Description of Unit 3

HELGESON SCIENTIFIC SERVICES
872 Abbie Street
Pleasanton, California, 94566-7502
Office Fax: 925-846-8042
Cell Phone: 510-928-7474 (Best chance of contacting me)
e-mail: lewhelgeson@helge.com

Updated May 6, 2008

Introduction

Helgeson Scientific Services celebrated its 38th anniversary on February 15, 2004. Since 1968, two years after the company was formed, Helgeson had a mobile scientific laboratory containing two in vivo counters. The first of these counters was designed for the express purpose of measuring various isotopes of uranium, plutonium, americium. The second counter was designed to measure mixed fission, activation, and corrosion products that are found that nuclear facilities throughout the United States and Canada.

Mr. Helgeson will reach 82 years young this fall and wishes to reduce his workload and spend more time with his wife of more than 59 years. Therefore, this unique one-of-a-kind scientific laboratory is available for sale to the highest bidder. This will include an approximately 40 ft. long semi trailer (but not the tractor), a duplicate set of pulse shape discrimination electronics and four phoswich detectors, a "humanoid" phantom, radioactive calibration sources, two computers, two shields, and all pertinent peripherals for the operation of this laboratory.

Let us now proceed to discuss the entire package.

The Trailer

Figure 1, Unit 3 Mobile Scientific Laboratory

Figure 1 shows a external view of the "curb" side of the trailer. Note that there is a platform with aluminum steps at the entryway door. Handrails are provided for the safety of persons entering and leaving the trailer.

Figure 2 shows the front end of the trailer. Hung on the front end is a high-quality heat pump used for air-conditioning and heating. This operates at 220 volts A. C. at approximately 30 amperes.

Figure 2, Front end of the trailer


Figure 3, General view	Figure 4, View of cable storage	Figure 5, Stairs and Railings

Figures 3, 4, and 5 shows the back end of the trailer with the two rear doors opened wide. This is where the power cables are stored, as well as the steps and handrails and miscellaneous equipment that is needed while on the road, such as snow shovel! The electrical power cables have adequate capacity to carry the necessary amperage for both air-conditioner as well as all the electronics. Individual circuits are used for these two purposes.

General Interior Views


Figure 6, Technician's work area	Figure 7, The lay-down, scanning geometry diagnostic counter

Please direct your attention to the dark doorway at the right side of the instrument panel. This is the entry to the in vivo counter for low energy emitters, such as uranium, plutonium, and americium. This instrument will be discussed near the end of this web page.

Figure 6 shows the technician's work area which is found immediately to the left (towards the front of the trailer) upon entering the trailer. Figure 7 shows the "lay down" diagnostic whole body counter, called the "DIYS" counter, which is found immediately to the right (towards the rear of the trailer). Ever since this counter was designed in early 1974 it has been called the "Do It Your Self," or "DIYS" whole body counter because it is so simple to operate that a person who is about to receive a whole body count can literally "do it your self."

The Technician's Work Area

Figure 8, Technician's work area

Figure 8 shows our technician sitting in front of the two computers. The computer on his left is used for the "DIYS" counter while a computer on his right is used for the measurement of the low energy emitters, such as the various isotopes of uranium, plutonium-238 and plutonium-239, and americium-241.


Figure 9, Printer and Storage areas for small items	Figure 10, Storage areas for larger items	Figure 11, Computer displays and upper storage areas

Figure 9 shows the work area beneath the computers. This base contains drawers for the storage of miscellaneous hardware as well as the LaserJet printer. Figure 10 shows another set of storage drawers that are located beneath the worktable. When a person enters the trailer to be counted, he logs in a this location. Figure 11 is a closer view of the two computers and the shelves above the computers.

Figure 12, Dual pulse shape discrimination electronics.
Usually one system is operating, the other is a spare.

Figure 12 shows the instrumentation rack with the two pulse shape discrimination electronics. This is immediately to the right of the technician.

The Totally Shielded Low Energy In Vivo Counter.

Figure 13, The Totally Shielded Low Energy In Vivo Counter

When you walk into the area of this in vivo counter, you will see the instrument shown in the photograph shown in Figure 13, above. This is the view you will have as you walk two feet past the electronics cabinets. The front hydraulically operated shielding door is down in its normal rest position. The naugahyde bed is on "slides" to allow the bed to pull out of the counter. The person to be counted gets on the bed with his head at the left end and his feet, obviously, at the right end. He is then pushed back into the counter and the two Phoswich detectors are positioned on his chest. These detectors are mounted so that there is only a slight downward pressure on the person's chest. As the person breathes, the detectors float up and down, staying in the same relative position.

Figure 14, These are the hydraulic controls for the front door.

The shielding door is raised before the count is started. The hydraulic controls are found at the left end of the platform which is in front of the shield. If electrical power should fail, the door will automatically open.


Figure 15, This shows the two quality control "cans."	Figure 16, This shows the insides of the quality control cans with sources located at the bottom.	Figure 17, This shows the detectors mounted on top of the cans for the daily quality control tests.

Figures 15, 16, and 17, above, show the daily quality control sources used to establish the proper energy vs. channel relationship of the detectors. Two two-pound coffee cans contain americium-241 and low enrichment uranium-235 check sources, see the next photograph. The detectors are then placed into the cans and because of the design of the detectors, they always go into a standard reference geometrical relationship between the front face of the detectors and the surfaces of the sources. The electronics are then set for a consistent relationship of the photopeaks. Typically, when counting for enriched or natural uranium, the instrument is calibrated at a nominal 5-keV per channel, which means that the 59.6-keV photopeaks from americium-241 would fall in channel 12. Likewise, the 186-keV photopeaks from uranium-235 would fall in approximately channel 37. When counting workers to be done for americium-241 or the plutonium isotopes, the typical energy calibration is 1-keV per channel. Since the electronics allow pulse shape discrimination, it is important that the gain and zero of the system be set up properly. The counting rates under the two photopeaks are recorded for quality control purposes. If there is significant deviation from the normal, no counting of humans would be done until the problem is resolved.

This is the end of the discussion.