Revis&ng radionuclide sources at the Marshall Islands Ken - PowerPoint PPT Presentation

Revis&ng radionuclide sources at the Marshall Islands Ken Buesseler, Ma- Chare-e, John Breier, Steve Pike, Paul Henderson, Lauren Kipp, Kaitlyn Tradd Woods Hole Oceanographic Inst.

Marshall Islands- ground zero for US nuclear tes&ng Baker 1946

Bravo First H bomb Bikini 1954 Bravo site 2015

Bikini- Bravo Crater

Enewetak- Runit dome

Enewetak Cesium-137 Water ac&vi&es Bq m -3 Sediment ac&vi&es Bq kg -1 137 Cs (Bq kg-1) Mike 0 1 2 3 4 50 100 150 200 250 crater 0 10 Runit Dome 20 up to 4.5 Depth (cm) 30 40 50 60 Runit Shore 1 Runit Shore 2 70 Mike Crater 80

Enewetak Americium-241 (from decay of plutonum-241 t ½ = 14 yr) Water ac&vi&es (est.) mBq m -3 Sediment ac&vi&es Bq kg -1 241 Am (Bq/kg) Mike crater 0 50 100 200 400 600 800 1000 0 Up to 480 Runit In lagoon Dome 20 Depth (cm) 40 Runit Shore 1 Runit Shore 2 Mike Crater 60 80

Marshall Islands- how does it compare? Cesium -137 100 1500 400 200 1250 inventory (kBq m -2 ) 80 sediment (Bq kg -1 ) Marshall Islands 1000 water (Bq m -3 ) 750 60 8 500 6 40 250 4 20 9 2 6 3 0 0 0 Bravo Mike Runit Lagoon global Fukushima H20 Sed Inventory

Marshall Islands- how does it compare? Plutonium-239+240 0.3 1250 or inventory (kBq m -2 ) 1000 sediment (Bq kg -1 ) water (Bq m -3 ) 750 0.2 500 250 0.1 15 10 5 0.0 0 Bravo Mike Runit Lagoon global Fukushima H20 Sed Inventory

Hydrogeology of Enewetak Atoll

Lagoon Flushing Times (T W ) Loca%on Flushing Time (d) Method Reference Bikini Atoll 37 (Jan. 2015) Ra isotopes This study 39 (winter) Field measurements- Von Arx (1948) 80 (summer) scale lab model 17 (Jul. 1946) Radioisotopes Ford (1949) Enewetak Atoll 16 (Jan. 2015) Ra isotopes This study 28 (n/a) Circula&on box Atkinson et al. model (1981) Majuro Atoll 15 Tidal Current Model At steady-state, lagoon export fluxes for 137-Cs and 241-Am can be calculated as: Flux (Bq/d) = (A lagoon – A Pacific )*V lagoon /T W

Submarine Groundwater Discharge using radium isotopes (m 3 /m 2 /d) Lagoon groundwater 137-Cs and 241-Am inputs can be calculated as: SGD Flux (Bq/d) = SGD*Area SGD *A GW Credit: Burneg and Dulaiova (2003) Loca%on 224 Ra 223 Ra 226 Ra Average Bikini Atoll 5.6 3.1 1.2 3.3 Enewetak Atoll 1.1 2.7 2.1 2.0

Lagoon 137-Cs and 241-Am Sources and Sinks (Bq/d) 1.E+10& 1.E+10& Enewetak Atoll Bikini Atoll 1.E+08& 1.E+08& 1.E+06& 1.E+06& Cs Bq/d& Bq/d& 137-Cs& 1.E+04& 1.E+04& Am 241-Am& 1.E+02& 1.E+02& 1.E+00& 1.E+00& Lagoon& GW&Input& Sediment& Lagoon& GW&Input& Sediment& Export& Input& Export& Input& • Groundwater inputs too small to be main source of both 137 Cs and 241 Am • Lagoon & crater sediments are likely source of water column Cs and Am (calculated here assuming Ra isotopes apply to en&re lagoon)

Marshall Islands today Ongoing source of radionuclides to the N. Pacific lagoon waters show elevated ac&vi&es bigger source for Pu than Cs to N. Pacific Pu isotopes show ongoing long range transport from MI Lagoon and crater sediments are likely source highest water column levels just above seafloor in craters Seafloor sediments are largest radionuclide inventory well mixed to >80 cm (most prior inventories to 20-30 cm) Groundwater inputs can be quan&fied with radium isotopes need more than single snap shot and limited loca&ons GW levels of Cs, Am (and likely Pu) elevated Plutonium isotopes will separate Runit Pu from other sources

Marshall Islands Future? Jet-Yak Autonomous cesium sampler

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Bikini - Cesium 137 in early 1970’s 20 Bq/m 3 20 Bq/m 3 = more than 100 &mes less than US drinking water limit = 10 &mes seawater in Woods Hole in 2015