scholarly journals Unexpected source of Fukushima-derived radiocesium to the coastal ocean of Japan

2017 ◽  
Vol 114 (42) ◽  
pp. 11092-11096 ◽  
Author(s):  
Virginie Sanial ◽  
Ken O. Buesseler ◽  
Matthew A. Charette ◽  
Seiya Nagao
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Coastal Ocean ◽  
Public Health Issue ◽  
Fluid Exchange ◽  
Radium Isotopes ◽  
Cesium 137 ◽  
Plant Monitoring ◽  
Beach Sands

There are 440 operational nuclear reactors in the world, with approximately one-half situated along the coastline. This includes the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), which experienced multiple reactor meltdowns in March 2011 followed by the release of radioactivity to the marine environment. While surface inputs to the ocean via atmospheric deposition and rivers are usually well monitored after a nuclear accident, no study has focused on subterranean pathways. During our study period, we found the highest cesium-137 (137Cs) levels (up to 23,000 Bq⋅m−3) outside of the FDNPP site not in the ocean, rivers, or potable groundwater, but in groundwater beneath sand beaches over tens of kilometers away from the FDNPP. Here, we present evidence of a previously unknown, ongoing source of Fukushima-derived 137Cs to the coastal ocean. We postulate that these beach sands were contaminated in 2011 through wave- and tide-driven exchange and sorption of highly radioactive Cs from seawater. Subsequent desorption of 137Cs and fluid exchange from the beach sands was quantified using naturally occurring radium isotopes. This estimated ocean 137Cs source (0.6 TBq⋅y−1) is of similar magnitude as the ongoing releases of 137Cs from the FDNPP site for 2013–2016, as well as the input of Fukushima-derived dissolved 137Cs via rivers. Although this ongoing source is not at present a public health issue for Japan, the release of Cs of this type and scale needs to be considered in nuclear power plant monitoring and scenarios involving future accidents.

scholarly journals Continuing <sup>137</sup> Cs release to the sea from the Fukushima Dai-ichi Nuclear Power Plant through 2012

2013 ◽  
Vol 10 (9) ◽  
pp. 6107-6113 ◽  
Author(s):  
J. Kanda
Keyword(s):  
Exchange Rate ◽  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Water Exchange ◽  
Water Release ◽  
Power Company ◽  
Cesium 137 ◽  
Harbour Water ◽  
Surrounding Seawater

Abstract. The rate of cesium-137 (137Cs) release to the sea from the Fukushima Dai-ichi Nuclear Power Plant for the period until September 2012 was estimated. Publicly released data on 137Cs radioactivity in seawater near the power plant by Tokyo Electric Power Company strongly suggest a continuing release of radionuclides to the sea. The plant has an artificial harbour facility, and the exchange rate of harbour water with surrounding seawater was estimated by the decrease in radioactivity immediately after an intense radioactive water release. The estimated exchange rate of water in the harbour was 0.44 d−1 during the period from 6 to 19 April. The 137Cs radioactivity in the harbour water was substantially higher than that of seawater outside and remained relatively stable after June 2011. A quasi-steady state was assumed with continuous water exchange, and the average release rate of 137Cs was estimated to be 93 GBq d−1 in summer 2011 and 8.1 GBq d−1 in summer 2012.

scholarly journals Radium-based estimates of cesium isotope transport and total direct ocean discharges from the Fukushima Nuclear Power Plant accident

2012 ◽  
Vol 9 (11) ◽  
pp. 16139-16160 ◽  
Author(s):  
M. A. Charette ◽  
C. F. Breier ◽  
P. B. Henderson ◽  
S. M. Pike ◽  
I. I. Rypina ◽  
...  
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Coastal Zone ◽  
Nuclear Power ◽  
Water Mass ◽  
Water Soluble ◽  
Surface Mixed Layer ◽  
Mass Source ◽  
Radium Isotopes ◽  
Oceanographic Model

Abstract. Radium has four naturally occurring isotopes that have proven useful in constraining water mass source, age, and mixing rates in the coastal and open ocean. In this study, we used radium isotopes to determine the fate and flux of runoff-derived cesium from the Fukushima Nuclear Power Plant (NPP). During a June 2011 cruise, the highest Cs concentrations were found along the eastern shelf of northern Japan, from Fukushima south, to the edge of the Kuroshio current, and in an eddy ∼ 130 km from the NPP site. Locations with the highest cesium also had some of the highest radium activities, suggesting much of the direct ocean discharges of Cs remained in the coastal zone 2–3 months after the accident. We used a short-lived Ra isotope (223Ra, t1/2 = 11.4 d) to derive an average water mass age (Tr) in the coastal zone of 32 days. To ground-truth the Ra age model, we conducted a direct, station-by-station comparison of water mass ages with a numerical oceanographic model and found them to be in excellent agreement (model avg. Tr = 27 days). From these independent Tr values and the inventory of Cs within the water column at the time of our cruise, we were able to calculate an offshore 134Cs flux of 3.9–4.6 × 1013 Bq d−1. Radium-228 (t1/2 = 5.75 yr) was used to derive a vertical eddy diffusivity (Kz) of 0.7 m2 d−1 (0.1 cm2 s−1); from this Kz and 134Cs inventory, we estimated a 134Cs flux across the pycnocline of 1.8 × 104 Bq d−1 for the same time period. On average, our results show that horizontal mixing loss of Cs from the coastal zone was ∼ 109 greater than vertical exchange below the surface mixed layer. Finally, a mixing/dilution model that utilized our Ra-based and oceanographic model water mass ages produced a direct ocean discharge of 134Cs from the FNPP of 11–16 PBq at the time of the peak release in early April 2011. Our results can be used to calculate discharge of other water-soluble radionuclides that were released to the ocean directly from the Fukushima NPP.

scholarly journals Radium-based estimates of cesium isotope transport and total direct ocean discharges from the Fukushima Nuclear Power Plant accident

2013 ◽  
Vol 10 (3) ◽  
pp. 2159-2167 ◽  
Author(s):  
M. A. Charette ◽  
C. F. Breier ◽  
P. B. Henderson ◽  
S. M. Pike ◽  
I. I. Rypina ◽  
...  
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Coastal Zone ◽  
Nuclear Power ◽  
Water Mass ◽  
Water Soluble ◽  
Surface Mixed Layer ◽  
Mass Source ◽  
Radium Isotopes ◽  
Oceanographic Model

Abstract. Radium has four naturally occurring isotopes that have proven useful in constraining water mass source, age, and mixing rates in the coastal and open ocean. In this study, we used radium isotopes to determine the fate and flux of runoff-derived cesium from the Fukushima Dai-ichi Nuclear Power Plant (FNPP). During a June 2011 cruise, the highest cesium (Cs) concentrations were found along the eastern shelf of northern Japan, from Fukushima south, to the edge of the Kuroshio Current, and in an eddy ~ 130 km from the FNPP site. Locations with the highest cesium also had some of the highest radium activities, suggesting much of the direct ocean discharges of Cs remained in the coastal zone 2–3 months after the accident. We used a short-lived Ra isotope (223Ra, t1/2 = 11.4 d) to derive an average water mass age (Tr) in the coastal zone of 32 days. To ground-truth the Ra age model, we conducted a direct, station-by-station comparison of water mass ages with a numerical oceanographic model and found them to be in excellent agreement (model avg. Tr = 27 days). From these independent Tr values and the inventory of Cs within the water column at the time of our cruise, we were able to calculate an offshore 134Cs flux of 3.9–4.6 × 1013 Bq d−1. Radium-228 (t1/2 = 5.75 yr) was used to derive a vertical eddy diffusivity (Kz) of 0.7 m2 d−1 (0.1 cm2 s−1); from this Kz and 134Cs inventory, we estimated a 134Cs flux across the pycnocline of 1.8 × 104 Bq d−1 for the same time period. On average, our results show that horizontal mixing loss of Cs from the coastal zone was ~ 109 greater than vertical exchange below the surface mixed layer. Finally, a mixing/dilution model that utilized our Ra-based and oceanographic model water mass ages produced a direct ocean discharge of 134Cs from the FNPP of 11–16 PBq at the time of the peak release in early April 2011. Our results can be used to calculate discharge of other water-soluble radionuclides that were released to the ocean directly from the Fukushima NPP.

scholarly journals Drone Fleet Survivability Evaluation Based on Lanchester’s Modified Deterministic Model

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Deterministic Model ◽  
Algorithmic Approach ◽  
Group Productivity ◽  
Monitoring Time ◽  
Plant Monitoring ◽  
Recovery Group

An algorithmic approach for the assessment of the survivability is proposed that is based on Lanchester’s modified deterministic model. Methods are suggested for increasing the available time capability for nuclear power plant monitoring and coverage, using the required or a limited number of the operable drones,. Dependencies of the variance between the residual fleet damage and permissible drone fleet damage on monitoring time as well as dependencies of the monitoring time on the recovery group productivity are analysed.

Sign in / Sign up

Export Citation Format

Share Document