The Human Plutonium Injection Experiments

The Human Plutonium Injection Experiments

192

Los Alamos Science Number 23  1995

Met Lab procedure to analyze urine

samples of four Los Alamos workers

who had already experienced instances

of high readings from their nose swipes

failed to detect concentrations of pluto-

nium alpha activity consistent with the

high nose-count records.  

As it turned out, one problem with the

Chicago procedure was that running a

complete 24-hour urine sample (1 to 2

liters) through the column overloaded

the resin with organic material.  A drop

in resin performance altered results and

nullified the expected increases in sen-

sitivity.  The Chicago method worked

well with 100-milliliter aliquots at the

activity level of excreted plutonium-

239 expected for 5-microgram body

burdens.  But detection of body bur-

dens of 1-microgram or less would re-

quire an analytical procedure that used

a 24-hour urine sample and eliminated

the organic material and urine salts.

Concerns were heightened by an acci-

dent in August in which part of a plu-

tonium-chloride solution sprayed into

the mouth of Don Mastick, a young

chemist (see “A Swallow of Plutoni-

um”).  How much of the plutonium had

been absorbed by his gastrointestinal

tract?  What fraction of a serious dose

did the absorbed plutonium represent?

Was it safe for him to go back to work

at his old job and possibly be exposed

again?  In fact, to avoid further expo-

sures, Mastick was transferred tem-

porarily to Hempelmann’s group “to

work on the problem of detection of

plutonium in the excreta.”  

The research team at Los Alamos that

attacked the problem of detection meth-

ods included Perley, who continued to

investigate the Chicago procedure,

Robert Fryxell, who studied a method

of separating plutonium from urine that

used cupferron as the main complexing

agent, and Mastick, who investigated

various ether extractions.  The analyti-

cal procedure for isolating plutonium

from one liter of urine (a 24-hour sam-

ple) was outlined by Arthur Wahl.  In

September, Roger Kleinschmidt joined

the team to investigate methods of iso-

lating plutonium from urine ash samples

using a lanthanum-fluoride carrier to

precipitate plutonium from the dissolved

ash.  He would also direct the plating

and measurement of the final precipitate

with a goal of 90-per-cent chemical re-

covery of spiked urine samples.

Fryxell consulted with Wright Lang-

ham on the cupferron technique for

plutonium isolation.  Langham was a

biochemist who had been transferred to

Los Alamos in July 1944.  Previously,

he had spent a short period at the Met

Lab in the analytical chemistry group

where he’d been involved in plutonium

purification research.  Before long,

Wright Langham would become one of

the major names associated with the

detection, analysis, and evaluation of

plutonium in humans.

Cupferron extraction.  By late 1944,

Hempelmann’s team had devised a sat-

isfactory technique, using cupferron ex-

traction, for analysis of urine contain-

ing tenths of a nanogram of plutonium.

After collection, the samples underwent

a multistep preparation that included

evaporation to dryness, treatement with

acid and peroxide to remove organic

matter, and the cupferron extraction

step.  Eventually, the plutonium was

carried out of solution as a co-precipi-

tate with lanthanum fluoride, and this

final precipitate was transferred to a

platinum disc.  The activity of the plat-

ed sample was measured by placing the

disc in an alpha counter.  

However, analyzing spiked urine sam-

ples—or even samples taken from ani-

mals—in a laboratory environment was

one thing.  Analyzing samples from

people working with plutonium on a

daily basis was another thing entirely.

Early assays of workers yielded surpris-

ingly high results, indicating  that if the

0.01-per-cent-per-day excretion rate de-

rived from the animal data were applic-

able to humans, then these workers had

significant levels (greater than micro-

gram amounts) of deposited plutonium.

Sample contamination. An analysis

technique sensitive enough to detect

tenths of nanograms would easily de-

tect tiny particles of plutonium dust or

contaminated skin that, say, dropped

from a worker’s hand into the sampling

flask.  As a result, a collection proce-

dure was set up in which the worker to

Estimates of the Detection Regime

 

Plutonium-239 has a specific activity of 0.06 curies per gram, which means

that a nanogram of the substance undergoes about 130 disintegrations per

minute ((0.06 Ci/g) (10

-9

g/ng) (3.7 x 10

10

d/s/Ci) (60 s/min)

<

130 d/min/ng).

However, the Hanford “product” contained small quantities of other plutonium

isotopes (at the time, it was commonly referred to as 239-240 Pu), and ac-

counting for such impurities increases the rate to about 140 disintegrations

per minute per nanogram.  If we want to detect a tolerance limit of 5 micro-

grams of “product” in the body and only 0.01 per cent of the plutonium is

being excreted per day (several weeks after the initial exposure), then a 1-

liter, 24-hour sample of urine will contain 0.5 nanograms of plutonium.  If

only 100 milliliters (10 per cent) is analyzed, the test must be capable of de-

tecting 0.05 nanograms of plutonium.  A sample at this level emits about 7

alpha particles per minute (0.05 ng

3

140 d/m/ng), which, in an alpha counter

with 50 per cent efficiency, corresponds to a reading of 3 or 4 counts per

minute.  If we want to detect a lower tolerance limit of 1 microgram—one-fifth

as large—the counting rate drops to less than 1 count per minute.

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