WARNING Revision & Update: Metascopes US/F & US/AM

A couple weeks ago there were 2 Lewyt US/AM's for sale on EBay. Can't find them at the moment. Unless EBay has recently banned them they have been the best bet for finding one. The US/F is far less common.

Introduction
If you own, know someone who owns or come across one of the Type US/F and/or Type US/AM infrared viewing metascopes these two specific metascopes contain radium. Radium is a cancer causing radioactive substance. It would be incorrect and unwise to assume the non working metascope is no longer a hazard. They no longer work when the infrared viewing phosphor within them has reached the end of it's limited lifespan. But the radium within them with a half life of 1600 years keeps on emitting radioactive emissions.

DO NOT attempt to open either of these two metascope models. They cannot be repaired or made to view infrared light again. Doing so will expose you to the radiation emitted by the radium. Read on to learn the hazards involved and precautions to take.

If you read only a small part of this make it "The Bottom Line" a few paragraphs below.

(Disclaimer: This is not nor is it intended to be an authoritative treatise on what you need to know about radium to keep yourself and others safe. It's a warning to prevent exposure to radioactive radium. Professional advice should be sought from the professionals at the links shown at the bottom of this post.)

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Understanding the Dangers of Radiation

The units of measurement standardized by the various radiology professions as well as the Geiger counters that attempt to quantify gamma radiation have led to the following official position.

"Current guidelines for radiation exposure are based on the conservative assumption that there is no safe level of exposure. In other words, even the smallest exposure has some probability of causing a stochastic effect, such as cancer. This assumption has led to the general philosophy of not only keeping exposures below recommended levels or regulation limits but also maintaining all exposure "as low as reasonable achievable" (ALARA). ALARA is a basic requirement of current radiation safety practices. It means that every reasonable effort must be made to keep the dose to workers and the public as far below the required limits as possible." (reference: https://www.nde-ed.org/EducationResources/CommunityCollege/RadiationSafety/safe_use/exposure.htm

Short Term vs Long Term
The level of gamma radiation emitted by these metascopes is unlikely to produce any short term effects that can be related to where the exposure to a radioactive substance occurred.

The very real danger is the effects of radiation exposure are accumulative over a lifetime. They are added to the normal radiation levels we are exposed to from the sun, medical tests and procedures and even some of the food we eat.https://www.nrc.gov/about-nrc/radiation/around-us/doses-daily-lives.html

With certain exposures having a higher risk significance due to the amount of radiation one is exposed to. Add to this the amount of time of an exposure also increases the risks.

THE BOTTOM LINE
All of us are familiar with how long a chest x-ray exposes us to radiation and the medical profession's level of caution to limit exposure and repeated exposures. Particularly exposure to our thyroid gland.

Put your chest adjacent one of these metascopes for the amount of time it takes to do a chest x-ray and you'll be exposed to the equivalent of about 3 chest x-rays. More significant, leave it next to your chest for longer than the brief part of a second it takes to do a chest x-ray and the radiation exposure increases x 3 every fraction of a second. Then consider you'll be adding this exposure to all the other radiation exposures over your lifetime. With the potential end result being bone cancer at some point.

But there are ways to limit this exposure if you understand radium and these two metascopes.

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The Metascopes - Background
Unlike the infrared viewers using an image tube (Sniperscope/Telescope) the Metascopes developed during WWII utilized the combination of an infrared sensitive phosphor with an excitor to stimulate the phosphor to view infrared light. The phosphors varied as did the excitors. The most common excitor was small battery operated incandescent bulbs.

The first two metascopes to go into mass production for use by U.S. Forces were the Type US/F for the U.S. Army and the Type US/AM for the U.S. Navy. Unlike other infrared viewing devices the excitor used for these two metascopes was radium. Tens of thousands were produced from the end of 1943 and into the early 1950's. After these two metascopes became obsolete many were sold on the civilian market and are owned by civilians to this day.

Both the US/F and US/AM utilized a swing arm with a radium coated disk. Pushing a button released the swing arm to fall into a position where radium alpha particles excited the phosphor. The devices were physically tilted to swing the radium disk back into a locked position away from the phosphor.

To protect the users and other personnel from exposure to radioactive radium alpha particles the Type US/F and Type US/AM metascopes were sealed when manufactured and not rechargeable. They were designed and intended to be replaced with a new one when they no longer worked.

(To view a larger version of an image click on the image)
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Type US/F

Manufactured by Electronic Laboratories of Indianapolis, Indiana & Samson United Corporation of Rochester, NY concurrent to one another. Each company produced a slightly different version of the Type F design though both operated the same.

Quantity manufactured during WWII was 55,000 for the U.S. Army Corps of Engineers.










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Type US/AM

Manufactured by the Lewyt Corporation of Brooklyn, NY.

Quantity manufactured during WWII was 21,000 for the U.S. Navy with at least one additional order after the war.


The metascope shown on the left was opened in an apparent attempt to repair it. When the repair failed the item was sold on EBay with the radium disk exposed. The photograph was taken from a safe distance using a telephoto lens. The metascope on the right was another also purchased off EBay and remained sealed. But the sealed unit cannot stop the emission of gamma radiation (see below).







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Radium

As mentioned above the US/F and US/AM metascopes used radium's radioactive alpha particles to excite the infrared sensitive phosphors for viewing infrared light. Radium emits both alpha and beta particles which remain sealed within the metascopes. Gamma radiation is very different and a primary focus of this post. It is explained in a bit more detail below.

At the time they were manufactured the emission of gamma radiation was minimal and not believed to be dangerous.

As you read the following keep in mind the half life of radium is 1600 years...

Alpha Radiation
Radioactive alpha particles travel only a very short distance and cannot penetrate your skin. The danger of exposure is by inhaling or ingesting.

Beta Radiation
Radioactive beta particles can penetrate your skin. The danger of exposure is by inhaling, ingesting or exposure to your skin.

Gamma Radiation
Radioactive gamma waves are invisible to the human eye. They penetrate steel, concrete, humans and just about everything other than a properly constructed lead shield. The exception is a naturally occurring substance, water.

At the time the US/F and US/AM metascopes were manufactured the level of gamma radiation being emitted was low and believed to be safe for a few years. With the older units being discarded after use and replaced by a newer one. They did not foresee the eventual sale of these units as surplus to the public nor their long term possession as a collectors item.

Radium decays over time significantly increasing the amount of gamma radiation it emits into the dangerous levels.

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Confirming the Gamma Radiation Danger

In mid 2018 two sealed Type US/AM metascopes and a third that had been opened were examined using a Geiger counter. Each was examined individually before readings were taken collectively.

The Observations are Summarized here.

• The readings were the same for each of the three
  
  
• Adjacent the closed front plate the Geiger counter reading was well into the dangerous levels. At a distance of 1 foot the Geiger counter reading dropped into the normal level.
  
  
• Adjacent the eyepiece at the rear of the scope the Geiger counter readings were substantially lower but not down into the level considered safe. 6 inches from the eyepiece the level returned to normal.
  
  
• The tests were repeated after each metascope was individually placed inside an air tight metal ammo can and the can was sealed. The Geiger counter readings were the same as absent the ammo can.
  
  
• All three metascopes were placed together inside one sealed ammo can atop one another. The Geiger counter readings directly adjacent the can and on top of the can were 3x the danger level observed individually adjacent the front of each scope with or without the ammo can. Readings at 1 foot were in the normal range.
  

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A Few Safety Tips with no Guarantees

Protection from Radiation is broken down into time, distance and shielding.

Time
Best case scenario is never own or go near one of these metascopes. If you already have one strictly limit the amount of time you are exposed.

Distance
The point at which to start your distance measurements is the location of the radium. The Type US/F being a relatively small cube with the radium potentially behind it's shield on onside. The radium is at the front of the Type US/AM metascope.

Keep in mind alpha and beta radiation can contaminate whatever comes close to them. If the metascope has been opened it requires extra caution. An air tight container can contain alpha and beta. But not gamma. This type and level of gamma doesn't contaminate other things.

• If you absolutely have to pick up the type US/AM the level of radiation at the eyepiece will be less than at the front of the scope. Not necessarily "safe" but safer than the front.
  
  
• A set of long sturdy tongs that will hold onto a metascope is safer than your hands.
  
  
• Storage should take into account the farther the distance the better. There is no guarantee the 1 foot safe level I experienced will apply to yours.

Shielding

• A lead x-ray vest (0.5 mm lead) wrapped twice around the ammo can containing one US/AM metascope cut the level of radiation in half.
  
  
• The lead pigs used to safely transport the small amounts of radium used by radiology labs are not large enough to hold one of these metascopes.
  
  
• Protective gloves for handling radium are expensive. Heavy duty chemical gloves offer zero protection from gamma radiation.
  
  
• Water is a very effective inexpensive shield from gamma radiation. Surround the metascope 360 degrees with jugs of water.
  

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Disposal

• Hazardous Material Collection sites will not accept radioactive material
  
  
• You might find a government agency (Board of Health, Radiation Branch) willing to turn a metascope over to but know the Federal, State and Local laws regulating the control and possession of radium tend to be punitive in nature.
  
  
• Contact with the Board of Health, Radiation Branch, in my area revealed there is no location to surrender radium and they knew of no agency willing to accept it.
  

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Finally, the last comment....

Who contracted for the manufacture of these metascopes is also who allowed them to be sold as surplus to civilians. Ignorance during the time these events happened should not alleviate them of their responsibility.

If anyone locates a location these can be legally and safely surrendered please PM me on this forum.

Jim


For Further Information:

U.S. Nuclear Regulatory Agency
https://www.nrc.gov/about-nrc/radiation.html

The U.S. Environmental Protection Agency (EPA)
https://www.epa.gov/radiation

American College of Radiology
https://www.acr.org/Clinical-Resources/Radiology-Safety/Radiation-Safety

Science Buddies (simple explanation for kids using x-rays)
https://www.sciencebuddies.org/science-fair-projects/references/radiation-introduction-radiation-safety