INL PROGRAMS

Nuclear Programs

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The ATR is a pressurized water test reactor

that operates at low

pressure and low temperature.

It is located at the Reactor

Technology Complex on the

Idaho National Laboratory

(INL) site, about 40 miles from

Idaho Falls, Idaho, and 120

miles from Jackson, Wyoming.

Reactor Type: The reactor is

pressurized and is cooled with

water. The reactor core

includes a beryllium reflector

(the reflector helps concentrate

neutrons in the reactor core,

where they are needed for

fuels and materials testing).

Reactor Vessel: The vessel is

a 12-foot diameter cylinder,

36-feet high, made of

stainless steel.

Reactor Core: The core is 4

feet in diameter and height

and includes 40 fuel elements.

Coolant Temperatures and

Pressure: The reactor inlet

temperature is 125°F, and the

outlet temperature is 160oF.

The reactor pressure is 390

pounds per square inch.

The ATR has many uses

National Security - The ATR

has provided the critical

testing capability that has

helped develop our nation’s

nuclear Navy:

• The Navy is the major customer and user of the ATR.

• The ATR testing has

contributed to the exceptional operational performance of our nuclearpowered fleet.

The Advanced Test Reactor (ATR)

The ATR is located at the Reactor

Technology Complex on the

Idaho National Laboratory site,

about 40 miles from Idaho

Falls, ID, and 120 miles

from Jackson, WY.

Idaho National Laboratory’s

Advanced Test Reactor has

many uses, including national

security and energy applications, and medical isotope

production.
INL PROGRAMS

produce both iridium and

cobalt isotopes needed for

radiography.

• The ATR has been selected

to produce plutonium-238

for space and security

power systems.

The ATR has a

confinement structure

The ATR is housed in a large,

heavy-walled, stainless steel

container (called a vessel) that

extends more than 20 feet

underground surrounded by

massive concrete walls and

support structure. As such, the

reactor is very well protected

from intentional or accidental

damage (such as a plane

crash). An industrial enclosure, called a confinement

structure, surrounds the

reactor area and serves as an

additional barrier in the

highly unlikely event of a

release of radioactivity. The

ATR’s confinement structure

is similar to that used to cover

most test reactors, but the

ATR vessel and vessel

enclosure structure is significantly stronger than typical

test reactors.

Commercial reactors, however, operate at much higher

temperatures and pressures

than the ATR and, in the

unlikely event of severe core

Nuclear Energy - The ATR

testing supports power

reactors around the world:

• Current nuclear power

plants – extension of

operating life

• Development of future

reactor designs

• Testing of new nuclear fuel

types that can reduce waste

generation and proliferation risk

Isotopes - The ATR fills a

critical need for isotope

production:

• Medical Isotopes - The ATR

is the only U.S. reactor

capable of producing

certain medical isotopes in

the quantity and quality

needed to support this ever

expanding and promising

field of medical treatment:

• The ATR produces the

cobalt isotope needed for

the “gamma knife” used to

treat brain tumors.

• The ATR is the reactor of

choice for the production of

a cesium isotope needed for

treatment of soft tissue

cancer.

• The ATR has had long

standing programs to

Continued from previous page

The high operating temperature

and pressure of commercial

reactors require them to have a

robust containment structure.

The ATR is pressurized and

cooled with water. The reactor

core includes a beryllium

reflector, which helps concentrate neutrons in the reactor core,

where they are needed for fuels

and materials testing.
INL PROGRAMS

San Francisco Jackson Los Alamos INL ATR

0%

10%

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damage, a commercial reactor

could release a great deal of

radioactivity. Accordingly,

commercial reactors are

required to have a more

robust enclosure called a

containment structure (two

large dome-shaped structures

shown in photo). A general

comparison between the ATR

and a commercial pressurized

water reactor provided at right

illustrates why a more

massive enclosure is required

for commercial reactors.

Continued next page

The seismic hazard faced by the ATR is well understood and manageable

Building Code (IBC). The

IBC is much more precise,

and considers earthquake

ground movements in percent

of ground motion acceleration

(%g). The U.S. Geological

Survey ground motion data

for various locations are

presented above.

The ATR is safe

While the ATR has been

operating for more than 35

years, the ATR’s unique

design allows for operation

well past its current age. For

most reactors, the factor that

“zone” in which INL resides.

The zone nomenclature was

part of the Uniform Building

Code, which was replaced in

2000 with the International

This comparison illustrates why

a more massive enclosure is

required for commercial reactors.

This graph compares

U.S. Geological Survey

groundmotion data for

various locations.

Many significant seismic events

have been recorded in the

mountains around the INL Site,

but the Site itself is well isolated

from these events.

The ATR is located on the

Snake River Plain, which is

seismically quiet compared to

the surrounding mountains.

The map below shows seismic

events from 1850-2003 with

magnitudes greater than 5.0.

As shown in the map, many

significant seismic events

(indicated in green dots) have

been recorded in the mountains around the INL Site, but

the Site, itself, is well isolated

from these events.

Claims have been made

regarding the seismic hazard
INL PROGRAMS

05-GA50834

A U.S. Department of Energy

National Laboratory

Teri Ehresman

(208) 526-7785

Teri.Ehresman@inl.gov

http://nuclear.inl.gov

For more information:

Continued from previous page

limits reactor life is

embrittlement of the reactor

vessel and core components

due to irradiation effects.

With the ATR, the key

components in the reactor

core are replaced every 8 to

10 years. Because of the

design of the reactor core, the

reactor vessel is exposed to

very little radiation, thus

significantly slowing the

effects of radiation

embrittlement. The reactor is

safe to operate today and

through proper maintenance

and periodic upgrades, the

reactor will be able to operate

safely, reliably and effectively

for many years to come.

The ATR has a long history of

safe operations. It has robust

and mature operations and

maintenance programs, a

conservative design and

operating philosophy, and

well-trained and dedicated

staff. Because of a solid

safety ethic at INL, the ATR

has never experienced a

serious accident or incident.

This strong safety culture at

INL is reflected in the fact

that radiation doses to the

public from INL operations

are so small that they are

more than 100 times less than

the regulatory limit.

With the upgrades that have

been completed over the

years, the ATR is safer today

than it has ever been.

The ATR can be safely

operated for the long-term

In 2003, a review of the ATR

by DOE Headquarters Office

of Independent Oversight and

Performance Assurance (OA)

examined the functionality

and operability of selected

safety systems for the ATR.

To ensure that the systems

could perform their intended

functions, the review focused

on adequacy of system

design, configuration control,

surveillance and testing, and

maintenance and operations.

As a follow-up to the issues

raised during this inspection,

in February 2004 the DOE

Idaho Operations Office

commissioned an independent

review of the ATR by a team

of recognized national experts

in reactor safety, regulation

and licensing, and nuclear

plant operations. The team

concluded that the capability

of the management and

operating staff and the overall

material condition of the ATR

supported its continued nearterm safe operations but that a

comprehensive plan was

essential to the long-term

operation of the reactor.

In response, DOE established

a life extension program,

aimed at identifying the

actions needed over the next

10 years to assure the currency of the safety documentation for the reactor and its

continued operation. Safety

analysis is an important tool

for understanding the operating envelope for a reactor, to

assure that the plant can be

operated in accordance with

the most current safety

standards.

The life extension program

plan addresses such issues as

the procurement and availability of critical spare parts,

including one-of-a-kind

components (e.g., safety rods,

core internal components,

beryllium reflector), staffing

requirements, and identifies

the funding, schedule, and

prioritization for replacement

of key components and

systems. This plan is a key

part of the strategic plan for

the long-term operation of the

reactor and the planning basis

for DOE’s budget requests.

Implementation of the plan

began in FY 2005 and funds

have been provided in FY

2006 to continue this important effort.

In 2005, OA conducted a

follow-up inspection of the

INL, which examined, in part,

the progress of the laboratory

in addressing the opportunities for improvement that had

been identified in the 2003

inspection. While the review

recommended that DOE take

steps to accelerate efforts

associated with the life

extension program, it concluded that:

• The ATR has a strong

nuclear safety culture.

• Operations and maintenance at the ATR are

performed with high regard

to safety.

• The ATR has made important progress in the update

of its safety documentation

and analyses.

• DOE is providing active

oversight over the life

extension program.

Importantly, the OA follow-up

review concluded that

important progress has been

made since the 2003 review

and that the team “did not

identify any specific conditions for the systems reviewed

that would warrant shutdown

of reactor operations.”