JP2000338295A - Cement material for solidifying liquid waste in reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent harmful interstices from appearing when a liquid waste is solidified in a drum and the like by setting the radio between vermiculite and cement at a specific value and further using a cement compounding ingredient mixed with a specific percentage of a prescribed inflating agent. SOLUTION: A cement material used in order to solidify a radioactively contaminated liquid waste and the like is a mixture of Portland cement and vermiculite, for example. As to the weight ratio between vermiculite and Portland cement, the former is set at 0.5 to 1.5 and the latter at 7 to 9. This cement material is mixed with an inflating agent of 3 to 5 wt.% obtained by burning and crushing lime, plaster, bauxite and so on to make a solidified material. Then, it is filled into a drum, for example, until is occupies 90% of the internal space of the drum, and a used resin fat elution liquid waste is infiltrated as a reactor liquid waste through a strainer and is cured for a prescribed days. In the generated solidified waste which has sufficient strength, a good value is also shown in the judgement of an interstice between the solidified waste and the drum by a supersonic propagation velocity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement solidifying agent used for solidifying radioactively contaminated waste liquid (hereinafter also referred to as spent resin elution waste liquid) discharged from a nuclear power plant or the like.

[0002]

2. Description of the Related Art Conventionally, the above-mentioned radioactive waste liquid has been impregnated with cement put in a drum can and solidified, and this is stored in, for example, six locations.

[0003]

The metal drum used for the above-mentioned applications is a so-called metal lining in which the inner surface is covered with concrete. The uncured cement powder is filled in the drum, and the used resin elution waste liquid is poured into the drum, and the solid is absorbed by the cement and solidified. Shrinkage will occur, creating a gap between the can wall and the inner surface of the lining.

[0004] In a place such as Rokkasho, which stores various substances contaminated with radioactivity, when the drum containing solidified waste liquid is received, the contents are completely solidified or harmful voids remain. As a means of knowing whether or not the ultrasonic wave has propagated, the method of measuring the propagation speed of the ultrasonic wave from the can wall to the opposite side through the contents has been adopted, but there is a gap between the drum and the solidified material ( (See FIG. 5) and the ultrasonic waves bypass the can wall without passing through the contents, and the exact nature of the contents cannot be determined, and the acceptance of the waste is refused.

[0005]

As a solidifying material for solidifying the cement material having absorbed the radioactively contaminated waste liquid in a non-shrinking state, vermiculite: cement is used in an amount of 0.5 to 50%.
1.5: 7 to 9 (weight ratio), and a cement compounded material in which an expanding agent is mixed with 3 to 5% by weight of the cement, put into a drum can, and inject the waste liquid therein to solidify The body was adopted. The cement in this case may be ordinary cement, for example boltland cement.

[0006] Here, a sintering agent obtained by pulverizing a calcined compound mainly composed of lime, gypsum and bauxite is used. This includes a concrete expanding agent specified in JIS A6202. By adding an appropriate amount of this expanding agent to the cement, shrinkage due to drying of the concrete is suppressed, the long-term hardness of the concrete is increased, and the watertightness is improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. The cement used in the present invention is a mixture of the above-mentioned bolt land cement and vermiculite, which is referred to as vermiculite cement, and the weight ratio is 0.5 to 1.5 of vermiculite and 7 to 9 of bolt land cement. did. To this cement material, a swelling agent shown in Table 1 was added and mixed in an amount of 3 to 5% by weight of the cement. Hereinafter, the vermiculite cement and the mixture of the vermiculite cement and the expanding agent are referred to as a solidified material.

[0008]

[Table 1]

[0009]

EXAMPLES The performance of the solidification material according to the present invention for solidifying the waste liquid of a reactor will be described with reference to examples. First, with regard to the spent resin elution waste liquid as the reactor waste liquid, sodium nitrate 13.8 is used.
g, ammonium chloride 0.45 g was mixed and stirred in 1 liter of water and used as a simulated waste liquid R.

[0010] The following five types of solidified materials are used, and their expansion or shrinkage due to solidification and their changes over time,
The uniaxial compressive strength was studied.

The solidified material for the experiment (test sample) 1 VC 100% No. 1 No. 2 VC95% + CSA5% No. 3 VC90% + CSA10% No. 3 No. 4 VC85% + CSA15% 5 VC 80% + CSA 20% (VC: vermiculite cement CSA: concrete expanding agent)

Preliminary experiments on expansion and contraction of the solidified material were performed using the container shown in FIG. That is, in the cylindrical container C having a diameter of 120 mm simulating a drum can, the above-mentioned No. No. 1 to No. The solidified material M of No. 5 was filled to a height of 100 mm, and the simulated resin elution waste liquid R was allowed to naturally penetrate,
The state of expansion and contraction during the curing period of one day was measured. As a result, no. 1 and No. No. 2 did not show any deformation in appearance, 3 to No. 5 was found to be unsuitable for practical use because the expansion was large and the mold swelled (see FIG. 1) and the surface of the solidified body was cracked. Among these, comparatively good No. 1 and No. FIG. 2 shows the time-dependent changes in expansion and contraction in Sample No. 2.

Therefore, No. 1 and No. 2 CSA
The solidified material and the specimen No. VC9 as 6
Demonstration experiments using drums were performed using three types, each containing a solidified material of 7% + CSA 3% (FIG. 3). In this case, a drum 12 having a lining 13 of 5 cm made of concrete and a lining 13 having no lining are used, and the solidified material M (11) is filled up to 90% of the inner volume of the drum, and the strainer 14 is used. Simulated spent resin elution waste liquid R was permeated through to achieve solidification.

After solidification, the presence or absence of a gap between the drum and the solidified body is determined by measuring the ultrasonic wave propagation velocity from one of the outer diameters of the drum to the opposing surface sandwiching the center of the drum. Was determined by core boring a solidified body obtained from the above solidified material to a diameter of 50 mm and a height of 100 mm and measuring the uniaxial compressive strength. Table 2 shows the measured values of the combination of the solidified material (test sample) and the drum.

In Table 2, the ultrasonic wave propagation velocity of (1) shows a value substantially equal to that of the drum can without lining. This is because ultrasonic waves cannot propagate in the solidified body because there is a gap between the solidified body and the drum can,
It is probable that it propagated along the peripheral wall of the drum. Also,
The ultrasonic wave propagation velocity in (4) shows a value smaller than the ultrasonic wave propagation velocity of the lined drum alone, but is lower than the propagation velocity of (5) with addition of 5% CSA. There is a slight gap between them to avoid and propagate to the can wall or lining.

[0016]

[Table 2]

A solidified material (No.
The propagation of the ultrasonic wave in the sample No. 6) was carried out for both the drum with and without the lining. Specimen no. Values greater than 2 (slower) were obtained. Therefore, the addition amount of the swelling agent is desirably about 5%, and it is considered that the addition of 3 to 6% is also practical.

The unconfined compressive strength should be a value sufficiently higher than the "unconfined compressive strength of solidified radioactive waste" (15 kg / cm ² ) specified in the Science and Technology Agency Notification No. 2 concerning the treatment of polluted waste liquid. Obtained.

Also, one month and 13 months after impregnating the solidified material and the simulated resin elution waste liquid, the drum can is cut in the axial direction, and it is visually observed whether or not a gap exists between the drum and the solidified body. However, a clear judgment could not be made. Therefore, the optimum value of the amount of the swelling agent was determined by the above-described determination based on the ultrasonic wave propagation speed.

Further, from various additional demonstration tests, VC
98% + CSA2% to VC94% + CSA6% (all by weight%) are good in ultrasonic wave propagation velocity measurement and compressive strength, most preferably VC96% + CS
It was found that the mixing ratio was A4% (% by weight).

[0021]

According to the present invention, a drum can is filled with a solidified material obtained by mixing a vermiculite cement with an expanding agent obtained by pulverizing a calcined compound mainly composed of lime, gypsum and bauxite by 3 to 6%, and impregnated with radioactive waste liquid. Upon solidification, the shrinkage was suppressed and the waste was disposed of under the disposal conditions, that is, a result in which no harmful voids were formed in the can.

[Brief description of the drawings]

FIG. 1 is a front view of a device for impregnating a solidified material with a simulated liquid to solidify the solidified material, and a cross-sectional view showing the expansion and contraction in a pictorial manner.

FIG. 1, No. 4 is a graph showing a change in outer diameter of a solidified body due to No. 2.

FIG. 3 is a front view of a sectional display showing a demonstration test apparatus using a drum.

FIG. 4 is a graph showing the relationship between the amount of expansion agent added and the compressive strength.

FIG. 5 is a front view of a central section showing a general method of solidifying radioactive waste liquid in a drum.

[Explanation of symbols]

 Reference Signs List 11 solidified material 12 drum 13 concrete lining 14 strainer

Claims (2)

[Claims] A weight ratio of vermiculite to cement of 0.5 to 1.5: 7 to 9 and an expansive agent mixed with 3 to 5% by weight of the cement are discharged from a nuclear reactor or the like. Material for solidification of waste radioactive waste. 2. The swelling agent is CaO (50.0 to 53.6).
%), Al ₂ O ₃ (12.0 to 15.0), SO ₃ (2
7. The cement material for solidifying radioactively contaminated waste liquid according to claim 1, which is an expanding agent for concrete containing 7.0 to 31.0) as a main component.