Stan Thompson
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Stan Thompson

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                                        3.0  SPENT FUEL HANDLING AT THE HANFORD SITE

3.1  ORIGINAL LAG STORAGE PRACTICES

          After irradiation in a reactor, nuclear fuel is known as "spent fuel."  In defense production at the Hanford Site, this fuel has always placed under water, allowed to undergo a period of radioactive decay, and then chemically dissolved and "re-processed" to separate the Pu product from associated fission products and other elements.  In HEW jargon, the solid U fuel elements were known as "lags" as soon as they became spent fuel.  B‑Reactor and HEW's other earliest reactors were constructed with spent fuel basins just below the rear faces.  The fuel was literally pushed out the rear face of each reactor by charging fresh fuel into the front.  Spent fuel basins at the earliest Hanford reactors each were 81 feet (24.69 meters) by 68 feet (20.73 meters), and were divided into two sections each.  The basins were 20 feet (6.10 m) deep, although the water was maintained at about 16 feet (4.88 m) deep.  Each basin was served by submerged buckets that were suspended from a monorail via 25‑foot (7.62‑meter) yokes.  Long rakes and tongs were used to load each bucket with one-half ton of fuel elements.

          Viewing of the discharge area was accomplished with two main periscopes, located on the ceiling of the discharge area and on the wall opposite the rear face of the pile.  Additionally, the latter location contained a "Fly-eye" viewer that consisted of four wide-angle lenses.  A shielded cab, which could be attached to the 50,000‑pound (22 679.62 kilograms), 8 to 10 feet (2.44 to 3.05 meters) wide "D" elevator, also had its own periscope.  One last periscope was located in the labyrinth that led to the discharge area balconies, but its view often was blocked by the "D" elevator (which had to be raised to the top of the reactor's rear face during discharge operations).  Thermocouples were placed at the inlet and outlet of the storage basin, and water temperature levels as indicators of radiation intensity were monitored carefully.

          The earliest spent fuel handling practice at the Hanford Site was to keep the lags in the basins at the reactor rear faces for a very short period of time (several hours to one day).  The irradiated fuel rods then were loaded into shielded rail cask cars and taken to the 200‑North Area for storage in the 212 Lag Storage Buildings.  Within any one of these three buildings, the rods were stored for periods of time ranging from a few weeks up to perhaps as long as 50 days, to allow for isotope decay, before they were taken to either T‑Plant or B‑Plant for chemical separation.[lxxx]

3.2  212 LAG STORAGE BUILDINGS CLOSE

          As the needs of the Cold War rapidly increased Pu-239 production at Hanford, difficulties developed with the 212 Buildings.  By 1950, Site planners realized that additional capacity for lag storage was needed.  One key factor was the AEC's decision to store spent fuel from 90-125 days before re-processing, in order to reduce the emissions of iodine 131 (I-131) and other gaseous fission products into the regional environs.  Other crucial factors included the increased amounts of fuel being produced and handled once the H and DR reactors came on line in 1949 and 1950 respectively, and the anticipation that various forms of E-metal would be tried in order to push production even higher.  In 1951, with C-Reactor under construction, as well as the desire to save the transportation costs to and from the 212 Buildings and to reduce radiation exposure to workers from fuel transfers, the 212 Buildings closed.  From that time forward, spent fuel at Hanford was stored only in the fuel basins at the rear faces of the reactors.[lxxxi]

          The reactor fuel storage basins, as had the 212 Buildings, operated within certain fundamental parameters.  All cooling was accomplished using either once-through or feed-and-bleed principles.  Filtered water was routinely added to the basins and water was discharged either via overflow weirs or floor drains.  The discharged water was routed to cribs for soil filtration.  As a result of this routine water addition, the fuel storage basins at Hanford were relatively clean radiologically.  Additionally, fuel was always stored in open containers.  This facilitated heat removal after discharge from the reactor.  Corrosion products were not an issue because following a relatively short storage time, fuel was processed.  The fuel storage basins at the KE and KW reactors operated in the same manner, although they were larger.  At these piles, the rectangular, reinforced concrete basins each were 125 feet (38.10 meters) long, 67 feet (20.42 meters) wide, 21 feet (6.40 meters) deep, and were divided into three sections.  By the early 1960, lag storage time at HW had increased to an average of 200-250 days.[lxxxii]

3.3  CLOSURE/RE-OPENING OF FUEL STORAGE BASINS

          As each HW reactor closed between 1964 and 1970, its spent fuel basin likewise closed.  In some cases, fuel storage basins at a given reactor would remain open a number of months after the pile itself had shut down, in order to accommodate fuel from another reactor.  However, all lag storage basins except for the N Reactor basin closed by 1971.  In 1972, the last radiochemical processing plant at the Hanford Site, the PUREX (plutonium uranium extraction) Plant entered a long shutdown period (although it later re-opened).  The N Reactor, because of its dual-purpose design, was kept operational to support Pacific Northwest electrical power needs.  N Reactor was operated in this mode throughout the decade, and continued to produce spent fuel.  The N Reactor fuel storage basin was not sized to support the resultant fuel inventories.  As a result, the decision was made to use the K Reactor spent fuel basins for additional storage space for N Reactor lags.

          The K East basin was the first to be modified to store N Reactor fuel.  It received only superficial cleaning, and the bare concrete walls of the basin were left uncoated.  All drains and overflow weirs were blocked off and a water recirculation system was installed.  The recirculation system consisted of two pumps, two underwater cartridge filters for particulate removal, and two water-to-water heat exchangers for basin cooling.  Storage racks were installed on the basin floor to support single tier storage of N Reactor fuel.  Filtered water was used to supply the basin water make-up needs.  A barrier was installed across the entrance to the North Loadout Pit to isolate it from the basin proper.  The actual construction activities were completed and the facility began accepting N Reactor fuel in 1975.  N Reactor fuel was shipped and stored in open containers.  The containers (canisters) were specifically designed for this purpose.  These canisters remained unchanged from the design used to support earlier N Reactor operational needs.

          The fuel inventory quickly grew in the K East basin and along with it, radiological problems.  With the basin sealed and with no ability to add clean water and discharge contaminated water, fuel corrosion products were captive in the facility.  Radioactive contamination and radiation exposure levels increased.  Steps were taken to mitigate this situation included the addition of a skimmer system along with a sand filter, and later, an ion exchange system.  As the PUREX Plant remained closed and N Reactor continued to operate, plans were initiated to modify the K West basin to accommodate the extra fuel.[lxxxiii]

          The K West modification was designed to prevent a recurrence of the K East Basin experience.  The K West Basin was drained and the walls and floor were cleaned and sealed with an epoxy material.  The drains and overflow weirs were blocked off.  All of the basin clean-up systems in operation at K East were installed in the K West Basin.  These included a basin recirculation system with cartridge filters and heat exchangers, a skimmer system with a sand filter, and an ion exchange system.  The decision was also made to fill the basin and maintain water level using demineralized water.  A lid design was developed for the existing fuel storage canisters which allowed them to be  closed.  The design allowed the canisters to vent if there was any gas generation.  Fuel shipments to the K West Basin began in 1981, with all fuel shipped to and stored in closed canisters.[lxxxiv]

          In 1983, when the PUREX plant was getting ready to resume reprocessing of spent fuel to recover plutonium and uranium, the fuel in the K East basin was sorted to separate the weapons-related fuel from that used to generate electricity.  The fuel was dumped from the canisters, sorted and placed back in the open canisters.  A proposal to place the K East fuel in sealed canisters, like those used in K West, was rejected.  Today, the K East Basin holds the nation's largest single concentration of stored spent fuel.  The existing fuel inventories include 3600+ open canisters of spent fuel stored in the K East Basin and 3800+ closed canisters of spent fuel stored in the K West Basin.  This inventory totals ~2100 MTUs.

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Last Edited 07/21/15 --Comments to Webmaster