You would use a segmented gamma scanner, if you are certain there are no localized absorbers, such as plutonium metal, large clumps of oxide, or very non-uniform matrices. SGS is a gamma spectroscopy technique that uses a transmission source to determine the attenuation correction of the material. The purchase price is often around $100-200K. If you have a few drums (maybe less than 100) it is practical to perform the measurement manually using a germanium detector and a hand placed transmission source.
You would use a pass!
ive neutron coincidence counter if you had reason to believe you had metal shavings etc. The essence is to measure neutrons which arise from the spontaneous fission of Pu-240 (2 or 3 neutron emissions during the fission event). The purchase price of such a system is often $500K+. The isotopic ratios must be well known, either from process knowledge, by mass-spec analysis of samples, or by a specialized isotopic measurement of the entire drum using a specialized gamma-ray spectroscopy technique called Multi Group Analysis (MGA) or FRAM code. Those codes examine the ratios of the isotopic lines. An Add-A-Source is often used to make a matrix correction, which is to place a known source on the outside of the drum and relate the measured response to the effect!
of the matrix inside of the drum.
You should avoid any inexpensive techniques that simply measures the total neutrons emitted. Many neutrons typically originate from alpha,n reactions and the rate of generation is entirely dependent on the chemical characteristics of the matrix, the thickness of the deposit, and how well mixed the matrix is.
You should also avoid active interrogation systems, unless you have large amounts of highly enriched uranium. Not only is it a much more c!
omplex and expensive, but has matrix uncertainties that effect both the neutrons evolved from fission and also the interrogating neutrons.
A reference book is: “Passive Non-destructive Assay of Nuclear Materials” by Los Alamos National Laboratory and issued as NUREG/CR-5550.
A wealth of additional references are available on-line from LANL’s technical library. I can recommend technical contacts as needed.
The same companies that sell the equipment will lease the equipment. They also will make measurements on-site. Possible vendors are: Canberra, BNFL Instruments, Antech, and Eberline.
Hope this helps,
Brian Keele
The segmented gamma scanner
Date: Fri, 17 Jan 2003 11:27:54 -0500
From: "Dave Biela" <Dave.Biela@wvnsco.com>
Subject: Pu pipe removal question
** High Priority **
We are about to D&D a Plutonium Purification Cell (PPC). We need to
prove that we have less than 125 g of PU-239 (site storage limit) in
each of our containers (30 gal drum). We will be putting product pipe
into the drums (1/8", 1/4", ˝"). The primary isotopes with any gamma,
are Pu-239 and Am-241.
We have complete isotopic ratios in the room and have the ability to
take samples of the pipes. The room that we will be working in has
cont!
amination levels in the millions of dpm/100 cm-sq alpha.
We have some ideas, but we do not want to re-invent the wheel if we
don't have to.
Thanks in advance for your help.
716-942-4423
716-942-2097 (fax)
Dave