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After the PUREX (Plutonium Uranium Extraction Plant) tunnel collapsed it was filled with sand and dirt and covered with what looks like plastic tarp “large protective ground-coverhttps://livestream.com/accounts/24284076/events/7559266/videos/159091020

Hanford Cleanup Priorities July 7th Comment Deadline: Trump Budget Wouldn’t Fund All Legal Requirements Even Prior to Tunnel Collapse in May. http://www.hanford.gov/pageaction.cfm/calendar?IndEventId=8175 https://miningawareness.wordpress.com/2017/07/05/trump-budget-inadequate-for-hanford-nuclear-site-cleanup-nuclear-waste-tunnel-collapsed-second-collapse-imminent-comment-on-cleanup-priorities-july-7th-deadline/

Meanwhile, the Hanford Reach “National Monument” which adds a bit of extra protective barrier from such accidents is on Trump’s chopping block along with 26 others. Comment Deadline is July 10th: https://www.regulations.gov/document?D=DOI-2017-0002-0001

Purex Tunnels Central Location http://www.hanford.gov/files.cfm/PUREX_Tunnels_Posters-2.pdf

Hanford Reach “National Monument” Map https://www.fws.gov/uploadedFiles/Region_1/NWRS/Zone_2/Mid-Columbia_River_Complex/Hanford_Reach_National_Monument/Documents/general-map.pdf

PUREX Tunnels

Hanford PUREX Tunnel No. 2 under construction


The [Hanford,Reach] Monument is also a reminder of our history as a nation. Plutonium reactors stand along the river, remnants of WWII and the Cold War. Plutonium from B Reactor fueled “Fat Man,” the atomic bomb dropped on Nagasaki, Japan, on August 9, 1945. No longer in production, these reactors are now being dismantled, and the lands and waters cleaned.” https://www.fws.gov/refuge/Hanford_Reach/About.html

Excerpted from PUREX Tunnels Engineering Evaluations:
2. Introduction
On May 9, 2017, a portion of the PUREX Tunnel 1 wood timber roof structure was observed to have collapsed into the tunnel resulting in a hole approximately 19 ft wide by 17 ft long. The actual time of the collapse and cause of the failure has not been determined. Potential factors contributing to the collapse are speculated to include heavy rainfall on May 4 and 5, 2017 deterioration of tunnel wood timber structural support members due to prolonged exposure to high levels of radioactivity, and influence of low vibration sources near the site such as local thunderstorms or distant low-magnitude seismic activity. Due to the uncertainty of the condition and structural integrity of the remaining roof and wall timber supports, measures were taken to prevent additional roof loads or personnel from being placed over the top of Tunnel 1 and within the roof load zone of influence until permanent stabilization measures can be taken.

“Construction of the PUREX Tunnel 2 addition was completed in 1964 involving placement of the cast-in-place tunnel spur between Tunnels 1 and 2 and installation of the 1,688 ft storage tunnel extension to the south. The Tunnel 2 consists of three sections, a water-fillable door, a storage area, and a ventilation shaft. The water-filled door is housed in a concrete structure and located at the north end of the storage area. The door serves as a barrier between the storage area and the railroad extension tunnel. The water-fillable door is 24.5 ft high, 22 ft wide, and 7 ft deep, constructed of 0.5 inch thick steel plate and hollow to permit filling with water for radiation shielding. The storage area of Tunnel 2 extends from the water-filled door south to the ventilation shaft. The tunnel is constructed in the shape of a Quonset hut with a series of transverse steel rib support beams on a 17 ft rolled radius (approximately 38 inches on-center spacing) that support 3/16 inch thick by 16 inch wide stamped corrugated steel plate roof panels that span between and bolt to steel rib supports. Interior and exterior surfaces of the roof system are coated with a bituminous material. Steel ribs are supported by a 21 inch minimum thick by 6 ft wide by continuous reinforced concrete wall thrust block foundation system. The steel roof structure was then further supported by a retrofit addition of a series of longitudinal steel wale beam wide flange supports that are supported by underhung anchor bolt connections embedded in 15 inch wide by 36 inch deep (minimum) reinforced arched concrete rib girders (approximately 16 ft on-center spacing). Concrete ribs are supported by additional 18 inch thick by 6 ft wide by 6.5 ft long reinforced concrete thrust blocks placed over the top of existing wall footings. A minimum depth of 8 ft of uncompacted soil fill was then placed over the tunnel storage area and the fill was contoured to provide slope stability. The nominal inside dimensions of the tunnel are 26 ft in height, 34 ft in width, and 1,688 ft in length with a downward slope of 0.1% grade from north to south. Due to the water-filled door clearance constraints, the usable storage area is 22 ft in height and 19 ft in width above the top of the rail which is the same as Tunnel 1. The floor consists of two railroad track rails supported by transverse 6 inch by 8 inch railroad ties at 2 ft spacing laid over a gravel bed. The spaces between ties are filled to the top of the ties with gravel ballast. The ventilation shaft is located at the south end of the tunnel. The shaft is approximately 5 ft by 5 ft in cross section and constructed of reinforced concrete. The ventilation shaft protrudes approximately 1 ft above grade and is capped with a single-stage high-efficiency particulate air filter, an exhaust fan, and a 20 ft tall stack. The ventilation system is not in operation. The tunnel is filled with 28 railcars containing radioactive process equipment.

As denoted in CAC-964, PUREX Equipment Disposal Tunnel Inspection Report, dated March 17, 1964, portions of Tunnel 2 catastrophically collapsed on two separate occasions during backfilling operations performed at different locations. The events led to design modifications including addition of interior steel Wale beams underhung and supported by new exterior arched concrete rib girders and to changes in construction soil placement procedures to prevent uneven placement of soil fill along both sides of the tunnel during backfilling operations . . . .

9 Conclusions

This structural evaluation of Tunnel 2 indicates that design loads on several structural support members exceed building code design capacities including arched steel rib supports, wide flange steel wale supports (members, splice connection, and failure sensitive underhung tension bolt connections), and foundation soil bearing pressures. Structural evaluation does not address further reduction in the structural capacity of members and connections due to adverse effects from corrosion, material defects, and increased stresses induced from documented unbalanced loading conditions applied to the structure during original construction backfill operations. Based on overstressed conditions in structural support members and connections and uncertainty of additional unknown stresses induced during original construction, Tunnel 2 has a potential high risk of localized collapse. Foundation support conditions are further subject to increased risk of failure during moderate to strong seismic activity. Although removal of soil fill over the tunnel could result in reduced applied loads, the potential reduction in loads may not eliminate all overstressed conditions and adverse effects from extended deterioration (e.g. corrosion, radiation exposure, etc.) but could in turn result in initiating a localized collapse caused by construction activities. Stabilization of the tunnel is recommended to be implemented as soon as possible to minimize risk of failure. For safety purposes (e.g. avoid potential collapse, avoid high level radiation exposure, etc.), placement of personnel and equipment on top of the tunnel and within the roof load zone of influence is not recommended without further evaluation.

10. Risk of Future Failure

The Tunnel 2 arched steel structure including retrofit addition of cast-in-place arched concrete rib supports with underhung structural steel wale supports has been in service for more than 50 years which is beyond the typical design life for similar structures. The risk of future failure of the tunnel (partial or global collapse) is considered high based on identified design overstress conditions and problems encountered during original construction including lateral displacement/distortion, partial collapse of the structure, and failure of a number of welded and bolted steel connections during backfill operations. As a result, the existing Tunnel 2 structure presents a high potential collapse hazard until such time that physical evaluation of the structural members including bolted and welded connections can be performed. ” CHPRC-03365, REV. 0
Emphasis our own throughout,

For those who wonder, the radiation would almost certainly kill the microbes which would normally rot wood, so the radiation itself would be the cause of damage. The wood was coated with creosote, as well.

Page with documents: http://www.hanford.gov/page.cfm/PUREXTunnelsEngineeringEvaluations

Many Thanks to FC https://flyingcuttlefish.wordpress.com/2017/07/04/hanford-4 of the Louisiana Sinkhole Bugle https://lasinkhole.wordpress.com for the heads up and to Christina of Nuclear News Net: https://nuclear-news.net/2017/07/03/us-federal-reports-that-another-hanford-radioactive-waste-tunnel-has-structural-pproblems/