SPACE APPLICATIONS OF

 RADIOACTIVE MATERIALS

 Prepared for:

 Office of Commercial Space Transportation

 Licensing Programs Division

 Prepared by:

 SRS Technologies

 Huntsville, AL 35806

 June 1990
INTRODUCTION

 There are a variety of space applications for

radioactive materials, both on spacecraft and on

launch vehicles. These applications range from

power generation to the use of radioactive sources

for radiation measurement references, instrument

calibration, irradiation experiments, electronic

circuit components, or for structural purposes,

usually as ballast. The key characteristics of safety interest

which differentiate these applications are the types and amounts of

radioactive source material they use and the levels of radiation

involved. 

 These materials emit ionizing radiation (as by-products of the

process of radioactive decay) of different types and at different

rates, according to the type, amount, and usage of the source.

This radiation may, therefore, be relatively benign, or may pose a

potential health hazard, or may be capable of damaging or affecting

the operation of some types of equipment. In the extreme, and in

sufficient quantities, certain of these materials can sustain the

critical or even super-critical reactions which result in meltdown

or detonation.

 Applicants for a license to conduct commercial launch activities

involving radioactive materials (radionuclides) must comply with

regulatory requirements concerning their use. As the regulatory

agency assigned the overall responsibility for ensuring public

safety from hazards associated with U.S. commercial space launch

activities, OCST must oversee that compliance. Licensees using

Federal ranges will have to comply with established Range Safety

procedures related to both regulatory and safety requirements. If

such a launch is to be conducted from a commercial facility, OCST

will have to provide more detailed oversight.

 As an aid to assessing and preparing for that oversight role,

this document addresses:

A Technical and Terminology Review

Typical Applications Relevant to Space or Space Launches

Classifications of Radioactive Sources

Agencies Involved in the Nuclear Safety Process

Public Concerns and Issues Raised Regarding Past Launches

of Payloads Using Radioactive Materials

Key Safety Issues, as Perceived by the National Ranges

1
TECHNICAL AND TERMINOLOGY REVIEW

 The following is a brief review of the physical mechanisms and

technical terminology associated with the subject, with which the

reader may not have maintained currency. While not a detailed

primer on nuclear physics, it is intended to address the subject in

sufficient depth to convey an understanding of the implications of

nuclear materials use in commercial space vehicles.

Atomic Number: the number of protons in the nucleus of an atom of

a given chemical element (as listed on the Periodic Chart);

its value establishes the basic characteristics of an element.

Atomic Weight: roughly, the total number of protons and neutrons

(which are of equal mass) in an element's nucleus;

Isotope: one of several forms of an element, having the same atomic

number but slightly different atomic weights; 

Nuclear Reaction: a reaction that alters the energy, composition,

or structure of an atomic nucleus;

Nuclide: an atomic nucleus specified by atomic number, atomic mass,

and energy state; "Radionuclides" are radioactive nuclides;

Figure 1. Relative Penetration

Capability

Nuclear Disintegration: natural

or induced transformation of

atomic nuclei from a more to a

less mas-sive configuration,

releasing one or more Ionizing

Radiation type: alpha (α) or

beta (β) particles and in some

cases, gamma (γ) rays. α

particles are positively charged

helium nuclei, while β are highspeed electrons or positrons; a

stream of either type may also

be called a ray. γ rays are

electro-magnetic radiation of

very short wavelength. Of the

three types, γ rays pose the

most severe hazard, followed by

β and α, respectively. The

relative penetrating power of

each type is shown in Figure 1.

Ionizing Radiation: radiation which can produce ions (atoms/groups

of atoms with a net negative or positive charge due to gain or loss

of an electron) in electrically neutral target material;

Radioactivity: emission and propagation of rays or particles from

unstable atomic nuclei (see Radioactive Decay) or as a result of a

nuclear reaction; inert materials may become radioactive when

exposed to this ionizing radiation.

2
Radioactive Decay: decrease in the radiation intensity of a radioactive material over time, generally accompanied by emission

α or β particles and/or γ radiation;

Radiotoxicity: poisoning effects of exposure to radioactivity; the

direct effects on humans, called Radiation Sickness, vary with

the intensity and duration of the exposure. They may progress

from fatigue, nausea, vomiting, headache, and diarrhea shortly

after exposure, to loss of hair and teeth, reduction in both

red and white blood cell count, inability to resist infection,

hemorrhaging, prostration, sterility, and death. The secondary

effects of exposure include increased occurrence of cancer.

The early clinical effects of acute radiation doses, i.e.,

received within a period of about one day, over the whole body

(as they might be in an accident or the explosion of a nuclear

weapon) are summarized in Figure 2. Because the effects from

a given dose of radiation vary according to the individual and

the circumstances, the figure shows five dosage ranges where

the effects are somewhat similar. For doses up to about 1,000

rads, the blood-forming system is most affected by radiation;

for larger doses, first the gastrointestinal tract and then

the central nervous system suffer major damage.1

ACUTE DOSE

IN RADS PROBABLE CLINICAL EFFECT

 0 to 25 No observable effects.

 25 to 100 Slight blood changes; no other observable effect 

 100 to 200 Vomiting in 5 to 50% within 3 hours; fatigue and 

 appetite loss. Moderate blood changes, but

 otherwise recover within a few weeks.

 200 to 600 Vomiting, etc. in 50 to 100% within 3 hours. For 

 doses over 300, effects in 100% within 2 hours.

 Hair loss after 2 weeks. Severe blood changes,

 hemorrhaging, infection; death in 0 to 80% with- 

 in 2 months. Survivors recover in from 1 month

 to a year.

600 to 1,000 Vomiting within 1 hour. Severe blood changes,

 hemorrhaging, infection, and loss of hair.

 Death of 80 to 100% within 2 months; survivors

 convalescent over a long period.

 Figure 2: Early Effects of Acute Whole-Body Radiation Doses

Rad: a unit of absorbed radiation equal to 100 ergs/gram (see Rep);

Radioactive Isotope or Radioisotope: an unstable isotope, produced

either naturally or artificially, which is subject to decay by

nuclear disintegration, thereby releasing ionizing radiation

(particles, rays) and/or energy in the form of heat;

3
Fission: the splitting of atomic nuclei, usually into two fragments

of comparable mass, releasing heat energy and neutrons. It is

commonly induced by the impact of slow neutrons, themselves

released by fission. Fission produces additional highly

active radioisotopes, and if uncontrolled, may reach a supercritical level, leading to a meltdown or nuclear explosion.

Controlled Fission: a self-sustaining chain reaction controlled at

some desired level, as to generate heat in a nuclear reactor.

The packaging of a reactor incorporates means to both moderate

(slow the speed) and control (limit or regulate their numbers)

the neutrons released.

Critical Mass: the minimum mass of a given fissionable material

needed to achieve a self-sustaining chain reaction;

Units of Measure

 Several measures are used to express the quantity of radioactive

material (by its mass or weight, usually in metric units) and/or

the amount of radiation emanating from it (by the number of nuclear

disintegrations per unit time which will yield ionizing radiation):

Curie: that quantity of a radioactive material which will undergo

3.7 x 1010 disintegrations per second. Since this is a very

high level of activity, either Millicurie (1/1,000 curie) or

Microcurie (1/1,000,000 curie) are more often encountered.

Half-life: the time required for the number of radioactive atoms

of an isotope (in a sample) to decay to one-half that number.

Each radioisotope has a characteristic, exponential rate of

decay, and thus a unique half-life (ranging from milliseconds

to many thousands of years for different radioisotopes) which

must be considered in safety requirements, especially those

for long-term storage. The radioactive decay process produces

a radioactive series of isotopes, successively lower in atomic

weight, the last or "lightest" of which will be stable.

Specific Activity: the relative intensity of the radioactivity of

a source, expressed in curies per gram of the material. For a

pure radionuclide, specific activity is inversely proportional

to the product of the isotope's* half-life and mass number.

The benchmark material for this measurement is Radium (88Ra226);

its specific activity has been assigned the value of unity2,

as its calculated activity is close to 1.

 

* The specific activity may be calculated using the following

relationship:

 1.13 x 1013

 Specific Activity ≈ (curies/gram)

 T A

where T = half-life (years, minutes, seconds, etc.)

 and A = atomic mass

4
Roentgen: that quantity of ionizing radiation (X-rays or γ rays)

that will produce one electrostatic unit (esu or statcoulomb)

of charge in one cubic centimeter of dry air, at standard

temperature and pressure.

Rem (roentgen-equivalent-man): that quantity of radiation which,

when absorbed by a human, will produce the same effect as

absorption of one roentgen of high-voltage X-rays.

Rep (roentgen-equivalent-physical): measure of the number of ion

pairs produced, per unit volume of target material, per unit

time. In tissue, one rep is equivalent to the absorption of

93 ergs (energy) per gram of the target material.

SPACE APPLICATIONS OF RADIOACTIVE SOURCES

 Radioactive sources have a variety of uses in space, ranging from

power generation to instrumentation. The following are examples of

typical space applications:

 Reactor Power Systems use the heat energy from controlled fission

to drive some form of electric power generator. The U.S. flighttested a reactor in 19653, with the launch of the SNAP-10A (Systems

for Nuclear Auxiliary Power) device aboard an Atlas-Agena vehicle,

the only such launch to date, while the U.S.S.R. has launched over

twenty reactors. The SP-100 will be the first test unit under the

Multi-Megawatt Reactor program, a joint venture by DOE, DoD, and

NASA to develop large reactors for space use.

 A new reactor fueled with enriched Uranium-238 remains relatively

benign with respect to the production of thermal and ionizing radiation until the fission process is initiated. The requirements for

shielding are at their minimums, and the radiation protection and

heat dispersion measures will not see their design loads until the

vehicle has reached orbit and the reactor is activated. Radiation

from the fission process may begin to activate previously inert

materials in the structure of the reactor "device" (generally at

low levels), and possibly parts of the vehicle in which the device

is installed, as well. Given these characteristics, the on-orbit

activation is an effective safety measure. 

 Radioisotope Power Systems, which either use the heat released

during radioactive decay (e.g., of Plutonium-238) to generate electric power or convert it directly into electricity, have been used

frequently in the U.S. space program, and even more frequently in

that of the U.S.S.R. Radioisotope Thermoelectric Generators (RTG)

convert heat energy into electricity through thermocouples. The

Dynamic Isotope Power Source (DIPS) uses heat in a closed Rankine

or Brayton cycle to power a turbine-alternator, operating at higher

thermal efficiency than the RTG.

5
 Devices using radioactive decay, rather than fission, as their

heat source are active at full thermal output4 as soon as they are

fueled, and both thermal and radiation protective measures must be

in effect at the time of fueling. In four accidents or incidents

involving U.S. spacecraft carrying RTGs, all safety systems have

functioned as designed, and no unplanned releases resulted.

Figure 3. Applicability of Space

Electrical Power Systems

 Figure 3 illustrates domains,

with respect to required power

level and mission duration,

where each type of space power

source (including non-nuclear

sources) seems to best suit

requirements. Other factors

may influence the choice,

including cost and the need for

radiation shielding, with

possible weight penalties. For

a vehicle which has to traverse

the Van Allen radiation belt,

an environment not conducive to

the use of solar panels, or go

into deep space, where solar

energy flux is of insufficient

intensity to permit the use of

solar panels, the NPS may be

indicated. 

 The design advantages of the NPS include their compactness and

long service life. Selection of a particular type of NPS would be

based on the functional mission and both the magnitude and duration

of the power requirements; current conceptual designs consider both

thermocouples (as on an RTG) and heat cycles with a turbogenerator

as the means of converting heat to electricity.

 Environmental Heaters utilize the heat from radioactive decay

directly, rather than to produce electricity; they are not a type

of NPS, and may use either major or minor sources, according to the

application. The Light Weight Radioisotopic Heater Unit (LWRHU) is

used to provide heat to surrounding equipment on interplanetary

spacecraft. 

 Minor Radioactive Sources, used in applications other than power

generation, may involve quantities in the millicurie or microcurie

range. One such application is in electronic circuit components

such as tubes of a class referred to as "gas" or "gas-filled". This

type of tube is used in the "electronic trigger" portions of the

engine igniters or flight termination system (FTS) firing circuits

on launch vehicles, rather than in payloads. They employ "cold

cathode" gas diodes containing a very small amount of radioactive

material, used to establish and maintain an initial level of ionization of the gas in the tube.

6
 The Centaur Upper Stage, used with the General Dynamics Atlas

Booster, employs two "discharger electron tubes"; one in each of

the RL-10 engine ignition circuits. These tubes use a radioisotope

of krypton gas (36Kr85)

* for gas tube excitation. The FTS circuits

on the Exoatmospheric Re-entry Interceptor Subsystem (ERIS) vehicle

employ a radioisotope of nickel (28Ni63). The circuit design uses

the tubes more as pulse-shaping devices than for the characteristic

constant voltage/varying (high) current capabilities of gas diodes.

 Larger quantities of radioactive material may be used on space

vehicles and still qualify as minor sources. Depleted Uranium-238

(from which the U-235 normally present has been extracted) is often

used as ballast; its density is approximately 1.67 times that of

lead. Its radioactivity makes no contribution in this application,

but it must be treated as a minor source.

 Other uses for minor sources are varied, but most involve minute

quantities. Radiation measuring instruments frequently employ a

sample of known intensity for calibration purposes, or to provide

a reference level against which to compare the target radiation.

Minor sources may be used in scientific experiments where the

thrust is to compare phenomena observed on earth with comparable

observations made in the space environment. 

 As noted previously, the characteristics of safety interest which

differentiate power generation applications from other applications

are the amounts of radioactive material and the radiation levels

involved. Typically, a nuclear power system will contain a "major"

source consisting of material which is highly radiotoxic; while a

"minor" source for some other use may also be highly toxic, the

quantities are smaller, as explained below.

 

 

* General Dynamics Corporation, Application for Launch License

to the Office of Commercial Space Transportation

7
CLASSIFICATIONS OF RADIOACTIVE SOURCES

 Two schemes of classification are relevant to space-related

applications; the one used by the Nuclear Regulatory Commission

(NRC)*, as the basis of its regulatory framework, and that used by

the National Aeronautics and Space Council (NASC)** (and followed

by the Department of Defense) as the basis for determining safety

review and reporting requirements. The NRC regulations address

"Special Nuclear Material" (enriched Uranium or Plutonium used for

weapons or nuclear power) and "Byproduct Material" yielded or made

radioactive when special nuclear materials are produced or used.

 In 19705, the NASC adopted the International Atomic Energy Agency

(IAEA) "Classification of Radioisotopes"6. Radioactive materials

are grouped according to relative radiotoxicity, a function not

only of the activity of the material, but also of the severity and

characteristics of the biological effects from exposure to their

radiation. Each radioisotope is assigned to one of four Groups;

Group I is the most hazardous and Group IV the least. These Groups

are based on maximum permissible intake, primarily by way of

inhalation (note: this is a different measure from "acute dose").

 The NASC classified radioactive sources incorporating 20 or more

Ci of material in Radiotoxicity Group I or II, or 200 or more Ci in

Group III or IV, as "Major". Any launch of a major source requires

Presidential level (or equivalent) approval. These sources are

usually for nuclear power system applications. "Minor" sources are

those containing Group I through IV materials in smaller amounts

than those cited above. While they do not require Presidential

approval for launch, minor sources are subject to a set of safety

analysis and reporting requirements which are described later in

this report. Figure 4 shows where some typical space and non-space

applications fit into the NASC classifications.

 

 

* The Atomic Energy Commission (established by the Atomic

Energy Act of 1946, as amended by the Atomic Energy Act of 1954)

exercised extensive licensing and related regulatory functions.

The Energy Reorganization Act of 1974, 42 U.S.C. 5801 et seq.,

abolished the AEC, and established the Nuclear Regulatory

Commission (NRC) as an independent regulatory agency, under

Congressional oversight and functionally separate from the

Executive Branch of the Government.

 

** The National Aeronautics and Space Council was established

by the National Aeronautics and Space Act of 1958, the same Act

that established NASA. It was chaired by the Vice President of the

U.S., with the Secretaries of Defense and Transportation, the NASA

Administrator, and the Chairman of the AEC as members. The council

functioned to advise the President on matters pertaining to aeronautics and space activities conducted by U.S. departments and

agencies. The NASC was abolished by Reorganization Plan No. 1 of

1973, effective June 30, 1973.

8
CLASSES APPLICATIONS RADIOACTIVE MATERIALS

MAJOR SOURCES

 POWER REACTORS ENRICHED URANIUM-238

 RADIOISOTOPE THERMAL PLUTONIUM-238

 GENERATORS CURIUM-242

 STRONTIUM-90

 DEEP-SPACE HEATERS PLUTONIUM-238

MINOR SOURCES

RADIO- STATIC ELIMINATORS POLONIUM-210

TOXICITY

GROUP I BOMB DETECTORS CALIFORNIUM-250

 CALIBRATION SOURCES AMERICIUM-241

RADIO- TUMOR IMPLANTS RADON-222

TOXICITY ("GOLD SEEDS")

GROUP II

RADIO- ELECTRON TUBES KRYPTON-85

TOXICITY COBALT-60

GRP III

 SPARK GAP IRRADIATORS COBALT-60

 RADIATION THERAPY

 SELF-LUMINOUS INSTRUMENTS KRYPTON-85

 COUNTERWEIGHTS (BALLAST), NATURAL OR DEPLETED

 SHIELDING, PHOTOGRAPHIC URANIUM

 MATERIALS, FIRE DETECTORS

 SYNTHETIC PLASTIC RESINS SCANDIUM-46

RADIO- ELECTRON TUBES NICKEL-63

TOXICITY CESIUM-137

GROUP IV PROMETHIUM-147

 MICROWAVE RECEIVER TRITIUM

 PROTECTOR TUBES

 SELF-LUMINOUS INSTRUMENT TRITIUM

 AND WATCH DIALS, MARINE PROMETHIUM-147

 COMPASSES

 FLOW METERS CESIUM-137

FIGURE 4: Example Applications

9
AGENCIES INVOLVED IN THE NUCLEAR SAFETY PROCESS

NRC Licensing

 The NRC licenses and regulates civilian uses of nuclear energy.

NRC licenses are required authorization for a variety of activities

involving manufacture, production, transfer, receipt, acquisition,

and ownership of nuclear materials, including the construction and

operation of power utility nuclear reactors7. The NRC is charged

to protect both public health and safety and the environment, and

its decisions are subject to judicial review by the Federal courts.

 NRC does not regulate most Department of Energy (DOE) activities,

except for licensing of DOE high-level radioactive waste disposal

repositories. Special nuclear materials which are produced by DOE

for DoD or NASA are exempt from NRC licensing, based on national

defense interests. Nor does the NRC regulate DoD nuclear power

reactors, such as those used on U.S. Navy ships. 

 The NRC regulations are contained in CFR 10, Chapter I, Nuclear

Regulatory Commission (Parts 0-199). The primary regulations that

cover licensed activities are:

 10 CFR 30 - Rules of General Applicability to Domestic

Licensing of Byproduct Material

 10 CFR 40 - Domestic Licensing of Source Material

 10 CFR 70 - Domestic Licensing of Special Nuclear Material

 Typically, the party responsible for the minor source radioactive

material must apply to the NRC for a license (under 10 CFR 30) for

possession or use of the material. The application will specify

that the source materials will be used in a launch. As they relate

to the use of nuclear materials in space, the NRC also controls

minor sources and activated materials under the terms of general

licenses4. Each regulation cited above also lists certain

exemptions, based on the use, concentration, or quantity of the

radioactive material. For example, 10 CFR 30 exempts electron

tubes containing less than 30 microcuries each*.

 NRC guidelines require that re-entering radioactive materials be

recovered, if they can be (NRC does not expect or require recovery

if the materials impact in deep ocean areas.) Recovered materials

must be placed in appropriate containers for shipment to, and then

burial at, a licensed radioactive waste disposal facility.

 

 

* These tubes, however, must be provided by a licensed manufacturer. The intent of this requirement is to ensure that the

quantity limitation is met, rather than to assure safety. The

licensing process for manufacturers also addresses disposal

concerns. 

10
The Department of Energy (DOE)

 The Department of Energy develops major source nuclear systems

for weapons and DoD or NASA power sources. DOE is the authority

assuring the safety of these systems while under development, but

an NRC license is required prior to system operation by the using

agency. Major sources in space applications undergo extensive

review by the Interagency Nuclear Safety Review Panel, with DOE

participation, as described later in this report. 

NASC/OSTP Review Process

 As introduced earlier, NASC classified radioactive materials for

space use into major and minor sources. Major sources are subject

to an extensive review process involving the user agency or organization, an Interagency Nuclear Safety Review Panel, and the launch

range. NASC defined three Nuclear Safety Review Categories ("A",

"B", and "C") of minor source analysis and reporting requirements,

and set upper limits for the amounts of material from each Group

which would require each Category of safety review, reporting, and

approval for launch. These Categories are shown in Figure 5. 

 NUCLEAR MAXIMUM QUANTITIES OF SOURCE MATERIALS IN CURIES (Ci) 

 SAFETY 

 REVIEW Radiotoxicity Radiotoxicity Radiotoxicity Radiotoxicity

 CATEGORIES Group I Group II Group III Group IV

Category A ≤ 20 Ci ≤ 20 Ci ≤ 200 Ci ≤ 200 Ci

 NASC/OSTP

 Staff Review 

Category B ≤ 1.0 mCi ≤ 50 mCi ≤ 3 Ci ≤ 20 Ci

Agency Approv;

OSTP Qtrly Rpt

Category C [See Appendix A to this report; Category C limits are 

 No Reports assigned by individual radionuclide, not by Group]

Figure 5: Nuclear Safety Review Categories

 When the NASC was abolished, its role in the review and reporting

process was assumed by the Office of Science and Technology Policy

(OSTP). The NASC guidelines for both major and minor source review

and approval remain in effect, and are also used in the reviews

conducted by the Department of Defense (DoD) ranges for both major

source (AFR 122-158) and minor source (AFR 122-169) launches.

 The Category A review process is the most extensive of the three,

and the review report must be submitted to OSTP for approval. This

report consists of a letter or memorandum discussing the purpose,

schedule, on-orbit duration, and orbital parameters of the mission;

the device(s) containing the nuclear materials, and the quantity

and type of materials used; and the conclusions drawn on the safety

11
consequences of any potential problem scenarios (including a launch

mission failure or abort), and of the planned re-entry.

 In certain cases, the action agency must provide a brief Safety

Analysis Summary (SAS) which lists the characteristics of the

radioisotope materials, the consequences of an abort or worst-case

accident, relevant safety procedures, and the recovery plans, where

appropriate. In order for the OSTP staff to accomplish its review,

the Category A report should be submitted a minimum of six weeks

prior to the planned launch date.

 Category B reviews require "user agency" approval, with quarterly

reporting to the OSTP; these reports must be submitted a minimum of

two weeks before launch. Category B reports list planned launches

of nuclear materials (in tabular form), specifying the spacecraft

and mission parameters, the launch site and schedule, the number of

sources, and types and amounts of radioactive materials contained.

 Category C materials are exempt from any reporting requirements

outside the user agency. No safety analysis is required, beyond

confirmation that good safety practices are in effect and that the

cumulative amount of an isotope does not, in fact, exceed Category

C limits, even in multiple sources. Appendix A to this report is

a listing of radionuclides by Group, showing the maximum quantity

(activity) of each for which Category C safety review.

 The cumulative quantity determines the appropriate Category for

each Radiotoxicity Group. Should there be sources from multiple

Groups on a single vehicle, each will be prorated and their sum

will determine the Category. In the Centaur example cited earlier,

Krypton-85 is a Group III substance, and the total activity in the

two tubes is approximately 49.4 microcuries, requiring Category B

review for the approximately 0.063 micrograms of material used per

tube. The four ERIS tubes total 160 microcuries of a Group IV

nickel isotope, requiring Category A review and approval.

The Interagency Nuclear Safety Review Panel (INSRP)

 During the 1960's, the Atomic Energy Commission (later changed to

DOE), DoD, and NASA developed an informal process for interagency

safety review and approval of launches involving nuclear materials.

On December 14, 1977, after studies were conducted to develop a

consistent and efficient review and approval process, Presidential

Directive/National Security Council Action Memorandum 2510 formalized the interagency review process. This Directive also established a requirement for all launches involving a nuclear power

system or other major source to be approved by the President or the

Director of the Office of Science and Technology Policy (OSTP).

 Upon request of the user agency (historically one of the three

INSRP member agencies), an ad hoc Interagency Nuclear Safety Review

Panel (INSRP) is chartered by OSTP for each planned mission which

will involve a spaceborne nuclear power system. The Panel is

charged to review and evaluate the risks associated with the

12
launch, operation, and re-entry. An INSRP is chaired by three

coordinators: one each from the DOE environmental, safety, and

health (ES&H) organization; the Air Force Inspection and Safety

Center (AFISC); and from the NASA Headquarters Safety Office.

These coordinators establish subpanels of experts in the areas

needed. The INSRP may remain involved with a mission through

several years of it's evolution.

 The INSRP process includes the review of safety analysis products

produced under the Air Force Regulations (AFR 122-15), the DOE

Overall Safety Manual, and the NASA Basic Safety Manual11 which are

followed by the organization planning the launch. The NRC is

invited to send representatives to INSRP meetings; the

Environmental Protection Agency (EPA), the National Oceanic and

Atmospheric Administration (NOAA), and/or other agencies may also

participate, as observers or subpanel members of the INSRP.

 The INSRP evaluation is based on review of three Safety Analysis

Reports [Preliminary (PSAR), Updated (USAR), and Final (FSAR)]

developed by or under contract to DOE, and of the documentation

packages prepared for the program preliminary and critical design

reviews. Contributions concerning the spacecraft, launch vehicle,

flight profile, and operations come from organization responsible

for the launch. The FSAR is issued approximately one year before

launch4, and is comprehensive. It contains risk analyses for

nominal performance and any failure modes or anomalies in or

affecting a nuclear power system, as well as hazard predictions

over the entire range of operation of the system. 

 The INSRP performs an independent evaluation of the risks, but

does not recommend approval or disapproval of the launch; findings

are submitted to the OSTP, with copies to the heads of the three

INSRP member agencies, in the form of the FSAR, for their use in

the launch approval request process. If the heads of the two

supporting agencies concur, the user agency submits a request for

launch approval, with a copy of the FSAR, to OSTP12. 

 The INSRP must address failure modes for a vehicle, including

launch anomalies and on-orbit failures, as well as re-entry and

disposition of spent sources. The purpose of these reviews is to

ascertain whether the containment provisions for the nuclear fuel

can withstand the failure mode and re-entry environments, retaining

integrity and preventing any unplanned release, which could pose a

potentially severe radiation hazard to any exposed populations.

 Figure 6 illustrates the process of Nuclear Safety Review and

approval for launches of major or minor nuclear sources.

13
14
International Influences

 The United States has cooperated and complied with the spirit and

letter of international agreements stemming from the United Nations

Committee on the Peaceful Uses of Outer Space (COPUOS). The focus

of these agreements was on the potential environmental effects of

the inadvertent re-entry and subsequent dispersion of radioactive

material carried aboard an earth orbiting spacecraft. The documentation3 listed below constitutes a history of these agreements:

1. United States of America, Uses of Radioactive (Nuclear)

Materials by the United States of America for Space Power

Generation, working paper submitted to COPUOS, U.N. Document

A/AC.105/L.102, United Nations, New York, 15 March 1978

2. United States of America, Use of Nuclear Power Sources in

Outer Space, working paper submitted to the Scientific and

Technical Subcommittee of COPUOS, United Nations, New York,

February 1979 

3. United States of America, Criteria for the Use of Nuclear

Power Sources (NPS) in Outer Space, working paper submitted to

the U.N. Working Group on the Use of Nuclear Power Sources in

Outer Space (WGNPS), U.N. Document A/AC.105/C.1/WG.V/L.8,

United Nations, 23 January 1980

4. Report of the WGNPS on the Work of Its Third Session, Annex II

of Report of Eighteenth Session, U.N. Document A/AC.105/287,

13 February 1981

 Presidential Directive/NSC-25 implemented the policy subsequently

covered in the U.S. working paper submittals and the U.N report,

which forms the basis of international efforts to regulate the

launch and orbit of nuclear materials. 

PUBLIC CONCERNS/ISSUES WITH THE LAUNCH OF RADIOACTIVE MATERIALS

 As mentioned, the United States first launched a SNAP-10A reactor

15
aboard an Atlas-Agena vehicle in 1965. Other major nuclear sources

have been launched through the years*, including NASA deep space

probes such as the Voyager series launched in 1977. The Soviet

Union routinely uses reactors in low earth orbit (LEO) and boosts

them to high earth orbit (HEO) after mission completion13. There

was no extraordinary news coverage or expression of public concern

with these events, and no significant protests or demonstrations.

 On January 24 1978, Cosmos 954, a reactor-bearing Soviet satellite, re-entered. A considerable amount of material survived reentry to impact in northern Canada, including radioactive material

from the reactor. This event, coupled with press reissue of the

details of the re-entry and impact of significant debris from the

U.S. Skylab satellite in Australia (which carried no major nuclear

sources), served to heighten public awareness of potential impact

hazards from re-entering space vehicles, particularly those with

nuclear sources. Notwithstanding this publicity, expressions of

public concern in this area never approached the intensity of those

routinely raised in regard to the potential for accidents within

the nuclear power industry.

 The events spurred efforts of the U.N. Working Group on the Use

of Nuclear Power Sources in Outer Space, which later reaffirmed its

conclusion that, provided all safety requirements are met, nuclear

power sources can safely be used in space13. The government space

community was given added impetus to continue to comply with both

the spirit and the letter of Presidential Directive/NSC-25,

requiring INSRP review of all intended uses of nuclear power

sources in space, while the international space community was

encouraged to adopt similar measures.

 

 

* Other major sources include: SNAP-27 RTG's employed with the

Apollo Lunar Surface Experiment Packages (ALSEP), SNAP-19 RTG's

launched with the NASA Pioneer deep space probes and Viking Mars

unmanned lander missions, and RTG's for DoD navigation satellites

and NASA's Nimbus B weather Satellite (SNAP-3, 9A, 19).

16
 The launch of the Galileo Spacecraft, with twin General Purpose

Heat Source Radioisotope Thermoelectric Generators (GPHS-RTG) in

October of 1989 was preceded by a flurry of anti-nuclear rhetoric

from a spokesman of a Florida protest group, including threats of

a "sit-in" to prevent the launch. Although this activity received

nationwide press coverage, it did not become a cause celebre. NASA

spokesmen appeared in public (news) interviews to answer the stated

concerns, principally by explaining the extensive safety review to

which the mission had been subjected. NASA explained that, in

conjunction with DOE, it had spent 10 years and $10 million dollars

studying the potential risks. 

 The Christic Institute and anti-nuclear activists petitioned a

Washington, D.C. court to enjoin the launch, based on claims that

it was too dangerous because the Jupiter probe contained a nuclear

power source14. The petition was denied after oral arguments, and

the launch was successful.

 This protest was the first attempt by a citizen's group to stop

a NASA launch by instituting legal proceedings, but the incident

may indicate a growing public propensity to protest against the

launch of major nuclear sources. The publicity given the results

of the investigation into the Challenger (STS-51L) accident may be

a contributing factor to this attitude, if it exists.

 With minor amounts of radioactive materials, there seems to be no

discernable public concern. A popular comparison, frequently used

when discussing minor sources at the National Test Ranges, states

that most minor sources are not as active as the material used for

luminescence on some wristwatch dials. Low hazard levels

associated with minor sources are not likely to raise public

concern.

KEY SAFETY ISSUES CONCERNING RADIOACTIVE MATERIALS, AS PERCEIVED BY

THE NATIONAL TEST RANGES

 The Galileo spacecraft, launched aboard the Shuttle Atlantis,

carried two GPHS-RTG power systems, which use Plutonium Dioxide

17
(Pu-238) for fuel. The exact amount of plutonium carried has been

treated as sensitive information; however, "Space News15" stated it

was 48 pounds. If this is the weight of the PuO2, then the actual

weight of the plutonium would be approximately 42.3 pounds.

 The most stressing failure mode addressed by the INSRP in their

analysis of the safety of the mission concerned an intact impact of

the orbiter/ET/booster aggregate, shortly after liftoff. In this

scenario, the high order detonation that would result was estimated

to have maximum credible yield values from 1 to 2.6 million pounds

TNT equivalence. Galileo originally was to use a Centaur stage to

boost it to earth escape velocity and then into its trajectory to

Jupiter. The contribution of the Centaur to the maximum credible

yield is not included in these figures. 

 Clearly, the INSRP members (and the agencies they represented)

were concerned that the RTGs could not withstand the severe overpressures and thermal stress of such a detonation. NASA, however,

decided that the risks to the crew from a Centaur stage [with its

cryogenic liquid oxygen (LOX) and liquid hydrogen fuel load] were

excessive, and chose to replace the Centaur with an Inertial Upper

Stage (IUS) booster.

 The INSRP conducted a thorough risk evaluation, including review

of the results of tests of RTG mock-ups in a shock tube, where

expected overpressures were simulated. The INSRP often helps to

define the requirements for such tests. They also conducted a

comprehensive study of both the STS-51L (Challenger) and Vandenberg

Titan 34D-9 accident data, in order to include as much recent

empirical data as was available in their analysis. The INSRP

presented its conclusions regarding the probabilities, quantities,

and possible health effects of a release due to failure during

launch of the Galileo with the IUS.

 The considerable work performed by the INSRP reflects the prime

concerns of its members, which include representation from the

National Test Ranges, that the structural integrity of a nuclear

power source be maintained in a worst-case failure scenario. It is

important to emphasize from a public safety and health perspective

18
that this concern for the integrity of the RTGs is not based on the

notion that they could produce a nuclear explosion and create casualties in that manner, as might be assumed from the discussions of

blast and overpressure.

 Concerning reactors, DOE's current specifications for the SP-100

reactor require a design that maintains the integrity of its core

in launch failure or re-entry modes leading to earth impact. The

reactor must be designed to survive a catastrophic explosion during

the launch phase or a re-entry and impact, in an essentially intact

condition. In the latter scenario, it would bury itself until it

could be recovered13, unless it impacted in the broad ocean area*.

 Two alternatives to re-entry exist for the disposition of spent

sources. Again maintaining an intact device, they are to either

provide the capability to boost the device into a high earth orbit

(thus delaying eventual re-entry for perhaps hundreds of years), or

to impart sufficient velocity to the device to achieve an escape

trajectory from the earth's gravity. The former alternative poses

a problem for future generations, and the latter may be difficult

to achieve due to the extra weight (and expense) to provide the

thrust necessary to achieve escape velocity. All three schemes,

intact impact, HEO, and escape, may involve separation of the

nuclear device from the rest of the satellite.

 There also exists the potential for on-orbit collision of the

satellite and other orbiting satellites or space debris. Relative

impact velocities in this circumstance may be extremely high, and

the effect of such a collision on the integrity of a nuclear power

source may be devastating, creating clouds of nuclear debris that

 

 

* Although generally associated with security rather than

safety, the possibility of an intact major nuclear source being

recovered by parties hostile to the U.S. exists. Consideration of

this aspect of space applications of nuclear sources would seem to

fall within OCST responsibilities if the launch were conducted from

a commercial facility. 

19
would eventually re-enter. NASA, the Air Force, and other users of

space are currently researching and analyzing this problem.

 Plutonium and the other transuranium elements (except Neptunium)

are radiological poisons with high rates of α particle emission and

a characteristic of specific absorption by bone marrow. The former

makes these elements lethal in minute amounts, and the latter means

that the human body cannot get rid of the material, once ingested. 

 Plutonium is one of the most dangerous poisons known; the worstcase scenario may therefore be a launch vehicle explosion which

results in Plutonium being vaporized or otherwise reduced to small

particles and released into the environment. The severity of the

short-term effects would depend on the timing of the failure. If

it occurred early enough in the flight, there could be casualties

on the range and/or in the surrounding area. Whether early or

later in the flight, a failure of this type over the ocean could

result in long-term contamination of the area's food chain. 

 No commercial space launch vehicle in the current inventory uses

an expendable booster which can approach the degree of hazard to

which the STS, in failure mode, exposes nuclear power systems. The

Centaur aboard the Shuttle was a special case, and analyses would

have to be performed of the case at hand, should a proposed launch

(e.g., using the Centaur as part of a more conventional commercial

Atlas configuration) involve a major source.

SUMMARY

 There are two general types of space-related applications for

radioactive materials. Major sources are used as heat sources for

power systems, while minor sources are used for most non-power

applications. Frequent use of minor sources can be expected in

future commercial launch vehicles, or their payloads, or both.

 For the near term, it appears unlikely that an application for a

license to launch a commercial payload would have a nuclear power

system as part of the launch configuration. Should the materials

20
processing in space (MPS) area develop to the point where there is

sufficient economic return, some MPS experimental or operational

payloads might require electric power at levels only available from

a reactor or radioisotope power system. Under the current federal

regulations, OCST would be directly involved in both the safety and

national security aspects of the approval process.

 Third party safety concerns are not treated separately from those

affecting first or second party safety, either in the NRC safety

evaluation requirements for licensing minor sources or those used

by DoD for approval to launch them, or in those applied by the

INSRP for major sources. Neither mission success nor public safety

is given overriding consideration; each set of procedures appears

adequate to satisfy OCST concerns for public health and safety.

 The INSRP review process was designed to address the launch of

all major nuclear sources, when NASA and the Armed Services [now

including the Strategic Defense Initiative Organization (SDIO)]

were the only proponents of missions incorporating nuclear sources,

and either Air Force or NASA vehicles would be used to launch those

missions. Should a commercial launch involve nuclear power or some

other major source application, and particularly if that launch is

to be conducted at a commercial launch facility rather than from a

DoD range, it may be advisable for DOT/OCST to seek representation

on the INSRP for that launch.

21
References:

1. Samuel Glasstone, Sourcebook on Atomic Energy, Third Edition, Van Nostrand

Reinhold, Co., 1967, §18.42, p747.

2. Samuel Glasstone, ibid, §17.

3. Air University Institute for Professional Development, Air University, Space Handbook,

Seventh Revision, July 1969.

4. The Aerospace Corporation, "Mishap Risks Due To Radiation From Nuclear Systems

Within The Consolidation Space Test Range," Edmund A. Vierzba, 23 June 1988.

5. National Aeronautics and Space Council Document, "Nuclear Safety Review and

Approval Procedures for Minor Radioactive sources in Space Operations," 16 June

1970.

6. International Atomic Energy Agency (IAEA), Regulations for the Safe Transport of

Radioactive Materials, 1967 Edition, Safety Series No. 6.

7. The United States Government Manual, Office of the Federal Register, National

Archives and Records Administration, Wash. D.C.: Nov 1989, "Nuclear Regulatory

Commission", p677.

8. Air Force Regulation 122-15, Nuclear Power System Safety Reviews and Surveys,

24 February 1978, as supplemented by AF Systems Command, 27 October 1986.

9. Air Force Regulation 122-16: Nuclear Safety Review Procedures For Space or Missile

Use of Radioactive Sources, 14 November 79, as supplemented by Air Force

Systems Command, 19 July 84, and by Air Force Space Division (currently Space

Systems Division), 30 December 85.

22
10. Presidential Directive/NSC-25: Scientific or Technological Experiments with Possible

Large-Scale Adverse Environmental Effects and Launch of Nuclear Systems into

Space, 14 Dec 1977.

11. NHB 1700.7A, Safety Policy and Requirements for Payloads Using the Space

Transportation System (STS), july 1980, Section 212: Radiation.

12. Department of Energy Document, "Flight Safety Review Process for Space Nuclear

Power Sources". Gary L. Bennett, August 1987.

13. The Aerospace Corporation, "Space Test Range Architecture Study". Prepared for

Air Force Systems command Space Division, Space and Missile Test Organization,

30 September 1988.

14. "Space News", Preview Issue, October 9, 1989, p1, p35, p42.

15. "Space News", ibid, p35.

1. Samuel Glasstone, Sourcebook on Atomic Energy, Third Edition,

 Van Nostrand Reinhold, Co., 1967, §18.42, p747.

2. Samuel Glasstone, ibid, §17.

3. Air University Institute For Professional Development, Air

 University, Space Handbook, Seventh Revision, July 1969

4. The Aerospace Corporation, "Mishap Risks Due To Radiation From

 Nuclear Systems Within The Consolidated Space Test Range,"

 Edmund A. Vierzba, 23 June 1988

5. National Aeronautics and Space Council Document, "Nuclear Safety

 Review and Approval Procedures for Minor Radioactive Sources in

 Space Operations," 16 June 1970

23
6. International Atomic Energy Agency (IAEA), Regulations for the

 Safe Transport of Radioactive Materials, 1967 Edition, Safety

 Series No.6

7. The United States Government Manual, Office of the Federal

 Register, National Archives and Records Administration,

 Wash. D.C.: Nov 1989, "Nuclear Regulatory Commission", p677

8. Air Force Regulation 122-15, Nuclear Power System Safety Reviews

 and Surveys, 24 February 1978, as supplemented by AF Systems

 Command, 27 October 1986

9. Air Force Regulation 122-16: Nuclear Safety Review Procedures

 For Space or Missile Use of Radioactive Sources 14 November 79,

 as supplemented by Air force systems Command, 19 July 84, and by

 Air Force Space Division (currently Space Systems Division), 30

 December 85

10. Presidential Directive/NSC-25: Scientific or Technological

 Experiments with Possible Large-Scale Adverse Environmental

 Effects and Launch of Nuclear Systems into Space, 14 Dec 1977 

11. NHB 1700.7A, Safety Policy and Requirements for Payloads Using

 the Space Transportation System (STS), July 1980, Section 212:

 Radiation

12. Department of Energy Document, "Flight Safety Review Process

 for Space Nuclear Power Sources", Gary L. Bennett, August 1987

13. The Aerospace Corporation, "Space Test Range Architecture

 Study", Prepared for Air Force Systems Command Space Division,

 Space and Missile Test Organization, 30 September 1988 

14. "Space News", Preview Issue, October 9, 1989, p1, p35, p42

15. "Space News", ibid, p35

24