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    "story_id": "mp-2026-07-31-001",
    "source_story_id": "tmp-lead-ziacore-zero-power-criticality",
    "edition_id": "mp-2026-07-31-morning-0022",
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    "headline": "The Chain Reaction Stopped Before the Heat",
    "slug": "the-chain-reaction-stopped-before-the-heat",
    "dek": "Los Alamos brought a compact reactor core to sustained criticality above 800 C while deliberately keeping the experiment at zero power.",
    "summary": "Los Alamos brought a compact reactor core to sustained criticality above 800 C while deliberately keeping the experiment at zero power.",
    "body_text": "Los Alamos National Laboratory brought its ZiaCore microreactor experiment to criticality at the National Criticality Experiments Research Center in Nevada after tests in April and May. The low-enriched uranium-dioxide core, zirconium-hydride moderator and heat-pipe design sustained a chain reaction above 800 C, but operators stopped before measurable fission heat was produced. The result is a proof-of-principle physics demonstration, not a power-generating reactor or commercial deployment.",
    "why_it_matters": "Los Alamos brought a compact reactor core to sustained criticality above 800 C while deliberately keeping the experiment at zero power.",
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      "Los Alamos National Laboratory brought its ZiaCore microreactor experiment to criticality at the National Criticality Experiments Research Center in Nevada after tests in April and May.",
      "The result is a proof-of-principle physics demonstration, not a power-generating reactor or commercial deployment."
    ],
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    "first_published_at": "2026-07-31T09:00:00.000-04:00",
    "modified_at": "2026-07-31T09:00:00.000-04:00",
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        "text": "Los Alamos brought a compact reactor core to sustained criticality above 800 C while deliberately keeping the experiment at zero power.",
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        "qualification": "Los Alamos National Laboratory brought its ZiaCore microreactor experiment to criticality at the National Criticality Experiments Research Center in Nevada after tests in April and May."
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    "source_ids": [
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    "tags": [
      "ZiaCore",
      "microreactor",
      "criticality",
      "nuclear research"
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    {
      "source_id": "source-2026-07-31-001",
      "title": "Los Alamos National Laboratory via Newswise: ZiaCore reaches criticality",
      "publisher": "Los Alamos National Laboratory",
      "url": "https://www.newswise.com/articles/ziacore-microreactor-successfully-achieves-criticality",
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      "accessed_at": "2026-07-31T08:31:33.328-04:00",
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  "publisher": {
    "name": "The Machine Press",
    "url": "https://themachinepress.com",
    "description": "A daily newspaper for the age of artificial intelligence."
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  "cite_this_report": {
    "title": "The Chain Reaction Stopped Before the Heat",
    "publisher": "The Machine Press",
    "published_at": "2026-07-31T09:00:00.000-04:00",
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