Environmental Monitoring for Nuclear

Safeguards

September 1995

OTA-BP-ISS-168

GPO stock #052-003-01442-4
Recommended Citation: U.S. Congress, Office of Technology Assessment, Environmental Monitoring for Nuclear Safeguards, OTA-BP-ISS-168 (Washington,

DC: U.S. Government Printing Office, September 1995).
iii

Foreword

n June 1995, the Office of Technology Assessment published

the report Nuclear Safeguards and the International Atomic

Energy Agency, the sixth in OTA’s series of publications on the

proliferation of weapons of mass destruction. That report found

that the International Atomic Energy Agency’s traditional mission of

detecting the misuse of known nuclear materials and facilities

addressed only part—and probably not the most important part—of

the proliferation problem. To assure that states are not violating their

Non-Proliferation Treaty commitments, the International Atomic

Energy Agency (IAEA) must also verify that states do not possess

covert nuclear facilities—a mission that prior to the 1991 Gulf War, it

had neither the political backing nor the resources to conduct. In the

June report, OTA concluded that providing the IAEA with the

resources, the information, and the political support it needs to look

for such sites may turn out to be the most important aspect of a reinvigorated safeguards regime.

The IAEA recognizes the importance of this new mission and is in

the process of assuming it. One of the tools it is exploring to provide

some indication of the presence of secret, or undeclared, nuclear

activities and facilities is environmental monitoring. Modern sampling and analysis technologies provide powerful tools to detect the

presence of characteristic substances that are likely to be emitted by

such illicit activities. This background paper examines the prospects

for such technologies to improve nuclear safeguards. It concludes that

environmental monitoring can greatly increase the ability to detect

undeclared activity at declared, or known, sites, and it can significantly increase the chances of detecting and locating undeclared sites.

Completed in the last month of the Office of Technology Assessment’s existence, this paper will be the last OTA publication related

to the proliferation of weapons of mass destruction. OTA appreciates

the invaluable advice and assistance of the people who contributed to

this project and reviewed the draft material.

ROGER C. HERDMAN

Director

I
iv

Reviewers

Roger Case

Sandia National Laboratories

Gary Dotson

Air Force Technical 

Applications Center

Brian Fearey

Los Alamos National 

Laboratory

William R. Fuhr

Air Force Technical 

Applications Center

John Phillips

Los Alamos National 

Laboratory

Al Ramponi

Lawrence Livermore National 

Laboratory

Don Rokop

Los Alamos National 

Laboratory

Jack Schendel

Sandia National Laboratories

Ned A. Wogman

Pacific Northwest Laboratory

ACKNOWLEDGMENTS

Audrey Buyrn

Office of Technology 

Assessment

Brookhaven National 

Laboratory

Lawrence Livermore National 

Laboratory

Los Alamos National Laboratory

Pacific Northwest Laboratory

Sandia National Laboratories

U.S. Department of Energy

U.S. Department of State

International Atomic Energy 

Agency
v

Project Staff

Peter Blair

Assistant Director

Industry, Commerce, and 

International Security 

Division

Alan Shaw

Program Director

International Security and 

Space Program

PROJECT STAFF

Gerald L. Epstein

Thomas H. Karas

Project Co-directors

ALAN T. CRANE

CONTRACTOR

E. Alan Phillips

ADMINISTRATIVE STAFF

Jacqueline R. Boykin

Office Administrator

N. Ellis Lewis

Administrative Secretary

Don Gallagher

Secretary
vii

Contents

1 Introduction and Summary 1

Major Findings 2

Nuclear Materials and Safeguards 2

The Potential of Environmental Monitoring 4

2 Detectable Emissions 9

Uranium Enrichment 9

Plutonium Production and Reprocessing 12

3 Technologies for Detection of Emissions 19

The Iraqi Experience 19

Sampling 21

Analytical Instruments 23

Bulk and Particulate Analysis 26

Data Interpretation 26

Conclusions 27

4 Status and Plans for Implementation 29

Field Trials 29

Training 32

Technical Capabilities and the New Clean Room 32

Quality Assurance 33

Implementing Environmental Monitoring 33

Concerns Over Environmental Monitoring 35

Conclusions 36

5 Future Technologies 37

Strategic Directions 37

Improving Technology 38

Specific Approaches 41
| 1

1

Introduction

 and

Summary

nvironmental monitoring is a potentially

powerful supplement to current safeguards techniques intended to prevent

the spread of nuclear weapons. Prior to

the 1991 Persian Gulf War, the International

Atomic Energy Agency (IAEA) administered

safeguards primarily on the nuclear materials

associated with known commercial or research

facilities. Accounting for this material would

provide notice were a proliferator to divert any to

obtain the necessary nuclear fissile material for

nuclear weapons.1

 Events in Iraq revealed after

that war have demonstrated that such a safeguards approach addresses only part of the problem. Probably more important to halting

proliferation is ensuring that countries do not

violate their non-proliferation agreements by

constructing covert facilities for nuclear material

production. Environmental monitoring, which

tests for the presence of materials that are likely

to be emitted by such activities, can help inspectors detect undeclared activities at safeguarded

sites and may be able to detect covert facilities at

undeclared sites.

1 For a review of the history of nuclear safeguards and the International Atomic Energy Agency that administers them, see: U.S. Congress, Office of Technology Assessment, Nuclear Safeguards and the International Atomic Energy Agency, OTA-ISS-615 (Washington, DC:

U.S. Government Printing Office, June 1995).

Environmental monitoring was first used by

the IAEA in Iraq following the Gulf War. The

agreement ending the war included the right for

the United Nations to inspect all Iraqi nuclear

facilities (declared and suspected) to determine if

any nuclear-weapon related activities had

occurred. The IAEA has a mandate from the

United Nations Security Council to perform

these inspections. In the month between the end

of the war and the start of the inspections, Iraq

removed much of the most incriminating equipment, such as the calutrons used for enrichment,

and concocted stories to explain the remainder.

Inspectors took samples of materials within and

near facilities, and swipes of dust that had collected on the surfaces of equipment. These were

analyzed at various laboratories, including in the

United States. These analyses played a key part

in demolishing Iraq's cover stories and exposing

its nuclear weapon program, which included uranium enrichment and plutonium experimentation. The program had not been detected in

earlier inspections despite the co-location of proE
2 | Environmental Monitoring for Nuclear Safeguards

totype facilities for the production of weapons

materials with civilian, safeguarded facilities.

Subsequently, the IAEA used similar techniques in South Africa to provide additional

assurance that all nuclear materials produced for

its voluntarily terminated weapon program were

fully accounted for. These techniques were also

used to check the North Korean declaration of

facilities and activities under the Non-Proliferation Treaty (NPT). The results from the application of these techniques, together with other

information accumulated by inspection teams,

led the IAEA to conclude that there were inconsistencies between the plutonium identified in

North Korea's initial report and the reprocessing

activities actually carried out.

The IAEA is now completing a series of field

trials in cooperating member states to determine

the efficacy of the techniques in a broad range of

applications, and the Agency proposes to make

environmental monitoring an integral part of the

inspection process for safeguarding peaceful

nuclear installations. The intent is to provide

additional assurance that a country is not

engaged in undeclared nuclear activity. Through

this and other proposals, the IAEA is assuming a

much more activist role in searching out any

efforts to produce weapons.

This report analyzes how environmental monitoring works and what can be expected of it as

part of safeguards. Chapter 2 reviews the emissions that can be expected from nuclear facilities

that are supporting a weapons program. Chapter

3 looks at the techniques used for detecting those

emissions, including sampling in the field and

laboratory analysis. Chapter 4 reviews IAEA

activities to implement environmental monitoring. Finally, chapter 5 looks at technologies now

in the laboratory that could improve the effectiveness of environmental monitoring in the

future. The remainder of this chapter provides a

summary of the report and additional background.

MAJOR FINDINGS

■ Use of environmental monitoring can significantly increase the ability of safeguards to

detect undeclared nuclear activities at declared

sites.

■ Environmental monitoring is not a panacea

and must be used in conjunction with other

non-proliferation tools. However, some relaxation of conventional safeguards may be warranted as the new techniques are implemented

in a broader, more integrated scheme.

■ Technologies under development can significantly increase the chances of detecting and

locating undeclared sites.

■ Costs to the IAEA will be modest as long as

efforts are focused on sampling in and around

declared sites. Wide-area monitoring of the

atmosphere to detect undeclared facilities

would be very expensive. Wide-area monitoring of waterways appears more practical, but

its application must be further investigated.

■ The support of the United States and other

member nations is essential to make the new

techniques work. In addition to financial support to get the program moving, laboratory

analysis, training of inspectors and IAEA laboratory staff, and research and development

are needed.

NUCLEAR MATERIALS AND 

SAFEGUARDS

Many nations have the capability to develop

nuclear weapons, though some would require

considerable investment in facilities and manpower. The most difficult part of producing

nuclear weapons is obtaining the fissile material

(unless it can be stolen).2

2 For a discussion of the technical requirements for making nuclear weapons, see U.S. Congress, Office of Technology Assessment,

Technologies Underlying Weapons of Mass Destruction, OTA-BP-ISS-115 (Washington, DC: U.S. Government Printing Office, December

1993), chapter 4 (“Technical Aspects of Nuclear Proliferation”) and especially appendix 4-A (“Components, Effects, and Design of Nuclear

Weapons”).
Chapter 1 Introduction and Summary | 3

Nuclear explosives can be based on uranium

or plutonium. Natural uranium can be found

everywhere, but in order to be used in a weapon,

it must be enriched. Natural uranium consists of

three isotopes, uranium-238 (99.3 percent), uranium-235 (0.7 percent), and a trace amount of

uranium-234. Only the uranium-235 can support

a chain reaction, meaning not only that its nuclei

can release energy by fissioning, or splitting,

when struck by a neutron, but also that each fission releases sufficient neutrons to continue the

process. Enrichment, an expensive and technologically difficult task, increases the concentration of uranium-235.3

 Fuel for light water power

reactors must be enriched to about 3 to 5 percent

uranium-235. A nuclear explosion cannot be

achieved with less than 20 percent enrichment.

For an effective weapon, the uranium-235 content must be much higher.

Alternatively, a proliferant can use plutonium,

which is produced by irradiating uranium-238 in

a nuclear reactor. Spent fuel from a conventional

power reactor contains plutonium, but using it

presents several difficulties (especially for the

covert proliferator). Every country known to

have produced a plutonium explosive has chosen

to build a reactor whose primary task is the production of plutonium that is optimized for use in

weapons.4 In addition to a reactor, the proliferator needs reprocessing capability to extract plutonium from the irradiated uranium-238.

The NPT came into force in 1970 to provide a

mechanism for nations to gain access to peaceful

nuclear technology without giving rise to suspicions that they were using their facilities to produce weapon-related materials. Safeguards were

instituted to check on their compliance as part of

the treaty. Signatories to the NPT that had not

tested a nuclear weapon before January 1, 1967

(i.e., all except the United States, the U.S.S.R.

[now Russia], Britain, France, and China),

3 Uranium enrichment technologies are discussed in ibid., appendix 4-B (“Enrichment Technologies”). 4 For discussion of the use of “reactor-grade plutonium” and “weapon-grade plutonium” for nuclear weapons, see ibid., pp. 131–134.

pledged not to acquire nuclear weapons or to

build nuclear facilities with unsafeguarded

nuclear material. Only Iraq is known to have violated its commitments on a significant scale, but

North Korea is not in compliance with its safeguards agreement with the IAEA because it

refuses to accept certain activities identified by

the Agency as necessary to assess the completeness of its declaration.

Most nations have signed the NPT. Exceptions include Israel, Pakistan, and India. Nonmembers are not legally bound to refrain from

developing nuclear weapons or to accept safeguards on their facilities. However, essentially

all nuclear exporters require all nuclear materials

and critical nuclear-related equipment purchased

by other countries to be placed under safeguards.

Thus only indigenously developed facilities (and

a few pre-NPT exports) are not safeguarded.

Safeguards by themselves cannot stop proliferation. They only provide warning that a nation is

not complying with its agreements. It is up to the

United Nations and the international community

to take action in response.

When a nation becomes party to the NPT, it is

required to conclude a safeguards agreement

with the IAEA, to declare all its nuclear materials, and to establish a system of controls for

them. When the safeguards are implemented,

each of the country’s nuclear facilities must be

specified (declared) in an attachment to the

agreement. However, prior to the Gulf War, the

IAEA did not verify the completeness of this

declaration. Nor could it inspect undeclared

facilities of non-members. It was never the

IAEA's expectation that its efforts would deter

all weapon programs, but it assumed that

national intelligence programs would uncover

covert efforts.5 Iraq, North Korea, and South

5 Bruno Pellaud, “Safeguards in transition: Status, challenges, and opportunities,” IAEA Bulletin, vol. 36, No.3, 1994, Vienna, Austria,

pp. 2–7.
4 | Environmental Monitoring for Nuclear Safeguards

Africa6, three very different cases, showed that

these assumptions could not be depended on in

all situations.

There are several aspects to safeguards. The

most prominent is materials accountancy, in

which the total inventory of nuclear material in a

country is monitored to ensure that none is

diverted to weapon purposes. Besides measuring

material inventories and material flows, inspectors check facility operating records to see if

everything is consistent. In addition, there may

be perimeter monitoring devices and cameras

around critical areas to detect any undeclared

removal of nuclear material.7

Consider the situation of an NPT signatory (or

a country that has agreed to equivalent safeguards in order to import equipment) that decides

to obtain nuclear weapons. It may have power

reactors or research reactors, all of which would

be under safeguards. Either might be used to produce fissile material, but the risk of detection

under current safeguards is high. The country

could abrogate its safeguards agreements and

prevent IAEA inspectors from discovering that

these facilities were being used for weapon purposes, but that would almost certainly end that

nation’s ability to import nuclear fuel and equipment, and would probably precipitate international sanctions. A large commercial

reprocessing plant (or enrichment plant) is far

harder to safeguard effectively than a reactor

used for research or for generating power, but no

nation suspected of entertaining thoughts about

6 The Iraqi program is discussed in chapter 3. North Korea apparently built its facilities prior to signing the NPT but has refused to declare

and accept safeguards on all of them even though the IAEA discovered the others. South Africa dismantled its weapon program prior to signing the NPT. Since the NPT applies only to its members, neither it nor the IAEA can be faulted for the behavior of non-members. It is important to remember that the NPT, even though the primary international non-proliferation mechanism, is not capable of addressing the entire

problem. 7 The safeguards process is discussed in greater detail in U.S. Congress, Office of Technology Assessment, Nuclear Safeguards and the

International Atomic Energy Agency, op. cit., footnote 1.

proliferating is operating one under full-time

safeguards.8

Therefore a potential proliferator is likely to

favor a small reactor/reprocessing plant or an

enrichment plant dedicated to the production of

weapon materials even if it has a power reactor.

IAEA inspectors do not typically have access to

facilities not on their list, even to buildings right

next door to ones they inspect regularly.9 In fact,

from the perspective of a proliferant state, colocating legitimate and illegitimate facilities has

several advantages. The peaceful facilities can

provide some camouflage for the illicit activities,

some personnel may work on both, and they can

share utilities, security arrangements, and other

functions.

To strengthen its safeguards system, including

the ability to detect undeclared nuclear activities,

the IAEA initiated Programme 93+2 in 1993.

Environmental monitoring is a centerpiece of

this effort, including field trials that are now

being completed. The IAEA's Board of Governors endorsed the general direction of Programme 93+2 in its meeting March 27-30, 1995,

and requested the Secretariat to prepare specific

proposals for implementation.10

THE POTENTIAL OF ENVIRONMENTAL 

MONITORING

Modern analytical technology has made environmental monitoring an effective tool. A series of

instruments has been developed that can identify

extremely small traces of materials. Uranium and

plutonium can be detected and identified by iso8 India, not an NPT party, operates reprocessing facilities that are under safeguards only when reprocessing safeguarded spent fuel. 9 The IAEA does have the authority to request so-called special inspections of any site if such inspections are necessary for the agency to

fulfill its safeguards responsibilities. However, requesting a special inspection must be firmly based on information that the agency is unable

to meet its safeguards obligations without access to specific named locations. This would be an extraordinary act that would not typically be

done in the course of a routine safeguards inspection. 10 IAEA Press Release, “IAEA Board of Governors Holds Spring Meeting, Considers Nuclear Safety Issues and Strengthening of Safeguards Verification System,” Mar. 31, 1995.
Chapter 1 Introduction and Summary | 5

tope in less than nanogram quantities (a nanogram is one billionth of a gram; there are about

28 grams to the ounce). Particles as small as a

micron (one millionth of a meter or about

0.000039 inches; the diameter of the period at the

end of this sentence is about 350 microns) can be

analyzed. Many instruments are sufficiently sensitive to detect the fallout of plutonium from

above-ground nuclear bomb tests, almost all of

which occurred more than thirty years ago.11

No industrial process can prevent minute

traces of materials from escaping. Even the most

sophisticated filtration systems can only reduce,

not eliminate, releases. In particular, enrichment

plants release traces of enriched and depleted

uranium, including highly enriched uranium

(HEU) for weapons if it is being produced. It is

easy to distinguish isotopically altered uranium

from natural uranium, and its presence is an indicator of enrichment activity (but not necessarily

near where it is found). A detection of HEU

where only natural or low enriched uranium

should be is a clear warning signal that activities

that could contribute to a weapons program are

underway. Reprocessing plants release many fission products and other products as well as uranium and plutonium. Plutonium is entirely manmade, so its discovery in any significant quantity

(i.e., at levels above those expected to be found

from known atmospheric nuclear tests or other

contamination) or with an isotopic composition

inconsistent with a State’s declaration is also a

warning signal. Emissions are discussed in chapter 2.

These releases can be readily detected at levels that are far below those that pose hazards to

human health. Tiny particles may settle out

within process buildings or float out and be carried by the wind, sometimes for very long distances. Wherever they settle—on plants, in the

soil, in waterways—they may be detected. Gaseous releases can be carried even further away,

11 The United States, the Soviet Union, and the United Kingdom ceased testing nuclear weapons above ground when they signed the

Limited Test-Ban Treaty in 1963. France continued atmospheric testing, at a level far below the pre-test-ban U.S. and Soviet rates, until

1975. China detonated the world's last above-ground nuclear test in 1980.

but dilution and varying wind patterns can make

them harder to detect.

The first step in environmental monitoring is

sampling: wiping surfaces in the facility with a

cloth or tissue, or collecting leaves or other parts

of plants, digging up soil, scooping up water, and

other means of collecting material that has settled outside the buildings. Sampling is not particularly difficult in most cases, but the inspectors

need training as to where to take the samples and

how to avoid cross-contamination (from one

sample to another, e.g., a trowel used to dig soil

samples must be cleaned between each use, or

particles from the first could give a false reading

in the next sample).

The samples are then sent to a laboratory for

analysis. Two general types of analysis are

used—bulk and particle. Bulk analysis looks at

the entire sample or a significant part of it. Analysis involves the application of many instruments such as mass spectrometers, which can

separate isotopes of an element by their masses,

allowing measurement of the relative abundance

of the isotopes. Other instruments measure the

emissions of radioactive decay to determine the

radioisotope. Particle analysis selects individual

particles, usually from the surface wipes, by

examination under a microscope. Once isolated,

the particle can be individually analyzed, using

many of the same techniques. Particle analysis is

more sensitive than bulk analysis because individual particle analysis can yield information on

the precise formation of the particle, while bulk

analysis averages the particles together. However, particle analysis also is significantly more

expensive.

The IAEA's field trials involved sample collection at known nuclear facilities in various

countries to explore the best ways to take samples and to determine the kind of information

that could be gleaned from the analyzed samples.

Facilities examined included enrichment plants,
6 | Environmental Monitoring for Nuclear Safeguards

reactors, reprocessing plants, and research complexes. These tests have been completed, but

public release of the results is contingent on the

approval of the host country. Preliminary indications are that the field trials were generally successful. In most cases, the sampling was able to

verify the declared activities at the facilities

tested.12 These activities sometimes could be

detected several kilometers from the plant.

The IAEA believes that if environmental

monitoring had been part of routine safeguards

inspections in the 1980's, it would easily have

revealed Iraq's weapons activities.13 Of course,

such monitoring would not necessarily have

deterred these activities, because Iraq may not

have co-located them with safeguarded activities

that were subject to environmental monitoring

had it known that this form of surveillance would

take place. However, as noted above, separating

weapon activities from legitimate nuclear activities would have significantly raised the costs and

difficulty of the weapon program, and would perhaps have made it easier to detect covert facilities through other forms of surveillance.

The United States supported the IAEA field

trials in several ways. Altogether, the U.S. financial contribution has been $6-8 million over 3

fiscal years.14 Inspectors were trained; DOE's

national labs did many of the bulk analyses; and

the Air Force Technical Applications Center

handled most of the particle analysis. The K-25

enrichment plant in Oak Ridge, Tennessee was

one of the field trial sites. In addition, the United

States is helping the IAEA design and construct a

new clean lab for contamination-free handling

and analysis of samples. Other IAEA members

also supported the environmental monitoring

program, and labs in many countries were used.

Few if any other countries, however, can match

the analytical precision of the U.S. labs, particularly for particle analysis.

12 Personal communication with International Atomic Energy Agency staff member, Mar. 31, 1995. 13 Personal communication with International Atomic Energy Agency staff member, Apr. 4, 1995. 14 Personal communication with Ira Goldman, U.S. Department of Energy, Jan. 11, 1995.

In most cases, environmental monitoring will

not produce a “smoking gun.” Rather, it will supply information that must be combined with

other sources to determine what activities have

taken place. Thus it is a supplement to conventional safeguards, not a replacement. It could be

an extremely important supplement, particularly

if the IAEA is successful in obtaining access to

sites and facilities related to the fuel cycle that

are currently not available for investigation.

Implementing environmental monitoring may

be controversial. The IAEA has determined that

it has the authority to institute such monitoring at

declared sites under agreements that have previously been negotiated with states with comprehensive safeguards agreements, but any change

from current practices may alarm some countries

even if they have no undeclared facilities. One

problem is in the detection of plutonium and

other radioisotopes. If sensitive environmental

monitoring detects emissions from facilities

claimed not to be emitting anything, public fears

may be raised—even though the emissions may

be far below levels that could threaten public

health and safety. Furthermore, licensing difficulties may be encountered if any contamination

is found in the area of a facility. Also, under

some conditions, competitive information may

be divulged, such as the operating conditions of

an enrichment or fuel fabrication plant. Thus the

nuclear industry in some countries may be concerned. On the other hand, the IAEA is used to

protecting any proprietary information it has

obtained under safeguards practices, and it would

reasonably withhold any such information collected through environmental monitoring,

assuming that no safeguards violations were

found. Implementation must be done carefully

and sensitively. One compensating factor is that

the information may be helpful to the host state

in meeting its own health and safety goals.
Chapter 1 Introduction and Summary | 7

The field trials have demonstrated that costs to

the IAEA of implementing environmental

monitiring should be modest. Sampling can be

done in conjunction with regular inspections.

Environmental sampling requires personnel with

only several days of training and relatively simple equipment. The lab analyses are more expensive than the sampling, especially for particle

analysis. The data indicate that bulk analysis is

probably adequate to detect undeclared activity

at most facilities, and that with appropriate selection of samples to be tested, the costs will not be

prohibitive.

In some cases, the IAEA may be able to

reduce inspections when environmental monitoring is introduced. For example, if environmental

monitoring confirms that a country is not operating a reprocessing plant, then inspection of spent

fuel need not take place as often in order to provide timely warning of diversion.15

Wide area monitoring to detect undeclared

facilities is much more problematic. Some materials can be carried long distances, either in the

air or in waterways. Monitoring rivers is not difficult, and positive findings can be traced

upstream. Furthermore, sediments often collect

at various places, establishing a record of what

has come downstream. The IAEA already is

monitoring water in Iraq. However, it is relatively easy for a small, covert facility to minimize liquid runoff, and in dry areas there may not

be sufficient rain to wash away and concentrate

material that settles out from the atmosphere.

Therefore, clear signals may not emerge. Effective air monitoring requires a great many stations, because a plume can follow an erratic

pattern. These stations must be monitored frequently over an extended period if they are to

catch a sporadic, short-duration plume, such as

might result from the opening of a reactor or the

15 Environmental monitoring will not detect a complete but unused reprocessing plant, nor any plans to send the spent fuel to another

country for reprocessing. However, both these approaches probably would entail considerable delay and uncertainty in the procurement of

plutonium relative to having a proven capability already.

reprocessing of a batch of fuel. Furthermore, all

samples collected by these stations would need

to undergo laboratory analysis. At a minimum,

samples would have to be screened with a relatively low cost technique to determine if any

require more precise analysis. Since the number

of samples would be high, costs would be also.

Hence air monitoring can be quite expensive.

Technology now under development should

improve the capability to conduct environmental

monitoring in several ways. Some will allow

real-time, remote sensing. The Department of

Energy's CALIOPE (Chemical Analysis by

Laser Interrogation of Proliferation Effluents)

Program, a collaborative effort at 5 national labs,

is intended to produce instruments that can, from

outside a site’s perimeter, measure the constituents of a plume of emissions in the air. Real-time

xenon and air particulate measurements are

being developed by the Department of Energy.

Other developments would increase the sensitivity of laboratory instruments, permitting the analysis of samples even more dilute than those that

can be studied today. Portability of instruments is

another goal so that inspectors can get an immediate indication of suspect isotopes or chemicals

and monitor more intensively. Successful development of these projects should significantly

improve the effectiveness of environmental monitoring. However, some of these projects may

involve technology that cannot be given to the

IAEA because of U.S. national security concerns.

If successfully implemented, environmental

monitoring will be an important part of international non-proliferation efforts. In addition, it

may prove to have a role in verifying the Comprehensive Test Ban Treaty and nuclear material

production cutoff agreements.
| 9

2

Detectable

Emissions

very industrial process releases some

trace of the materials involved. With

modern pollution control equipment,

releases usually can be kept well below

regulatory standards for protection of human

health and the environment. Even with the most

rigorous controls, however, some gases, liquids,

and solid particles escape to the environment.

High pressure fluids may seep past pump or

valve seals. Every time solid materials are

moved, tiny particles are produced that pass

through the finest ventilation filters. During

moments of carelessness or equipment failure,

gross releases may occur.

Processes to produce nuclear materials are no

exception. No matter which route is selected to

obtain fissile nuclear material, some traces of

materials used in the process will be released.

Some of these materials are unique to the production of nuclear weapons, while others are

indicative of nuclear activities in general. Some

are not suspicious by themselves, but would provide a warning signal if detected as part of a pattern of releases or in conjunction with auxiliary

data such as from export controls.

This chapter reviews the steps that must be

followed by a nation clandestinely producing

nuclear material, and identifies the signatures, or

potentially detectable indications, that might be

detected via environmental monitoring. There

are two basic routes to produce fissile material

for nuclear weapons: enrichment of uranium to

obtain highly enriched uranium (HEU); and irradiation of uranium-238 in a nuclear reactor to

convert it to plutonium, which must then be separated from the remaining uranium and by-products in a reprocessing plant. These are

diagrammed in figure 2-1. Both approaches are

feasible (both were pioneered in the Manhattan

Project) and present approximately equal difficulty overall.1 Iraq considered both routes prior

to 1991 but chose enrichment as its primary

focus.

URANIUM ENRICHMENT

Virtually all uranium occurring naturally in the

world consists of the same isotopes: 99.3 percent

1 For further information on the two approaches, see U.S. Congress, Office of Technology Assessment, Technologies Underlying Weapons of Mass Destruction, OTA-BP-ISC-115 (Washington, DC: U.S. Government Printing Office, December 1993).

E
10 I Environmental Monitoring for Nuclear Safeguards

D

Fabricate

highly enriched

+ uranium into

bomb core PI +

~

Enrich uranium

 to weapon

grade

Uranium route

r

n

Natural uranium

mining and

processing L_J Purchase/steal/

obtain weaponusable

nuclear material

● +plutonium into

Reprocess to

obtain pure L]Irradiate uranium

->

within reactor

to generate

plutonium

n

HE or propellant

testing

Delivery vehicle

Plutonium route ~-

Ii —-+ Weapon assembly

Design/fabricate

high explosive

(HE) components

or propellants parts

I 1

I

Delivery vehicle

R&D (aircraft,

h

testing and

missile, or other) exercising

> Weapon capability

SOURCE Office of Technology Assessment, 1993

U2q8, preferentially removing U2S8 so that 0.7 percent U2S5, and a trace of U2q4.2 To be

useful as fuel in a conventional light water reactor (LWR), the level of U235 must be raised to

about 3 percent, which is known as low enriched

uranium (LEU). Weapons require HEU, which is

at least 20 percent U235 and preferably much

higher. Commercial enrichment plants producing

LEU currently use either gaseous diffusion or

centrifuge technology.s Either technology can

also be used to produce HEU, but a plant

designed to produce LEU would have to be

reconfigured, at least in part, to produce HEU.

The process of enrichment is difficult because

U2~5 and U238 are chemically identical and only

slightly different in weight. Basically the process

consists of

the end product has a higher fraction of U2q5.

However, current technologies cannot economically achieve a clean separation, so the waste

stream (called tails) of depleted uranium still

contains a significant amount of U235. Commercial enrichment plants typically produce tails

containing about 0.3 percent U235, instead of the

original 0.7 percent. Calutrons can achieve

greater separation and might produce tails of 0.2

percent or even less.

Uranium for the Hiroshima bomb was

enriched using calutrons, a form of electromagnetic isotope separation (EMIS). This is a relatively simple but expensive and inefficient

2 A minor exception is the uranium ore found in Gabon, which had undergone a slow chain reaction over a billion years ago, depleting

some of the U-235.

3 Another technology, advanced vo~ex tu~, was used in a South African commercial enrichment plant that was shut down ‘n ‘arch

1995.
Chapter 2 Detectable Emissions | 11

technique that the United States quickly replaced

with gaseous diffusion methods. However, Iraq

successfully constructed equipment similar to

calutrons and produced a small quantity of HEU.

Lasers have also been used for enrichment, but

those technologies (atomic vapor laser isotope

separation—AVLIS, and molecular laser isotope

separation—MLIS) have not yet progressed outside the laboratory. Several other technologies

have been considered, including aerodynamic

methods such as the Becker nozzle.

An NPT signatory intent on building an HEU

nuclear weapon could, if it had one, convert a

commercial diffusion or centrifuge plant from

LEU to HEU production. It is very unlikely that

the entire plant could be converted covertly, so

the country would have to abrogate its safeguards agreements. Alternatively, it could try to

evade safeguards by converting only part of the

plant to HEU, hoping that such actions would

escape detection, or it could build an undeclared

facility using any of the technologies which it

could master.

Both diffusion and centrifuge plants are

designed with large numbers of individual units.

In a diffusion plant, each unit slightly increases

the enrichment of a large process stream. Many

diffusion stages are required—about 1000 to produce LEU and maybe 3000 are required for

HEU, so the stages are linked in a cascade. In a

centrifuge plant, each unit achieves a higher level

of enrichment but can handle less material. Many

units are connected in parallel to form a stage,

but fewer stages are required than in a diffusion

plant (fewer than 20 for LEU, about 60 for

HEU). For either diffusion or centrifuge, each

unit (and the entire plant) has two exit streams:

enriched uranium and depleted uranium. The

enriched stream proceeds through a series of

enrichment levels until the desired level is

attained. The depleted stream from each stage

(which has slightly less U235 than when it entered

the stage) drops back one or more stages and is

re-enriched, until the desired level of the tails is

reached.

A commercial enrichment plant is a highly

complex facility that must operate in a carefully

prescribed manner. Conventional safeguards are

designed to detect if the facility had been reconfigured to produce HEU. However, it is conceivable that a small portion of the cascade could be

isolated and dedicated to the production of HEU,

particularly if it used LEU as feed material.4

Safeguards based on materials accountancy

would have to be very thorough to detect this.

More worrisome, a centrifuge plant could be

temporarily reconfigured to produce HEU and

then converted back to LEU between inspections.5 To forestall such a conversion and reconversion, safeguarded centrifuge enrichment

plants are subject to a certain number of unannounced IAEA inspections per year. Alternatively, a proliferator might build a new facility

close by in order to reduce costs by sharing technical, infrastructure, and administrative support.

Materials accountancy would not detect this

facility, if it did not feed from or supply any safeguarded facilities.

Natural uranium is ubiquitous, so its detection

does not, per se, signify any unusual activity.

Any discovery of uranium with isotopes in other

than natural proportions (or in chemical form different from natural uranium) is a sure indication

of nuclear activity. Emissions from the enrichment process can occur at many places. Natural

uranium must be converted to a gaseous form,

usually uranium hexaflouride (UF6). UF6 is a colorless solid at room temperature, but becomes a

gas at temperatures above 134 degrees F at atmospheric pressure. In itself, UF6 with any isotope

of uranium is an indicator, albeit a secondary

one, of enrichment because no other processes

are known to involve it. Within the enrichment

process itself, small quantities of uranium may

4 Producing LEU requires over half the separative work (enrichment effort) of producing HEU. Thus starting with LEU instead of natural

uranium more than doubles the capacity of the HEU cascade. 5 This could not be done with a diffusion plant which takes much longer to reach equilibrium, leaving the action open to detection.
12 | Environmental Monitoring for Nuclear Safeguards

escape from anywhere in the cascade, at whatever enrichment level the specific piece of equipment happens to be operating. As the released

UF6 reacts with water vapor in the air, it precipitates out and can migrate from the process area

as airborne particles that are deposited outside

the plant. UF6 also reacts chemically with the air

to form UO2F2. These particles can show the full

range of enrichment, from depleted uranium to

the maximum enrichment attained. Thus the

detection of HEU at an LEU plant is strong evidence that at some time the plant was operated in

a HEU mode.

For use as fuel or as weapons material, the

UF6 must be re-converted to metallic uranium

following enrichment. This process provides

additional opportunities for the release of emissions.

Two other isotopes of uranium are also important—U234 and U236. As noted above, U234 is a

trace constituent of natural uranium, but the fraction is variable, unlike the other natural isotopes.

Most uranium contains about 52-54 parts per

million (PPM) of U234, but some ores contain

several PPM more.6 U234 provides two important

pieces of information. It can be used as a tracer

to determine the origin of the uranium ore. It also

can indicate the type of enrichment used. This is

because some enrichment technologies (EMIS

and lasers) distinguish between U234 and U235,

while others pass them through together.

U236 appears only in uranium that has been

irradiated. It is produced when an atom of U235

absorbs a neutron and fails to fission. When

spent fuel is removed from a reactor, it may still

have more U235 than does natural uranium. The

fuel can be reprocessed to recover the valuable

U235, which must be re-enriched before it can be

recycled. The U236 will remain with the U235 during these processes. Detecting U236 at an enrichment plant is proof that the facility has handled

6 U238 decays to thorium (Th234), which in turn decays to U234. Intermediary products can have different chemistry than uranium, and

therefore may not remain in proportion to the original U238.

reprocessed uranium, and therefore it's likely that

plutonium was separated from spent fuel. U236

can remain in an enrichment plant for many

years after it was introduced, contaminating subsequent loads of natural uranium.

Most large, commercial enrichment plants can

be detected through their emissions. If a proliferator wishes to remain covert, emissions can be

reduced to the point where they are significantly

harder to detect. A small, carefully designed,

constructed and maintained plant producing only

enough HEU for one or two bombs per year, if

equipped with a ventilation system using highefficiency filters, could be quite difficult to

detect.

In addition to isotopically altered uranium, an

enrichment plant may emit several other types of

signals that could be detected. Gaseous diffusion,

aerodynamic, and electromagnetic separation

plants are quite inefficient and release a large

amount of heat. This might be detected by satellite observation or perhaps measurement of the

temperature increase of a river if cooling water is

dumped there. Centrifuge plants are much more

energy efficient, but they place unusual loads on

the electric power system. In particular, the centrifuges operate at high speed and require conversion of the line frequency to much higher

frequency. The converters reflect a distinct signal

back into the line that can be detected. Finally,

under some conditions, the distinct noise generated by centrifuges might be detected and recognized.

PLUTONIUM PRODUCTION AND 

REPROCESSING

An NPT proliferator has two main choices in

producing plutonium for weapons:7 reprocess

spent fuel from its own power reactors, or build a

covert production reactor. A country could divert

7 A third choice, buying or stealing plutonium, either from the commercial nuclear power fuel cycle (if and when plutonium becomes a

routine part of the cycle) or from a nuclear weapons state, is not considered here because the role of environmental monitoring would be

peripheral.
Chapter2 Detectable Emissions I 13

safeguarded spent fuel only fit is willing to conspicuously violate safeguards agreements. The

reprocessing could be attempted at a commercial

reprocessing plant with the intention to divert the

ensuing plutonium. For the foreseeable future,

however, no potential proliferator is likely to

operate a commercial reprocessing plant because

of restrictions by supplier countries and poor

economics. If the reprocessing plant were safeguarded, the diversion would have to be covert,

risking detection. A variation to the approach

would be to construct a small, covert reprocessing plant which could extract plutonium from the

spent fuel. However, diversion of spent fuel from

a safeguarded reactor runs a high risk of detection by current safeguards procedures.

The second approach probably would involve

a research-type reactor, not a power reactor. This

fuel would also have to be reprocessed, presumably at a covert reprocessing facility.

However it is done, each step releases emissions that can contribute to detection of the activities. Figure 2-2 shows the major points of

emissions where environmental monitoring can

play a role. Understanding the signatures from

the activities required to produce nuclear weapons is critical to finding and identifying them.

The IAEA currently is documenting signatures

from all activities.8 The United States has made

considerable effort in this area.

Airborne Airborne Tritium and

particulate particulate other gases Particulate

I

Uranium

conversion and > Reactor > Spent fuel

fuel fabrication

7 7 -1

Liquid runoff Liquid runoff Liquids

Particulate Particulate Gases Particulate

[ T ‘YJ

Weapon

<

Plutonium 4 Reprocessing \

manufacture Conversion

\

Liquids

SOURCE: Office of Technology Assessment, 1995

8 ~erqonal communication with IAEA staff, MM. 31, 1995.
14 | Environmental Monitoring for Nuclear Safeguards

❚ Reactors

Producing plutonium is technically simpler than

enriching uranium,9 but more steps are involved.

Uranium must be fabricated into fuel which is

irradiated in a reactor. Plutonium results when an

atom of U238 absorbs a neutron and, through a

decay process, is transmuted to Pu239. All plutonium isotopes are fissile (fission when struck by

a neutron) but, instead of splitting, some atoms

of Pu239 absorb a neutron and become Pu240. This

process can continue to produce Pu241 and

heavier isotopes. The longer the fuel is left in the

reactor, the more plutonium is created, and the

more is converted to the heavier isotopes.

LWR fuel is in the form of enriched UO2, pelletized and encased in metal tubes (usually a zirconium alloy, but stainless steel has also been

used). LWR fuel technology has been mastered

by many countries and some potential proliferators could also be expected to produce adequate

fuel. This is a plausible route under some conditions, such as if a country were to abrogate its

safeguards agreement and keep the reactor operating with indigenously produced fuel. This

approach is not very plausible if the proliferator

attempts to remain covert. Furthermore, normal

power cycles produce reactor grade plutonium

(with a high content of Pu240 and heavier isotopes

relative to Pu239). Reactor grade plutonium can

be used to make an effective nuclear bomb, but it

is distinctly inferior to weapon-grade plutonium

(which has a low fraction of Pu240).10 Weapongrade plutonium can be produced in an LWR, but

the reactor must be shut down frequently and the

fuel removed and replaced. The lack of power

generation during shutdowns is visible and

expensive, adding significantly to the cost of the

weapon program.

9 Designing and building a plutonium bomb is more difficult than producing a uranium “gun-type” weapon. Thus the two routes are comparable in overall difficulty. 10 Use of reactor-grade plutonium in weapons has a significant probability of substantially reducing the weapon yield. Furthermore, reactor-grade plutonium generates significantly more heat from radioactive decay than does weapon-grade plutonium, complicating weapon

design. See U.S. Congress, Office of Technology Assessment, Technologies Underlying Weapons of Mass Destruction, OTA-BP-ISC-115

(Washington, DC: U.S. Government Printing Office, December 1993), p. 133.

Heavy-water-moderated reactors, such as the

CANDU reactor produced in Canada, would be

easier to use as a source of plutonium. The

CANDU uses unenriched uranium fuel, which

would be far easier for most countries to produce. It also is refueled continually instead of

being shut down. This provides two advantages

to the proliferant: some fuel elements can be

exposed only briefly, yielding weapon-grade plutonium; and power is not lost during frequent

refueling as in an LWR. However, there are relatively few heavy-water reactors in the world,

most of them in Canada. India has several also.

Small, plutonium-production reactors could

be built covertly by many countries. Such a reactor could be moderated by graphite or heavy

water (if these can be obtained without triggering

investigation) and operated with natural uranium,

which would eliminate the need for enriched

fuel, greatly simplifying the fuel cycle. The fuel

itself is also easier to manufacture since it is irradiated under less demanding conditions than in a

light water reactor, allowing the use of cladding

such as aluminum. A non-power reactor which

operates at a thermal output of about 30 MW

could produce enough weapon-grade plutonium

for 1 or 2 weapons per year.11 Larger reactors are

also possible. The Hanford B Reactor, a very

large, graphite-moderated reactor that uses natural uranium, could be a model.12

Reactor operation produces a wide range of

isotopes. There are three types: fission products;

activation products (when an atom of nonnuclear material such as steel in reactor components absorbs a neutron); and actinides (an atom

of uranium absorbs a neutron to produce plutonium and higher elements). Some of the isotopes

formed in these ways are naturally occurring,

11 U.S. Congress, Office of Technology Assessment, Technologies Underlying Weapons of Mass Destruction, op.cit., p. 138. 12 Personal communication with Ned A. Wogman, Pacific Northwest Laboratory, Aug. 17, 1995.
Chapter 2 Detectable Emissions | 15

stable atoms which, not being peculiar to nuclear

activities, do not provide unique information.

Others are highly radioactive and decay so rapidly that they are unlikely to be detected in the

environment in sufficient quantity to be a useful

signal.

The isotopes that are useful for detection of

covert nuclear activities are those that:

a. are produced in reasonable quantity;

b. are not natural;

c. do not decay too rapidly to be detected;

d. have chemical properties favorable for

transport and collection;

e. are easily identified, especially through

characteristic decay radiation;

f. can be distinguished from those widely distributed by weapons tests or reactor accidents, especially Chernobyl.

Table 2-1 lists the radioactive isotopes that

meet these requirements. The exact emissions

from any given site would depend on the specific

technology chosen and the systems and care

applied to minimize them.

Emissions from reactors generally are small.

In conventional power reactors, the fuel is sealed

inside tubes which in turn are inside the pressure

vessel. Leakage of fission products and actinides

occurs only if the tubes leak (an increasingly rare

occurrence as the technology improves) into the

cooling water. From the cooling water, these and

other radioactive products must escape past high

pressure barriers. In a boiling water reactor, the

cooling water directly powers the turbine, providing additional opportunities for emissions.

Contamination is routinely removed from the

water to maintain its purity. Degasifiers, ion

exchange units and other systems are used. These

are likely to be the source of most emissions,

particularly tritium and the noble gases such as

argon and krypton. Solid and liquid matter is

generally collected inside sealed systems and

should not escape in significant quantities.

Small plutonium production reactors would

not need the same barriers. Fuel might be

encased in a simple metal jacket not designed to

withstand great pressure, and the coolant might

be air. Gaseous products are likely to be released,

but the level of radionuclides is much lower than

in a power reactor.

Reactor operations are more likely to be discovered when something goes wrong. Even a

minor upset, such as a thermal excursion that is

reversed before any damage occurs, stresses the

reactor and may result in short-term emissions.

A different type of signature associated with

reactors is the heat they generate, which usually

is dissipated to the air or a waterway. Even a

small reactor capable of producing only 8 kg of

plutonium per year releases about 30 MW of

heat. This level can be detected by infrared

devices on high-flying aircraft or satellites even

if the heat causes a temperature rise of only a few

degrees above the ambient. A small reactor could

be hidden in an industrial area or near a thermal

power plant, which would make the heat emissions less conspicuous.13 However, the signature

would still be useful information.

Whatever kind of reactor is used, the fuel will

probably be stored, following exposure, to allow

the short-lived fission products to decay. Power

reactor fuel is stored in a spent fuel pool because

the level of decay heat production requires efficient heat removal. Fuel from a small production

reactor could be stored in air. Emissions could

occur at this stage also. Liquid emissions could

occur from a storage pool because the water must

be circulated and cooled. Storage could eliminate

gross emissions of short half-life products (e.g.,

iodine-131, xenon-133) from reprocessing.

❚ Reprocessing

Reprocessing of the irradiated reactor fuel is far

more likely to produce telltale emissions than

operating a reactor. Typical reprocessing

involves chopping up the fuel rods, dissolving

13 Anthony Fainberg, “Strengthening IAEA Safeguards: Lessons from Iraq,” Center for International Security and Arms Control, Stanford University, April 1993.
16 | Environmental Monitoring for Nuclear Safeguards

TABLE 2-1: Isotopes Indicative of Reactor Operation

FISSION PRODUCTS

Mass Element Half-life Radiations (energies in Mev)

85 Krypton (Kr) 4.5 hours 0.151 γ (75%), 0.305 γ (14%); 0.8 β

85 Krypton 10.8 years (21%) 0.514 γ (.4%); 0.7 β

88 Krypton 2.8 hours 0.196 γ (26%), 0.835 γ (13%), 0.898 γ (14%), 1.530 γ (11%), 1.836 γ

(21%), 2.196 γ (13%), 2.392 γ (35%); 2.8-5.0 β

93 Zirconium (Zr) 1.5 million years no detectable emissions

95 Zirconium 64 days 0.724 γ (45%), 0.757 γ (55%)

Nb cascade: 0.766 γ (100%)

95 Niobium (Nb) 35 days 0.766 γ (100%)

99 Technetium (Tc) 210,000 years no detectable emissions

103 Ruthenium (Ru) 39 days 0.497 γ (86%)

105 Ruthenium 4.4 hours 0.316 γ (11%), 0.676 γ (16%), 0.724 γ (48%); 1.2 β

106 Ruthenium 374 days 0.512 γ (19%), 0.622 γ (10%), 1.050 γ (.9%); 3.5 β

129 Iodine (I) 16 million years no detectable emissions

131 Iodine 8.0 days 0.364 γ (81%), 0.637 γ (7%)

132 Tellurium (Te) 3.04 days 0.228 γ (88%), I cascade (below)

132 Iodine (I) 2.3 hours 0.523 (16%), 0.668 γ (99%), 0.773 γ (76%), 0.955 γ (18%); 1-2 β

133 Iodine 20.8 hours 0.530 γ (86%); 1.3 β

133 Xenon (Xe) 5.2 days 0.081 γ (37%)

135 Iodine 6.6 hours 0.527 γ (14%), 0.547 γ (7%), 0.837 γ (7%), 1.132 γ (23%), 1.260 γ

(29%), 1.458 γ (9%), 1.678 γ (10%), 1.791 γ (8%); 1.3 β, Xe cascade: 

0.250 γ (90%)

135 Xenon 9.1 hours 0.250 γ (90%); 0.9 β

135 Cesium (Cs) 2.3 million years no detectable emissions

137 Cesium 30.1 years 0.662 γ (85%)

140 Barium (Ba) 12.8 days 0.537 γ (24%); 1.0 β, La cascade (below)

140 Lanthanum (La) 1.7 days 0.329 γ (19%), 0.487 γ (43%), 0.816 γ (22%), 1.596 γ (96%); 1-2 β

144 Cesium 285 days 0.134 γ (11%), 0.696 γ (1.3%), 1.489 γ (.3%), 2.186 γ (.7%); 3.0 β

ACTIVATION PRODUCTS

Mass Element Half-life Radiations

3 Hydrogen (H) 12.3 years 0.019 β

14 Carbon (C) 5730 years 0.15 β

24 Sodium (Na) 15 hours 1.369 γ (100%), 2.754 γ (100%); 1.4 β

56 Manganese (Mn) 2.58 hours 0.847 γ (99%), 1.811 γ (27%), 2.113 γ (14%); 2.8 β

59 Iron (Fe) 44.5 days 1.099 γ (56%), 1.292 γ (43%); 1.5 β

60 Cobalt (Co) 5.3 years 1.173 γ (100%), 1.332 γ (100%)

63 Nickel (Ni) 100 years 0.07 β

64 Copper (Cu) 12.7 hours 0.6 β (40%), 0.6 β+ (20%)

NOTE:

a. Isotopes with half-lives of less than 2 hours were excluded because they are likely to decay before they can be detected. The only isotopes

included with half-lives less than 100 days are krypton, ruthenium, iodine, and xenon, which are transported rapidly through the environment, and

those which emit strong gamma rays for easy detection.

b.Isotopes with half-lives of more than 100 million years were excluded because they occur naturally.

SOURCE: Office of Technology Assessment, 1995
Chapter 2 Detectable Emissions | 17

the fuel in acid, separating and purifying the plutonium using solvent-extraction, precipitation,

and ion-exchange, and converting the plutonium

to a metallic form. The PUREX process, the

most common method, uses well-known chemical processes.

When the fuel is chopped up and dissolved in

an acid bath (usually nitric acid), all gaseous

products (e.g., krypton, argon) are released.

Some of them are hard to trap. Therefore this

stage can provide strong evidence of covert

activity. The acid bath can also lead to other

emissions. The acid itself can fume or leak and

be a chemical indicator. Traces of uranium and

plutonium as well as other products are likely to

be contained. Other chemicals used in the process such as tributyl phosphate (TBP) also may

be released.14 Waste products from the purification process can produce airborne particles or

liquid runoff. Cooling water also could carry out

various products.

Based on emissions from fuel reprocessing at

Sellafield (United Kingdom) in 1991, a small

(8 kg of plutonium/year), emission-controlled

reprocessing plant is likely to release annually:

12 mg carbon-14 split between air and water;

125 g iodine-129 (for old fuel) to off-site

water;

15 g technetium-99 to off-site water;

2 mg strontium-90 split between air and

water.15

These are small quantities which are then

spread over a wide area as the releases disperse.

While the concentrations appear to be minute,

ultrasensitive equipment such as the accelerator

mass spectrometer and processes such as neutron

activation analysis (see chapter 3) could detect

them in environmental samples.

Final purification and conversion of plutonium to metallic form is likely to produce parti14 Richard R. Paternoster, Nuclear Weapon Proliferation Indicators and Observables, LA-12430-MS, Los Alamos National Laboratory,

December 1992. 15 Briefing notes supplied by Ivan Proctor, Lawrence Livermore National Laboratory, March 1, 1995.

cles. Machining of the material to produce the

weapons component will add more particles to

an effluent stream.

❚ Countermeasures

Any country trying to produce plutonium

covertly will try to limit key emissions to the

greatest extent possible. Ventilation from the

process rooms can be filtered with high efficiency filters that remove almost all particles.

Even ordinary pollution control equipment can

be effective without triggering any export control

notice.16 Liquids can be held within the plant (at

least until the volume becomes unmanageable).

Gases can be trapped. Even the noble gases can

be adsorbed on activated charcoal or removed

cryogenically and isolated, although these methods are difficult and not 100 percent effective.17

Such measures will reduce emissions, greatly

complicating the detection of undeclared facilities and activities. However, they will not eliminate the risk. In addition, on-site storage

increases the possibility of major accidental

releases, for example if a storage vessel ruptures.

Such releases may be easier to detect than continual small emissions.

Under some conditions, a proliferator might

even deliberately release contamination to confuse inspectors. This might slow down efforts to

locate the key sites, but it also increases the likelihood that a major search will be mounted.

The possibility of countermeasures suggests

two things: development of ever more sensitive

instruments may be essential; and baseline analyses of suspect sites should be made as soon as

possible. The latter, particularly for complicated

facilities that already have released some contamination, may make it possible to detect any

changes in activity.

16 David A. Kay, “Denial and Deception Practices of WMD Proliferators: Iraq and Beyond”, The Washington Quarterly, 18:1, Winter

1995. 17 Anthony Fainberg, op.cit. p. 30.
| 19

3

Technologies for

Detection of

Emissions

etecting the emissions discussed in the

last chapter requires a variety of techniques. The samples must be collected

from carefully selected locations using

procedures to prevent cross-contamination. They

must then be transferred to the analytical laboratory. Many different lab instruments are available. Selecting the instruments to be used

depends on the type of sample, the materials that

might be found in it, the precision needed for the

answers, and other factors. Then the results must

be interpreted.

This chapter starts with a description of environmental monitoring as used in Iraq, the first

public demonstration of its value. Then it

describes the various steps that constitute environmental monitoring. Progress in making environmental monitoring a routine part of IAEA

safeguards is discussed in the next chapter.

THE IRAQI EXPERIENCE

The agreement ending the Gulf War included

Iraq’s acceptance of United Nations inspection

of all facilities suspected of contributing to a

nuclear weapon capability. Within six weeks,

inspectors from the International Atomic Energy

Agency arrived to begin an exhaustive, and at

times dramatic, survey of Iraq’s nuclear weapon

facilities.

Much of the equipment and materials had

been hastily removed and hidden during the war

and the month following, so the inspectors used

means other than conventional materials accountancy and equipment examination to detect activities. Hundreds of samples were collected and

sent to various labs for analysis. Many of these

samples were quite nontraditional. Inspectors

took smears from the surfaces of equipment and

from the buildings themselves. They also collected samples of soil, vegetation and water outside the buildings. The first eight inspections in

1991 produced 464 samples of non-nuclear

materials.1 The first set of analyses of samples

provided information to guide subsequent sampling. It was important to get the results of the

analyses rapidly so that subsequent inspections

could be designed to build on that information.

1 Including samples of construction materials such as concrete and steel, which are not considered part of environmental monitoring. D.L.

Donohue and R. Zeisler, “Behind the Scenes: Scientific Analysis of Samples from Nuclear Inspections in Iraq,” IAEA Bulletin, January,

1992.

D
20 | Environmental Monitoring for Nuclear Safeguards

The analyses were performed by the IAEA

itself and at labs in several member states,

including the United States. The IAEA has two

labs at Siebersdorf, Austria: the Safeguards Analytical Laboratory (SAL) and the Physics, Chemistry and Instrumentation (PCI) Laboratory.

SAL, the prime safeguards laboratory, analyzes

nuclear materials for uranium and plutonium

content and isotopic composition. PCI uses a different set of techniques to analyze for radionuclides and other elements in the environment;

much of its work has been on the International

Chernobyl Project.2

 Specific techniques are dis2 D.L. Donohue and Rolf Zeisler, “Analytical Chemistry in the Aftermath of the Gulf War,” Analytical Chemistry, 1993, 65,359A-368A,

American Chemical Society.

cussed in the following sections. The analyses

for the Iraqi samples are listed in table 3-1.

The most surprising result of the analyses was

the discovery of isotopically altered uranium

which did not match any known (declared) materials. Iraq was not known to have any enrichment

capability at all, making any evidence of enrichment a surprise. That surprise was greatly compounded with the discovery of extremely

depleted uranium (i.e., with a very low fraction

of U235) that could only have been produced with

electromagnetic or laser separation techniques—

techniques not known to be in commercial use

TABLE 3-1: Samples from Iraq Processed at IAEA Laboratories in 1991

Inspection Non-nuclear materials Nuclear materials

1st 48 31

2nd 35 0

3rd 139 51

4th 41 0

5th 49 61

6th 7 0

7th 139 141

8th 6 105

Total 464 389

Measurements requested

Sample category Sample types Analyses requested

Non-nuclear materials

(Environmental)

Smears

Vegetation

Soil

Debris

Rocks, Ores

Water

Presence of U, Pu, or radionuclides

Amount of U, Pu

Presence of F, Cl

U, Pu isotopics

Presence of high explosives

(Materials of construction) Graphite

Steels

Beryllium

Unknown metals

Purity, type or identity

Nuclear materials Uranium metal

Uranium compounds

Plutonium compounds

Polonium

U, Pu waste and scrap

Amount of U, Pu

U, Pu isotopics

Amount of polonium

Compounds of U, Pu

Trace elements in U compounds

SOURCE: D.L. Donohue and R. Zeisler, “Behind the Scenes: Scientific Analysis of Samples from Nuclear Inspections in Iraq,” IAEA Bulletin, January 1992.
Chapter 3 Technologies for Detection of Emissions | 21

anywhere in the world. As discussed in chapter

2, the only commercial-scale enrichment technologies—gaseous diffusion, centrifuge, and

advanced vortex tube—discharge depleted uranium with tails of about 0.3 percent U235. No one

believed that Iraq was ahead of western developers of laser enrichment, but it still took a while

for experts to accept that anyone would use such

an old, energy-inefficient technology as electromagnetic separation.3

 After three inspections the

evidence from sample analysis and other means

was compelling, and Iraqi officials were forced

to reveal the EMIS program. Enrichment equipment had been operated at Tarmiya and

Tuwaitha, and additional facilities were under

construction at Ash Sharkat. When calutron components themselves were recovered and materials analyzed, uranium in one sample was found

to have only 0.06 percent U235.

4

Other analyses also disclosed undeclared irradiation of uranium to produce very small quantities of plutonium. However, this activity,

detected by analyses of conventional nuclear

material samples, was a minor part of the Iraqi

program. In addition, uranium from three different ore bodies was discovered, including indigenous production as a byproduct from an Iraqi

phosphate plant.5

Environmental monitoring was used to verify

the accuracy of the final Iraqi declarations. It is

still used to verify that no covert nuclear material

production is underway. In particular, wide-area

monitoring of waterways is performed, yielding

a high probability of detecting any significant

production of plutonium.6 The IAEA takes

water, sediment, and biota (plants and animals)

samples at 50 river stations in Iraq every two

years. The IAEA does not maintain air monitoring stations because of the expense. It is, how3 Anthony Fainberg, Strengthening IAEA Safeguards: Lessons from Iraq, Center for International Security and Arms Control, Stanford

University, April 1993, pp. 11–15. 4 Since this sample was found on the collector of a calutron, it was not the result of environmental monitoring. See D.L. Donohue and R.

Zeisler, “Behind the Scenes: Scientific Analysis of Samples from Nuclear Inspections in Iraq,” IAEA Bulletin, January 1992. 5 Personal communication with IAEA staff, Apr. 3, 1995. 6 Personal communication with IAEA staff, Apr. 4, 1995.

ever, considering air particulate samplers

mounted on its vehicles. These would direct air

through a filter as the vehicle moves, collecting

dust and other materials. This is a promising

approach in Iraq because the agency has many

vehicles and access everywhere. Car engine air

filters have also been used as collectors. Other

forms of environmental monitoring, such as the

collection of soil and plant samples, are still

being performed to verify compliance with

agreements. On the average, one IAEA inspector

is in the field every day in Iraq.

Early problems in the Iraqi environmental

monitoring program have largely been overcome. Contamination ruined some samples. The

trace quantities characteristic of environmental

samples can be contaminated by exposure to

almost any source of radionuclides. For example,

one scientist from a U.S. national lab apparently

left tiny particles of nuclear materials from his

home lab at several sites, giving erroneous readings when they were unknowingly collected with

the environmental samples.7 Greater attention to

cleanliness and double bagging of samples has

been important. In addition, contamination from

Chernobyl, especially cesium-134 and -137, was

measured in Iraqi samples and had to be taken

into account. Even natural uranium created problems. One building was made of concrete that

had 25 parts per million of uranium, a level close

to minable ore quality.8

SAMPLING

The collection of samples is conceptually simple,

but there are some complicated aspects. The

object is to collect gaseous, particulate or liquid

emissions from a covert nuclear operation. The

intent could be to determine if undeclared activi7 Ibid.

8 Ibid.
22 | Environmental Monitoring for Nuclear Safeguards

ties are taking place at a declared facility, or to

search for an undeclared facility. As practiced so

far by the IAEA, sampling has mainly been conducted at declared facilities. The most important

technique has been taking swipes from equipment or other surfaces in the targeted facility.

Swipes (or smears) are simply pieces of cloth or

paper (kept scrupulously clean to avoid contamination) which are wiped on the surface and

stored in a plastic bag. Wiping picks up particles

that have settled on the surface. Even thorough

washing of surfaces is unlikely to remove all the

particles, and inspectors learn where to find the

optimum places to take swipes. The swipes need

not be taken directly in the process area to detect

what activities took place there; common areas

and adjacent rooms collect enough telltale particles also, carried in by personnel, equipment, or

by air currents.9

Taking swipes inside a facility is the most

effective technique of environmental monitoring.

It is a powerful tool that is generally unavailable

to national intelligence efforts, which normally

do not have such facility access.

Outside the plant, sampling can still involve

swipes, for example on window ledges, signs, or

shiny leaves such as aloe. However, it is often

easier to simply pick the leaves or other parts of

the plants. Pine needles are good collectors

because they have a sticky residue that is particularly likely to hold particles. Not only do plants

(biota) capture particles that have settled on their

surfaces, but they also collect soluble material

carried to their roots in groundwater. Thus biota

act as integrators of emissions over periods of

weeks to years. Grazing animals can also collect

particles, which are concentrated in their excrement.

Similarly, soil near the surface can be collected. Particles settle from the air and can

remain on the surface for many years.

Air samples, either gaseous or particulate, can

be taken either at stationary sampling stations or

from vehicles traveling in suspected areas. If the

9 Personal communication with IAEA staff, Apr. 3, 1995.

plume from the facility is caught, very accurate

and timely information can be gleaned. Gaseous

plumes can, under some conditions, be detected

for hundreds of miles. There are several problems with gas and particulate sampling, however.

First, some emissions from nuclear activities

occur in puffs rather than on a continuous basis.

For example, when a reactor is opened for refueling, or a batch of spent fuel is chopped to extract

the plutonium, gaseous emissions occur briefly.

Second, the movement of the plume can be very

erratic, depending on local winds. Thus the network must be fairly dense to have a high probability of capturing the signatures. Not only is

such a network expensive to construct, but the

stations need to be visited frequently to collect

samples or otherwise service the equipment. The

dense network required with different sampling

techniques for gases and particulates, their maintenance, and particularly the laboratory analysis

of the large number of samples required add up

to a very large operating expense. Furthermore,

once a plume is detected, it must be attributed to

a source. This requires a meteorological database

as well as models to analyze the transport and

dispersion of effluents.

Emissions can get into water from liquid runoff from the facility, by settling out onto the

ground and getting washed away by rain, or by

settling directly into the water. Holding ponds

are particularly desirable as sources because they

catch the runoff directly. There are two techniques for sampling water. One is to just fill a

bottle. The other is to pump water through a filter

to collect suspended material or an absorber to

collect soluble or colloidal species. Lakes, small

streams, rivers, and seas/oceans are all possible

sources, though oceans tend to dilute the signal

rapidly due to mixing.

A related collection medium is sediment in a

river or the ocean, which can be dug up and

bagged. Sediment can accumulate over a long

period of time, providing a record of what came

down river over time. It is tricky to select a rep-
Chapter 3 Technologies for Detection of Emissions | 23

resentative deposit; depending on the river flow

pattern, a specific piece of sediment could be a

single recent deposit or an old one with no recent

material. In either case, the sediment could be

deposited when no nuclear material was present

even though at other times it was present. Collecting water plants is another option, as with terrestrial plants. One advantage of water as a

source is that it is much easier to trace a detected

substance up-river than up-wind. Whereas winds

change, the watershed remains fixed.

Construction materials, while not literally a

source for environmental sampling, are also considered because the same analytical techniques

can be used on them. Moreover, they are likely to

be collected along with environmental samples

as part of the IAEA’s upgrading of safeguards.

Steel and other materials from a reactor can carry

considerable information on the operation of the

reactor. Even analysis of unirradiated material

can be useful as with, for example, steel pieces in

Iraq that had been thought to be parts of centrifuges for enrichment, but which were shown not

to be maraging steel, a material critical for centrifuge rotors.

A careful plan is needed to know where and

how to sample to have the greatest chance of

finding telltale emissions with a minimum of

effort. Inspectors cannot simply arrive at a facility and start collecting samples. For example, if

prevailing winds blow consistently in one direction, there is little point in sampling intensively

upwind. If an HEU plant is suspected, tritium or

noble gases are unlikely to be emitted, so gas

sampling will serve little purpose. The plan must

take into account the type of suspected activity,

the terrain, local vegetation, weather patterns,

funds available for analysis, and other factors.

Once collected, the samples are doublebagged to prevent contamination, and sent to the

IAEA’s laboratories which protect the samples

from particle contamination. A clean room is

being built there with U.S. assistance. The clean

room, which will have carefully controlled and

filtered ventilation, will contain the shipping

area, storage areas for sample archives, and analytical instruments. The requirements for the

clean room far surpass anything the IAEA has

had to construct in the past, because environmental samples contain so much less critical material

than do the traditional safeguards samples of process materials. It is critical to avoid cross contamination.

ANALYTICAL INSTRUMENTS

A broad range of analytical techniques is needed

for light and heavy radionuclides with different

modes and rates of decay (see box 3-1), inorganic chemicals, and organics. The specific analytical technique chosen for a sample depends on

the type of sample, the signature suspected, accuracy required, the rapidity with which results are

needed, and costs. Samples may be divided and

tested by several means. As environmental monitoring becomes routine, the IAEA will archive

samples, or parts of them, to establish a baseline

that can be compared with anomalies discovered

in the future, perhaps with more sensitive instruments.

The major categories of analytical lab instruments are:

■ Radiometers (counters) which measure the

type and intensity of radioactive decays (alpha

particle, beta particle, gamma ray).

■ Spectrometers to characterize the radiation

emitted by decaying or excited atoms; may be

combined with counters.

■ Mass spectrometers, that separate isotopes

according to their different masses and measure their relative abundance (i.e., they derive

a spectrum of masses). Several technologies

may be combined with the mass spectrometer

to improve sensitivity.

■ Microscopes and electron microscopes, for

examination of particles.

■ Traditional chemical instruments such as titration or chromatography apparati, which determine which chemicals are present and their

concentration.

■ Specialized instruments such as lasers and

reactor irradiation for activation analysis.
24 | Environmental Monitoring for Nuclear Safeguards

Some of the most important instruments that

can be used to analyze environmental monitoring

samples are described here. Microscopes and

conventional chemical techniques, such as are

already used for safeguards materials analysis,

are not included.

Gamma-ray spectrometry—measures energy

of gamma rays from radioactive decay. Each

decay has a specific energy level(s) which may

be identified easily. This method is used for

screening samples as it is quick and requires no

elaborate preparation. It also can identify a broad

range of isotopes, including fission products

(e.g., cesium-134 and -137, ruthenium-106), activation products (e.g., cobalt-60), and actinides

(e.g., uranium-235, plutonium-239, and americium-241). It does not require isotope-specific

preparation, and can be used for any of the environmental samples discussed above. Sensitivity

can be high; short half-life isotopes can be identified from samples containing only thousands of

atoms.

Alpha-particle spectrometry—measures the

energy spectrum of alpha particles emitted by

plutonium and other actinides so that the isotopes

present can be identified by their characteristic

energy levels (similar to the gamma-ray spectrometer). This technology can measure the ratio

of uranium isotopes in a 1 microgram sample,

providing useful information as discussed below.

Plutonium can also be detected in amounts less

than one nanogram.

Beta spectrometry—a counter for beta

decay. The emitted beta particles (electrons) are

BOX 3-1: Radioactive Decay

Radioactive nuclei spontaneously decay (break up), emitting observable radiation and transmuting

themselves into other nuclei. This process continues until a stable form is reached. Transmutation can be

accomplished by the emission of alpha rays (helium nuclei), or beta rays (electrons or positrons), or by

the absorption (capture) of an orbiting electron. Gamma rays and x-rays, which are part of the electromagnetic spectrum that includes visible light, may also be emitted, but this changes only the energy

level, without itself causing transmutation.

Only the heaviest nuclei emit alpha particles. These are mainly actinides, elements of atomic number

89 (actinium) and higher. Uranium (92) and plutonium (94) are actinides. Alphas are emitted with characteristic energies that can be measured accurately to identify the isotope of origin. Alpha spectrometry is

used to characterize nuclear weapon material.

Isotopes lighter than actinides that indicate nuclear reactor operation are fission products (from the

fissioning of nuclear fuel) or activation products (non-nuclear materials such as fuel cladding or reactor

components that have absorbed neutrons). These usually have excess neutrons, and so decay by emitting electrons (positron emission or electron capture occur in nuclei that have too few neutrons). The beta

particles emitted by a given isotope range in energy from zero to a characteristic maximum. Measuring

the energy of a given beta particle gives very little information about its source, although a spectrum or

collection of beta particle energies can be used to identify a particular beta emitter. Thus, substances

such as tritium (hydrogen-3, which has an unusually low-energy beta) can be measured by a combination of chemistry and beta spectrometry.

Each decay carries with it a characteristic pattern of gamma rays and x-rays. In many cases, gammaray spectrometry can identify an isotope by measuring the energies and relative abundance of the gammas it emits. However, many isotopes do not emit an identifiable spectrum; the spectral lines can be too

weak or so myriad that a pattern cannot be identified. Also, the “fingerprints” of different isotopes overlap,

so that an abundant constituent can mask a rare one. Experience is needed to understand the cases

where gamma rays yield useful information.

SOURCE: Office of Technology Assessment, 1995.
Chapter 3 Technologies for Detection of Emissions | 25

directed through a fluid. In a liquid scintillation

counter, fluid molecules struck by particles are

excited and emit flashes of light. The liquid scintillation counter is used to measure strontium-90,

an important fission product that can be released

during reprocessing. Tritium is measured by gas

proportional counters, which produce current

pulses whose magnitude is proportional to the

energy of the incoming beta particle.

Neutron activation analysis—the sample is

irradiated with neutrons from a reactor or other

source to generate radioactive isotopes. Then the

gamma ray spectrum lines are measured to identify the radioisotopes; the intensities of the

gamma emission lines indicate the concentration.

The process can be automated and rapid. It is

especially good for iodine-129, technetium-99

and elemental fluorine.

Delayed neutron counting—the sample is

irradiated with neutrons. Fissioning isotopes

(U235 or Pu239) emit more neutrons, but not all at

the moment of fissioning. Some are delayed for a

matter of seconds. Counting the delayed neutrons

gives a measure of the fissile isotopes present.

Nanogram quantities of uranium or plutonium in

the sample can be measured.

X-ray fluorescence (XRF)—the sample is

stimulated by X-rays, gamma rays, or energetic

particles to produce fluorescent emissions. Emissions from elements ranging from sodium to the

heaviest elements of the periodic table can be

measured and identified by comparison to standards for the various elements. This technique is

used for rapid screening of samples. It identifies

chemical elements—and is good at detecting

metals, including uranium and plutonium—but it

does not differentiate among isotopes of the

same element.

Laser fluorimetry—the sample is ashed

(burnt or oxidized under controlled conditions to

remove combustibles and preserve the noncombustibles) and dissolved in hot nitric acid. It is

then illuminated with an ultraviolet (UV) laser

and any fluorescence measured. Many uranium

compounds fluoresce, and this instrument can

measure them with high sensitivity and accuracy.

Inductively Coupled Plasma Mass Spectrometry (ICPMS)—the sample is atomized in

a high temperature plasma and directed into a

mass spectrometer. Once inside, the atoms pass

through a magnetic field which forces them to

move in a curve, with the lighter atoms curving

more sharply than the heavier ones. This separation allows them to be collected separately and

measured, permitting their identification. ICPMS

can measure nanogram-quantities of uranium or

plutonium with good accuracy. For example, the

uranium-235/238 ratio of a sample with several

tens of nanograms of uranium can be measured

with 2 percent accuracy.10 The procedure is

rapid and requires no elaborate preparation. It is

particularly good for water samples because the

suspect material must be in solution anyway.

Over 70 elements can be surveyed.

Thermal Ionization Mass Spectrometry

(TIMS)—the sample is ashed and the residue (or

just a particle) is attached to a filament. The filament is heated by an electric current to a high

temperature, which vaporizes the sample. The

vapor is ionized and the ions directed into a mass

spectrometer, as with the ICPMS. The TIMS

technique can detect small deviations from natural isotope ratios. It is the most accurate instrument in common use to measure uranium and

plutonium composition and is especially valuable for low concentration samples (e.g., nanograms per liter). TIMS is more accurate than

ICPMS, allowing the detection of more dilute

samples. The ratio of uranium 235 to 238 can be

measured to at least 0.5 percent accuracy.11

However, the cost can be several thousand dollars per sample, about 2 to 5 times higher than

that of ICPMS.

Accelerator Mass Spectrometer (AMS)—

uses a particle accelerator as input to the mass

spectrometer to achieve greater separation. This

10 Personal communication with Philip Miller, Lawrence Livermore National Laboratory, Mar. 1, 1995. 11 Ibid.
26 | Environmental Monitoring for Nuclear Safeguards

is the most sensitive instrument currently available, and relatively few labs have one. It can be

used to measure small changes in the concentration of naturally occurring but rare radioisotopes

with long half-lives (e.g., carbon-14 and iodine129, which are created by cosmic rays as well as

by nuclear activities). AMS can detect isotopic

concentrations of 1 atom in 1015, making it excellent for trace samples collected far from the emitting site.12

BULK AND PARTICULATE ANALYSIS

Once a sample is collected, it can be examined in

two major ways. First, the entire sample (or just a

portion) can be tested using one or more of the

instruments discussed above. This is called bulk

analysis. Not only the radioactive or chemical

material sought, but the medium (e.g., soil, vegetation) and sometimes the collecting agent

(swipes, filters) are tested. Bulk analysis reveals

information about average properties of the sample and indicates the presence of anomalous

components.

Alternatively, suspect particles themselves

can be isolated and analyzed. A swipe of a dirty

piece of equipment can collect many thousands

of particles, so identification of the relatively few

interesting ones can be difficult. The method

used by the Air Force Technical Applications

Center (AFTAC) laboratories is to extract the

particles from the sampling media (swipe), attach

them to a clear plastic (Lexan) and irradiate them

in a nuclear reactor. Uranium and plutonium

atoms fission during irradiation and leave tracks

in the Lexan. When viewed under a microscope,

the particles that produced the tracks can readily

be identified and isolated.13

Individual particles can be examined optically

and with an electron microscope, and then tested

by TIMS or other mass spectrometers as discussed above. Much can be learned visually by a

12 Ibid. 13 Personal communication with Peter Aldred, Advanced Nuclear Applications (AFTAC analytical lab), Vallecitos Nuclear Center, Mar.

2, 1995.

trained observer. In fact, Russian particle analysis is largely based on intensive visual inspection. This is a very different approach from U.S.

analytical techniques and can discover different

things about a particle.14 The morphology, or

structure of a uranium or plutonium particle

bears information as to how it was formed. For

example, a particle of uranium might contain

UO2, U3O8, and U4O9 in various structures,

depending on the temperature at which it was

formed. That indicates the process that was used.

A scanning electron microscope (SEM) is used

to provide a preliminary analysis, such as

whether the particle is crystalline or amorphous,

and whether other materials are embedded in the

particle.

Particle analysis is considerably more labor

intensive and costly than bulk analysis. Thus it is

used only where extreme sensitivity and precision is needed. In the IAEA field trials, bulk and

particle analysis yielded approximately the same

results when samples rich in particles were

directly compared. Thus the two approaches

complement each other, serving somewhat different purposes.

DATA INTERPRETATION

The information produced by the techniques

described above cannot be expected to unambiguously define whatever activities have taken

place. It may be conclusive, as when HEU is

found in a variety of samples at a LEU plant.

Most activities, however, can be concealed sufficiently that only some samples will have any

indications, and these may be inconclusive. A

few particles of plutonium do not guarantee that

reprocessing is taking place, as they may be fallout from the Chernobyl accident or weapons testing, or contamination from a legitimate research

center. Analysts must be experienced with the

operations that could have produced them, and

14 Personal communication with IAEA staff, Mar. 31, 1995.
Chapter 3 Technologies for Detection of Emissions | 27

the tools, such as burn-up computer codes, that

can be used to understand the possibilities. In

addition, they must know how much data is

required to reach conclusions, and how reliable

the data must be. Further sampling and analysis

may have to follow the first indication to determine if it was an isolated anomaly or truly indicative of illicit operations.

Reaching conclusions on the existence of

undeclared activities is likely to require a multidimensional analysis, of which environmental

monitoring will be only one part. Environmental

monitoring itself will make a strong case if several different signals (as discussed in chapter 2)

can be verified, especially for reactor operation

and reprocessing. Uranium and plutonium isotopes, perhaps in conjunction with other

actinides, are a good indication of reprocessing.

Finding other radionuclides such as fission and

activation products, and chemicals such as tributyl phosphate, would greatly strengthen the indication. Finding tritium in waterways or the air

strongly suggests reactor operations.

As has been noted above, even minute traces

of radioisotopes can be detected. With the more

sensitive instruments, a few million atoms of uranium can be sufficient for measurement and a

few billion can determine the full isotopic fingerprint, as shown in table 3-2. The ratio of certain

isotopes can yield valuable information. For

example, the ratio of uranium-234 to -235 can

indicate the type of enrichment that was used.

The bigger the sample, the more information that

it yields. With a sample containing 0.1 to 1.0

grams of plutonium (implausibly large for an

environmental monitoring sample, but easily

available from conventional safeguards or a

smuggling case), an analyst may be able to tell

the date of separation from spent fuel; the

method of casting; irradiation time; the original

enrichment; and the reprocessing technique.15

The lab information must be analyzed by an

experienced analyst to extract the appropriate

conclusions. What are the possible sources of the

15 Personal communication with Sid Niemeyer, Lawrence Livermore National Lab, Mar. 1, 1995.

isotopes or chemicals found? How consistent

with these sources are the forms of the discovered substances? If the suspect activity is taking

place, what else should be found? How long, and

at what scale, has it been taking place? Is additional sampling necessary to confirm these findings, and what sort of sampling should it be?

This information also must then be analyzed

on a country- and site-specific basis before any

accusations can be made. What other activities

are known to be taking place? Is the country

capable of mounting this kind of operation?

What other indications (e.g., imports of equipment, movement of technical personnel) support

or contradict the conclusions? Are the topography and local weather patterns of the suspected

site consistent with finding samples where they

were found?

Analyzing large numbers of environmental

samples will generate huge amounts of data.

Keeping track of all the data will be difficult.

Adequate provisions must be made for computers and software to handle, process, and store the

information.

CONCLUSIONS

The analytical techniques described in this chapter can detect and characterize routine emissions

from nuclear facilities. They are sufficiently sensitive to have a high probability of detecting

covert activities to produce nuclear weapons

materials if the sampling is close to the facility.

Long-distance monitoring, especially of the air,

is more problematical. The more dilute the emissions become, the less likely that critical

TABLE 3-2: Measurement Sensitivities (TIMS)

Element Detection Isotopic analysis

U 5×106 atoms 5×109 atoms

Pu 5×105 5×108

Am 2×105 2×108

Np 2×105 2×108

SOURCE: Don Rokop, Los Alamos National Laboratory, 1995.
28 | Environmental Monitoring for Nuclear Safeguards

materials can be distinguished from background,

or that they can be traced back to the source.

Sampling and analysis will improve over the

next few years as the IAEA becomes more experienced and uses already available, more sensitive equipment. Technologies under

development may improve analytical capabilities, as discussed in chapter 5.
| 29

4

Status and

Plans for

Implementation

he International Atomic Energy Agency

(IAEA) is moving to take advantage of

environmental monitoring to strengthen

its safeguards. The United States and

other members have strongly supported this initiative with funding, expertise, and assistance

with lab analysis. Implementation will call for

careful planning to minimize costs and maximize

effectiveness.

FIELD TRIALS

The IAEA has conducted a series of field trials in

11 cooperating member nations to determine

how best to conduct environmental monitoring

and the results that can be expected. A variety of

installations were tested in order to gain experience with reactor operation, enrichment, reprocessing, and other functions that are likely to be

employed in a weapon program.

Results from several countries have been

released including Sweden, South Africa, Australia, Argentina.1

1 These results are drawn largely from: Bruno Pellaud and Richard Hooper, “IAEA Safeguards in the 1990s: Building on Experience,”

IAEA Bulletin, vol. 37, No. 1, March 1995.

Sweden—tests were conducted in the vicinity

of five separate nuclear facilities. Three were

nuclear power stations with a total of 10 reactors.

The others were a nuclear research facility and a

fuel fabrication plant. All were on or near the

coast (Baltic Sea or Kattegat, across from Denmark), and samples were taken of coastal water,

sediment, and biota up to 30 km away. Analyses

proved capable of detecting activation products

from reactor operation (e.g., Co-60) up to 20 km

from the site. In addition, a small amount of

high-burnup plutonium, clearly distinguished

from fallout, was found near the research center.

South Africa—an enrichment plant at the

Pelindaba site produced the highly enriched uranium used in South Africa’s seven nuclear weapons.2

 A second plant on the site produced LEU

for South Africa’s power reactors. These plants

are now closed. Soil, vegetation, and water samples were collected in and near the facility

grounds. Swipes were taken in and near the process buildings. The vegetation samples, including those taken well away from the facility,

2 For further information, see Adolf von Baeckmann, Garry Dillon, and Demetrius Perricos, “Nuclear Verification in South Africa,”

IAEA Bulletin, vol. 37, No. 1, March 1995.

T
30 | Environmental Monitoring for Nuclear Safeguards

showed traces of enrichment activities. Particle

analysis of swipes was consistent with bulk analysis and showed in detail various levels of uranium enrichment, including depleted and natural

uranium, and LEU and HEU. The swipes gave

comparable results whether taken in the process

area, auxiliary rooms, or outside the buildings.

Australia—the Lucas Heights Research Laboratories has conducted a variety of activities.

Swipes inside a building housing a small centrifuge enrichment development program that was

closed and dismantled 14 years ago still showed

evidence of enrichment, including LEU and

depleted uranium. One surprising result was the

discovery of uranium depleted below declared

levels, as low as 0.3 percent. Investigation

revealed that this was from initial tests, when the

centrifuge was fed with depleted uranium.3

 Starting off with depleted uranium, which has a uranium-235 fraction lower than that of natural

uranium, produces tails that are more strongly

depleted than are produced from natural uranium. Isotope production included molybdenum99 (for medical use) from irradiating targets in a

reactor. Swipes showed both target material and

the irradiated products.

Argentina—the Pilcaniyeu gaseous diffusion

enrichment plant produced LEU until 1991. The

output was used to improve performance in a

heavy water reactor, so the enrichment level was

low, only 1.2 percent. This level is harder to distinguish from natural uranium than the 3 percent

enriched LEU used for light water reactors.

Swipes were taken inside the process and other

buildings. Other samples included vegetation and

soil around the site, and river water, sediment

and biota both up- and downstream of the facility. Analysis showed depleted and natural uranium and LEU consistent with declared activities

at the site.

Other countries participating in the field trials

included the United States (the K-25 enrichment

plant at Oak Ridge, Tennessee), Hungary, Japan,

3 Personal communication with IAEA staff, Apr. 4, 1995.

the United Kingdom, Indonesia, Netherlands,

and South Korea. A total of 12 trials (two in

Japan) were conducted.

Inspectors visited the sites, collected the samples, and sent them to IAEA headquarters. From

there they were distributed to various laboratories, including the IAEA’s own lab at Seibersdorf, as noted in chapter 3. Labs in the United

States, United Kingdom, Russia, Hungary, Finland, Canada, and Australia also participated in

the analysis. In the United States, bulk samples

were sent to the Oak Ridge National Laboratory,

which distributed them among the analytical labs

at Oak Ridge, Savannah River Technology Center, Los Alamos and Lawrence Livermore

National Laboratories, and Pacific Northwest

Laboratory. For example, Livermore analyzed

more than 200 samples for the field trials, using

ICPMS and TIMS for uranium isotopics, and

AMS for iodine-129 from reprocessing or reactor

operation. Samples intended for particle analysis

were sent to the Air Force Technical Applications Center for distribution to its network of

labs, such as at the Vallecitos Nuclear Center and

McClellan Air Force Base in California.

The field trials demonstrated the practicality

of environmental monitoring under a broad range

of conditions. Most declared activities were verified, although in some cases, particularly in the

ocean sampling off Japan, the signatures had

been so diluted that the results were limited. As

would be expected, streams are better sources for

samples than oceans. The process can be

improved as more experience is gained. Inspectors will be trained to avoid contamination and to

pick the best locations for sampling. Distribution

and analysis should become more efficient. Data

interpretation, in particular, is a skill that takes

time to learn. For example, correlations among

the isotopes detected in a sample often are more

informative of the process under investigation

than the quantity of any isotope alone.4

4 Briefing by IAEA staff, IAEA, Apr. 3, 1995.
Chapter 4 Status and Plans for Implementation | 31

In addition, not all samples will have to be

analyzed. Some can be archived until anomalous

results suggest a more intensive analysis. Further

work will also identify the key signatures that

environmental monitoring can expect to identify,

allowing improved focus and fewer analytical

deadends. Both sampling and analysis will be

better in a few years, allowing improved results

at lower cost.

If the field trials had only verified activities

that were known to have taken place at known

sites, then little could be concluded on the feasibility of discovering clandestine activities. However, several anomalies were also discovered that

turned out to be due to activities that were

unknown to the inspectors. One was the detection of depleted uranium at the Australian site

noted above. Another was the detection of plutonium at the Oak Ridge enrichment plant. The

source turned out to have been reprocessed uranium with traces of plutonium from the Hanford,

Washington facility that had been re-enriched at

Oak Ridge many years earlier. Clearly, environmental monitoring can uncover previously

unknown activities.

Other anomalies have yet to be fully

explained. Cesium found in Hungary could have

been from leaky fuel at the reactor, or it could

have been from Chernobyl. More was found in

downstream sediments than upstream, indicating

a reactor source, but the difference could also

have been a result of variable fallout or poor

sampling.5 If from the reactor, one would have

expected to find cobalt-60 (an activation product

of steel) also, as was the case in Sweden, but

none was associated with the Hungarian cesium.

At another site, a particle of HEU (30 percent

enriched) was found that had no relationship to

any activities at the site. It may have come from

a previous visitor. Contamination, whether from

an inspector or introduced in staging areas, is the

most probable explanation for most anomalies.

5 Personal communication with IAEA staff, Apr. 4, 1995.

As indicated in chapters 2 and 3, enrichment

plants and reprocessing plants are easier to detect

than reactors. In particular, reprocessing plants

produce a variety of emissions that can be found

in several different types of samples. Iodine from

Dounreay and Sellafield in the United Kingdom

has been detected in samples taken at the Chalk

River facility in Canada by using a very sensitive

accelerator mass spectrometer. Vegetation samples 30 km from Dounreay showed clear radionuclide evidence of reprocessing.6 Of course,

Dounreay is a very large source; a small, clandestine reprocessing plant probably could not be

“seen” from as far away. Enrichment plant signatures are hard to detect using water sampling

techniques, even those that concentrate radionuclides from high volumes of water. Lichens and

moss are better media for detecting signatures

from enrichment plants. Reactors were detected

mainly from on-site water samples. A small,

clandestine reactor would be quite hard to detect,

especially if the background included a significant amount of contamination from fallout from

nuclear weapon tests, Chernobyl, or the production and use of radioisotopes for medical or

research purposes. R&D facilities were best

characterized by swipe sampling inside the

buildings; these samples produced unambiguous

signatures, especially for isotopes such as uranium-235. Outside such facilities, vegetation and

water samples showed evidence of nuclear activities as far as several km away.

The measurement of radionuclides from onsite sampling proved particularly effective. For

isotopes of uranium and plutonium, particle analysis gave more precise results than bulk analysis.

The combination of on-site samples and particle

analysis was so sensitive that samples taken in

common areas in enrichment plants showed

comparable results to process room samples.

However, the field trials also demonstrated that

other sampling and analytical techniques work

well too; nuclear activities can be detected at

6 Ibid.
32 | Environmental Monitoring for Nuclear Safeguards

least several kilometers away from the emission

point, and bulk analysis gave the same general

results as particle analysis, although not as

clearly. However, bulk techniques could analyze

a larger portion of the sample, increasing the

chances of getting a “hit.” The different techniques complement each other and any of them

may be most appropriate for particular conditions.

TRAINING

Taking samples for environmental monitoring is

somewhat different than conducting conventional safeguards inspections, and inspectors

must be adequately trained. Most inspectors are

technically competent (they routinely sample

process lines and operate sophisticated instruments), and environmental sampling tasks are

relatively straightforward. However, the sampling strategy must be carefully planned, and

contamination standards are much more stringent

than for conventional safeguards. Furthermore,

the quality assurance procedures are demanding.

For example, inspectors have to record exactly

where a sample is taken. The mechanics of the

sampling can be taught in a day or two, but

proper procedures must be learned over a longer

period. In addition, enhanced observational skills

(e.g., the ability to notice suspicious or anomalous equipment) must be taught so that inspectors

can comply with the new activism in seeking out

evidence of proliferation, as suggested by the

IAEA Programme 93+2.

Only a few inspectors have had training in

environmental sampling techniques. Oak Ridge

provided training for most of those involved in

the field trials (about 10). An initial training program has been conducted at Seibersdorf, with the

first group in June 1995.

TECHNICAL CAPABILITIES AND 

THE NEW CLEAN ROOM

The IAEA did relatively little of the lab analysis

for the field trials and expects to continue to rely

on member states for much of the analytical

work as environmental monitoring becomes a

routine part of safeguards inspections. In fact, it

may have to expand its network of laboratories

as the work load grows.

The IAEA is building one essential facility for

the new safeguards program—a clean lab to

receive samples from the field, perform some

analyses, and hold other samples until they can

be transferred to its network of outside labs.

Samples cannot be sent directly to an outside

analytical lab because it is necessary to maintain

confidentiality for the inspected facility. The

samples are kept anonymous, which may involve

repackaging and splitting them. As has been

noted, it is essential to avoid contaminating these

samples, and a clean room—where the air flow is

carefully designed and filtered—is necessary to

properly handle them. The clean lab will be at

Siebersdorf, Austria, where the IAEA already

has a large laboratory, but it will be kept separate

from the other labs to minimize the risk of cross

contamination. It will contain some of the basic

instruments such as an electron microscope and a

TIMS. The IAEA must be able to independently

confirm results (especially positive results) to

maintain its credibility with inspected states, but

for analyses requiring expensive techniques such

as AMS and particle analysis it must continue to

rely on member states.

The clean lab is expected to be in operation by

the end of 1995. The total cost for the lab itself

(not including instruments) will be $3 million, of

which $1.5 million is being covered by the

United States. The equipment to be housed in the

facility will cost approximately another $2 million, which will come from the IAEA’s regular

budget.7

 Additional funding ($160,000) could be

used for a low-level gamma spectroscopy system

to screen samples. The clean lab operations will

require two professionals and two technicians.

U.S. help is technical as well as financial. An

American expert has been loaned to the IAEA

7 Briefing by IAEA staff, Apr. 3, 1995.
Chapter 4 Status and Plans for Implementation | 33

for two years to help design and construct the

lab, and other expertise also is being transferred.

Many improvements are expected in the

future. Instruments and techniques under development in the United States are reviewed in

chapter 5. Other work that may be relevant

includes environmental restoration of weapons

facilities. Studies of soil, radionuclide absorption

by vegetation, and groundwater or ocean current

movement provide information and models that

the IAEA could use.

QUALITY ASSURANCE

The trace levels of materials sought in most samples require very stringent quality control in

order to avoid contamination and inaccurate

results. For example, inspectors may need new

throwaway suits and booties every day. The

IAEA is establishing proper procedures for taking and handling samples. Sampling kits have

been designed and provided to inspectors with

U.S. lab help. Generally two inspectors are

needed—one to collect the sample and the other

to hold the bag it goes into. The two cannot

change roles during the day because of the risk of

cross contamination.

Analytical labs also must practice strict quality control, both in the handling of samples and

in the analysis. Some of the network labs may

have been unaccustomed to the need for such

quality control, because contamination occurred

several times.

One of the clean lab’s important functions will

be to ensure adequate quality assurance at all

stages.

IMPLEMENTING ENVIRONMENTAL 

MONITORING

The IAEA has been shifting its fundamental

approach to safeguards. In prior years, particularly before the 1991 Persian Gulf War, its objective was primarily to verify that a state was doing

what it said it was doing. States were required to

declare all their nuclear material and establish a

system of controls for it. The IAEA measured the

material and verified that none had been misappropriated. Verification that no other activities

were taking place was not seen as part of the

IAEA’s job, even though countries commit under

the Non-Proliferation Treaty (NPT) to refrain

from developing nuclear weapons in any way.

This approach was adequate only if all members

could be trusted, in which case such verification

arguably would not be needed at all. It was

shown to be fundamentally flawed when countries such as Iraq and North Korea proved themselves willing to ignore their commitments.

The new approach embodied in the IAEA Programme 93+2 is much more activist. If fully

implemented, as the Board of Governors indicated it would be at the March 1995 meeting, the

IAEA will search for undeclared activities. The

State’s declaration will still be the starting point

for verification, but the IAEA will look for signs

that contradict it. For example, the IAEA could

cooperate with supplier states to determine if any

countries are importing equipment inconsistent

with peaceful, declared uses of nuclear power. It

could also conduct literature searches and

demand more information from inspected

states.8 The IAEA might take a country-wide

approach—where might an undeclared facility

be, considering factors such as national abilities,

expertise, and topography, and how does one

find it?

The main safeguards focus will still be on

nuclear material, but the scope of verification

activities will be expanded considerably. Environmental monitoring will be a key part of this

approach. Environmental monitoring may serve

as a warning flag that other inspections are

needed. By itself, it is more likely to indicate

subtle inconsistencies, rather than gross discrepancies, if in fact undeclared activities are taking

place. It will also raise confidence where they are

not taking place. Thus it will be a sorting tool

used in combination with other conventional

8 Personal communication with IAEA staff, Mar. 31, 1995.
34 | Environmental Monitoring for Nuclear Safeguards

safeguards, not a replacement. For example, if a

country has reactors but no reprocessing facilities, the IAEA could use environmental monitoring to verify that no reprocessing is taking place.

With that assurance, the frequency of inspections

to verify that spent fuel has not been diverted

(now every three months) could be reduced,

since environmental monitoring can give a

timely warning.9

Such a reduction in inspections entails some

risk because a country might send its spent fuel

to another country for reprocessing without notifying the IAEA. Alternatively, it could construct

a clandestine reprocessing plant and not operate

it until ready to quickly construct nuclear weapons. Environmental monitoring would not detect

either of these avenues. However, both introduce

considerable uncertainty and the potential for

delay. Shipping spent fuel could be slow and

might itself be detected. The reprocessing country might not apply the same level of secrecy,

increasing the potential for detection, or might

not even return the plutonium. Unused reprocessing plants, even small ones, are likely to require a

significant shakedown period and are likely to

release detectable emissions before purifying

substantial amounts of plutonium. Therefore,

environmental monitoring can support a reduction of inspections if accompanied by political

analysis and broader information gathering.

❚ Planning

Further study will be required before environmental monitoring can be fully integrated into

the safeguards system. The major uncertainty is

over the ability to find undeclared sites. Finding

these will be very different than finding undeclared activity at declared sites. Potential proliferants will have greater incentive to build

undeclared, covert facilities if they judge that

weapon activities co-located with safeguarded

facilities will be detected. More field trials are

9 Personal communication with IAEA staff, Apr. 4, 1995.

likely to be necessary to develop and test the

means to find undeclared sites, especially reprocessing and enrichment plants. By definition, this

means long-range monitoring, especially of rivers, which were not intensively examined in the

earlier field trials.

The IAEA and several member states, including Canada and several Scandinavian countries,

already are discussing field trials specifically

designed to detect such activities.10 Tests in

weapon states would be particularly useful,

but—given the power of environmental monitoring—they would have to be carefully

designed to avoid compromising national security. The United Kingdom might be a possibility.11

A detailed plan for implementing environmental monitoring will be needed. An outline was

prepared for the June IAEA Board of Governors

meeting, but the full plan will not be ready

before 1996. The full plan should cover topics

such as facilities that will be subjected to environmental monitoring, the level of effort of

inspectors at each kind of site, the training and

equipment they will need, the labs to which their

samples will be sent and the type of analysis to

be done, procedures for quality assurance, how

current safeguards will be modified, and the

cooperation that may be needed with the host

state. This plan will need considerable input from

IAEA operations personnel and review and

acceptance by member nations.

In addition to the general plan, specific plans

will be needed for each site. Sampling must be

done on the basis of the known operations at the

site and expected signatures, possible undeclared

activities, and the specific site characteristics

such as topography and environmental conditions. The IAEA is documenting signatures from

all relevant activities (see chapter 2). A current

project at the Pacific Northwest Laboratory is

developing a computer program, the EM

10 Briefing by IAEA staff, Mar. 31, 1995. 11 Personal communication with IAEA staff, Apr. 4, 1995.
Chapter 4 Status and Plans for Implementation | 35

Assessment Tool, which helps the user to plan

inspections based on site and operational characteristics, and on safeguards needs and capabilities. This tool could be quite useful for wide area

monitoring.

Initially, the plan will have to focus on sampling at declared sites. It will be very expensive

if every safeguarded site has to be exhaustively

sampled and analyzed. Nevertheless, the IAEA

has to be sensitive to member concerns about

being unfairly singled out for closer examination.

Perhaps a list of critical facilities can be selected

initially, with the number (e.g., 50) large enough

to avoid charges of discrimination but small

enough to be manageable. Baselines for these

facilities could then be established.12 Baselines

will be especially important at research complexes that have a variety of activities that could

produce emissions similar to weapons production. (Such places would be logical sites for

covert nuclear facilities if remote siting is not

possible.) Future samples can then be compared

with the baseline to see if any new activities have

been introduced.13

❚ Data interpretation

Interpreting the information that is developed

will be a particularly important function that will

also be especially difficult to implement. If a

confrontation with an inspected state ensues, it

must be based on very strong evidence with virtually no chance of error. The IAEA must spend

considerable effort on this area. Confidence is

hard to quantify, especially since environmental

monitoring is so different philosophically from

current safeguards. The United States is providing assistance in this critical area.14 Russia and

the United Kingdom also could provide useful

help. However, much of the equivalent work

done by member nations is classified and will be

difficult to share.

12 Briefing by IAEA staff, Mar. 31, 1995. 13 Anthony Fainberg, Strengthening IAEA Safeguards: Lessons from Iraq, Center for International Security and Arms Control, Stanford

University, April 1993. 14 Personal communication with IAEA staff, Apr. 4, 1995.

❚ Costs

Adding environmental monitoring to the IAEA’s

activities should not greatly affect its budget.15

Over the past nine years, the Safeguards Division

budget has been under a zero growth restriction

(actually it has been slightly negative when corrected for inflation). Additional costs for inspection and analysis will have to be largely balanced

by reductions in other activities, such as material

accountancy, and by learning to do more with

less. As noted above, the frequency of some

inspections may be reduced because of environmental monitoring. The United States paid for

most of the field trial laboratory analysis, but the

IAEA will have to cover these costs when the

activities become routine. U.S. assistance has

also included cost-free experts, who are individuals whose services are provided free of charge to

the IAEA, but both the United States and the

IAEA have limits on how many such experts can

be supported. Safeguards in general, and environmental monitoring in particular, cannot be

seen as a U.S. operation. Other nations must also

be involved both financially and technologically

for the IAEA to maintain its credibility. Fortunately, the level and breadth of support from

other members has been quite good.

CONCERNS OVER ENVIRONMENTAL 

MONITORING

The IAEA will have to deal with several concerns on the part of inspected nations. Environmental monitoring is predicated on finding

radionuclides released from nuclear facilities to

the local environment. Many people are worried

about exposure to any radioactive materials.

Even though the level of radiation sought by

environmental monitoring is far below any that

might cause health problems, some people may

become concerned that any radioactivity is being

15 Personal communication with IAEA staff, Mar. 31, 1995.
36 | Environmental Monitoring for Nuclear Safeguards

found. Public opposition could increase just by

the knowledge that inspectors are looking for

such radioactivity. Release of information on the

material found could increase opposition even

more, no matter what the levels are. Plutonium is

particularly worrisome, as many people are

unaware of how ubiquitous it is. Regulatory

problems also are possible if radioactive materials are found.

Some states will have to make significant

adjustments to accommodate environmental

monitoring. Where operators have downplayed

the emissions of plutonium and other radionuclides, new approaches to explaining the results

will be needed, especially if standards have actually been exceeded. A compensating factor is

that environmental monitoring may be quite useful for the state to achieve its own health and

safety goals. Overall, most nations should be

able to accept environmental monitoring, though

they may want to place some conditions on it,

such as the release of information.

A second concern is over competitiveness.

Emissions can contain information on the process used in an enrichment or fuel fabrication

plant. If this information falls in the hands of

competitors, it could be damaging. The IAEA

employs nationals of many different states, and it

is not impossible that one would pass the

information to a company back home. This is a

more easily managed problem than public opposition. The IAEA already has access to plants

with competitive concerns and is able to maintain confidence. Strict confidentiality of the samples, as will be accomplished by repackaging at

the Siebersdorf facility, will help.

In addition, the advanced states may worry

about compromising their own national security

technology secrets. Some of the analytical techniques that are used for environmental monitoring were developed for national security

purposes, and these states may not wish them to

become more widely known.

CONCLUSIONS

Environmental monitoring will significantly

increase the effectiveness of IAEA safeguards,

especially for the detection of undeclared activities at declared sites. Implementation should be

relatively straightforward, though considerable

planning and consultation with all parties to the

activity will be necessary. As the IAEA becomes

more proficient, and improved technologies are

made available, capabilities should expand considerably. U.S. assistance will be essential in this

process.
| 37

5

Future

Technologies

esearch currently under way is developing new technologies that could

improve significantly the effectiveness

of environmental monitoring. This

chapter first discusses how monitoring effectiveness might be improved, next summarizes the

general directions of laboratory research, and

then describes some specific approaches.

STRATEGIC DIRECTIONS

One significant improvement expected in future

environmental monitoring is remote sensing, the

ability to collect information without physically

collecting samples. Remote sensing could be

valuable for rapid screening of many sites, especially if that must be done without the cooperation of the state. (Note that this is not an IAEA

function.) Two approaches are possible: aerial

and ground-based, remote surveillance. Spacecraft already have unrestricted overflight rights,

and flights for aircraft at altitudes above 10 kilometers could become acceptable under an Open

Skies Treaty.1 Sensors that operate at these

ranges could be used routinely to monitor areas

1 U.S. Congress, Office of Technology Assessment, Verification Technologies: Cooperative Aerial Surveillance in International Agreements, OTA-ISC-480 (Washington, DC: U.S. Government Printing Office, July 1991).

of concern without on-site inspection. The other

approach is for shorter-range technologies that

could sample a stack plume from a convenient

nearby ground location.

The schemes for remote environmental monitoring discussed here are optical in nature, using

ultraviolet or infrared light. There are active

schemes that supply the light they need, and passive schemes that use existing sunlight or thermal radiation. In either case, the monitoring

instrument views the area under investigation

and analyzes light received from it.

As discussed in the section Improving Technology, such techniques can identify airborne

molecules, but with only moderate accuracy and

specificity. They are much less sensitive to solid

material, and—in most cases—they cannot differentiate among isotopes of the same element.

However, they are naturally adapted to surveying

a large area for suspicious occurrences, and can

select and focus on a small spot within that area.

Another direction of significant improvement

will be instruments of greater sensitivity and/or

selectivity. This would allow future investigations to use smaller samples (possibly down to

R
38 | Environmental Monitoring for Nuclear Safeguards

single dust particles), process samples that are

more dilute, measure additional contaminants, or

provide higher-quality answers. The most dramatic improvement comes from combining two

different technologies so that the substance being

measured passes two independent selection

screens. Greater speed would allow the processing of more samples for greater statistical accuracy.

Portability is also desired. Some new technologies are intrinsically small-scale, and other

technologies are being miniaturized. An instrument that can be hand-carried at an inspection

site can provide immediate results to guide the

inspection strategy. At present, an instrument

weighing 61 pounds can be called portable;2

standards will change with further miniaturization.

Features of remote sensing and portability

could be combined by mounting instruments on

an aircraft and flying it to the inspection site.

There it can fly through an exhaust plume, collect samples, and analyze them immediately.

IMPROVING TECHNOLOGY

Two kinds of technologies are under development for environmental monitoring to detect a

clandestine weapon program. One kind looks for

suspicious isotopes, such as uranium-235 or

technetium-99 (as does most current technology

as discussed in chapter 3). The other kind looks

for suspicious molecules, such as HF (hydrogen

fluoride) or TBP (tributyl phosphate). (See the

end of this chapter for another possibility: looking for waste heat from a concealed nuclear reactor.)

❚ Identifying Molecules

The chemist has many analytical tools to identify

molecules of interest: infrared spectroscopy,

2 Brian Andresen et al., “A Small, Portable Gas Chromatograph-Quadrupole Mass Spectrometer for On-Site Analysis,” Lawrence Livermore National Laboratory, UCRL-ID-116939, April 1994.

mass spectrometry, chromatography, and benchtop chemical analysis. Finding specific molecules in the environment is useful for many

missions, from detecting a chemical weapon program to measuring pollution; new technologies

may be truly dual-use, with application both to

national security and to civilian needs. On the

other hand, a specific molecule may have many

legitimate sources, and its presence only indicates an anomaly worth further investigation;

also, some signature molecules will not be found

in the environment for reasons such as low vapor

pressure or because they react with atmospheric

gases to form other species.

Infrared Spectroscopy

Infrared “fingerprints” observed by infrared or

Raman spectroscopy (box 5-1) can be used to

identify particular molecular species. Chemists

usually record the entire fingerprint spectrum

using a laboratory infrared source, and laser

Raman spectroscopy3

 naturally gives the entire

spectrum. Another technique under development

that will cover a broad spectral region is a passive airborne infrared spectrometer.4 Alternatively, it may be possible to look at individual

spectral features using DIAL (differential

absorption LIDAR), in which a laser alternates

between the frequency of a characteristic molecular absorption line and a different nearby frequency, and the receiver looks for a

corresponding change in return signal due to the

presence of the absorbing molecule.5

Infrared or Raman spectroscopy is able to

detect molecules as vapor in air, and in solution.6

For the lighter elements (hydrogen to oxygen),

different isotopes of the same element are distinguishable because their vibration frequencies,

which depend on mass, can be differentiated. It is

less suited for analyzing solid material, or for

3 Briefing by C. Chen, Brookhaven National Laboratory, Jan. 10, 1995.

4 Briefing by A. J. Ramponi, Lawrence Livermore National Laboratory, Mar. 1, 1995.

5 Briefing by Lyn Pleasance, Lawrence Livermore National Laboratory, Mar. 1, 1995.

6 Briefing by C. Chen, Brookhaven National Laboratory, Jan. 10, 1995.
Chapter 5 Future Technologies | 39

distinguishing among isotopes of heavy elements, for which the relative changes in vibration

frequency due to mass differences are much

smaller.

In a mixture of many different molecular species the fingerprints are likely to overlap, obscuring some of the lines and complicating

identification. Also, large and interesting molecules tend to have poorly defined spectral features with broader absorption lines than smaller

simple molecules. As a result, infrared or Raman

spectroscopy can be expected to identify and

characterize simple molecules but may not be

very sensitive to the large complex molecules

important to environmental monitoring. Remote

sensing by infrared spectroscopy does offer the

possibility of rapidly screening large areas to

locate any regions of suspicious activity.

Mass Spectrometry

Chemists use mass spectrometry to identify molecules based on their masses, and are therefore

concerned with measuring a wide range of

masses. The heaviest atoms weigh about 250

atomic mass units (amu—approximately equivalent to the mass of a hydrogen atom). Interesting

organic molecules range up to 10 times this

value, and biological molecules can reach several

hundred thousand amu. Molecules are broken up

by the ionization necessary for mass spectrometry. Thus a single molecular species can give rise

to a spectrum of different fragment masses,

which define the mass spectral fingerprint for

that molecule.

Conventional mass spectrometers (see chapter

3) separate and identify atoms or molecules

according to their response to magnetic forces.

Ionized molecules are accelerated electrically

and follow a narrow path through a magnet,

which bends their trajectories: the larger the

mass, the smaller the deflection angle. These systems need relatively large samples because the

ionizer and molecular throughput are not very

efficient.

Improvements in magnetic spectrometer efficiency are discussed below in connection with

identifying particular nuclei. In addition, more

BOX 5-1: Infrared Spectroscopy

Different colors of light are waves with different oscillation frequency and correspondingly different

wavelength (which is the speed of light divided by the frequency). The characteristic vibration frequencies of molecules are in the infrared (IR) spectrum; the much higher frequencies to which atoms respond

are in the ultraviolet (UV). Visible light occupies the intermediate region between UV and IR, to which

many substances do not respond. These substances are therefore transparent.

Light frequencies are so large that the numbers are hardly meaningful. For example, water vapor

makes air essentially opaque to a broad band of infrared radiation near a wavelength of 6.2 micrometers.

This corresponds to a frequency of 5 × 1013 Hertz (cycles per second). It is more usual to specify this frequency as 1600 waves per cm, or a wave number of 1600 cm-1.

Most molecular species have a number of infrared absorption lines, or characteristic frequencies that

they absorb strongly. The spectrum of light that has passed through air containing these molecules will

show narrow dark bands (spectral lines) due to that absorption. The pattern of lines forms a “fingerprint”

that identifies that molecular species.

Raman spectroscopy is another way to measure a molecule’s infrared fingerprint. Here light of high

frequency (visible or UV) interacts with the molecule, and re-emitted (scattered) light is analyzed. Due to

the Raman effect, some of the scattered light will be shifted in frequency by an amount equal to a characteristic frequency of the molecule. With a single-frequency laser source, the returning light will display a

spectrum with bright lines corresponding to molecular frequencies—also a fingerprint.

SOURCE: Office of Technology Assessment, 1995.
40 | Environmental Monitoring for Nuclear Safeguards

sensitive technologies using electric forces have

been demonstrated. Ion trap7 and time-of-flight8

mass spectrometers do not need a narrow path,

and the latter can measure molecules of biological size. These technologies can be combined

with laser ionization, which causes less damage

to molecules and further increases the efficiency,

compared to other types of ionization.

Future mass spectrometers will have greatly

improved sensitivity, making this already useful

technique much more useful.

Other Tools

Molecules can also be identified by their chemical properties. Liquid and gas chromatography

are techniques where the sample is mixed with a

carrier that flows through a column to separate

mixtures of chemicals; different substances are

carried through the column at different rates,

depending on how they interact with the surface

coating of the column. Thus chromatography

separates the sample into fractions that come out

of the system at different times. The molecule of

interest comes out at a time established by previous tests, and that fraction can be analyzed further. Electrophoresis is a similar technique,

where substances are mobilized by an electric

current instead of a flow of material across a surface.

These analysis techniques are considered

destructive in that they use up the sample, precluding further tests. However, it is possible to

construct a surface which selectively attracts

some molecules and holds onto them without

destroying them. A micromechanical surfaceacoustic-wave sensor9 can compare the density

of molecules held by different surfaces, providing still another “fingerprint” that can be used to

identify the molecular species (see Specific

Approaches).

Tools that use chemical interactions require

the development of a “cookbook” of recipes,

7 Briefing by Aaron Garrett, Los Alamos National Laboratory, Feb. 27, 1995.

8 Briefing by Charles Wilkerson, Los Alamos National Laboratory, Feb. 27, 1995.

9 Briefing by Tony Ricco, Sandia National Laboratories, Feb. 28, 1995.

specifying reactants and procedures, before they

can be used in practice. Chromatography is an

established technique that is already in use for

environmental monitoring.

❚ Identifying Isotopes

The nuclear scientist also has a number of tools

with which to find nuclides of specific interest.

Most of the key nuclides are radioactive, and the

radiations they emit can be detected and analyzed (see chapter 3). Mass spectroscopy can

determine the relative abundance of different isotopes. Other techniques involve inducing the

atoms to emit characteristic radiations. Activation analysis (neutron bombardment resulting in

new radioactive isotopes due to transmutation or

fission) was covered in chapter 3. There are also

optical resonance (scattering of characteristic

light frequencies) and induced radiation (emission of characteristic x-rays or gamma rays).

These tools are more specific than those used

to identify molecules, and the nuclei they detect

are much less ambiguous indicators of a clandestine weapons program. The tools are also less

suitable for dual-use. However, some of them

have been applied to studying the fossil record of

the earth's history by measuring elemental and

isotopic abundance ratios, yielding information

on various geological and meteorological processes.

Measuring Radioactivity

Counting atomic disintegrations is a mature discipline (see chapter 3), and this chapter is concerned only with advanced state-of-the-art means

of doing so. Radioactivity provides a highly sensitive means of detecting atoms or molecules that

have previously been selected and concentrated.

Its application to capillary electrophoresis and

tritium measurement will be mentioned later (see

Specific Approaches).
Chapter 5 Future Technologies | 41

Mass Spectrometry

As already mentioned, the weak point of conventional mass spectrometers is collection efficiency. An instrument with greatly improved

efficiency has been developed by combining

state-of-the-art technology in isotope separation

and ion optics.10 It has a better ionizer and a

broader beam path.

Optical Resonance

Individual atoms can respond strongly to light

that is tuned to an atomic transition frequency.

For example, extremely small quantities of

sodium can be measured by resonant excitation

and re-emission of yellow light at 589 nanometers wavelength. This method is very selective

for atomic species (nuclear charge); combining it

with mass spectrometry to select for nuclear

mass provides an absolutely unambiguous identification of a particular isotope. Unfortunately,

the strongest responses come from the alkali

metals (sodium, potassium, rubidium, and

cesium), and the application of this technique to

other elements is not obvious.

Induced Radiation

When a solid sample is bombarded by a particle

beam (of electrons or ions), or by gamma rays,

the atoms and nuclei in it can be stimulated to

emit radiations. All except the lightest atoms will

produce x-rays characteristic of the atomic species. X-ray tubes use electron bombardment; use

of ions or low-energy gamma rays to irradiate

samples can give a cleaner signal. In addition,

ion bombardment of many of the heavier nuclei

causes Coulomb excitation, in which the nucleus

is stimulated to rotate and to emit gamma rays

characteristic of the nuclear species. These methods are sensitive and selective for most nuclei of

interest, and will be applied more often in future

instruments.

10 Briefing by Jane Poths, Los Alamos Scientific Laboratory, Feb. 27, 1995.

SPECIFIC APPROACHES

❚ Laser Remote Sensing

The U.S. Department of Energy (DOE) has a

program called CALIOPE (Chemical Analysis

by Laser Interrogation of Proliferation Effluents). This is a collaborative effort involving five

national labs, which are pursuing various ideas

for laser remote sensing. It is intended to culminate with an airborne field demonstration of the

most promising ideas. Current research efforts

include:

■ Enhanced UV Raman Spectroscopy: A

characteristic of the Raman effect is that the

return signal is weak. Using ultraviolet instead

of visible light can increase the signal by a factor of 1000, and changing (modulating) the

laser output and looking for changes in the

return can result in suppressing the noise by a

similar factor.11 Ultraviolet light does not

travel well through the atmosphere, limiting

this technique to distances less than 1 kilometer. Its best application may be on-site characterization (of stack plumes, for example)

instead of airborne use.

■ MWIR (Mid-Wave Infrared) DIAL (Differential Absorption LIDAR): Recent

advances in tunable infrared laser technology

have made it possible to probe the spectral fingerprint lines of many molecules with a single

instrument covering the spectral range from

2.5 to 4.5 micrometers.12 This instrument

could be used at airborne ranges of many kilometers.

Early tests are encouraging, but much development work remains before any of these concepts could be used routinely in the field. The

ultimate sensitivity and specificity of these technologies are still to be determined; it is not easy

to detect the fingerprints of molecules in trace

concentrations, and most molecules, even if

detected, are uncertain indicators of clandestine

activity.

11 Briefing by C. Chen, Brookhaven National Laboratory, Jan. 10, 1995. 12 Briefing by Lyn Pleasance, Lawrence Livermore National Laboratory, Mar. 1, 1995.
42 | Environmental Monitoring for Nuclear Safeguards

❚ Airborne Measurements

The Department of Energy also has a program

called AMPS (Airborne Multisensor Pod System). Three different sensor pods have been built

and are being tested on a P-3A aircraft:13

1. Synthetic aperture radar;

2. Optical imaging sensors

3. Effluent species identification.

While all three pods are intended to gather

information on clandestine activity, only pod 3

will demonstrate technologies for environmental

sampling and analysis. Three instruments will

sample the air through which the plane flies

(which can include an exhaust plume of a suspected facility), with high sensitivity due to the

large volume of air sampled, and two additional

instruments will view the area within several

kilometers of the plane:

■ Real-time radionuclide analyzer: Collects

particles and some vapors on filter cartridges

and promptly records their high-resolution

gamma-ray spectra. With a cycle time of 1

minute, it can detect short-lived radionuclides

with a sensitivity that can reach 5000 atoms

per cubic meter of air (for substances with a 4-

hour half-life).

■ Ion trap mass spectrometer: Collects chemical vapors and analyzes them, with a sensitivity that can reach parts per trillion.

■ Whole air sampler: Collects air components

for later analysis.

■ Echelle grating spectrometer: Analyzes sunlight reflected off the ground to determine the

molecular absorption in an exhaust plume.14 It

covers a wide spectral range, from 2.0 to 4.2

micrometers, records continuously over the

entire range with very high spectral resolution,

and is sensitive to parts per million in a 1-

meter-wide plume.

13 Briefing by Bruce Roberts, Pacific Northwest Laboratory, Mar. 3, 1995. 14 Briefing by A. J. Ramponi, Lawrence Livermore National Laboratory, Mar. 1, 1995.

■ IR tracking system: Correlates an IR signature with the other sensor data.

This program will reduce to practice several

technologies already available in the laboratory.

A pod carrying multiple instruments is an excellent way to collect airborne data. Experience will

tell whether the instruments chosen are the right

ones—for example, whether the molecule detectors (ion trap and echelle grating) see any useful

signals.

❚ Chemical Identification

Several different advanced ideas for identifying

molecules are being developed and improved.

They include:

■ Ion trap mass spectrometry: Catches ionized

atoms or molecules in an electrostatic trap

where they can be held and measured precisely. Sensitive to parts per billion or less (see

above).15

■ Time-of-flight mass spectrometry

(TOFMS): Electrically accelerates molecules

and measures how rapidly they move, with

heavier molecules moving more slowly than

lighter ones for a given accelerating voltage.

TOFMS can measure the weight of molecules

up to several hundred thousand amu in mass.16

■ Microsensor arrays: A micromechanical surface-acoustic-wave sensor is built with a

coated chemical reagent that selectively

attracts some molecules and holds onto them

without destroying them. Since the propagation of sound waves along the surface depends

on the density of adsorbed molecules, such a

sensor can measure the concentration of the

substance that binds to it. An array of these

with different chemical surfaces will show different densities of attracted molecules, and

15 Briefing by Aaron Garrett, Los Alamos National Laboratory, Feb. 27, 1995. 16 Briefing by Charles Wilkerson, Los Alamos National Laboratory, Feb. 27, 1995.
Chapter 5 Future Technologies | 43

thus offers some hope of identifying the

molecular species.17

The two electrostatic mass spectrometers have

been demonstrated in the laboratory, and they

offer significant performance benefits. They also

may offer easier portability, because they do not

contain magnets. The microsensor array is in the

research stage; it seems better suited for monitoring changes in abundant molecules (that is, process control) than for identifying rare ones.

❚ Nuclear Mass Spectrometry

Various improvements to ordinary magnetic

mass spectrometry (chapter 3) are under development. They include:

■ Laser ablation source: Laser light is focused

on a single dust particle or a small region,

vaporizing only the selected material for input

to the mass spectrometer.18

■ Improved design: A mass spectrometer several thousand times more efficient and more

sensitive was constructed using modern

advances in isotope separator and ion optics

technology. It can measure the isotopic composition of atmospheric Kr and Xe from 10-cc

air samples, and it can do so accurately enough

not only to detect reactor emissions (natural

and fission-product Kr and Xe have different

isotopic ratios), but to distinguish between

uranium and plutonium reactor sources.19

■ Accelerator mass spectrometry: This

extremely sensitive technique (chapter 3) is

being extended to a large part of the periodic

table.20

■ Projectile x-ray detection: The accelerator

mass spectrometer can be modified to select

for atomic species as well as nuclear mass, by

observing the x-rays that result when the

selected atoms hit a target at the end of the

17 Briefing by Tony Ricco, Sandia National Laboratories, Feb. 28, 1995. 18 Briefing by Brian Andresen, Lawrence Livermore Laboratory, Mar. 1, 1995. 19 Briefing by Jane Poths, Los Alamos National Laboratory, Feb. 27, 1995. 20 Briefing by Ivan Proctor, Lawrence Livermore Laboratory, Mar. 1, 1995.

machine. The result is an unambiguous identification of the nuclide.21 (Ordinary mass spectrometers do not produce x-rays because the

atoms have too low a speed.)

Mass spectrometer designs of the future will

draw on these technologies, as well as electrostatic mass spectrometer (see above) and optical

detection (see below) technologies, to produce

the best instrument for each application. Greater

sensitivity and selectivity is the major benefit.

❚ Optical Resonance Spectrometry

Different isotopes of the same atomic species

absorb and scatter light at slightly different characteristic frequencies. With extremely precise

frequency control, a laser can be tuned to interact

selectively with one isotope and detect it. Practical applications include:

■ Photon burst detection: The atoms pass

through a series of detectors while being illuminated with light at the desired isotope’s

characteristic frequency. The correct isotope

will scatter light into each detector as it passes

by. The wrong isotope may occasionally scatter light, but will not trigger all of the detectors. This method has demonstrated the ability

to detect a rare isotope at a dilution of 10 parts

per billion in ordinary krypton, and the current

goal is 10 parts per trillion (the natural abundance of radioactive krypton-85). The method

may apply to 40 or 50 atomic species, including many important fission products.22

■ Optical trap detection: The atoms are caught

and held in a magneto-optical trap, due to the

combined effects of resonance light and a

magnetic field. Their presence is measured by

21 Ibid. 22 Briefing by H. Oona et al., Los Alamos National Laboratory, Feb. 27, 1995.
44 | Environmental Monitoring for Nuclear Safeguards

the intensity of scattered light. This technique

may be limited to the alkali metals.23

In the laboratory, both of these methods have

been applied to atoms coming out of a mass

spectrometer, with the promise of much greater

sensitivity and selectivity.

❚ Nuclear Identification

Several miscellaneous ideas for identifying

nuclei are being researched. These include:

■ Capillary electrophoresis: A small instrument that analyzes nanoliter quantities of liquid in minutes; it has been used to separate

fission products. In this application, a counter

detects the radioactivity of different fractions;

other detection schemes are possible. The system offers small size and speed; may be more

adapted to process control than to trace element detection.24

■ Particle-induced x-rays: Bombards a filter or

swipe containing particles of interest with ions

from a high-voltage accelerator. The system

can locate a particle and then focus on it. The

resulting x-rays and gamma-rays give a nondestructive simultaneous measurement of all

atomic species from sodium to the high end of

the periodic table, and can also provide some

indication of isotope ratios in heavy nuclei.25

Relatively costly.

■ Laser ionization mass spectrometry of

iodine-129: Improves the efficiency of a mass

spectrometer to detect I129 by a factor of 1,000

over conventional techniques, by using a laser

to selectively ionize the iodine atoms.26 A special-purpose tool.

■ Automated hydrogen isotope system: Automated system to extract tritium from air and

count it. One measurement every three hours,

23 Briefing by Dave Vieira, Los Alamos National Laboratory, Feb. 27, 1995. 24 Briefing by Brian Andresen, Lawrence Livermore Laboratory, Mar. 1, 1995. 25 Briefing by Arlyn Antolak, Sandia National Laboratories, Feb. 28, 1995. 26 Briefing by Bret Cannon, Pacific Northwest Laboratory, Mar. 3, 1995.

expected to be sensitive to tritium at background levels (the abundance at which it is

found in the absence of a local source: two disintegrations per minute per cubic meter of

air).27 Not yet built.

In addition to technology development, new

methods of data analysis are being pursued.

“Nuclear Archeology” analyzes the isotopic

ratios of impurities which have been irradiated in

reactor components. Given a sample of graphite

moderator taken from a nuclear reactor (i.e., a

research reactor or a gas-cooled power reactor),

the method measures the isotopic ratios of impurities such as barium and titanium. This determines how many neutrons were generated over

the reactor’s lifetime, and therefore its power history. Discrepancies with reported use can indicate that the reactor was used for undeclared

purposes, possibly including the production of

plutonium.28 This is a new application of relatively conventional technology.

❚ Thermal Imaging

DOE is also building an experimental satellite

that will view the earth in 15 different spectral

bands covering the visible and infrared.29 It will

measure local ground and water temperatures to

an absolute accuracy of 1 degree K (Kelvin).

This should be sufficient to detect the waste heat

from a clandestine plutonium production reactor.

For example, the flow of cooling water from

such a reactor into a river or lake has been modeled and would appear as an easily detected

plume of higher water temperature. This is a

demonstration program, not a monitoring program, and the satellite is expected to operate for

only one to three years.

27 Briefing by Paul Reeder, Pacific Northwest Laboratory, Mar. 3, 1995. 28 Briefing by Bruce Reid, Pacific Northwest Laboratory, Mar. 3, 1995. 29 Personal communication with Bob Courtney, Sandia National Laboratories, Apr. 6, 1995.