%MurNBreactor040251; ]> Memorandum from A. C. Menius, Jr. and R. L. Murray to Clifford K. Beck [a machine-readable transcription] Murray, Raymond L. Menius, Arthur C., Jr. Creation of machine-readable version: Russell S. Koonts Creation of digital images: Russell S. Koonts Conversion to TEI.2-conformant markup: NCSU Science and Technology Electronic Text Center. ca. 9 kilobytes NCSU Libraries. Raleigh, NC. Modern English, MurNBreactor040251

Available from: NC State University Archives

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URL: http://www.lib.ncsu.edu/archives/etext/engineering/reactor/murray/

 2000

Nuclear Reactor Digitization Project

Raymond L. Murray Reactor Project Notebook

 Illustrations have been included from the print version. Scanned by Russell Koonts with Photoshop 5.0 software. Memorandum from A. C. Menius, Jr. and R. L. Murray to Clifford K. Beck <author>Raymond L. Murray</author> <author>Arthur C. Menius, Jr.</author> <respStmt> <resp/> <name/> </respStmt> </titleStmt> <editionStmt> <p></p> </editionStmt> <extent>1 p.</extent> <publicationStmt> <publisher></publisher> <pubPlace></pubPlace> <date></date> <idno>Manuscript copy consulted: NCSU Libraries call number UA105.16</idno> </publicationStmt> <seriesStmt> <p/> </seriesStmt> <notesStmt> <note></note> </notesStmt> </biblFull> </sourceDesc> </fileDesc> <encodingDesc> <projectDesc> <p>Prepared for the NCSU Libraries Science and Technology Electronic Text Project.</p> </projectDesc> <editorialDecl> <p>Spell-check and verification made against printed text using Notetab spell checker.</p> <p>The lineation of the manuscript has been maintained and all end-of-line hyphens have been preserved.</p> <p>The images exist as archived TIFF images, one or more JPEG versions for general use, and thumbnails.</p> <p id="ETC">Keywords in the header are a local Electronic Text Center scheme to aid in establishing analytical groupings.</p> </editorialDecl> <refsDecl> <p>ID elements are given for each page element and are composed of the text's unique cryptogram and the given page number, as in NEprop033050a for the title page of Clifford Beck's Proposal.</p> </refsDecl> <classDecl> <taxonomy id="LCSH"> <bibl> <title>Library of Congress Subject Headings 1951 English non-fiction; prose LCSH 24-bit color; 400 dpi Memorandum from A. C. Menius, Jr. and R. L. Murray to Clifford K. Beck Typescript 1 p. April 2, 1951 MurNBreactor040251

Apr 2, 1951 NCSC-8 TO: Clifford K. Beck FROM: A. C. Menius, Jr. and R. L. Murray SUBJECT: Reactor Period vs. Reactivity

The relation between excess reactivity and period (e-folding time) is given by the inhour equation
where τp is the average time between fissions due to prompt neutrons, τ is the period of the reactor, γf is the effective fraction of neutron delayed, qi is the fraction of the delayed neutrons with period τi (mean life).

The half-lives and yields for delayed neutrons in each group are available. Experiments at Los Alamos with the "water-boiler" (hypo) have shown that γf = 0.0086 and τp = 135 x 10-6 seconds. Theoretically τp = 1/VΣa, thus, considering only fissionable material we have the ratio of the N. C. State Reac tor prompt period to Los Alamos given by
τp = τp1 = 135 x 10-6 seconds.

We have, then, for the inhour equation

A plot of this is attached to the original report. With an excess reactivity at 20°C of 0.0157, which is the calculated value for the N. C. State Reactor, a minimum period of about 0.02 seconds is obtained. This value should be used in the design of the ceontraol amplifiers.

cc: Members of the Reactor Committee

Hughes, Dobbs, Cohn and Hall, Physical Review, 73, 111 (1948).