def def_archetypes():
    """
    Produces the default niche-archetype links for a rickshaw simspec.

    Returns
    ----------
    spec : dict
        Dictionary representation of the niche-archetype links.
    """
    arches = {'mine': {':cycamore:Source'}, 'conversion': {
        ':cycamore:Storage'}, 'enrichment': {':cycamore:Enrichment'},
        'fuel_fab': {':cycamore:FuelFab'}, 'fuel_fab:uo2': {
        ':cycamore:FuelFab'}, 'fuel_fab:triso': {':cycamore:FuelFab'},
        'fuel_fab:mox': {':cycamore:FuelFab'}, 'reactor': {
        ':cycamore:Reactor'}, 'reactor:fr': {':cycamore:Reactor'},
        'reactor:lwr': {':cycamore:Reactor'}, 'reactor:hwr': {
        ':cycamore:Reactor'}, 'reactor:htgr': {':cycamore:Reactor'},
        'reactor:rbmk': {':cycamore:Reactor'}, 'reactor:pb': {
        ':cycamore:Reactor'}, 'storage': {':cycamore:Storage'},
        'storage:wet': {':cycamore:Storage'}, 'storage:dry': {
        ':cycamore:Storage'}, 'storage:interim': {':cycamore:Storage'},
        'separations': {':cycamore:Separations'}, 'repository': {
        ':cycamore:Sink'}}
    return arches
