Atomic Access Categories from 1947

by Alex Wellerstein, published March 14th, 2012

The English word “secret” comes from the Latin sēcernĕre, meaning “to separate, divide off.” Secrecy is the dividing of the world into those who know and those who don’t. With every act of separation comes an act of classification — you designate what is to be divided out, what is to be separated, what is secret.

So it should come as no surprise that so much of the work of secrecy is creating ever more baroque and detailed categorization schemes.

This week’s featured document is a case in point: a lettered list of categories of access to specific nuclear secrets, probably from sometime in 1947.1 It is a Borgesian encyclopedia of sensitive nuclear knowledge.2

Click image to view the full PDF.

It’s an odd jumble of a list — some of the categories are categories are about access to knowledge, some to places, some to things.

A few of my favorites with commentary:

  • A. Size, weight, center of gravity, ability to withstand accelerations, ballistic properties.

An interesting first choice. How much access the armed forces should have to these specific properties was a matter of hot debate through the 1940s and early 1950s; they were necessary to know for fielding or planning the weapons, but also told you quite a lot about their design.

  • C. Structure of an atomic weapon, “Little Boy” and “Fat Man” details of construction; visit to Delta Building.

Aka weapon design, 101. Delta building housed plutonium chemistry, metallurgy, and processing.

  • D. Use of nuclear energy for atomic power, details of fast reactor.

That nuclear power was itself a closely-held secret until the early 1950s is sometimes surprising to people; reactors were, at this time, exclusively associated with plutonium production or learning about nuclear constants and properties.

  • E. Use of atomic power for guided missiles, planes, etc.

Interesting that at this early stage — when there were no concrete plans to use atomic power in any of these situations — this was considered worth having as a separate category.

  • L. Stockpile and storage problems of atomic weapons. Each case will be cleared by General Groves personally; information will not be disseminated thereon without positive assurance that General Groves has so cleared the person in question.

The only category that makes explicit exactly how secret it is — it actually spells out a separate procedure in its description, and emphasizes the lack of disclosure. “Those that belong to the Emperor,” indeed.

  • N. Fission physics including fast reactor, water boiler.

One of the broadest categories — “fission physics.” The “water boiler” was a research reactor at Los Alamos.

  • O. Future developments in atomic weapons; implosion type weapons, gun type weapons, smaller weapons.
    OA. Physical characteristics of new developments.
    OB. Nuclear characteristics of new developments.

It’s interesting that the subcategories “OA” and “OB” have been added here. “OA” is presumably so that the aforementioned military people could start to think about how to deliver a new bomb without learning how it was designed; “OB” is probably for scientists. It’s a curious place to put in a firm division.

  • P. “Super.”

Worth its own category, worth its own code-name, worth not elaborating on — the hydrogen bomb.

  • S. “Cooks Tour.” For distinguished visitors, normally non-technical. Includes limited technical details of general knowledge only nut is primarily to shaw magnitude, complexity and difficulties of plant.

A “cook’s tour” is a “a guided but cursory tour of the major features of a place or area” named after Thomas Cook, a 19th-century British travel agent. Apparently by the 20th century it had entered into military jargon for a tour around a site. From the description, it seems like the sort of thing they intended for visiting Senators and the like.

  • T. Comprehensive Clearance. Includes detailed information of all categories, except L, LA, and LV.

“L,” “LA,” and “LV” relate to stockpile storage and size — so the stockpile was deliberately excluded from “Comprehensive Clearance.”

  • W. Pumpkins, i.e ., exterior characteristics of pumpkins — mainly applicable to AAF and AAF coordinated activities (example: pit loading equipment, etc).

Pumpkins refer to the original “Fat Man” bomb casings that were filled with high explosives and used for training and dry-runs during World War II. (Watch out, Charlie Brown!)

What’s this all add up to? I cherish these kinds of taxonomies, because they reveal quite a lot about how the real thinking about secrecy was being done at the time. This mixing of secret knowledge, places, and things in one large, complicated list gives a slight hint at the conceptual slack that still existed in thinking about what it meant to have access to a “secret” at this particular point in the early postwar period.

The cacophony that results from attempting to draw such taxonomies never really goes away, though it does get normalized. One of my favorite quotes on this comes from J. Robert Oppenheimer, in classified testimony given to the Joint Committee on Atomic Energy in 1949: “The fiction that some supreme intelligence exists that can paint red for danger, and green for caution — that’s not so. … I don’t believe a disembodied agency has a Chinaman’s chance of wisely deciding what to make public.”

  1. The document is undated, but its position within the file, and several specific details in the document, lend towards my guess at the date. Additionally, from its contents it is clear that it is postwar because it discusses stockpile storage issues — not a problem during the Manhattan Project, since none were being stockpiled — and assigns permission for that to General Groves, who would then have been head of the Armed Forces Special Weapons Project. It refers to the Army Air Forces (AAF), which suggests it is not later than September 1947, when the US Air Force was split into an independent organization. The mentioning of Silverplate and the C-97 modification at the end suggests that it is in a window where B-29s are still be used, where the C-97 is being fielded, and the B-50 is not yet around, which also fits snugly into 1947. []
  2. Source: Undated, untitled list of classification categories (ca. 1947), Manhattan Engineer District (MED) records, Records of the Army Corps of Engineers, RG 77, National Archives and Records Administration, Box 64, “Security and Intelligence.” []

4 Responses to “Atomic Access Categories from 1947”

  1. Mark L. says:

    Regarding category E: Use of atomic power for guided missiles, planes, etc., the NEPA program was well under way by 1947, and doing its level best to make concrete plans. They’d certainly cranked out enough secret documents to kill a small forest. So if they’re going to make this kind of list of every possible classified atomic energy topic, it makes sense to give them their own letter.

    • Hi Mark: I hadn’t realized that NEPA was in full swing at that point, but I see you’re right, and that it began as early as 1946! That’s kind of incredible, given the state of reactor technology in 1946.

      • Mark L. says:

        You can trace the origins of the program even earlier – the congressional hearings that led to NEPA began in late 1945, and then-Col. Keirn was bugging Vannevar Bush about the idea in July 1945. (Apparently Dr. Bush told him it was a terrible idea and to forget about it.)

        And thank you for your blog – I just recently discovered it, and, as a layman interested in atomic history, I’m really enjoying it.

        • I’ll probably write something about NEPA at some point. It’s one of those things that in hindsight looks like one of the colossal boondoggles in atomic history, but tracing out why it appealed to various people in positions of influence (at the expense of attention for what proved to be the “winning” technology, long-range rockets) would be a fine historical exercise. Thanks again, Mark.