Regulating Nuclear Fuel Regulating Nuclear Fuel

U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission
Cover Photo: Irradiated fuel assembly and reactor core.

Courtesy of Framatome ANP, Inc.

First Page Background Photo: Switching Yard. Courtesy of USEC.
The nuclear fuel cycle covers the entire

process of mining uranium, to turning it

into fuel, to using it in a nuclear power

plant to produce electricity, and finally,

to disposing of “spent,” or used nuclear

fuel, in a special repository.

This booklet focuses on the responsibilities of the U.S. Nuclear Regulatory

Commission (NRC) in the first part of the

fuel cycle—the mining of uranium and

its conversion and enrichment into a

form that is used in a nuclear power

plant to produce electricity.

The nuclear fuel cycle begins when

uranium ore is extracted from the

ground. Two types of uranium mines

are in use today: conventional mines

and in-situ “leaching” facilities. The

Office of Surface Mining, the U.S. Department of the Interior, and individual

States, regulate mining. The NRC regulates in-situ leaching facilities, uranium

mills, and the disposal of tailings in

certain States, while State agencies

regulate these activities in so-called

“Agreement States”—States that have

entered into an agreement with NRC to

regulate certain nuclear materials.

In a conventional mine, uranium is

removed from deep underground shafts

or shallow open pits. The rock is then

crushed at a uranium mill, where an

extraction process concentrates the

uranium into a compound called

“yellowcake.” The remainder of the

Uranium

Mining and

Milling

REGULATING

NUCLEAR

FUEL

1
crushed rock is placed in a “tailings”

pile. Mill tailings are fine-grained, sandy

waste materials left over from uranium

processing and must be disposed of in

special facilities because of their residual concentration of radium. This

residual radium decays to produce

radon. Radon is a radioactive gas that

has been linked by some researchers to

an increased incidence of lung cancer

when present in confined areas such as

homes or mines.

Uranium can also be “leached” out

of the ground by pumping a water

solution through wells to dissolve the

uranium in the ore. The uranium is

then pumped to the surface in a liquid

solution. About

20 such in-situ

leach facilities

operate in the

United States.

The NRC regulates several

such facilities

in the Western

states and

conducts

routine annual

inspections to

ensure that

they are operated safely. Safety violations at these

sites have been few and relatively minor.

Acid “heap leach” processes have also

been used at conventional mills to extract

uranium from ore, and ion-exchange

Production well

service at Ria

Algom Smith

Ranch in-situ

leaching facility

in Wyoming

2
procedures have been used to separate uranium from the liquid extract.

Acid leach operations involve placing

uncrushed ore on a pad and dissolving

the uranium in an acid bath. The uraniumrich liquid is then processed through an

ion-exchange

circuit to

separate the

uranium from

the liquid. The

ion-exchange

method is

similar at both

conventional

mills and in-situ

leach facilities.

The International

Uranium

Corporation’s

White Mesa mill

in Blanding, Utah, is the only conventional

mill processing uranium ore into yellowcake

at this time. Several other mills may resume

operation in the future. Uranium mills are

located mostly in the western United

States, where deposits of uranium are

more plentiful.

Many NRC-licensed uranium mills have

shut down, and owners have already

started cleaning up the sites to the

point where they can be declared safe

by the NRC. At these sites, clay is compacted on top of the tailings pile as a

barrier to prevent radon from escaping

into the atmosphere and to reduce

the amount of water that seeps into

Quality control

test on mill

tailings cover at

L-Bar site in

New Mexico

3
the waste. The embankments are then

covered with soil, rock, or other materials to prevent erosion. Other sites accept waste from in-situ leach facilities.

After the

uranium is

processed

into yellowcake at a

mill, it is sent

to a facility

to be converted into

uranium

hexafluoride

(UF6

). The

only conversion facility in

the United

States is

located in Metropolis, Illinois. The UF6

 is

solid under normal temperatures and

pressure, but becomes a liquid at higher

temperatures. It may produce a gas

from a solid or liquid state. The material

is then sent to one of the country’s two

gaseous diffusion plants to enrich its

uranium concentration.

Natural uranium is composed mainly of

three isotopes: U-234, U-235 and U- 238.

To be used for nuclear fission in most

U.S. reactors, the concentration of the

U-235 isotope must be increased.

Natural uranium contains less than

1 percent of U-235. To increase the

percentage of U-235, the uranium must

Aerial view

of Atlas mill

tailings site near

Moab, Utah, with

Colorado River

in background

4
be “enriched” to about 4 to 5 percent.

Enriched uranium is produced in the

United States using the gaseous diffusion

method.

First, the solid UF6

 sent from the conversion facility is heated to form a liquid.

The gas that is “boiled” off is then used

in the gaseous diffusion process. While in

a gaseous state, the lighter molecules

of U-235 are separated from the heavier

molecules of U-238 by forcing them

through a membrane with tiny openings.

Because the U-235 is lighter, it moves

through the membrane more easily,

and the two gases can then be separated, increasing the concentration

of U-235,

thereby

“enriching”

the uranium.

The gas that

escapes

through the

membrane

is then

slightly

enriched in

the lighter

isotope. The gas retained by the membrane is slightly “depleted” in U-235 while

the concentration of U-238 increases.

The enriched gas condenses into a

liquid, solidifies, and is transported to

a fuel fabrication facility where it can

be converted into reactor fuel.

Gaseous

Diffusion

Gaseous Diffusion Stage

LOW PRESSURE

ENRICHED

STREAM

DEPLETED

STREAM

HIGH

PRESSURE

FEED

STREAM

LOW PRESSURE

5
Two gaseous diffusion plants currently

operate in the United States, one at

Portsmouth, Ohio, and the other at

Paducah, Kentucky. The Portsmouth

plant closed enrichment operations in

2001, but is still being used for shipping

and transfer operations. Both plants

are operated by the United States

Enrichment Corporation (USEC) under

leases with the U.S. Department of

Energy. The Paducah facility is located in

the northwestern corner of Kentucky

about 10 miles west of Paducah,

Kentucky, and 3 miles south of the Ohio

River. The Portsmouth facility is located

in south central Ohio, approximately 70

miles south of

Columbus,

Ohio.

The Energy

Policy Act of

1992 established USEC

and authorized

the NRC to

regulate the

health and

safety aspects

of the gaseous

diffusion plants.

After a rigorous

safety review,

the two plants

came under

NRC regulation

A large pump

house at the

Paducah uranium enrichment plant

circulates

cooling water

between the

enrichment

process buildings and

cooling towers

Photo courtesy of USEC.

6
The control room

at the Paducah

uranium enrichment plant is the

center of all

plant activity.

From here, operators can

monitor and

control all enrichment

operations on

the plant site

1

The gaseous diffusion plants are the only

“certified” facilities under NRC oversight.

The term originated from the Energy Policy

Act that transferred the uranium enrichment function from the Department of

Energy to a government corporation, which

became a private company in 1998.

Certification consists of a review of safety

and safeguards for the plants against the

NRC regulations.

on March 3, 19971. These facilities have

the capacity to supply a majority share

of the United States’ nuclear power

market, while

also supplying a significant portion

of the world’s

nuclear power

market. The

remainder is

provided by

other countries. The NRC

has two fulltime resident

inspectors at

each site.

Also, specialized inspections are conducted using personnel

from NRC headquarters in Maryland

and the NRC Regional office in Lisle,

Illinois.

Photo courtesy of USEC.

7
Fabrication is the final step in the

process used to produce uranium fuel.

It begins with the conversion of enriched uranium hexafluoride (UF6

) gas to

a uranium dioxide solid. Nuclear fuel

must maintain both its chemical and

physical properties under the extreme

conditions of heat and radiation present

inside an operating reactor vessel.

Fabrication of commercial light-water

reactor fuel consists of three basic steps:

1. the chemical conversion of UF6

to uranium dioxide (UO2) powder;

2. the ceramic process that converts

uranium oxide powder to small

pellets; and

3. the mechanical process that loads

the fuel pellets into rods and

constructs finished fuel assemblies.

After the UF6

 is chemically converted to

UO2

 , the powder is blended, milled,

and pressed into ceramic fuel pellets

about the size of a fingertip. The pellets

are stacked into long tubes made of

material called “cladding” (such as

zirconium alloys) and, after careful

inspection, the resulting fuel rods are

bundled into fuel assemblies for use

in reactors. The cladding material

provides one of multiple barriers to

contain the radioactive fission products

produced during the nuclear chain

reaction.

Following final assembly operations,

the completed fuel assembly (about

12 feet long) is washed, inspected, and

finally stored in a special rack until it is

ready for shipment to a nuclear power

plant site.

Fabrication

8
Nuclear Fuel

Fabrication

Incoming

UF6 Cylinders

UF6 Vaporization UO2 Powder

Production

Powder Processing/

Pellet Manufacturing

Fuel Rod/

Bundle Assembly/

Quality Check

Transport to

Nuclear

Reactors

Uranium Recovery Waste Treatment

Fuel fabrication facilities mechanically

and chemically process the enriched

uranium into nuclear reactor fuel.

The NRC licenses seven commercial

nuclear fuel fabrication facilities in the

United States:

Westinghouse Electric Company LLC

Hematite, Missouri

(ceased conversion and removed all

UF6

 from the site as of March 31, 2001)

Framatome ANP, Inc.

Lynchburg, Virginia

Richland, Washington

BWX Technologies, Inc.

Lynchburg, Virginia

Global Nuclear Fuels–Americas LLC

Wilmington, North Carolina

Nuclear Fuel Services, Inc.

Erwin, Tennessee

Westinghouse Electric Company LLC

Columbia, South Carolina

Fuel

Fabrication

Process

9
UF6 is received

in cylinders (a),

converted to UO

2

powder (b),

and pressed

into fuel pellets,

which must pass

strict quality

inspections (c)

before columns of

pellets are loaded

into fuel rods (d)

a

b

c

d

Photos courtesy of Framatome ANP, Inc.
e

All fuel components

are built to exact

specifications and

are thoroughly

inspected during

the fabrication

process (e, f, g)

Finished assemblies

are inspected both

before shipment (h)

and upon arrival at

f the reactor site (i)

h

g

i

e
The most significant hazard at a uranium

conversion facility exists at the stage

where liquid UF6

 is stored and processed.

When liquid UF6

 is released to the atmosphere, it reacts with the moisture in the

air to form a dense vapor cloud that

contains hydrogen fluoride (HF) gas, a

non-radioactive, extremely toxic substance. In 1986, at the Sequoyah Fuels

Corporation conversion facility in Gore,

Oklahoma, an overfilled cylinder of UF6

ruptured, resulting in a major release of

hydrogen fluoride that killed a worker.

This facility was later closed by its owner.

Since the enrichment facilities handle

and process large amounts of UF6

, the

same chemical hazards exist at an

enrichment facility. In addition, the

production of

enriched uranium

at enrichment

facilities could

potentially produce an inadvertent nuclear chain

reaction, known as

“criticality.” Such

an accident occurred in

Tokaimura, Japan,

in September, 1999.

A criticality may

release significant,

localized amounts

of radiation that

can be harmful

and even fatal to workers or people in

the immediate vicinity, as was the case

with two workers in Japan. The enriched

uranium also requires that significant

Possible

Hazards

Fuel Assembly

Inspection

Photo courtesy of Framatome ANP, Inc.

12
security measures be taken to safeguard such material against theft or

sabotage.

Since it’s creation in 1995, an incident of

this type has never occurred at an NRClicensed facility. A potential criticality

accident was averted in 1991 at the

fuel fabrication facility in Wilmington,

North Carolina. The incident began

when liquid waste material was inadvertently transferred to a tank which,

because of its configuration, type, and

the amount of uranium it contained, led

to the potential for a criticality accident. The former owner, General Electric, took steps to ensure the incident

should not recur.

Fuel fabrication facilities have essentially the same types of hazards as

enrichment facilities (i.e., radiological,

chemical, and criticality hazards). Fuel

fabrication facilities also have extensive

security procedures to guard against

the loss, theft, and diversion of enriched

uranium. Fires can pose significant

hazards at conversion, enrichment, and

fuel fabrication facilities. NRC has

regulations in place to protect against

these safety hazards and security

concerns. Regular inspections at fuel

fabrication facilities enforce these

regulations, ensuring safe operation.

All commercial fuel facilities in the

United States are licensed or certified

by the NRC. The licensing process

begins with rigorous evaluation and

safety checks, to ensure the facilities will

Regulation,

Inspection,

and Safety

13
be built and operated to NRC’s strict

regulations, designed to ensure protection of the public and the environment.

Other agencies, such as the Occupational Safety and Health Administration,

and Federal and State environmental

protection agencies, also have key

oversight roles at these facilities.

Approximately 8 to 10 times per year

NRC inspections are conducted at

each fuel facility, from one of NRC’s

four regional offices or from its headquarters in Rockville, Maryland. The

regional offices are located in King of

Prussia, Pennsylvania; Atlanta, Georgia;

Lisle, Illinois; and Arlington, Texas.

The exact number of inspections and

their focus varies, depending on the

relative safety and safeguards risks at

each facility and its overall performance level. Resident inspectors, living

nearby, perform daily inspections at the

gaseous diffusion plants. The NRC also

has resident inspectors at the BWXT fuel

facility in Virginia and the Nuclear Fuel

Services plant in Tennessee because

those facilities handle material enriched

at a higher level for national defense

and other purposes.

NRC’s inspections focus on those areas

that are most important to safety and

security, using objective measures of

performance. In general, inspections

may cover activities such as nuclear

criticality control, chemical process,

14 emergency preparedness, fire safety,
Framatome ANP, Inc.

Fuel Fabrication

Facility in Richland,

Washington

and radiation safety. For those facilities

that store or process higher enriched

nuclear material, the NRC requires

certain safeguards to protect such

material from loss, theft, or diversion.

Violations of NRC requirements are

evaluated to determine their impact on

safety. If the violation is of low safety

significance, it may be discussed with

the licensee with no formal enforcement action taken. The licensee is

expected to resolve the problem and

prevent recurrence. If the violation is of

larger safety significance, NRC may levy

a written Notice of Violation, or, in

certain circumstances, a fine.

Photos courtesy of Framatome ANP, Inc.

15
Inspection reports, correspondence,

and other information about the performance of fuel cycle facilities are available to the public, both on the

agency’s document management

system and at its Public Document

Room in Rockville, Maryland.

Nuclear power currently supplies about

20 percent of our nation’s electricity

needs. Through rigorous adherence to

NRC’s safety regulations, the agency is

confident that the production of

nuclear fuel is a safe and valuable

contribution to the continued supply of

nuclear power in the United States.

16
For Additional Information Contact:

Office of Public Affairs

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

Telephone: (301) 415-8200 or (800) 368-5642

Fax: (301- 415-2234

Internet: OPA@NRC.GOV

Website: www.nrc.gov

Regional Public Affairs Offices:

Region I - 475 Allendale Road

 King of Prussia, PA 19406-1415

 (610) 337-5330

Region II - 61 Forsyth Street

 Suite 23T85

 Atlanta, GA 30303-0199

 (404) 562-4416

Region III - 801 Warrenville Road

 Lisle, IL 60532-9663

 (630) 829-9663

Region IV - 611 Ryan Plaza Drive

 Suite 400

 Arlington, TX 76011-8064

 (817) 860-8128
NUREG/BR-0280, Rev. 1

September 2001