Get the Facts on Nuclear Power and the Pilgrim Station

How does a nuclear power plant work?

Power plants, whether they are coal, gas, oil or nuclear, use steam to make electricity. They operate like a giant tea kettle, turning water into steam which spins giant turbines that power generators to make electricity. The primary difference between fossil and nuclear power plants is that nuclear plants use uranium as the fuel to produce steam instead of burning fossil fuels.

Nuclear fission

In a nuclear power plant reactor, water is heated by a process called nuclear fission.

  1. Uranium atoms are split when they are struck by neutrons.

  2. When the atoms split, they release heat, along with two or three more neutrons.



  1. These neutrons then strike other uranium atoms, again causing the atoms to split, release heat and two or three more neutrons. This is a continuing reaction.

  2. The heat then produces steam which spins the turbines that are connected to the generators to produce electricity.

Is Pilgrim Nuclear Power Station a safe plant?

Nuclear power plants are very safe and nuclear power generation has proven to be the safest way to produce large amounts of electricity.

The U.S. nuclear industry has operated for more than 30 years without a single nuclear-related fatality.

Pilgrim Nuclear Power Station, like all nuclear power facilities, was designed with multiple and redundant safety systems and components - first, to prevent accidents, and second, to minimize the effects of any malfunction, if one did occur.

The plant staff is frequently and rigorously trained, drilled and evaluated to deal with any emergency. The plant can be shut down and the nuclear fission process stopped in less than two seconds. In fact, the plant will shut down automatically if even one safety component malfunctions.

Structural safety is another intrinsic element to ensure the continued operation of the plant. The containment structure around the reactor provides multiple physical layers of protection. In fact, the containment building has four primary layers of safety built in:

  1. Nuclear fuel - The fuel itself is actually designed to contain the radioactive gases generated during the fission process.

  2. Reactor coolant system - Within the system there are multiple cooling capabilities, each with back up systems in place to ensure the cooling process continues without interruption.

  3. Primary containment structure - This consists of a one-inch thick steel wall surrounded by a wall of steel-reinforced concrete five feet thick. This ensures that radioactivity is contained even in the most serious situations.

  4. Reactor building - This is the secondary containment level. In addition to having walls of two more feet of steel-reinforced concrete, the building itself is kept at a lower atmospheric pressure level than the outside air to keep any radioactivity inside. Anyone entering this building must pass through an air-lock door which helps to maintain the negative pressure area.

In fact, Three Mile Island is a perfect example of how well all of these components work. Studies conducted by the University of Pennsylvania at 10 and 20 years following the 1979 incident show there were no adverse health affects from the event, further supporting the claim that the safety systems worked as they should have.

To read more about nuclear safety at Pilgrim Nuclear Power Station, click here.

Is Pilgrim Nuclear Power Station secure?

Pilgrim Nuclear Power Station is both safe and secure against natural and man-made events for several reasons. Pilgrim Nuclear Power Station provides protection at the plant through a highly trained security force, detection capabilities and physical barriers, as well as a highly qualified brigade of first responders and local, state, and federal security agencies.

In addition to skilled security personnel, there are several security barriers on-site within each building and only a limited number of employees are able to access to the highly restricted areas. Assuming one has the authority to access sensitive areas, there are cameras, stationary and patrolling armed guards, turn-styles and, digital access points, which make it nearly impossible for any individual to go unnoticed.

The containment structure, while it plays a significant safety role, also plays a major security role as well. In addition to the numerous safety measures in place to protect contain the materials in the reactor core, the rugged and robust physical structure also plays a key role in securing keeping the core from outside attacks of any kind.

Can a nuclear plant explode?

No, a nuclear explosion cannot occur at commercial nuclear plants. Fuel for nuclear plant uranium is mined from the earth and then goes through the process of "enrichment." From that process, comes uranium-235 (which makes up approximately 4% of nuclear fuel used at a commercial facility) and uranium-238 (which makes up the other 96% of the fuel). In order to have an explosion, uranium-235 must make up nearly 100% of the fuel. Scientifically speaking, an explosion at a nuclear facility in the U.S. would counter the laws of physics.

Can Chernobyl happen here?

No. Though people often compare U.S. nuclear facilities to Chernobyl, U.S. nuclear facilities have several safeguards that Chernobyl did not, including a high-integrity containment building and multiple safety systems.

There are several significant distinctions that should be understood:

  1. There was no containment structure at Chernobyl. Instead, there was a graphite cylinder with a tin roof that surrounded the nuclear fuel. All U.S. plants are required to have a high-integrity containment structure in place.

  2. Safety systems at the Chernobyl facility were disconnected prior to the explosion.

  3. The explosion at Chernobyl was a hydrogen explosion, not a nuclear explosion. Hydrogen was used to generate the heat that powered the turbines and generators to create electricity. In the U.S., steam is used to operate the turbines.

  4. Once the top of the reactor was literally blown off by the hydrogen explosion, irradiated graphite was scattered into the distance which is why the effects were seen so far away. The radioactive isotopes from the nuclear fuel (because of their weight) remained in the reactor.

The type of uranium used at a commercial facility in the U.S. and the structure of the containment dome required to operate a plant here would rule out the possibility of any Chernobyl-type event. That type of plant could NOT be - nor has one ever been - licensed in the U.S. because of the substantial design flaws at Chernobyl. Thus, the accident that occurred there could not be duplicated here in the U.S.

Consider the only nuclear accident that has occurred in the U.S. in the 35-year history of nuclear power, Three Mile Island - the containment dome successfully contained the radioactivity preventing dangerous exposure levels from ever leaving the core, much less reaching the public. And, even though no one was harmed in that accident, the industry learned from the event and implemented even more safeguards in the form of plant equipment and training.

How is spent fuel stored at Pilgrim Nuclear Power Station?

Spent fuel is stored in a spent fuel pool which is also housed in the reactor building inside of secondary containment at Pilgrim Nuclear Power Station. The walls of the storage facilities for nuclear fuel are five feet thick, reinforced concrete with a steel-reinforced liner to ensure safety and protection from all kinds of natural disasters or manmade assaults.

Water provides shielding from radioactivity and keeps the fuel cool. Redundant safety systems ensure that the water level is maintained and fuel integrity is not compromised.

For additional information, visit the environmental section of our Web site.

What is the emergency plan for Pilgrim Nuclear Power Station?

Pilgrim Nuclear Power Station works together with the Emergency Planning Zone (EPZ) towns and the Massachusetts Emergency Management Agency's (MEMA) Nuclear Preparedness Division, to oversee the planning, training, exercises and equipment necessary to support the radiological emergency response for the Massachusetts population within the 10-mile emergency planning zone.

The Nuclear Preparedness Division has developed and maintains detailed radiological emergency response plans and implementing procedures for communities and facilities for the EPZ. All plans and procedures are reviewed and updated annually, tested in regular drills, and evaluated by the federal agencies.

Has security been updated at Pilgrim Nuclear Power Station since September 11, 2001?

Since September 11, 2001, a focus on security has become increasingly visible everywhere, including the security measures on site at Pilgrim Nuclear Power Station Station. Since that time, more than $10 million has been spent to upgrade security, equipment and highly-trained security forces. The Nuclear Regulatory Commission (NRC) has two full-time resident inspectors at Pilgrim Nuclear Power Station who monitor all operations daily. For additional information, visit the security section of our Web site.

Is the age of Pilgrim Nuclear Power Station a security or safety factor?

No. Opponents charge that Pilgrim Nuclear Power Station's age renders the plant less safe than newer plants. The fact is that the external structure of Pilgrim Nuclear Power Station was constructed to last well beyond its original license of 40 years. Internally, millions of dollars in upgrades have been made to the plant since Entergy purchased it back in 2002 - to the point where its parts are almost entirely new.

There is also routine maintenance that occurs every day to ensure the safe continued operation of the plant and to minimize the need for unscheduled shutdowns.