FAQ - Japanese Nuclear Energy Situation (Nuclear Energy Institute

1. What will be the impact of the Fukushima Daiichi accident on the U.S. nuclear program?

It is premature to draw conclusions from the tragedy in Japan about the U.S. nuclear energy program. Japan is facing what literally can be considered a “worst case” disaster and, so far, even the most seriously damaged of its 54 reactors has not released radiation at levels that would harm the public. That is a testament to their rugged design and construction, and the effectiveness of their employees and the industry’s emergency preparedness planning.

Until we understand clearly what has occurred at the Fukushima Daiichi nuclear power plants, and any consequences, it is difficult to speculate about the long-term impact on the U.S. nuclear energy program. The U.S. nuclear industry, the U.S. Nuclear Regulatory Commission, the Institute of Nuclear Power Operations, the World Association of Nuclear Operators and other expert organizations in the United States and around the world will conduct detailed reviews of the accident, identify lessons learned (both in terms of plant operation and design), and we will incorporate those lessons learned into the design and operation of U.S. nuclear power plants. When we fully understand the facts surrounding the event in Japan, we will use those insights to make nuclear energy even safer.

In the long-term, we believe that the U.S. nuclear energy enterprise is built on a strong foundation:

* reactor designs and operating practices that incorporate a defense-in-depth approach and multiple levels of redundant systems

* a transparent regulatory process that provides for public participation in licensing decisions, and

* a continuing and systematic process to identify lessons learned from operating experience and to incorporate those lessons.

2. What will be the impact of the Fukushima Daiichi accident on new nuclear plant construction in the United States?

Nuclear energy has been and will continue to be a key element in meeting America’s energy needs. The nuclear industry sets the highest standards for safety and, through our focus on continuous learning, we will incorporate lessons learned from the events in Japan into the ongoing process of designing, licensing and building new nuclear power plants.

New nuclear power plant construction in the United States is in the early stages and proceeding in a deliberate fashion. Two companies have started site preparation and other construction activities for new nuclear power plants in Georgia and South Carolina, with the expectation that they will receive their combined construction-operating licenses from the Nuclear Regulatory Commission in late 2011 or early 2012. We expect those new reactor projects to proceed. Both projects use a light water reactor design with advanced safety features – i.e., the reactors rely on natural forces like gravity (rather than engineered safety features like pumps) to deliver cooling water to the reactor core.

In addition, a number of companies are moving forward with design, licensing and – at the appropriate time – construction of small modular reactors (SMRs), which also incorporate design features that provide additional safety margin.

Although America’s 104 nuclear power plants are safe and meet all requirements necessary to protect public health and safety, these new designs are even safer.

3. Could an accident like the one at Japan’s Fukushima Daiichi nuclear plant happen in the United States?

It is difficult to answer this question until we have a better understanding of the precise problems and conditions that faced the operators at Fukushima Daiichi. We do know, however, that Fukushima Daiichi Units 1-3 lost all offsite power and emergency diesel generators. This situation is called “station blackout.” U.S. nuclear power plants are designed to cope with a station blackout event that involves a loss of offsite power and onsite emergency power. The Nuclear Regulatory Commission’s detailed regulations address this scenario. U.S. nuclear plants are required to conduct a “coping” assessment and develop a strategy to demonstrate to the NRC that they could maintain the plant in a safe condition during a station blackout scenario. These assessments, proposed modifications and operating procedures were reviewed and approved by the NRC. Several plants added additional AC power sources to comply with this regulation.

In addition, U.S. nuclear plant designs and operating practices since the terrorist events of September 11, 2001, are designed to mitigate severe accident scenarios such as aircraft impact, which include the complete loss of offsite power and all on-site emergency power sources.

U.S. nuclear plant designs include consideration of seismic events and tsunamis’. It is important not to extrapolate earthquake and tsunami data from one location of the world to another when evaluating these natural hazards. These catastrophic natural events are very region- and location-specific, based on tectonic and geological fault line locations.

4. What would U.S. nuclear plant operators do if they faced a loss of power from the grid and loss of emergency diesel generators like that faced by the operators at Fukushima Daiichi?

Nuclear power plant operators are trained to ensure that the plant will achieve and maintain safe shutdown during a station blackout scenario (loss of offsite power and loss of onsite emergency AC power). They have operating procedures that guide them on actions to be taken in responding to this scenario. The training includes regular classroom work as well as plant-specific simulator exercises.

5. Do NRC regulations require nuclear plant operators to have back-up power long enough to maintain safe conditions when power from the grid is not available for several days?

Yes, nuclear plants are required to have emergency AC power sources (diesel generators) to provide electrical power to plant safety equipment when there is a loss of power from the electrical grid. These backup generators are tested on a monthly basis to ensure that they successfully start and accept electric loads. Additionally, there are also battery powered DC support systems for some emergency DC power to critical valves, etc.

A nuclear plant can maintain a shutdown condition isolated from the bulk power transmission system for an indefinite period of time.

6. How many U.S. reactors use the Mark I containment design used at Fukushima Daiichi Unit 1?

Six U.S. nuclear reactors (Monticello in Minnesota, Pilgrim in Massachusetts, Dresden 2 and 3 and Quad Cities 1 and 2 in Illinois) are the same base design as the Fukushima Daiichi Unit 1 design (BWR-3 design with Mark I containment). Twenty-three U.S. nuclear plants are boiling water reactors (either BWR-2, BWR-3 or BWR-4) and use the Mark I containment: Browns Ferry 1, 2 and 3; Brunswick 1 and 2; Cooper; Dresden 2 and 3; Duane Arnold; Hatch 1 and 2; Fermi; Hope Creek; Fitzpatrick; Monticello; Nine Mile Point 1; Oyster Creek; Peach Bottom 2 and 3; Pilgrim; Quad Cities 1 and 2; Vermont Yankee. Although these are the same basic reactor design, specific elements of the safety systems will vary based on the requirements of the U.S. NRC.

The explosion appears to have been caused by a build-up of hydrogen in the reactor building. The uranium fuel pellets are enclosed in steel tubes made of zirconium alloy. When exposed to very high temperatures, the zirconium reacts with water to form zirconium oxide and hydrogen. This appears to have happened at Fukushima Daiichi Unit 1when a portion of the uranium fuel was uncovered. It is assumed that the hydrogen found its way into the reactor building, accumulated there, and ignited. Although significant, the explosion did not appear to compromise the integrity of the primary containment or the reactor vessel.

8. Given that Fukushima Daiichi Unit 1 is a 1970s-vintage plant, do you anticipate increased regulatory requirements and scrutiny on U.S. plants of similar vintage? Do you think the accident will have an impact on license renewal of the older U.S. nuclear power plants?

The U.S. nuclear energy industry and the Nuclear Regulatory Commission will analyze the events at Fukushima Daiichi, identify lessons learned and incorporate those lessons, as appropriate, into the design and operation of U.S. nuclear power plants.

The U.S. industry routinely incorporates lessons learned from operating experience into its reactor designs and operations. For example, as a result of the 1979 accident at Three Mile Island, the industry learned valuable lessons about hydrogen accumulation inside containment. After Three Mile Island, many boiling water reactors implemented a modification referred to as a hardened vent or direct vent. This allows the plant to vent primary containment via high pressure piping. This precludes over-pressurization of containment.

9. There have been questions raised in the past about the BWR Mark I containment like that at Fukushima Daiichi Unit 1? Some critics have pointed to a comment by an NRC official in the early 1980s: “Mark I containment, especially being smaller with lower design pressure, in spite of the suppression pool, if you look at the WASH 1400 safety study, you’ll find something like a 90% probability of that containment failing.”

The Mark I containment meets all Nuclear Regulatory Commission design and safety requirements necessary to protect public health and safety. The WASH-1400 safety study referenced was performed in 1975. The Nuclear Regulatory Commission has analyzed the Mark I containment design in great detail. The NRC analysis found that the BWR Mark I risk was dominated by two scenarios: station blackout and anticipated transient without scram. The NRC subsequently promulgated regulations for both of these sequences as well as other actions to reduce the probability.

10. What happens when you have a complete loss of electrical power to operate pumps in a BWR-3 reactor with Mark I containment like the one at Fukushima Daiichi Unit 1?

If plant operators cannot move water through the reactor core, the water in the reactor vessel begins to boil and turn to steam, increasing pressure inside the reactor vessel. In order to keep the reactor vessel pressure below design limits, this steam is then piped into what is called a “suppression pool” of water or “torus” – a large doughnut-shaped ring that sits beneath the reactor vessel.

Eventually, the water in the suppression pool reaches “saturation” – i.e., it cannot absorb any additional heat and it, too begins to boil, increasing pressure in containment. In order to stay within design limits for the primary containment, operators will reduce pressure by venting steam through filters (to scrub out any radioactive particles) to the atmosphere through the vent stack.

If operators cannot pump additional water into the reactor vessel, the water level will begin to drop, uncovering the fuel rods. If the fuel remains uncovered for an extended period of time, fuel damage, possibly including melting of fuel, may occur. If there is fuel damage, and steam is being vented to the suppression poll, then to primary containment, then to secondary containment (in order to relieve pressure build-up on plant systems), small quantities of radioactive materials will escape to the environment.

11. How serious are the releases of radiation from Fukushima Daiichi? Do they represent a threat to human health? Will we see an increase in cancer rates in future years?

The most effective options for protecting the public have already been instituted. In the early stages of this event, authorities ordered evacuation of the people who live around the Fukushima Daiichi site to prevent or mitigate radiation exposure from any releases. Authorities are also distributing potassium iodide tablets to specifically protect against exposure from radioactive iodine that may be present in the releases. Any speculation about possible health effects would be premature until more accurate and complete data becomes available.

12. Did the reactor cores melt at any of the Fukushima Daiichi reactors? Was there any fuel damage?

It appears that Fukushima Daiichi Units 1 and 3 have experienced some fuel damage, since we understand that the upper portion of the fuel rods were uncovered (not covered with water) for some period of time. There is no evidence of a complete core meltdown at either unit, however. The information we have suggests that the basic core configuration so far remains intact, so some water or steam cooling through the core is occurring.

13. Is this accident likely to result in changes to regulatory requirements for U.S. nuclear plants in seismically active areas? Will those regulatory requirements be revisited and made more robust?

The nuclear energy industry believes that existing seismic design criteria are adequate. Every U.S. nuclear power plant has an in-depth seismic analysis and is designed and constructed to withstand the maximum projected earthquake that could occur in its area without any breach of safety systems. Each reactor is built to withstand the maximum site-specific earthquake by utilizing reinforced concrete and other specialized materials. Each reactor would retain the ability to safely shut down the plant without a release of radiation. Given the seismic history in California, for example, plants in that state are built to withstand an even higher level of seismic activity than plants in many other parts of the country.

Engineers and scientists calculate the potential for earthquake-induced ground motion for a site using a wide range of data and review the impacts of historical earthquakes up to 200 miles away. Those earthquakes within 25 miles are studied in great detail. They use this research to determine the maximum potential earthquake that could affect the site. Each reactor is built to withstand the respective strongest earthquake. Experts identify the potential ground motion for a given site by studying various soil characteristics directly under the plant. For example, a site that features clay over bedrock will respond differently during an earthquake than a hard-rock site. Taking all of these factors into account, experts determine the maximum ground motion the plant must be designed to withstand. As a result, the design requirements for resisting ground motion are greater than indicated by historical records for that site.

It is also important not to extrapolate earthquake and tsunami data from one location of the world to another when evaluating these natural hazards. These catastrophic natural events are very region- and location-specific, based on tectonic and geological fault line locations.

14. Are U.S. emergency planning requirements and practices adequate to deal with a situation like that faced at Fukushima Daiichi?

Yes. Federal law requires that energy companies develop and perform graded exercises of sophisticated emergency response plans to protect the public in the event of an accident at a nuclear power plant. The U.S. Nuclear Regulatory Commission reviews and approves these plans. In addition, the NRC coordinates approval of these plans with the Federal Emergency Management Agency (FEMA), which has the lead federal role in emergency planning beyond the nuclear plant site. An approved emergency plan is required for the plant to maintain its federal operating license. A nuclear plant’s emergency response plan must provide protective measures, such as sheltering and evacuation of communities within a 10-mile radius of the facility. In 2001, the NRC issued new requirements and guidance that focus in part on emergency preparedness at plant sites in response to security threats. The industry has implemented these measures, which address such issues as on-site sheltering and evacuation, public communications, and emergency staffing in the specific context of a security breach. Several communities have used the structure of nuclear plant emergency plans to respond to other types of emergencies. For example, during the 2007 wildfires in California, county emergency officials drew on relationships and communications links they had established during their years of planning for nuclear-related events.

In addition, as part of the emergency plan, nuclear plant operators would also staff Emergency Centers within one hour to provide support to the plant staff during the event. This support would be in the form of:

* Technical expertise (engineering, operations, maintenance and radiological controls)

15. Should U.S. nuclear facilities be required to withstand earthquakes and tsunamis of the kind just experienced in Japan? If not, why not?

U.S. nuclear reactors are designed to withstand an earthquake equal to the most significant historical event or the maximum projected seismic event and associated tsunami without any breach of safety systems.

The lessons learned from this experience must be reviewed carefully to see whether they apply to U.S. nuclear power plants. It is important not to extrapolate earthquake and tsunami data from one location of the world to another when evaluating these natural hazards, however. These catastrophic natural events are very region- and location-specific, based on tectonic and geological fault line locations.

The U.S. Geological Survey (USGS) conducts continuous research of earthquake history and geology, and publishes updated seismic hazard curves for various regions in the continental US. These curves are updated approximately every six years. NRC identified a generic issue (GI-199) that is currently undergoing an evaluation to assess implications of this new information to nuclear plant sites located in the central and eastern United States. The industry is working with the NRC to develop a methodology for addressing this issue.

16. Is this accident as serious as the Three Mile Island accident in 1979? As serious as the Chernobyl accident?

According to the International Atomic Energy Agency’s seven-level International Nuclear and Radiological Event Scale (INES), the accident at Fukushima Daiichi is a Level 4 accident.

INES defines Level 4 as an “Accident With Local Consequences,” which is lower than the Level 5 rating given to the 1979 Three Mile Island accident in Pennsylvania. The major accident at Chernobyl in 1986 was classified at the highest INES rating of 7.

17. Do you expect an impact on public opinion about nuclear power or public support for nuclear power in the United States as a result of the Fukushima Daiichi accident?

Given the safety record in this country, the robust regulatory infrastructure, the defense in depth that governs operations and designs, and the seismological differences between the U.S. and Japan, we believe that public support for nuclear power should not decline dramatically.

The events at Fukushima Daiichi show that nuclear power’s defense-in-depth approach to safety is appropriate and strong. Despite one of the largest earthquakes in world history, with accompanying tsunamis, fires and aftershocks—multiple disasters compounded one on top of the other—the primary containments at reactors near the epicenter have not been breached and the radioactive release has been minimal and controlled. This event will show that even under very severe circumstances, nuclear power plants are designed to withstand natural disasters. Still, the industry takes the incident with utmost seriousness and will strive to continually incorporate any lessons to enhance the safety of nuclear power plants. Opinion surveys show that public confidence in nuclear energy in the United States is strong and we believe it will continue to grow.

18. Do the events indicate that iodine tablets should be made widely available during an emergency?

The thyroid gland preferentially absorbs iodine. In doing so it does not differentiate between radioactive and nonradioactive forms of iodine. The ingestion of nonradioactive potassium iodide (KI), if taken within several hours of likely exposure to radioactive iodine, can protect the thyroid gland by blocking further uptake of radioactive forms of iodine. KI does not protect any other part of the body, nor does it protect against any other radioactive element.

The NRC has supplied KI tablets to states that have requested it for the population within the 10-mile emergency planning zone (EPZ) of a nuclear reactor. If necessary, KI is to be used to supplement other measures, such as evacuation, sheltering in place, and control of the food supply, not to take the place of these actions. The Environmental Protection Agency and the Food and Drug Administration have published guidance for state emergency responders on the dosage and effectiveness of KI on different segments of the population. According to the EPA guidance, “KI provides optimal protection when administered immediately prior to or in conjunction with passage of a radioactive cloud.”

Populations within the 10-mile emergency planning zone of a nuclear plant are at greatest risk of exposure to radiation and radioactive materials including radioactive iodine. Beyond 10 miles, the major risk of radioiodine exposure is from ingestion of contaminated foodstuffs, particularly milk products. Both the EPA and the FDA have published guidance to protect consumers from contaminated foods within a 50 mile radius.

19. Do the events indicate that evacuation zones around plants should be extended?

The 10-mile emergency planning zone around nuclear power plants as determined in 1978 by a multi-agency federal task force is appropriate and should not change due to the accident at Fukushima Daiichi. In the United States, a nuclear plant’s emergency response plan must provide protective measures, such as sheltering and evacuation of communities within a 10-mile radius of the facility. Japan used a similar plan. During the accident there, the Japanese government has issued evacuation orders for a 20-kilometre (12.5-mile) radius around Fukushima Daiichi, and a 3-kilometre radius around Fukushima Daini.

A couple of my own conclusions...

** When this is said and done, Japanese nuclear operating engineers will be hailed as National Heroes.

** American anti-nuclear activists are already having orgasms over this accident with little regard for what the truth of the situation really is.

** The American media are proving themselves to be the severely ignorant hysterical morons we always though they were.

** These reactors are testaments to the skill and wisdom of Japanese nuclear designers, builders and operators, who continue to control a beyond worst case scenario with great courage. The fact these reactors are still being managed speaks volumes about the many levels of safety built into these units.

Designing a system that vents hydrogen into the enclosure assuring an explosion and possible damage to the venting itself seems like a flawed strategy.

I notice you write "seems" which indicates you are not conclusive. Are you recommending ventilation of the gasses out of the containment building? Is that even practical in the situations encountered? Was the buildup a design issue or an operator choice or something in between?

I am not certain we know all the particulars at this time. Taking an action or not taking an action involves tradeoffs. To illustrate by way of devil's advocate: what if the gasses are radioactive, but the area around the building is evacuated? Personally I do not think I know enough to guess all the details that lead the operators there to do what they do and to be their back-seat driver.

I am reasonably certain that over time there will be analyses, investigations, design modification improvements, and new designs.

Blaming operators? Hardly.

That's like blaming grunts for command decisions. Since I was a grunt I'm loathe to do either.

But it would seem that srubbing the steam and venting it to the atmosphere would be a better idea no?

Now my BS is in Electronic Engineering so I'm not pretending to be a Nuclear Design Engineer. And I hesitated commenting when the 1st building blew but since number 3 blew as well it became evident that the system was designed to vent steam into the building. If that isn't the case then my question does not obtain. If it is the case then the question stands and it has no bearing on the operators and techs at all. I salute all of them.

From what I can gather is that in a blackout situation, water is not circulating through the reactor core (which is quite warm). The coolant water in direct contact with the zironium tubes containing the uranium pellets boils and turns to steam. This steam is routed to a torus pool of stagnant water below the reactor core and is allowed to percolate throughout the cooler liquid water; heat from the reactor core is thereby exchanged from the reactor fuel elements; some of the percolating steam condenses, albeit the temperature of the torus pool rises (and pressure builds as uncondensed steam accumulates in the torus pool reservoir tank); eventually the torus pool itself boils. In order to maintain structural integrity of the primary core containement vessel - and to allow continued heat exchange from within the primary core - pressure within the torus pool tank is relieved by venting its steam into to the atmosphere.

If operators cannot pump additional water into the reactor vessel, the water level will begin to drop, uncovering the fuel rods. If the fuel remains uncovered for an extended period of time, fuel damage, possibly including melting of fuel, may occur. If there is fuel damage, and steam is being vented to the suppression pool, then to primary containment, then to secondary containment (in order to relieve pressure build-up on plant systems), small quantities of radioactive materials will escape to the environment.

The money sentances are here:

When exposed to very high temperatures, the zirconium reacts with water to form zirconium oxide and hydrogen. This appears to have happened at Fukushima Daiichi Unit 1 when a portion of the uranium fuel was uncovered. It is assumed that the hydrogen found its way into the reactor building, accumulated there, and ignited.

That is in extremely ignorant statement; its not that they don't know how the hydrogen got into the secondary containment vessel - which houses both primary reactor core containment and the secondary torus reservoir - its presence being putatively expected during emergencies of such magnitude as 'blackout' operation.

What they don't know is how to get water into the primary reactor core at thousands of PSIG in blackout condition. The system is designed such that the weight of the water in the secondary torus water reservoir acts as a cap against the explosive expansion of gas from within the primary reactor core; should that happen, the entire reactor core would not enjoy the heat sink properties of water and those in the vicinity of the nuclear plant will suddenly encounter a very bad day in an extremely short period of time.

Getting water into the secondary torus pool reservoir itself is not so much of an issue; cap the steam line from the reactor core and allow the secondary torus pool to fill via gravity feed. The problem is budgeting the mass of water contained in the primary loop such that sufficient heat can be exchanged from the reactor core.

Japan is facing what literally can be considered a “worst case” disaster and, so far, even the most seriously damaged of its 54 reactors has not released radiation at levels that would harm the public. That is a testament to their rugged design and construction, and the effectiveness of their employees and the industry’s emergency preparedness planning.

A point which is TOTALLY lost on the US Media. At least Anderson Cooper had the guts to admit on camera yesterday that he didn't understand nuclear power at all, and he was interviewing a man who was trying to assure him that, yes, he was upwind of the plant, so he was OK. Fortunately, the guest went on to say that even if Anderson were downwind of the Fukushima plants, there was such a small of radioactivity released in the steam, in the wake of the explosions at the reactors, there was no danger of radiation poisoning, or anything like it.

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