Research and Development Relating to the Accident at the TEPCO’s Fukushima Daiichi NPS

1-9

Water Purifier for Securing Water－ Development of Grafted Adsorbent for Cs Removal －Stability of the crosslinking
structure adsorbent (times)

169G10M

9G1M

(a)

4G1M
12TAIC1M
84G10M

KranCsair ®
14G1M

4Without
Crosslinking0(b)TAIC10M

Water flow

Plastic plate
for retaining adsorbent
Activated carbon

00.3

0.6

0.9

1.2

Amount of Cs adsorbed (μmol/g-adsorbent)

Adsorbent

The notation shows the name and added amount ofcrosslinking reagent.
ex.)
9G 1M
Name of crosslinking
Added amountreagent(mol%/ GMA)
Fig.1-18 Efficiency of crosslinking structure for adsorbent
stability
Amount of Cs adsorbed and adsorbent stability (defined as theamount of Mo eluted from the adsorbent without crosslinking
structure divided by that with crosslinking structure). Highefficiency adsorbents are plotted in upper right corner.

Fig.1-19 (a) Water purifier for Cs removal and (b) internal
structure of cartridge
We have commercialized a cartridge-type water purifier.
This original cartridge, which incorporates the developedadsorbent, is replaced easily.

More than two years have elapsed since the accident at theTEPCO’s Fukushima Daiichi NPS, and the radioactive cesium(Cs) concentration in environmental water has been reduced.
However, the results of a 2012 monitoring investigation of thedrinking water in Fukushima reported by the Ministry of theEnvironment showed that radioactive Cs was detected in 6 of
436 samples. Therefore, securing ‘water’ is demand.
We developed a grafted adsorbent for removing soluble
Cs immediately after this accident. The developed adsorbent
consisted of ammonium 12-molybdophosphate (AMP) as
the adsorbent functional group supported on a nonwoven
polyethylene fabric acting as the substrate by radiationinduced graft polymerization. In a previous result, thisadsorbent exhibited instability: The supported AMP released
easily from the adsorbent. In this study, the unstable adsorbent
was improved by introducing a crosslinking structure torealize very little AMP elution. Introducing a crosslinking
structure to the grafted glycidyl methacrylate (GMA) chainof the adsorbent was attempted by adding three types ofpolyethylene glycol dimethacrylate (4G, 9G, or 14G) or

triallyl isocyanurate (TAIC) as the crosslinking reagent to amonomer.
The efficiency of the improved adsorbent was investigatedby batch-wise adsorption tests. The adsorbent was cut intopieces 1 cm2 (0.02 g) in size and immersed in 50 mℓ of 50 μg/ℓ
Cs solution under stirring for 24 h.
It was clarified that the amount of AMP eluted (calculated
as the eluted Mo) from the adsorbents with the introduced
crosslinking structure was less than that without the structure(Fig.1-18). Further, the amount of Cs adsorbed on mostadsorbents with the crosslinking structure was greater thanthat adsorbed without the structure.
An evaluation by an external organization verified that
this improved adsorbent satisfies the Food Sanitation Act
and Water Supply Act, and we developed a cartridge-typewater purifier called KranCsair® (Fig.1-19(a)). This original
cartridge, which incorporates the developed adsorbent,
is replaced easily (Fig.1-19(b)). A monitoring test of thedeveloped purifier was conducted in Fukushima. On the basisof the result, we will determine the final product specifications.

Reference
Mikami, T., Shibata, T. et al., Development of a Water Purifier by EB-Grafted Fiber, Setsubi to Kanri, vol.47, no.4, 2013, p.95-99 (in Japanese).

20JAEA R&D Review 2013