Plutonium Powered Pacemaker (From 1974) (opens in new tab)

(orau.org)

63 pointsBafS9mo ago28 comments

28 comments

For context, the 0.1 rem yearly dose to the patient is about 1/6th of the average background dose we all get every year.

This Pu-238 is the same stuff that's powering the Voyager probes and a few Mars rovers.

Note that it's not Pu-239, which is fissile nuclear fuel for chain reactions (power plants, bombs, etc.)

stinkbeetle9mo ago

> For context, the 0.1 rem yearly dose to the patient is about 1/6th of the average background dose we all get every year.

Wouldn't you be more concerned about dose rates in tissues near the device though, rather than whole body dose? At the surface of the pacemaker it would be about 90 rem / year.

BurningFrog9mo ago

Since it's a device that saves the life of the patient, you can accept a lot of patient risk as a tradeoff.

1 more reply

SoftTalker9mo ago

Pu-238 decays mainly by alpha decay which would be easily contained by the titanium casing.

2 more replies

kondro9mo ago

REM is already an adjusted measure for absorption, not an general quantity of radiation.

1 more reply

jmb999mo ago

If I die without a pacemaker, or maybe have an increased risk of certain cancers with a pacemaker but get to live, I’d choose the pacemaker.

1 more reply

_kb9mo ago

Or approximately 100 bananas, for scale.

acidburnNSA9mo ago

Banana equivalent dose is 0.01 mrem, so 0.1 rem = 100 mrem = 10,000 bananas.

ChuckMcM9mo ago

Yeah but their spouse :-) 75x larger dose.

acidburnNSA9mo ago

No it's less! They switched from rem to millirem for the spouse.

1 more reply

jandrewrogers9mo ago

> Dose rates at the surface of the pacemaker are approximately 5 to 15 mrem per hour from the emitted gamma rays and neutrons.

Where are these gamma rays and neutrons coming from? The decay chain for Pu-238 is via alpha emission (Pu-238 -> U-234 -> Th-230 -> ...) which won't penetrate the casing.

acidburnNSA9mo ago

Not sure about neutrons. Gammas, or x-rays at least, could come from bremmstrahlung.

pfdietz9mo ago

Alpha particles will produce secondary radiation occasionally when they hit light nuclei. The oxygen in the Pu oxide is almost entirely O-16 to minimize neutron production.

Horffupolde9mo ago

Possibly Pu-239 or other impurities.

cyberax9mo ago

All U and Pu isotopes undergo spontaneous fission, producing neutrons and random daughter products.

bobmcnamara9mo ago

Some very small portion of Pu-238 will eventually pass through Tl-210 -> Pb-209.

sanarothe9mo ago

For similar / further reading on historical pacemakers, check out https://www.implantable-device.com/category/implantable-comp... where David Prutchi has amassed what I think is a comprehensive history of pacemakers / neurostimulators ranging from these early atomic designs up through current day devices / companies.

xattt9mo ago

More interesting to me is how this tech was programmed. There would have been some external unit to set parameters.

userbinator9mo ago

Since it's from 1974, my guess is a few trimpots behind a sealed cover.

anovikov9mo ago

Pu-238 in this thing would cost $14K in today's prices!

j / k navigate · click thread line to collapse

28 comments

acidburnNSA9mo ago

For context, the 0.1 rem yearly dose to the patient is about 1/6th of the average background dose we all get every year.

This Pu-238 is the same stuff that's powering the Voyager probes and a few Mars rovers.

Note that it's not Pu-239, which is fissile nuclear fuel for chain reactions (power plants, bombs, etc.)

stinkbeetle9mo ago

> For context, the 0.1 rem yearly dose to the patient is about 1/6th of the average background dose we all get every year.

Wouldn't you be more concerned about dose rates in tissues near the device though, rather than whole body dose? At the surface of the pacemaker it would be about 90 rem / year.

BurningFrog9mo ago

Since it's a device that saves the life of the patient, you can accept a lot of patient risk as a tradeoff.

1 more reply

SoftTalker9mo ago

Pu-238 decays mainly by alpha decay which would be easily contained by the titanium casing.

2 more replies

kondro9mo ago

REM is already an adjusted measure for absorption, not an general quantity of radiation.

1 more reply

jmb999mo ago

If I die without a pacemaker, or maybe have an increased risk of certain cancers with a pacemaker but get to live, I’d choose the pacemaker.

1 more reply

_kb9mo ago

Or approximately 100 bananas, for scale.

acidburnNSA9mo ago

Banana equivalent dose is 0.01 mrem, so 0.1 rem = 100 mrem = 10,000 bananas.

ChuckMcM9mo ago

Yeah but their spouse :-) 75x larger dose.

acidburnNSA9mo ago

No it's less! They switched from rem to millirem for the spouse.

1 more reply

jandrewrogers9mo ago

> Dose rates at the surface of the pacemaker are approximately 5 to 15 mrem per hour from the emitted gamma rays and neutrons.

Where are these gamma rays and neutrons coming from? The decay chain for Pu-238 is via alpha emission (Pu-238 -> U-234 -> Th-230 -> ...) which won't penetrate the casing.

acidburnNSA9mo ago

Not sure about neutrons. Gammas, or x-rays at least, could come from bremmstrahlung.

pfdietz9mo ago

Alpha particles will produce secondary radiation occasionally when they hit light nuclei. The oxygen in the Pu oxide is almost entirely O-16 to minimize neutron production.

Horffupolde9mo ago

Possibly Pu-239 or other impurities.

cyberax9mo ago

All U and Pu isotopes undergo spontaneous fission, producing neutrons and random daughter products.

bobmcnamara9mo ago

Some very small portion of Pu-238 will eventually pass through Tl-210 -> Pb-209.

sanarothe9mo ago

xattt9mo ago

More interesting to me is how this tech was programmed. There would have been some external unit to set parameters.

userbinator9mo ago

Since it's from 1974, my guess is a few trimpots behind a sealed cover.

anovikov9mo ago

Pu-238 in this thing would cost $14K in today's prices!

j / k navigate · click thread line to collapse