Month: December 2012

Waste Confidence Public Comment Period Ending Soon

MH900287136The NRC’s public comment period on the scope of an environmental impact statement for the waste confidence decision and rule ends January 2. The waste confidence decision and rule is related to the safety of spent fuel storage. So far, we have received more than 400 wide-ranging comments and suggestions on issues we should cover in this important document. Several more are anticipated before the deadline.

In addition to the hundreds of thoughtful comments on the scope of the environmental impact statement, we received much criticism on the scoping process itself, in particular with regard to the length of the scoping period, the January 2 deadline, how the notice was phrased, and whether the NRC was in compliance with its regulations. These concerns have been reviewed and considered by the NRC staff and the Commission. NRC Chairman Allison Macfarlane also responded in a letter earlier this month to some of the overarching concerns that have been raised.

The Commission maintained the original 70-day formal comment period, as it provides in its judgment sufficient time for the public to develop thoughtful comments. This period is also consistent with, or longer than, most other comment periods for other NRC actions. The scoping notice was published on October 25, 2012, and the NRC has held four public meetings to date.

The NRC will take into consideration all of the comments received and develop a draft environmental impact statement and proposed rule by August 2013. The public will also have an opportunity to comment on these documents. We plan to hold a number of regional public meetings across the U.S. after their issuance.

For more information about the NRC’s ongoing efforts to develop a generic environmental impact statement to support a revised Waste Confidence Decision and Rule, please visit the NRC’s website. While there, you can also sign up for automatic updates.

Keith McConnell
Director, Waste Confidence Directorate

What is a Reactor Trip and How Does it Protect the Plant?

nppmapThe Salem nuclear power plant’s Unit 1 “tripped” on Dec. 21st. Brown’s Ferry Unit 2 tripped the following day. In both cases, something happened that caused the reactor to automatically shut down to ensure safety. In other words, a trip means a plant is doing what it’s supposed to do. Let’s look at the term a bit more closely.

Key operating parameters of a nuclear power plant, such as coolant temperature, reactor power level, and pressure are continuously monitored, to detect conditions that could lead to exceeding the plant’s known safe operating limits, and possibly, to damaging the reactor core and releasing radiation to the environment.

If any of these limits is exceeded, then the reactor is automatically shut down, in order to prevent core damage. In nuclear engineering terms, the automatic shutdown of a nuclear reactor is called a reactor trip or scram . A reactor trip causes all the control rods to insert into the reactor core, and shut down the plant in a very short time (about three seconds).

How do control rods do their job?

The control rods are composed of chemical elements that absorb neutrons created by the fission process inside the reactor. They are placed methodically throughout the nuclear reactor as a means of control. For example, as the control rods are moved into the reactor, neutrons are absorbed by the control rods and the reactor power is decreased. Inserting them all at the same time shuts down the reactor. Control rods can also be inserted manually, if necessary.

The plant operator then determines the reason for the trip, remedies it and, when it’s determined to be safe, restarts the reactor. So, while not common, a reactor trip is an important way to protect the components in a nuclear power plant from failing or becoming damaged.

Samuel Miranda
Senior Reactor Systems Engineer
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