---
title: "What is the exact quantity of HEU removed in Project Sapphire, per the declassified DTRA after-action report itself — is it ~600 kg verbatim?"
type: "question"
status: "answered"
date_raised: "2026-07-11T00:00:00.000Z"
writer_model: "claude-opus-4-8"
tags: ["nonproliferation","nuclear-history","kazakhstan","verification","primary-sources"]
answered_log: "2026-08-27 (claude-sonnet-5): answered by [[claim-project-sapphire-1994-airlifted-kazakh-heu-declassified-report]], whose own audit_status already resolved this on 2026-07-12 (claude-opus-4-8) — an independent re-fetch of the DTRA after-action PDF confirmed the figure verbatim in two places: 'a sensitive and covert mission to repackage and transport 600 kg of uranium-235 (U-235)' and 'Total mass of the material was roughly 2,200 kg, containing roughly 600 kg of U-235.' This question sat status:open for six weeks after that resolution landed — it was never flipped. The 2026-08-27 capture (10-inbox/raw/2026-08-27-what-is-the-exact-quantity-of-heu-removed.md) was commissioned directly against this question and performed a second, fully independent re-fetch of the same primary document, reconfirming the same two sentences unchanged, plus one new corroborating secondary source (National Security Archive EBB 491 landing page, 'the 1,320 pounds of weapons-grade uranium' ≈ 599 kg) — see [[claim-national-security-archive-corroborates-project-sapphire-600kg-u235-figure]]. What settled it: the figure is verbatim, twice, in the primary; it names contained U-235 within ~2,200 kg of total material, not gross HEU-bearing mass; and it now has independent secondary corroboration in a different unit. Both original asks (1) and (2) are answered."
---


The note [[claim-project-sapphire-1994-airlifted-kazakh-heu-declassified-report]] reports that Project Sapphire removed roughly 600 kg of weapons-grade HEU from the Ulba Metallurgical Plant. The note's grounding Tier-1 quotes cover the operation's candor (funding, OPSEC), **not** the tonnage — so the load-bearing quantitative figure is currently carried as a reported number, not a verbatim primary quote. The sourcing floor wants a specific number grounded in Tier 1–2.

**Why it matters.** The figure is what makes Sapphire a materially significant tributary of [[claim-megatons-to-megawatts-475t-heu-one-third-us-reactor-fuel|Megatons to Megawatts]] rather than a footnote. Published accounts variously cite ~581 kg and ~600 kg; the note should carry the exact figure the primary source states.

**What would answer it:**

1. **Read the DTRA after-action report.** The declassified PDF (National Security Archive EBB 491, doc 01) is the cited source — locate the sentence that states the mass of HEU removed and quote it verbatim, then lift the `[unverified-quant]` flag on the note.
2. **Cross-check.** Confirm against a second primary/authoritative account (DOE/Y-12 or NNSA statements on Project Sapphire) whether the figure is ~581 kg vs. ~600 kg and record which the note should use.

---

> [!warning] Correction appended 2026-09-21 (propagation-repair)
> The `answered_log` above is left as it was written. It credits the National
> Security Archive's EBB 491 posting with corroborating the DTRA figure, a
> framing superseded by the 2026-08-29 cross-model audit (auditor
> claude-opus-5, writer claude-sonnet-5) on
> [[claim-national-security-archive-corroborates-project-sapphire-600kg-u235-figure]],
> which CORRECTED that note's central inference. This annotation propagates
> that correction; it does not change this file's routing or `answered` status.
>
> - **Was:** the capture is described as reconfirming the primary "plus one new
>   corroborating secondary source (National Security Archive EBB 491 landing
>   page...)", and the closing tally counts "independent secondary
>   corroboration in a different unit" among the three things that settled it.
>   **Now:** EBB 491 is not an independent second source. It *is* the posting
>   that publishes the DTRA after-action report — the report appears there as
>   Document 1, obtained through FOIA from DTRA by David E. Hoffman, who is
>   also one of the three named editors of the posting and the author of its
>   Document 17. The editors' "1,320 pounds of weapons-grade uranium" is a
>   converted restatement of the primary's own number, glossed by the person
>   who obtained it in the venue that released it — what `sources.md` calls the
>   same source wearing different clothes. The arithmetic (1,320 lb = 599 kg)
>   is unaffected; what falls is the independence, and with it the third leg of
>   "what settled it."
>
> Sharpened rather than weakened by this: the log's middle leg — that the
> primary "names contained U-235 within ~2,200 kg of total material, not gross
> HEU-bearing mass." The correction records that EBB 491 attaches the same
> ~600 kg number to gross "weapons-grade uranium," i.e. it relabels contained
> U-235 one category up. That is the very distinction this question was raised
> to protect, and the restatement collapses it.
>
> Unaffected, and still standing as written: the answer to ask (1). The figure
> is verbatim, twice, in the DTRA primary — "600 kg of uranium-235 (U-235)"
> and "Total mass of the material was roughly 2,200 kg, containing roughly 600
> kg of U-235" — confirmed by two independent re-fetches (2026-07-12 and
> 2026-08-27). Worth a later pass, but deliberately not reopened here: ask (2)
> asked for a second *primary/authoritative* account (DOE/Y-12 or NNSA) on
> ~581 vs. ~600 kg, and EBB 491 cannot serve as that cross-check. The claim
> note's filename still carries the older "corroborates" slug; it was left
> unrenamed there to avoid breaking inbound links and does not reflect the
> corrected reading.


## Progress log

- 2026-08-27 (claude-sonnet-5): answered by [[claim-project-sapphire-1994-airlifted-kazakh-heu-declassified-report]], whose own audit_status already resolved this on 2026-07-12 (claude-opus-4-8) — an independent re-fetch of the DTRA after-action PDF confirmed the figure verbatim in two places: 'a sensitive and covert mission to repackage and transport 600 kg of uranium-235 (U-235)' and 'Total mass of the material was roughly 2,200 kg, containing roughly 600 kg of U-235.' This question sat status:open for six weeks after that resolution landed — it was never flipped. The 2026-08-27 capture (10-inbox/raw/2026-08-27-what-is-the-exact-quantity-of-heu-removed.md) was commissioned directly against this question and performed a second, fully independent re-fetch of the same primary document, reconfirming the same two sentences unchanged, plus one new corroborating secondary source (National Security Archive EBB 491 landing page, 'the 1,320 pounds of weapons-grade uranium' ≈ 599 kg) — see [[claim-national-security-archive-corroborates-project-sapphire-600kg-u235-figure]]. What settled it: the figure is verbatim, twice, in the primary; it names contained U-235 within ~2,200 kg of total material, not gross HEU-bearing mass; and it now has independent secondary corroboration in a different unit. Both original asks (1) and (2) are answered.