To determine how much output an enhanced radiation neutron warhead needed to kill or incapacitate a human, Pentagon scientists have used irradiation experiments on animals, particularly monkeys.

Over the past eight years, monkeys, including some trained to perform simple tasks, have been dosed in laboratory experiments with neutron radiation of up to 10,000 rads to determine the levels at which they could no longer work and at which they would die, according to Defense Department officials.

A dental X-ray delivers about one rad, according to a government report, and a dose of 500 rads would kill half the humans exposed to it.

Neutrons destroy and change cell structure, particularly in the central nervous system. Victims havce fits of nausea, loss of muscle control and eventually die, if the dose is great enough, primarily from heart ort respiratory failure.

How much radiation was needed from a tactical weapon to make it useful against enemy troops was a question turned over to Pentagon scientists years ago.

Last year the Defense Department asked for and received approval from then President Ford to go ahead with production of an enhanced radiation warhead designed for battlefield use.

That warhead, according to defense officials, would affect individuals in its "kill radius" within minutes and permit occupation of the attacked area within several hours.

Because the neutron warhead - nicknamed the "cookie cutter" - would confine its radiation to a specific target and limit collateral blast and heat damage, it is considered a more credible nuclear weapon by its supporters.

The pentagon and the Energy Research and Development Administration are now seeking funds in ERDA's fiscal 1978 budget to start production of this enhanced radiation warhead for the 56-mile-range Lance missile.

It would be the first publicly acknowledged tactical nuclear weapon specially designated to kill people by radiation rather than destroy installations and equipment by heat and blast.

The new warhead has never been tested against humans, according to defense officials.

Instead, from the tests on monkeys and other animals, a Defense Nuclear Agency statement notes,"estimates of biological effects" on humans from the proposed Lance warhead "have been sythesized."

A defensed scientist involved in the experiments said recently that the tests have all been at dosages designed to kill both the animals and people.

"There have been no low dose studies," he said, "where survivability was involved."

He added that he believes casualties from a neutron warhead attack would recover at approximately the same rate as those Japanese who survived the Hiroshima and Nagasaki atomic bombs.

A recent series of experiments at the Armed Forces Radiobiology Research Institute illustrate the testing techniques used over the past years.

Ten monkeys, averaging 3 1/2 years in age, were trained to operate treadmills. Each animals exercised on the machine for eight weeks to a point where he could run 10 minutes and rest five over six hours without tiring.

Each monkey was then placed in a compact cubicle called a "squeeze box," according to an official report of the experiment, and "exposed to a single whole-body dose of mixed gammaneutron radiation " totaling 4,600 rads.

The radiation did not pain the monkeys, according to defense officials.

Five seconds after exposure, each animal was put back on the treadmill and tested to see how much the radiation affected his performance and how long it took for him to die.

Results varied from monkey to monkey although 80 per cent became incapacitated within eight minutes after exposure.

All the monkeys eventually died from their radiation exposure but survival time according to the report, "ranged from seven to 132 hours."

One scientist involved in the monkey experiments said recently that because of the range of responses, there was no "certainty that the results in monkeys would be directly translatable to humans.

"Clinical information," he said, was the only way to determine human reaction and that was not available except in the few cases of radiation accidents.