Analysis of Soviet smoke detector plutonium

Plutonium is a practical and versatile substance, having applications that range from planetary extinction to routine fire protection, depending on the user’s fancy.  The element has been mass-produced in nuclear reactors since World War Two, and occurs in various isotopic compositions in the discharged reactor fuel, reflecting variables such as fuel burnup, initial uranium enrichment, and neutron spectral characteristics of the reactor design.  The Soviet Union cooked up more plutonium than any other nation.  Most of this was slated for the noble purpose of containing capitalist imperialism, but some found its way into commercial ionization smoke detectors like the KI-1, RID-1, and RID-6M.  (The bourgeois warmongers themselves preferred, and still prefer, americium-241 for this application.) Occasionally, people in the former USSR try to peddle their old smoke detector plutonium on the nuclear black market, thinking that it may attract top dollar from terrorists with an appetite for nuclear warfare.  We’ll examine that possibility in more detail shortly.

Since I was curious about the technical characteristics of Soviet smoke detector plutonium, I picked up an old KI-1 smoke detector and sacked it for the source.  The source design bears much resemblance to the “lipstick” sense chamber sources in early Pyrotronics detectors made in the USA.  This one is brass and a bit wider than its Pyrotronics analogue.  An internal axial thread positions a cup-shaped alpha particle shield around a band containing the active deposit, thereby regulating the amount of ionization produced by the source in the chamber and controlling the sensitivity of the detector.  The sections below describe my analysis of the gamma and alpha radiations emitted by this source, and my conclusions about the plutonium’s age, activity, mode of production, and suitability for nuclear combat.

A beat-up old KI-1 smoke detector found in an industrial facility in the former USSR dating from the mid-1970s.

Cute, isn’t it? This is the ~1-milligram plutonium source from a Soviet KI-1 smoke detector.

Plutonium source from the Soviet KI-1 smoke detector contains about 1 mg of Pu, deposited on the grayish ring in the middle. The position of the umbrella cap is adjustable.

Plutonium isotopics by gamma spectrometry

High-resolution gamma spectroscopic measurements allow direct determination of the relative concentrations of Pu-238, Pu-239, Pu-240, and Pu-241 in a plutonium sample.  In such measurements, Pu-242 is customarily inferred from heuristic correlations to the other isotopes; it can be directly measured only with costly and destructive mass spectrometry.  Additionally, the ratio of daughter Am-241 to parent Pu-241 can be used to date plutonium.  The basic methodology is discussed in good detail in Sampson, T. E., Plutonium Isotopic Composition by Gamma-Ray Spectroscopy (1986).  I employed the multiple linear regression (MLR) formula of Sarkar, Shah, et al. (2014) to estimate Pu-242.

My gamma detector is a PGT n-type coaxial HPGe detector that lives in the guest bedroom of the home (the least radioactive room, as it should be), shielded with lead bricks and a graded inner shield of copper and tin sheet.  One preparation that is almost essential with plutonium is selective attenuation of the 59-keV gamma radiation from Am-241, as discussed in Sampson’s article above.  If you don’t do this, then the pileup and sum peaks caused by the intense Am-241 radiation will swamp the rest of the plutonium spectrum.  To hold the “lipstick” source, I made an attenuator out of rolled cadmium sheet and endcaps stuffed inside of a piece of copper water pipe with copper endcaps.  Such an arrangement works by strategically situating the K-edge energy of the absorber materials close to the energy of the offending radiation.  In quantitative gamma spec measurements, another important point is to avoid getting the source too close to the detector.  Otherwise, coincidences will distort the spectrum.  With the right attenuation and geometry, all that remains is to gather a statistically-useful number of counts in the spectrum–in this case, about 42 hours of counting.

The “lipstick” plutonium source from a KI-1 smoke detector is wrapped in cadmium and then stuffed in a copper pipe. These metals selectively attenuate the 59-keV Am-241 gamma energy.

Graded attenuator capsule (copper pipe) holding the smoke detector source is placed in front of the HPGe detector. Note the lead shielding and the tin-copper graded liner.

HPGe detector (right, on floor) and associated NIM electronics.

The gamma spectrum is shown, annotated, in the gallery below.  It can be downloaded in ASCII format as an Excel spreadsheet here.  (Note that there are no channel numbers or energy calibration in the ASCII format, so you will have to add them.) As can be seen, Am-241 and Pu-239 peaks are scattered throughout, while Pu-238, Pu-240, and Pu-241 are represented by a single good peak each in the 150-keV neighborhood.  Am-241’s granddaughter Pa-233 is also in evidence, attesting to the unseen Np-237 daughter.  U-237 is a product of the minor alpha decay branch of Pu-241, and it interferes with some lines in the Am-241 decay spectrum as both nuclides decay to Np-237.  Those energies subject to interference cannot be used for quantitative analysis.   Click any image for the larger original:

Calculating relative activities from the peaks in the spectrum involves the following:

• Measuring counts in each peak by peak-fitting algorithms.  I use the free software Hypermet-PC 5.12 to do this. Its algorithms are old, but well-known and still widely used.  Modern users will need to run it in DOSBox.
• Correcting measured counts by an efficiency function of energy.  I fit this function in Hypermet-PC using a sealed Ra-226 source that can be placed in the same graded attenuator (and the same counting geometry) as the “lipstick” plutonium source.
• Calculating relative activities from efficiency-corrected counts using the tabulated yields per decay of each radiation.  I used this website for my data.
• Estimating Pu-242 activity using a suitable model.  My reference is here.

Once relative activities were established, I estimated total activities by comparing the gamma count rate on a Geiger counter between the KI-1 source and the ~60 microcurie Am-241 source from a Pyrotronics F-3/5A in the same counting geometry.  The overwhelming majority of the gamma rays emitted by both sources are 59-keV photons from Am-241.  These estimates are limited by the uncertainty surrounding the total activity of the Pyrotronics source.  The relative activities are known to much higher precision.  (I should note that the uncertainties given in the table relate to the relative measurements.)  As the table below illustrates, the KI-1 source contains a total activity of about 700 microcuries today, most of which is the 14-year weak beta emitter Pu-241.  The runner-up is 88-year alpha emitter Pu-238.  On an activity basis, the other nuclides are lower in the lineup.  The plutonium mass can be calculated, and it is about 1 mg.

The alpha spectrum

Alpha spectroscopy of plutonium is confounded by the fact that Pu-239 and Pu-240, and Pu-238 and Am-241, emit alpha particles with very similar energies.  The general technique is also laborious, involving chemical preparation of samples in virtually all cases.  Like Pyrotronics sources, there is some removable contamination on the KI-1 detector source.  I wiped a tissue on the source surface, ashed it, dissolved the residues in nitric acid, and evaporated them onto a stainless steel disc to make the spectrum shown below using an Ortec solid-state detector.  Despite this effort, it is not of great technical quality compared to what one could expect with a rigorous radiochemical technique.  All that said, though: the spectrum confirms the expectation of two main alpha energy groups, the larger at 5.4-5.5 MeV (Pu-238+Am-241) and the smaller at 5.1-5.2 MeV (Pu-239+Pu-240).

Dating plutonium using the Am-241:Pu-241 ratio

The Am-241:Pu-241 atom ratio is a daughter-parent ratio, a clock that allows us to date the plutonium.  More specifically, the method determines when Am was last chemically separated from the Pu, assuming that all the material in the source traveled together through the same process.  (The assumption may not be very good if multiple batches of Pu were mixed.)  A graphical solution of the coupled Bateman equations modeling Am and Pu ingrowth and decay is shown below.  The sample age is the point on the horizontal axis where the solution intersects the measured value of Am-241:Pu-241, represented by the one-standard-deviation band between the red and blue lines.  This plutonium appears to be 44.9 ± 0.4 years old, meaning it was probably processed in 1972.

Other dating ratios

Another member of the Pu-241 decay chain, Pa-233, can also be used for dating.  In its ratio with Am-241, we get an estimate of 55.4 years; in its ratio with Pu-241, we get an estimate of 48.2 years.  The Am-241:Pu-241 method above predicted 44.9 years.  These three ages would be harmonized if there were a bit more Am-241 in the mix, specifically about 18% more, suggesting that some may have been removed in the earlier history of the sample.  The removal may have coincided with initial fuel processing delayed appreciably after fuel discharge from the reactor, or it may have been undertaken some time after the initial processing.  I am in favor of a view that americium was last chemically separated about four years after fuel discharge, the fuel itself being about 49 years out of the reactor (discharged in 1968), and that the separatory chemistry in the early 1970s was selective for Am and largely left ingrown Np-237 (parent of Pa-233) with the Pu.  This hypothesis harmonizes all three age estimates.

Original plutonium composition

Armed with an age estimate and current activity ratios among all the Pu isotopes, the calculation of mass composition at the time of preparation is straightforward using tabulated values of the half lives (or decay constants) of the isotopes.  Once again, there are assumptions in this calculation and in the conclusions derived from it.  The most important is probably that the plutonium was “fresh” when it was processed (or, more specifically, that the time difference between when irradiation stopped and when processing occurred was small enough to be insignificant to the isotopics).  Is that a good assumption?  Because the half-life of Pu-241 is only 14 years, and because the logistics of nuclear fuel processing usually dictate several years of cool-down during which time the fuel is in storage, transit from the reactor, and standing in queue for processing, this number is perhaps most suspect–and we would expect its calculated value and that of the correlated Pu-242 estimate to err on the low side.  Keeping this caveat in mind, here is the composition of the original KI-1 smoke detector plutonium as calculated from the Am-241:Pu-241 age:

What if the plutonium is actually four years older (1968) and was just processed in 1972, as the Pa-233 dating methods hint?  Then, the composition looks like the table below.  I believe this is more accurate:

Conclusions: Low-burnup, reactor-grade plutonium from 1970 is nothing to fear

With original Pu-240 concentration near 20%, the ~1 mg of plutonium used in this Soviet KI-1 smoke detector falls into the “reactor grade” classification rather than “weapon grade.”  The classification convention distinguishes plutonium compositions on the basis of Pu-240 content because of this isotope’s high spontaneous-fission neutron yield and its consequences for pre-initiation in nuclear weapons.  However, weapons made from reactor-grade plutonium are known to work.  Their yield may not be statistically reliable or as high as could be expected with weapon-grade fissile material, but they are useful weapons nonetheless.  The real barrier to would-be proliferants hoarding Soviet smoke detectors is the sheer number–millions!–of the motherfuckers they would in principle need to acquire through the typical nuclear smurfing networks.  (The entire output of the Soviet smoke detector industry is unlikely to have involved more than one formula quantity of plutonium.)

Now that we can sleep easily on the nuclear holocaust issue, I’ll add a few more observations about this plutonium.  Although reactor grade, its high fraction of Pu-239 and low fractions of Pu-241 and Pu-238 suggest moderately low burnup, probably not in excess of 5 GWd/t, in a reactor amenable to such light utilization (e.g. an isotope production reactor or online-refuelable type).  The measured dates of production (1968) and last separation (1972) rule out VVER and RBMK power reactors as sources.  Some of the RBMK’s graphite-moderated, low-enrichment-fueled predecessors designed for isotope production and co-located with processing plants (such as the ADE types) are likely origins.  These reactors also turned out a weapon-grade stream as the USSR frantically raced for nuclear parity with the Yankee imperialists.

A Nuclear Jockstrap

The Radiendocrinator with its gold-leaf and velvet-lined case.

Radiendocrinator, a profoundly radioactive radium quack remedy sold from 1922-1929 by William J. A. Bailey.

Radiation from a Radiendocrinator causes a medical fluoroscope screen to glow. Some blue light is emitted from the Radiendocrinator itself and may be seen behind the wire mesh. The source of this light is unknown, but could be scintillation, air ionization, or Cherenkov light emitted in the celluloid source covering.

Note: Click on any image for a larger version and a caption.

William J. A. Bailey (1884-1949) was a quack-cure huckster.  After dropping out of Harvard without a degree, he briefly engaged in mail fraud, served a prison term, and then entered the lucrative and minimally-regulated patent medicine trade with a fraudulent European doctorate.  His chosen specialty was “male enhancement.” (As anyone with an email account will attest, this dubious market has survived the intervening century and all attempts at regulation.)  Bailey’s first boner pills contained strychnine.  He entered business at a time when popular enthusiasm for radioactivity was ascendant, and he is mostly remembered today for his lethal radioactive quack cures, including Radithor and the Radiendocrinator (above).  Most hucksters did not actually include radioactive ingredients in their products; they lied.  On this matter, though, Bailey was deadly honest.  Evidence suggests he used his own products, believed in them, and in all possibility, died from them (bladder cancer).

The Radiendocrinator is a credit-card-sized radium source of spectacular activity (originally 100 microcuries of Ra-226 and 150 microcuries of Ra-228) intended to be stuffed into a man’s jockstrap and worn “under the scrotum” for extended duration. Production spanned 1922-1929, and with prices set in the thousands of dollars (1929 basis), only the Jay Gatsby set could afford these gilded nut-roasters. Users were instructed to orient the wire-mesh window towards the skin to ensure maximum beta dose to shallow tissues.  In measurements on my Radiendocrinator (and it must be noted that the Ra-228 is long gone now and only Ra-226 remains), the beta-gamma reading on a Fluke 451B ion chamber was 390 mR/h at 1/8 inch, and the gamma-only reading was 52 mR/h.  It is not straightforward to extract a beta dose rate from such measurements, but assuming a correction factor of ~0.1 Gy/R (dependent on beta energy, source geometry, and ion chamber geometry), a total scrotal skin and gonadal dose rate of 30-40 mGy/h is probably not unreasonable.  Far from causing a boost to male potency, wearing a Radiendocrinator according to the manufacturer’s instructions would have likely led to temporary sterility and, of course, elevated risk of cancer.  In other words, it was a male contraceptive of sorts.  As an unsealed radium source, the wearer’s clothing, nutsack, schlong, bedsheets, sexual partners, and probably anything in the vicinity would have been rendered contaminated by Pb-210, Po-210 and other radon daughters.  Lord, what a mess.

Modern owners of these radioactive collectibles should be cautious about proper storage, as they are among the hotter of the classic quack radium cures.  Most important is a hermetic container (e.g., a small dive box) to control radon daughters emitted from the source itself.  The blue velvet-lined Radiendocrinator case is likely to be roaring with radon daughter activity as well, and should be kept separately in a bag or other sealed container.  Shielding from the penetrating gamma radiation is strongly advised.  2-4 cm of lead is reasonably effective.  The source and its case should only be handled with gloves and the source itself should NEVER be opened except in a radiochemical glovebox facility, as there is a grave risk of airborne radium alpha activity being liberated.

UPDATE: VARSKIN 4 model

The question of dosimetry from a Radiendocrinator continues to interest me because of how high the doses could potentially be from this particular device in its suggested mode of long-term use pressed against the skin.  To provide more insight into the doses, I downloaded VARSKIN 4, a deterministic radiation transport tool developed for the US NRC often used to model beta doses to skin, and I modeled the geometry and source activity of a Radiendocrinator at the peak of its beta-emitting powers (which occurs when it is 3.5 years old).  The model makes numerous assumptions, and some may not be very good:

• Source area is the Radiendocrinator’s front “window,” 6.23 cm long and 3.63 cm wide (measured).
• The source itself is 7 sheets of absorbent paper uniformly loaded with radium sulfate, 0.33 mm thick each, with a density of 0.55 g/cc.  The paper’s density and thickness are a total guess.  The number of source sheets is borrowed from Paul Frame’s online description of the innards of his device.  Note: NEVER TAKE ONE OF THESE APART (unless, like Paul Frame, you have the facilities to handle a loose alpha source of this intensity).  Initial activity of 100 μCi Ra-226 and 150 μCi Ra-228 were inferred from Kolb’s and Frame’s description in Living with Radiation: The First Hundred Years.
• At the time of peak beta intensity–when the source is 3.5 years old–it will contain the following important beta-gamma activities:
  • Pb-214, 100 μCi
  • Bi-214, 100 μCi
  • Ac-228, 98.4 μCi
  • Pb-212, 84.2 μCi
  • Bi-212, 84.2 μCi
  • Tl-208, 30.3 μCi
• Pb-210 and Bi-210 are omitted as they will not have had much opportunity to grow in at 3.5 years.  Alpha emitters are omitted.
• There are two overlain sheets of 16-mesh woven metal screen composed of 0.009-inch wire that are interposed between the source material and the human target.  VARSKIN does not model such geometries. I calculate a transparency of 53%, and assume the metal blocks 100% of intercepted beta particles and 0% of intercepted photons.
• There is a plastic sheet, probably nitrocellulose, over the front of the device that I model in VARSKIN as 0.5 mm thick with a density of 1.3 g/cc.  This is a total guess.
• I assume a 1-mm gap between the source and skin.
• VARSKIN’s default skin dose averaging area is 10 sq. cm., in recognition of the US NRC’s current rule for computing shallow dose equivalent in 10 CFR 20.1201(c).  I did not alter this in the calculation.

Results: In vintage condition (3.5 years old), the Radiendocrinator’s predicted shallow dose rate due to beta particles is 88 mGy/h, and with the gamma contribution added in is up to 91 mGy/h.  Deep dose rate (from gamma contributions only) is 2.0 mGy/h.  In the Radiendocrinator’s present condition, assuming the contributions of ingrown Bi-210 and the total decay of the Ra-228 chain, the beta-gamma shallow dose rate is 57 mGy/h, and the deep dose rate is 0.9 mGy/h.  So…what does this mean, practically, for the wearer?

• 2 Gy is the threshold for skin erythema: waves of redness and itching sensation over several months, culminating in skin death and replacement as in a sunburn.  The Radiendocrinator wearer potentially earns an itchy, inflamed scrotum with a few nights of wearing the device.
• 15 Gy marks the onset of painful burning with moist desquamation following browning of the skin, i.e. a “nuclear tan”, with the possibility of long-lasting ulceration.  This is a hardcore radiation burn.  If you wore the Radiendocrinator all the time, every day, for a week, this might be your reward.  As there are no records of gruesome and agonizing injuries associated with the device, I assume there were no users hardcore enough to “ride the radium” full-time.
• Temporary sterility can happen with doses of 150 mGy or greater to the testes.  With a deep dose rate of 2 mGy/h, it would take a guy three whole days on the nuclear pad to achieve temporary sterility.  Libido would not be impacted.
• Stochastic effects: using ICRP weighting factors, I calculate an effective dose rate of about 1.2 mSv/h from the skin (shallow) and deep (general tissue) dose rates given above.  The excess risk of fatal cancer is on the order of 5%/Sv.  Though the dose rate is on the higher side, your real problem with this source is the skin damage you would endure.

Chernobyl Turbine Hall, November 2016

Please select any photo in the galleries for a larger version and descriptive caption.

The mercury-vapor lights in the ChNPP turbine hall barely turn on in the freezing darkness of Ukrainian winter, emitting a harsh buzz but only weak, jaundiced illumination.  With no climate control (the on-site heating plant is shut down because the fuel needed comes from Russia and is prohibitively expensive), corrosion has set in on every available surface.  Across the turbine decks, in vast heaps, lie demounted valves, piping, bearings, casings, and of course, pieces of the turbines themselves, all of it too radioactive to go anywhere else but here.  Made in Ukraine at the Kharkov Turbine Factory (now Turboatom), the vast machines are destined to rust away while similar turbines continue to turn at more auspicious nuclear power plants throughout the former USSR.

Remains of a low-pressure double-flow turbine rotor in the dark, freezing Turbine Hall at Chernobyl.

Eastward view toward No. 4 Turbogenerator in the ChNPP Turbine Hall. If you look at the roof paneling above TG-4, you can see that it is a different (lighter) color. This is the part of the roof that collapsed in October 1991, when an electrical accident and subsequent fire destroyed the generator. Unit 2 never operated again. The red tank is for lubricating oil.

View westward toward the TG-5 turbogenerator belonging to Unit 3 at the Chernobyl Nuclear Power Plant.

Disassembled turbine parts, including blades and bearings, lie strewn about the Chernobyl turbine hall as the power plant undergoes decommissioning.

Entrance to the Turbine Hall on the +10m elevation from the Deaerator Building, between Unit 2 and Unit 3.

Highly radioactive support elements from the striped ventilation chimney that once stood between the Units 3 and 4 reactor buildings are now stored temporarily in the Turbine Hall, adjacent to TG-5.

Rusting remains of a steam turbine lie on the floor of the Turbine Hall at the Chernobyl Nuclear Power Plant.

Feedwater pumps belonging to Unit 2 at ChNPP. A fire in 1991 cause the turbine hall roof to fall on the pumps, disabling them all (and their emergency backups). The damage was repaired and the protective metal roof seen here was installed over the feedwater pump well to prevent a recurrence of similar accidents. However, Unit 2 was never operated again.

Unit 2 condensate pump well next to No. 3 Turbogenerator at Chernobyl.

Part of a turbine shaft belonging to TG-3 stands next to a decommissioned control station for the machine. The Turbine Hall is not climate controlled, and condensing humidity is causing rusting on many surfaces.

Sergey Krivtsun, a 30-year veteran turbine operator at the Chernobyl Nuclear Power Plant, was working in Unit 1 in 1986.

In addition to the turbogenerators, the turbine hall also contains condensate and feedwater machinery, some of which may be seen in the photos in the gallery here.  The hall is being temporarily used to store radioactive structural components of the highly-contaminated ventilation stack that once stood between the Units 3-4 reactor buildings. Click below to watch a Bionerd video about the turbine hall:

 

Chernobyl Unit 4, November 2016

Please select any photo in the galleries for a larger version and descriptive caption.
In November 2016, the massive New Safe Confinement arch slid over Unit 4 of the Chernobyl Nuclear Power Plant, and the old “Sarcophagus” that had defined the appearance of the damaged unit for 30 years receded from view.  Over the last three years, the iconic ventilation chimney shared by Units 3 and 4 has been disassembled as well, and now rests in pieces in various places (including the deck of No. 5 turbogenerator).  Inside the unit, work continues to finish the Perimeter Closure Project–the effort to hermetically seal off the east and west boundaries of the New Safe Confinement from the rest of the power plant.  Floor by floor, barriers are going up.  The memorial to Valery Khodemchuk, the first victim of the 1986 accident whose remains have never been recovered, has been removed from its old location at the northwest end of the chemical treatment and ventilation block, and will be reinstalled somewhere else once the project is finished.  The photos in the second gallery show the state of the Arch and the Local Zone around Unit 4 only several days before the Arch began its movement, and are certainly among the last photos of the old Unit 4 exterior we have come to know and love.

Stanislav Shekstelo, an employee of the Chernobyl Nuclear Power Plant, contemplates the remains of the Unit 4 control room in November 2016. The wall at left is not original, and the last bench of A Desk and T Desk have been removed to allow the wall to be installed through the control room. Behind the wall is a corridor to allow worker movement. The original “gold corridor” that runs the length of the deaerator building is blocked in this area by the supports for the “Mammoth Beam” in the Sarcophagus.

Unit 4’s reactor cartogram displays behind A Desk (the reactor control engineer’s position) at the east end of the Unit 4 control room. Only a few of the ~200 control rod servoindicators remain in the panel, the others having been scavenged for other units and / or souvenirs.

Servoindicator for a control rod in the Unit 4 control room, Chernobyl Nuclear Power Plant, measuring rod insertion depth from 0 to 8 meters. The reading is no longer meaningful. The descending main control rod in Channel 40-37 would have become stuck at about 2m before the core disintegrated.

Slot for No. 8 turbogenerator’s tachometer on T Desk, the turbine control engineer’s position, Chernobyl Nuclear Power Plant. The 1986 accident took place in the context of an inertial run-down experiment on TG-8. A thick coating of pink polymer designed to trap contamination now lies over everything in the Unit 4 control room.

Annunciator lamps for Unit 4’s main circulation pumps, covered in contamination-immobilizing polymer.

Turbogenerator No. 8’s electrical output, from 0-600 MWe. The normal value was 500 MWe at full power. The accident of April 26, 1986 occurred in the context of an experiment on TG-8.

A pancake Geiger counter measures 33 kCPM on the balance-of-plant console (P Desk) in the Unit 4 control room.

Switch on A Desk (the reactor control engineer’s position) for the Unit 4 reactor’s automatic power regulators. The power regulators derive signal from lateral ionization chambers and are used to manage control rod movement under high-power operating conditions. The chain of events leading directly to the accident began with the automatic regulators, which stopped regulating power for some indeterminate reason at 12:30AM on the night of the accident. The operators failed to maintain power with the AR systems, leading to xenon poisoning and the unfortunate conditions for reactor runaway later on.

Slots for the reactor period monitors in Unit 4 control room at Chernobyl. These monitors probably derived their signal from the lateral ionization chambers, and would have read “0 seconds” for a brief, hair-raising moment on April 26, 1986.

A hot-spot warning is stenciled on the wall that now terminates the west end of the +10m deaerator corridor at Axis 53. The Fluke 451B ion chamber measures a respectable 22 mR/h here.

The original deaerator corridor on +10m outside the Unit 4 control room is rarely seen by visitors to the control room, but we had to use it because of work on the Perimeter Closure Project. The reserve control room to Unit 4 is behind the wall on the right, shielded with heavy lead plate. It looked directly out on the vast heap of radioactive debris from the reactor building. Some original linoleum flooring is also visible.

Looking east now, toward the barrier across the +10m deaerator hallway at Axis 53. Behind the wall are supports for the “Mammoth Beam” in the Sarcophagus. The lead paneling at left provides shielding from radiation shining into the plant from outside, via the Unit 4 reserve control room.

The G110/2 stairway at the end of the deaerator building in Unit 4 is in pretty ragged shape, and has been painted with some kind of immobilizing polymer that is pink in color. We are on our way to the Unit 4 control room via a somewhat unusual route on the +16.4m level.

Blast-resistant door leading to one of the steam and feedwater piping compartments below Unit 4’s deaerators on +16.4m elevation. Like all of Unit 4’s primary cooling circuit, it is probably quite contaminated.

Dating from Unit 4’s operational days–as attested by the overlying stratum of pink anti-contamination polymer–is a poster advising about safe welding practices.

The short western hall at the end of the Unit 4 deaerator building was once a “place for smoking”, per the red signage. A new sign has been posted, instructing workers that “smoking in the Object Shelter is PROHIBITED!” (Clearly the prohibition is widely ridiculed, as cigarette butts are everywhere in the Unit 4 control room.) Closer inspection of the sign reveals sarcastic additions, including a “penalty-100 Hryvnia” (about $5) modified to read “$1000000.”

I was honored to have Bionerd along for this trip, and her video record of the visit inside Unit 4 is on YouTube here:

Finally, here is a gallery showing the Arch of the New Safe Confinement and some of the “Local Zone” surrounding Unit 4.

The New Safe Confinement Arch at Chernobyl, only days away from its highly-anticipated move over the damaged Unit 4. PHOTO CREDIT: LUCAS HIXSON

American-made overhead cranes in the New Safe Confinement arch. The cranes will be used for various purposes relating to the study and deconstruction of Unit 4.

Workers in the “Local Zone” surrounding Unit 4 rush to finish the New Safe Confinement Technological Building, Perimeter Closure in the turbine hall, and other projects so that the Arch can be moved before the onset of bitter Ukrainian winter weather. Note that the ventilation stack visible on V Block is not the original, but a much smaller, offset stack that will not interfere with the New Safe Confinement.

Unit 4 is scarcely recognizable from the west, with the technological building of the New Safe Confinement nearing completion (left). The old western counterforce wall that keeps the Sarcophagus from collapsing is behind it. The striped ventilation chimney is a diminutive, offset version of the original. About the only original plant structure visible here is the western end of the deaerator building.

The Arch is designed to slide on rails. This is the southern rail. A lead-sheet shield for workers, at left, reduces the ambient dose rate by about a factor of 4.

One of hundreds of stray dogs on the Chernobyl Power Plant site. This one, however, is on the dirty side of the clean line in the 1430 Change Facility, and I doubt it has been taught to use the contamination monitors visible at left.

A stray dog, one of hundreds that roam the grounds of the Chernobyl Nuclear Power Plant, enjoys the meager nourishment of a radioactive boot heel inside the hot entrance to the 1430 Change Facility. In the foreground is a visitor with a jacket labeled “OU” (“Object Shelter”).

Chernobyl Unit 2, November 2016 (Part 2)

Please select any photo in the galleries for a larger version and descriptive caption.

The reactor hall and control room of Unit 2 at the Chernobyl Nuclear Power Plant are documented in these photo galleries and companion video.

Room 612/2 (Central Hall); Room 804/2 (Refueling Machine Control Room)

The RBMK reactor design features an ability for online refueling: withdrawal and insertion of fuel bundles while the reactor is at power.  The charge face with its 2000-some channel covers is sited above the reactor within a massive “central hall” that is built like a hot cell, with concrete entryway mazes and leaded-glass windows for refueling operators.  The dominant piece of equipment is, of course, the crane-mounted RZM (refueling machine).  Also in the central hall are two spent-fuel basins, fresh fuel and instrumentation storage hangers, and metal plate covers for accessing the upper steamwater pipelines from the reactor and the peripheral ionization chambers.  Unit 1 and 2’s central halls are on the +20.2m elevation, typical of first-generation RBMK plants, while the later Unit 3 and 4 central halls are on +35.5m.  The chief reason for this is the introduction of a steam-suppressing pool and “Accident Localization System” below the reactor in the later design.  Unit 2 has been offline since a turbine hall fire in 1991, and is defueled and dry (all spent fuel is in the ISF-1 facility).  The spent fuel pools in the reactor hall are also dry, but are currently being used to store fuel support stringers.  Measured exposure rates in the reactor hall range from surprisingly low (3 mR/h on uncovered fuel channels on the “pyatak” or reactor lid) to surprisingly high (2 R/h close to a point source-maybe a fuel flea?-on a fuel stringer).  Like other RBMK reactors, including Unit 3 at Chernobyl, ChNPP-2 participated in transmutation doping of silicon for the Soviet semiconductor industry.  A single channel ordinarily used for the control and protection system was assigned for this application.

Central Hall of Unit 2, ChNPP, looking south from the fresh fuel storage area. In the distance is the refueling machine and the circular reactor lid. In the foreground is a round portal in the floor for transferring fuel in casks out of the reactor building and onto a rail car beneath.

On the Unit 2 reactor lid, there is some streaming gamma radiation from the empty fuel channels. The exposure rate amounts to about 3.3 mR/h. Note the heavy removable steel blocks used to protect the channels.

2 R/h (yes, that’s two roentgens per hour!) from a local source, suspected of being a fuel flea, on one of the used fuel stringers in the spent fuel storage pool of Unit 2 reactor at ChNPP. Good times.

The crane-mounted RZM (fuel loading and unloading machine) in Unit 2 at ChNPP. Notice the person at the bottom for scale! The lead-glass window to the operator’s room is seen on the wall at right.

This is the reactor lid for Unit 2, Chernobyl Nuclear Power Plant. Metal blocks protect the upper penetrations for some 2000 channels through the graphite moderator of the reactor. The colored lids house electric control-rod drive mechanisms and in-core instruments, while the unpainted ones cover fuel channels and one special channel used to irradiate silicon. To the side of the reactor lid are smaller covers for the upper steamwater pipelines and the lateral ionization chambers.

Upper stringers for fuel bundles in the Unit 2 reactor hall. These pieces have a pin in the foreground for coupling to the RZM machine. At the far end is a spiral geometry designed to help shield streaming neutrons. Two fuel bundles, each about three meters long, would have been attached at the far ends for insertion into the reactor core.

Visitors prepare to enter the Central Hall of Unit 2 at Chernobyl, from the 607/2 anteroom on +20.2m. The Central Hall is a fuel handling area, and consequently has some loose radiological contamination.

Visitors prepare to enter the Central Hall of Unit 2 at Chernobyl from the 607/2 anteroom on +20.2m.

Electrical panels for the RZM refueling machine in the operator’s booth, Room 804/2. PHOTO CREDIT: LUCAS HIXSON

View through the RZM operator’s lead-glass window into the Central Hall, Unit 2, Chernobyl Nuclear Power Plant. PHOTO CREDIT: LUCAS HIXSON

Unit 2 reactor building, Chernobyl Nuclear Power Plant, +20.2m elevation

Video (via YouTube)

Room G364/2 (Unit 2 Control Room)

The control room, like all others at RBMK plants, is situated nominally at +10m elevation in the “deaerator stack” abutting the turbine hall.  The tray-type deaerators themselves, and reactor steam and feedwater piping, are in compartments directly above the control rooms, leading to some interesting hypothetical accident scenarios whereby radioactive water might invade the control rooms from above.  At ChNPP, the Unit 2 control room has a notable radiation “hot spot” above T Desk at the west end, possibly due to contamination in the steamwater piping compartment upstairs.

A visitor stands behind A Desk (reactor control engineer’s position) in the Unit 2 control room, ChNPP. On the panel behind him is a reactor core cartogram with lamps for each of the ~1700 fuel channels (white) and ~300 other channels for control rods and instrumentation. The lamps were used to indicate various parameters or activities in the individual channels. On the right is another cartogram with servoindicators displaying the position of control and protection rods in the reactor. PHOTO CREDIT: LUCAS HIXSON

Visitors enter Unit Control Room II, Chernobyl Nuclear Power Plant, from the “Gold Corridor” on +10m. PHOTO CREDIT: LUCAS HIXSON

A visitor and a career turbine engineer share a smoke in the Unit 2 control room at Chernobyl, hastening their demise by cancer much faster than radiation will. The engineer’s jacket has “ZSR” (“Strict Control Zone”) initialed on it, referring to more highly contaminated areas within the plant.

Servoindicators for the reactor control and protection system (“SUZ”) in Unit 2 control room at Chernobyl. Blue indicators are for the shortened absorbers (“USP”) that are pulled up from the bottom of the core, while all others descend from the top of the core. The channel marked “Si” was specially allocated to the neutron transmutation of silicon for the Soviet semiconductor industry.

The west end of the Unit 2 control room, where controls for plant electrical systems and the Nos. 3 and 4 turbogenerators are located. In October of 1991, No. 4 turbogenerator accidentally motorized and caught on fire, bringing the turbine hall roof down onto the reactor feedwater pumps. Unit 2 was permanently shut down following this accident.

Operational reactivity reserve (OZR) chart recorder in the Unit 2 control room at Chernobyl. Handwritten note on the paper indicates its decommissioning in October of 1991, following the fire that ended Unit 2’s service life. The OZR quantity–essentially the number of full-worth control rods remaining in the reactor core–has great safety significance in RBMK reactors, and the inclusion of displays of this quantity for the operators in the control room was one of the improvements adopted after the Unit 4 accident in 1986.

Controls for the No. 1 automatic power regulator on A Desk (reactor control engineer’s position) in Unit 2 at Chernobyl. This computerized regulator was one of two that were typically engaged under full-power routine operation.

Local Automatic Regulator (LAR) on A Desk (reactor control engineer’s position) in Unit 2 at Chernobyl. This regulator used in-core instrumentation to monitor and adjust the spatial neutron flux distribution at intermediate power levels during transition to or from full power.

Two visitors investigate the notable radiation hot spot in the Unit 2 control room, in front of T Desk (turbine controls for Turbogenerator No. 4 are visible). The radiation seems to be streaming from above, perhaps from the steamwater compartment that directly overlies the control room. (Purely by coincidence, the men’s pose resembles the famous Soviet socialist-realism sculpture, “Worker and Kolkhoz Woman.”)