Archive for September, 2009

Los Alamos Incident One (LA-1)

September 24, 2009

Tales from the Nuclear Age:

copyright © 2009 by Charles Glassmire _________________________________________________________________

Sept. 23, 2009

Los Alamos Incident One (LA-1)…

     The day was August 21, 1945. The event occurred in a small wooden shack known as “Room 49”, although 49 wasn’t the room number. Rather, it was a code designation for the element Plutonium. Nobody at Los Alamos was allowed to mention “Plutonium”, let alone the specific isotope 239. So 94Pu239 was coded as “49” and this location was where experiments were done on the material. It was positioned on the side of a steep hill far from the main lab buildings and concealed in the Sangre de Cristo forest of the Manhattan Engineering District (soon to be known as Los Alamos Scientific Laboratory).

      By this date, the first Plutonium bomb (Fat Man) had already been dropped on Nagasaki, and performed as expected. Consequently, the Empire of Japan had surrendered a few days later. The War in the Pacific was over and the world fell into a fitful peace, but a lot was still unknown about the newly discovered element, and scientists were still probing its secrets.

      Harry K. Daghlian Jr. (pronounced “Dolly-an”) was a 24 year old Armenian-American physicist with the Manhattan Project. He was fresh from an assignment to assemble the plutonium core of the Trinity Shot, which had been tested successfully in July. Now he was assigned the task of gathering more data on Plutonium criticality. Born in Waterbury, CT, Harry was the child of Harry Sr. and Margaret Rose. His father was an X-ray technician at a hospital. His uncle was professor of physics at Connecticut College, and fostered Harry’s interest in math and physics. Harry Jr. studied Mathematics at MIT, and then transferred to Purdue, obtaining a B.S. in Physics in 1942.

      On the day of the incident, Harry attended a concert in the early evening, and then went back to his lonely shack in the woods to continue working; arriving about 9:30 p.m. (The site was called the “Omega Site”.) Inside the 49 room, seated at a desk across the room from the assembly, was Army Private Robert Hemmerly, on guard duty from the Special Engineer Detachment. Whenever Plutonium was in use, a guard had to be present. Hemmerly greeted him with a curious “Hi Harry” and resumed reading his newspaper, with his back to the experimental area. It was against procedure for persons to work alone on critical materials.

      Harry removed the Plutonium core from the vault and began to assemble his apparatus. The core weighed about 6.2 Kg, and it had been enhanced by processing to the enrichment needed for weapons use. This processing had eliminated other isotopes of Plutonium such as Pu 240, which would contaminate the fission process. This sphere was now very highly enriched in the 239 isotope, and was thus capable of thermal neutron fission. This material was of a high enough purity to be classified as “Weapons Grade”, meaning it would sustain a chain reaction, and could be directly used as the core material for an atomic weapon. Under the right conditions, this core could produce a nuclear detonation.

      Harry had been working since the early winter in the drafty makeshift wooden structure, all throughout the snows and finally into the warm summer, each day meticulously filling a hand written notebook with data. He was building a stack of Tungsten Carbide (symbol WC) to surround the metal 49 sphere. Tungsten Carbide had the ability to reflect neutrons back into the core and that would increase the fission rate inside the material. It was called “increasing the criticality” of the assembly. That afternoon in an earlier experiment, he had found the rig went critical after a stack of five layers of WC bricks. Now he was determined to make the stack into a smaller and tighter arrangement, and re-run the test.

      The rig was surrounded with neutron detectors, and gamma counters, measuring released alpha particles, neutrons and gamma radiation flux. Like any good scientist, as each layer of bricks was stacked, the neutron flux and gamma radiation would increase, whereupon, oblivious to any danger, he would dutifully record the new data. Then the reaction would slowly die as the new assembly reached equilibrium. 

       As the stack grew, the Geiger Counters filled the room with audible clicks, which rose to a buzz as the rig approached dangerous levels. Neutron counters were silent, and registered their particles by a flashing light. Harry relied on both of these signals to judge the status of the experiment. Slowly he stacked the heavy bricks around the bomb core. He had completed the fifth layer of bricks when he attempted to add an additional brick to the stack with his left hand. As he lowered the brick toward the core, the detector buzzing and flashing shifted into high gear, alerting the room to approaching Supercriticality. Harry jerked his hand back but the 4.4 Kg heavy brick slipped from his grasp and landed on the top of the 49 sphere.

      This instantly caused a supercritical chain reaction. This was not an atomic explosion, but there was an immediate release of large amounts of energy. Neutrons, gamma rays, other particles and visible light flooded into the air in a huge flash burst. The light was so intense it passed through the wooden walls and lighted the newspaper the guard was reading some distance across the room. Private Hemmerly became the first man in history to actually see a criticality and live to tell the story. He described it as a brilliant blue flash in the air. The blue light was probably Cerenkov Radiation, characteristic of neutron fission.

      Realizing the terrible danger, instinctively Harry grabbed the brick with his right hand and pushed it away. He later described a tingling sensation in his hand as it entered the blue glow surrounding the spherical core. Hemmerly turned from his newspaper to see Harry standing near the core, hands at his side in embarrassment at what he had caused. Standing beside the critical core, Harry received a huge dose of radiation, higher than any man had ever received before. It was later estimated the radiation dose rate at this moment was 10 to the eight roentgen per second near the rig. A mere 600 roentgen absorbed dose is sufficient to kill more than half of those irradiated at that dose.

        Harry explained to Hemmerly what had happened in the accident and haltingly disassembled the rig. A graduate student had just arrived at the site, and she drove Harry to the Los Alamos Hospital. He was given immediate blood transfusions and fluids, and later awakened enough to be coherent and talk to his care givers. All knew he was dying. Hemmerly stayed behind to alert his Sergeant to the accident.

      Sadly, a scientific opportunity presented itself in this most bizarre situation. This was the first casualty in peacetime history to receive a lethal dose of radiation, and the effect of this much radiation on the human body was completely unknown. So for the next days while Harry slowly deteriorated, he methodically related the effects on his body to medical personnel observing his condition. His thoughts, physical symptoms, blood work, gastrointestinal symptoms, radiation burn trauma as a function of time after exposure, were all rigorously documented for the first time in the annals of medicine. This physical distress is now known as the “Acute Radiation Syndrome”.

      This Health Physics criticality accident was later assigned the designation of “LA-1” (for “Los Alamos event one”). Private Hemmerly survived relatively well but was to die 33 years later of blood cancer.

      Neutron radiation has the capability of making other inert materials themselves radioactive. Now Daghlian’s body was neutron activated, and was now emitting gamma radiation and was dangerous to be near. He lived for twenty one days before his body surrendered. He had tickled the tiger’s tail, and was laid to rest in a lead lined casket. The Plutonium core he used was named “The Demon Core”, and was later to cause further death. He died a casualty of World War II who never went near a battlefield; perhaps the first known peacetime victim of the Nuclear Age.

(to be continued)

 

First Criticality

September 12, 2009

Tales from the Nuclear Age:

 Copyright © 2009 by Charles Glassmire

(Stories as true as my memory recalls)

_________________________________________________________________

Sept. 12, 2009

First Criticality

          I was visiting the Los Alamos Scientific Laboratory (LASL) in New Mexico, on the NERVA program, along with my friend and Nuclear Engineer Dave. We were to examine radioactive samples of NERVA (Nuclear Engine for Rocket Vehicle Applications) fuel in the gigantic “Hot Cells” at Los Alamos. The samples were to be examined under microscope, then polished and photographed as examples of NERVA fuel material after it had been irradiated with high doses of neutrons. This would show how the fuel metal structure in the Nuclear Rocket Engine would behave after a period of operation in space. LASL had one of the few radiation qualified Metallographic facilities to handle the hot material.

          The Los Alamos Scientific Laboratory is nestled high in the Sangre de Cristo (Blood of Christ) Mountains of New Mexico. It is a desolate yet beautiful area which covers the Pajarito Plateau, featuring tree-filled canyons and parched high altitude scrub growth typical of the high plains of that state, and abounding in wildlife. It was first established in strict secrecy during World War II. Back then it was identified only by its government code name “Site Y”. Groves named it “the Manhattan Engineering District”, (MED) because there weren’t any operations in Manhattan. It later became known as The Manhattan Project.

          The government facility had been purchased from the locals and was chosen because it was very remote and access through the mountains was limited. It was created from the lands surrounding a private boy’s school and a hunting lodge (known as “The Ranch”) owned by Site Y’s first Scientific Director, Dr. J. Robert Oppenheimer. After he was appointed by General Groves, “Oppie” moved his family into the Ranch, and rumor has it the Bomb was designed at breakfasts around the Ranch’s big wooden dining table. Preliminary sketches were actually done on a napkin, which is preserved in the LASL bomb museum.

          The mission of the Manhattan Project was to research, design and then build the first Atomic Bombs for the United States, which was then involved in defeating the Axis Powers (Germany, Japan, Italy) in open combat. Originally, the lab was built by an Army Colonel (later General), Leslie Groves. Groves was used to running big projects and was fresh off an assignment charged with building an odd shaped building known as the Pentagon. The Army was in charge of Site Y because scientists were worried that Nazi Germany was hard at work building their own version of the bomb. Letters from Albert Einstein and Leo Szilárd directed to President Roosevelt noted the fact that the element Uranium could be used to create a “Chain Reaction” with the release of enormous amounts of energy. Einstein/ Szilárd said this could probably be used to create a new kind of gigantically powerful “bomb”. Albert Einstein really didn’t know anything about nuclear fission, but the scientists knew his name was important enough to be credible. The letter certainly got the president’s attention.

          Ultimately, the lab was to employ over 130,000 army and civilians, and was to cost over $2 billion dollars ($24 billion in today’s dollars).  The Manhattan District involved over 30 different locations around the United States. It was tasked to develop the first two Atomic Bombs (code named “Little Boy” and “Fat Man”) which ushered the modern world into the Nuclear Age.

          On the day before Dave and I began work, we were being driven about Los Alamos by engineer friends who lived in the area and wanted to show us around. I was riding in the back seat while the driver narrated information about what we were seeing. Much of the area was heavily forested and interspersed with laboratory buildings and crude Army barracks, given various code number designations. As we drove down a hill in Omega canyon, the driver pointed to a forested area to the right of the car and said

 “Of course you know about the first criticality incident. There’s where it occurred in a wooden shack back in the woods there. We can’t go in there; it’s fenced off now and it’s still rather hot…”

           I had no idea what he was talking about, and quickly asked for details as we continued driving on down the road. It turns out the wooden shed he casually pointed out had developed a rather ominous history. Here is the story he told:

(Current declassified accounts of this incident now differ somewhat, but this is what I was told in 1965 by the nuclear engineer who lived near Los Alamos ) :

           The time was 1945, and valuable data still was needed on the criticality of Plutonium, the element used in the Fat Man bomb. “Criticality” was a term implying how much Plutonium was needed to cause a nuclear explosion. Calculations had been made but nobody really knew. Plutonium was a new element, only discovered in 1941, and very little had been made and refined. Thus, it was precious and expensive stuff, and not much was available for measurement on bomb grade material.

          So a researcher was charged with determining the criticality measurements on the isotope, and was given enough in the form of two half spheres (later estimated to be about 6 Kg of Pu239) to experiment with.

          He was assigned a rickety wooden shack in the woods and some measuring equipment, so that any accidental contamination might not turn into a serious expensive cleanup. (You did things this way because there was a war on.) It was his job to confirm experimentally exactly how much Pu would create an atomic explosion, and how close the two half-spheres had to come to initiate a fission chain reaction. Knowing this, one could estimate the neutron “cross section” for Pu239. (i.e. how big of a target did the Plutonium 239 atom make when being hit by a neutron. This number then gave the probability of a fission event).

          I found it amusing that neutron cross sections of fissile nuclei were measured in a unit called “Barns”. More Barns meant the nucleus made a bigger target for incident neutrons. The cross section data was collected into a series of graphs for each nucleus, and the data was put into a book which was called the “Barn Book”. This book was colored green, we used it all the time in our work, and the book had a line drawing of a farmer’s barn on the cover!

          Now bringing two halves of a nuclear bomb together was not a terribly wise experiment to do, but lots of people risked their lives under the duress of wartime. When one has assembled enough enriched material (Plutonium 239 or Uranium 235) to produce a nuclear chain reaction, simply accidentally bringing that amount together in the nearby space can produce a nuclear chain reaction and release of energy into the surrounding air. This is called a “Criticality Event”. It is not a bomb explosion, but lots of energy, fission products and lethal radiation is released. It can be deadly to anyone nearby. It is even possible to occur in a modern laboratory when two lab technicians are transferring enriched material from one room to another. Should they pass close by in the hallway, carrying enough material, the two masses can interact with emitted neutrons to “flash” into a critical event chain reaction.

          So, personnel from the Health Physics department are employed to track the movements of all radioisotope materials in a laboratory. The amount in a room is weighed and measured, and recorded by the Health Physics people. One cannot transfer material without the permission of the isotope control folks, who will record how much is moving, where it is going to, whether the destination is “overloaded” and who else is in transit in that local area. This insures no persons will accidentally pass in the hallways and go critical.

          But these controls had not yet been developed in the early days of the Manhattan Project. The Criticality Event was an unknown effect no one had ever seen occur, and there was little experience of this in the short history of atomic research.

          So our researcher had mounted the two half spheres of a bomb core on a lathe bed, and, accompanied by the clicking of Geiger counters and neutron detectors which measured emitted radiation, he was slowly cranking the two Plutonium halves of an Atomic Bomb closer and closer together, and recording the data in a little notebook, to see what would happen…

(To be continued)

The Tybee Island Bomb

September 5, 2009

Tales from the Nuclear Age:

 Copyright©2009 by Charles Glassmire

_________________________________________________________________

Sept. 5, 2009

The Tybee Island Bomb

           Tybee Island sits peacefully at the mouth of the Savannah River, at the eastern most point of the state of Georgia. The island forms the breakwater at the mouth of the River where it empties into the Atlantic Ocean, and its’ seaport is the second largest seaport in the United States. It’s a quiet place, filled with summer tourists, lots of hotels, and bars with names like Uncle Bubbas, StingRays and The Wild Rose. The favorite dish in these establishments is often Red Beans and Rice. Tybee even has its own lighthouse, ($5 to walk to the very top). The 40,000 summer tourists do touristy things like sailing, swimming and walking in the sun, and if you time it just right, you can see an occasional Alligator in a habitat on the beach.

          It’s been 51 years since a wounded Strategic Air Command B-47 dropped an H-Bomb in the waters of Wassaw Sound, some sixteen miles from Savannah, and just south of Tybee Island. Each day, the tides come in and go out with a gentle rhythm, and seem to have washed away the memories of that fateful night so long ago. Many of the natives have forgotten or perhaps never knew of those dark events in February of 1958.

          Afterward, the Air Force searched the waters of Wassaw Sound diligently with a team of UDT navy divers, boats with Sonar, and troops from the 270th Explosive Ordinance Disposal Squadron. They even had a blimp hovering overhead, looking for a hole in the salt marshes or nearby beaches. The search went on for over nine weeks, until well into April of that year and, in the end, nothing was found. Some theorized the weapon was buried into the mud many feet below the mud surface. Finally, admitting to a classic Broken Arrow, the United States Air Force, on April 16th 1958, cancelled the search, and declared the bomb “irretrievably lost”. Then the Pentagon wrote a nice letter to the Atomic Energy Commission (which technically still “owned” the bomb) politely asking the AEC to replace the H-Bomb they had lost:

          “…the weapon is considered irretrievably lost. It is requested that one [redacted] weapon be made available for release to the DOD as a replacement.”

         Certainly Tybee’s City Council wanted everyone to forget what had happened. Councilman Jack Youmans in 2004, said

          “I wish they’d forget about the whole thing. They’re just wasting their time. It ain’t going to hurt anybody. And it scares the hell out of the tourists….”

          It also bothered an Air Force Lt. Colonel by the name of Derek Duke. Colonel Duke lived in Kingston Ga. about 90 miles from the incident. He had operated a National Security Agency operation in Vietnam, and he’d been searching for the lost weapon since 1998, to the annoyance of everyone except a few concerned residents. Pamela O’Brien, A member of Tybee’s Council, stated:

          “I’m pleased to see the attention this is getting…When others in government say they would prefer to put their heads in the sand and forget about it, they should remember that it is the same island that the bomb is buried in.”

          Colonel Duke hired a small crew in the late 90’s including a “retired” CIA officer and some local shrimpers. They examined Air Force records of the bomb release, and estimated where the bomb was deposited. By 2004, he and his crew had been carefully dragging the waters of the sound with Geiger counters and metal detectors, searching for radiation leaking from the weapon.  In that year he claimed to have found an area of “high radiation”. Rep. Jack Kingston, a Georgia Republican said:

         We’re horrified because some of that information has been covered up for years…”

           In August of 2000, after civilian inquiries, Kingston requested the investigation be reopened. The government did so, could not find the weapon (although some indicators found higher than background radiation levels) and did not change its position afterward.

          The 2004 “discovery” by Duke, created outrage in the local population, and Rep. Kingston called for a congressional investigation as to why the Air Force had ceased hunting for the missing bomb. The investigation search was reopened in September of 2004. In a report to Congress back then, the government had admitted there was a chance of dislodging the weapon during accidental dredging or fishing in the area. The area has a lucrative shrimp and fishing industry, and officials were concerned that the high explosive in the weapon could detonate if disturbed. This would scatter radioactive material over the area and contaminate the sea life, pollute the drinking water table, and would be disastrous to the local economy.

          After this third investigation, the Air Force insisted the wisest course was to let the weapon rest, and there was no possibility of a nuclear detonation, since they claimed the “capsule” detonator (called the “pit”) had not been installed in the bomb. This point would be called into question later:

          “…the likelihood that a particular accident would involve a nuclear weapon [detonation] is extremely limited …Our biggest concern is that of localized heavy metal contamination…”

          The question of whether the Plutonium core had been inserted into the bomb was (and is) very much of interest. Without the fissile material, the object is simply a shell containing high explosive. There could be no nuclear detonation. If the Pit was inserted into the weapon, there is a very small possibility of nuclear detonation.

          In 1966, the Chairman of the Congressional Joint Committee on Atomic Energy, Chet Holifield, held closed door hearings on missing weapons. He asked Mr. Jack Howard, assistant to the Secretary of Defense Robert McNamara, to provide a list of lost weapons. The response by Mr. Howard listed two classes of weapons. One class was “weapon-less capsules” and the other “complete weapons”. The Tybee bomb was called a complete weapon. This “Secret” document was declassified in 1994.

          Bert Soleau, the CIA officer from Dukes team, wonders whether the bomb could be recovered by terrorists, and used for their own purposes. The Plutonium is a chemical poison and would be difficult to handle. It would be a serious hazard if disbursed in a dirty bomb, although the alpha radiation it emits is a hazard only if ingested.

          Don Moniak is a nuclear weapons expert with the Blue Ridge Environmental Defense League in Aiken, South Carolina. He says:

          “I believe the plutonium capsule is in the bomb, but that a nuclear detonation is improbable because the neutron generators used back then were polonium-beryllium, which has a very short half-life. Without neutrons, weapons grade plutonium won’t blow…”

          However, in any fissile material, there are always stray neutrons wandering around. If they bump into a Plutonium 239 nucleus, it could fission, releasing two more neutrons to wander around, and …

                                                 (to be continued)