COBALT ACTIVITY BUILDUP IN THE NUCLEAR MERCHANT SHIP REACTOR

In a pressurized water reactor constructed with stainless steel such as the Nuclear Merchant Ship Reactor, a radioactive deposit (commonly called crud) tends to buildup on the walls of the primary system. This activity buildup is particularly bothersome during maintenance, i.e. plugging a boiler tube. Two of the most active radioisotopes in the deposit are Cobalt-58 and Cobalt-60. Cobalt-58 is formed from the n,p reaction of Nickel-58 while Cobalt-60 is formed from thermal neutron absorption by Cobalt-59. In a material such as 304 stainless steel, it is obvious that the nickel cannot be eliminated. However, the Cobalt (which is 100% Cobalt-59) is present as an impurity, and it is possible to reduce its concentration considerably. The amount of Cobalt in 304 stainless steel varies considerably but is generally on the order of 0.1%. If this is reduced to 0.01%, the Cobalt-60 buildup will be reduced accordingly. The greater the reduction in the cobalt impurity, the more expensive the steel becomes. Accordingly, there is some economical limit on the degree of reduction. Practically, there is no object in reducing the Cobalt impurity to a point where the Cobalt-60 activity becomes less than the Cobalt-58 activity. Accordingly, the object of this investigation was to determine the concentration of Cobalt allowable as an impurity in the steel which would give no greater activity from Cobalt-60 than from Cobalt-58. The approach was to derive a set of differential equations which should describe the activity buildup phenomenon. Solutions were found for the equations and the constants evaluated from APPR-1 data. Calculations were then made for the Nuclear Merchant Ship Reactor. The results appear reasonable. Their accuracy is limited, of course, by the validity of the assumptions used in setting up and solving the equations, and by the accuracy of the evaluation of the constants.

  • Supplemental Notes:
    • This document is available for review at the Department of Commerce Library, Main Commerce Building, Washington, D.C., under reference number BAW-1130.
  • Corporate Authors:

    Babcock and Wilcox Company

    Atomic Energy Division
    Lynchburg, VA  USA  24504
  • Authors:
    • Meem, J L
  • Publication Date: 1958-10-1

Media Info

  • Features: References;
  • Pagination: 19 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00026082
  • Record Type: Publication
  • Source Agency: Maritime Administration
  • Contract Numbers: AT(30-3)-274
  • Files: TRIS, USDOT
  • Created Date: Feb 14 1973 12:00AM