protons and 143 neutrons. Protons and neutrons are some of the almost unimaginably tiny particles that make up the nucleus of an atom — see Science 101 Blog #1. All other isotopes of uranium also have 92 protons, but different isotopes have slightly different numbers of neutrons.

Uranium is a radioactive element. Uranium atoms break apart, or disintegrate, into smaller atoms, releasing energy and a few leftover neutrons in the process. This happens very slowly for U235. If you have some U235 today, in about 700 million years you will have only half as much. You will have the remaining U235, plus the smaller atoms. The energy released will have gone into the environment too slowly to be noticed, and the extra neutrons will have been absorbed by other atoms.

While this happens very slowly, the disintegration of each individual atom happens very quickly, and the fragments are ejected at a very high speed. Those high-speed fragments are the source of the heat generated by the reactor. Under the right man-made conditions, the number of U235 atoms that disintegrate each second can be increased.

When a U235 atom disintegrates, it releases some neutrons. Some of those neutrons can be made to interact with other U235 atoms, causing them to disintegrate as well. Those “target” atoms release more neutrons when they disintegrate, and then those neutrons interact with still other U235 atoms, and so on. This is called a “chain reaction.” This process does not work well for other isotopes of uranium, which is why the uranium needs to be enriched in U235 for use as nuclear fuel.

Most of the energy released when a U235 atom disintegrates is in the form of kinetic energy — the energy of physical motion. The fragments of the disintegrated atom collide with nearby atoms and set them vibrating. That vibration constitutes heat. The fuel rods get hot as the reaction progresses. The faster the chain reaction — that is, the larger the number of U235 atoms that disintegrate each second — the faster energy is released and the hotter the fuel rods become.

The uranium in a U.S. commercial nuclear reactor is thoroughly mixed with neutral material and formed into pellets about half inch wide and three-quarters of an inch long. The pellets are stacked tightly in metal tubes, forming “fuel rods” that are several feet long. Each fuel rod is just wide enough to hold a single column of pellets. The fuel rods are sealed, to keep all of the radioactive materials inside. There are thousands of these fuel rods in a typical reactor. They contain around 60 tons of uranium – but only about three tons are U235. (The majority of the uranium in the reactor is in the form of the most abundant naturally occurring isotope of uranium, U238, which cannot sustain the fission process without the help of an elevated concentration of the isotope U235.)

The people in charge of the reactor can control the chain reaction by preventing some or all of the released neutrons from interacting with U235 atoms. The physical arrangement of the fuel rods, the low U235 concentration, and other design factors, also limit the number of neutrons that can interact with U235 atoms.

The heat generated by the chain reaction is used to make steam, and that steam powers specialized machinery that drives an electrical generator, generating electricity. Science 101 will look at how that works in more detail in a later issue.

The author has a BS in Electrical Engineering from Carnegie-Mellon University.

 

The NRC Commission Has Held 5,000 Meetings—Give or Take

Annette Vietti-Cook
Secretary of the Commission

 

After one of our commissioners noted a milestone in July – the 5,000th meeting of the NRC’s Commission – we thought it might be useful to share what the Secretary of the Commission does behind-the-scenes in planning Commission meetings. There is much more planning than you might think.

The NRC Commissioners conduct a public meeting. Annette Vietti-Cook is on the left.

The NRC Commissioners conduct a public meeting. Annette Vietti-Cook is on the left.

First some background. The “Commission,” in NRC-speak, means the presidentially-appointed, Senate-confirmed Commissioners acting together. At full-strength there are five Commissioners. The Commission sets policy for the NRC, develops regulations on nuclear reactor and nuclear materials safety, issues orders to licensees and adjudicates legal matters.

The federal Sunshine Act requires that any time the Commissioners meet to conduct agency business, the meeting must be public. Exceptions to this requirement are made when the Commission discusses matters such as security or confidential legal, personnel, personal or proprietary information. Our regulations lay out how we will meet the Sunshine Act requirements.

Public Commission meetings are held at NRC headquarters in the Commissioners’ Conference Room, with planning starting months in advance. This is where the staff members in the NRC’s Office of the Secretary (we call it SECY) come into play.

To prepare for the meeting, SECY works with NRC staff to plan agendas for proposed public meetings, including lists of potential internal and external contributors, which are intended to provide the Commission with a range of perspectives.

In the weeks ahead of a meeting, the NRC staff and other presenters send background materials and slides to the Commissioners. This advance information allows the Commissioners to come prepared to get their questions answered. Meanwhile about a half-dozen people in SECY are making sure of the details— arranging parking and pre-registration for external participants, getting relevant information posted on our public website, creating a seating chart for those who will brief the Commission.

As meeting day approaches, SECY ensures other logistics are in order. They make sure the room is set up properly, with name tags, microphones, and water pitchers placed on the conference table, chairs arranged, flags properly positioned. On meeting day, these preparations probably won’t be noticed by the 50-60 people who may come to the meeting and the untold number tuning into the webcast. (Incidentally, the room holds 155). The Chairman opens the meeting and turns the meeting over to the presenters. Following, the presentations, the Commissioners have an opportunity to ask questions.

Even after the meeting ends, SECY has more to do. All public Commission meetings are webcast, recorded and transcribed. The transcript must be validated and posted to the NRC website. The webcast is archived. And following most every meeting, SECY develops a memo to give the staff direction (we call this an SRM, or staff requirements memorandum), which must be approved by the Commission.

So you see, a lot of work goes into organizing the 5,000 or so Commission meetings we’ve held since the inception of the NRC almost 40 years ago – not just in my office. We hope you’ll tune in or attend a Commission meeting in the future. You can find the Commission’s meeting schedule here and a complete schedule of NRC public meetings here.

REFRESH: Do Not Fear Your Smoke Detector – It Could Save Your Life

Maureen Conley
Public Affairs Officer

refresh leafWe sometimes get calls from people worried about radiation from smoke detectors in their homes. There are many reasons why the public need not fear these products.

Ionization chamber smoke detectors contain very small amounts of nuclear material. They might use americium-241, radium-226 or nickel-63. These products detect fires early and can save lives. [We explained how smoke detectors work in greater detail in an earlier blog post.]

The Atomic Energy Commission granted the first license to distribute smoke detectors in 1963. These early models were used mainly in factories, public buildings and warehouses. In 1969, the AEC allowed homeowners to use smoke detectors without the need for a license. Their use in homes expanded in the early 1970s. The NRC took over from the AEC in 1975.

Makers and distributors of smoke detectors must get a license from the NRC. They must show that the smoke detector meets our health, safety and labeling requirements.

smokedetectornewMost smoke detectors sold today use 1 microcurie or less of Am-241. They are very safe. A 2001 study found people living in a home with two of these units receive less than 0.002 millirems of radiation dose each year. That is about the dose from space and the earth that an East Coast resident receives in 12 hours. Denver residents receive that dose in about three hours. These doses are part of what is known as “background radiation.”

The radioactive source in the smoke detector is between two layers of metal and sealed inside the ionization chamber. The seal can only be broken by the deliberate use of force, which obviously we discourage. Still, even then it would result in only a small radiation dose. The foil does not break down over time. In a fire, the source would release less than 0.1 percent of its radioactivity. It’s important to understand that none of the sources used in smoke detectors can make anything else radioactive.

What about disposing of smoke detectors? A 1979 analysis looked at the annual dose from normal use and disposal of Am-241 smoke detectors. The study used actual data and assumptions that would overstate the risk. It allowed the NRC to conclude that 10 million unwanted smoke detectors each year can be safely put in the trash.

The 2001 study looked at doses from misuse. It found that a teacher who removed an americium source from a smoke detector and stored it in the classroom could receive 0.009 millirems per year. If the teacher used the source in classroom demonstrations, handling it for 10 hours each year would give less than a 0.001 mrem dose. A person who swallowed the source would receive a 600 mrem dose while it was passing through the body.

I hope this information allays concerns. Unless you remove and swallow the source, your dose from a smoke detector could not be distinguished from what you get throughout your day. And that smoke detector could save your life.

 REFRESH is an occasional series during which we revisit previous blog posts. This originally ran on June 11, 2013. We are rerunning now in honor of Fire Prevention Week. According to the National Fire Protection Association, the week was established to commemorate the Great Chicago Fire, which killed more than 250 people, left 100,000 homeless, destroyed more than 17,400 structures and burned more than 2,000 acres. This year’s theme is Smoke Alarms Save Lives: Test Yours Every Month.

 

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