Appendix B: Indentification of Potential Hazards, Energy Sources, and Generic Accidents for Fusion Facilities

DOE-STD-6003-96

APPENDIX B

IDENTIFICATION OF POTENTIAL HAZARDS, ENERGY SOURCES, AND GENERIC

ACCIDENTS FOR FUSION FACILITIES

B.1 Introduction

This appendix presents a discussion of the potential hazards, energy sources, and

generic accident scenarios associated with fusion facilities. A bibliography of the large amount

of similar work that has been done in the worldwide fusion safety community in the past is

included at the end of the document. Because of the generic nature of this list, a particular

hazard, energy source, or accident scenario may or may not be relevant to every fusion system.

The existence of a hazard and its magnitude are dictated by the specifics of a facility design

including its mission, function, materials, size, and power level. The intent of the listing is to

provide a starting point to implement the requirements in the main text related to hazard identifi-

cation and development of event trees or accident scenarios for the specific fusion facility. A

secondary but equally important use of this listing is to ensure that hazards that are not an inte-

gral part of a specific system but that can have an interfacing effect are also identified.

B.2 Hazards

The hazards associated with fusion consist of radiological, chemical, and industrial

hazards. In addition, fusion has a number of energy sources that must be managed effectively

to prevent accidents that would result in release of chemical and radiological hazards. The

hazards are discussed below.

B.2.1 Radiological Hazards

The dominant radiological hazards are tritium, which is the fuel in the deuterium-tritium

(D-T) fusion reaction, and activation products that are produced as a result of neutron interac-

tion with materials and fluids surrounding the plasma. Hazards from direct exposure to fusion

neutrons will normally be mitigated by design features and administrative controls.

Tritium inventories are a strong function of the fusion facility design. Tokamak Fusion Test

Reactor (TFTR) is limited to contain less than 5 g of tritium, whereas the inventory of tritium in

the International Thermonuclear Experimental Reactor (ITER) is expected to be between 1 and

10 kg. Tritium can be found in plasma-facing components (PFCs) in the fuel process system,

the vacuum pumps and fuel injectors, in the blanket and associated processing system, and in

storage. Tritium is also present in neutral beam injectors and associated cryopanels. The tritium

inventory in each of these systems must be assessed to determine the associated hazard. The

dispersion and oxidation characteristics in an off-normal event will influence the degree or

severity of the hazard for tritium that may be released.

For machines such as ITER that will experience a high neutron fluence, activation prod-

ucts will constitute the largest source of radioactivity. For ITER, an inventory of 1020 Bq (3

109 Ci) is estimated for the stainless steel shield and vacuum vessel during the later phases of

operation. The inventory in the structure and the potential hazard to the public are directly

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