liquid radioactive waste inside the shelter

1066-3622/02/4406-0601$27.00C2002 MAIK [Nauka/Interperiodica]

Radiochemistry, Vol. 44, No. 6, 2002, pp. 6013 608. Translated from Radiokhimiya, Vol. 44, No. 6, 2002, pp. 5453552.Original Russian Text Copyright C 2002 by Korneev, Krinitsyn, Strikhar’, Shcherbin.

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Liquid Radioactive Waste Inside the ShelterA. A. Korneev, A. P. Krinitsyn, O. L. Strikhar’, and V. N. Shcherbin

Shelter Interbranch Scientific and Technical Center, National Academy of Sciences of Ukraine, Chernobyl,Kiev Oblast, Ukraine

Shelter Pilot Plant, Chernobyl, Kiev oblast, Ukraine

Received October 17, 2001

Abstract-Recent data on the sources, routes, and dynamics of water penetration into Block B and temporalcollector of radioactive waste (TCRW) rooms were reported. The mechanism of liquid radioactive waste(LRW) formation in the Shelter rooms was discussed. The results of tracer analysis of the routes and dynamicsof LRW formation both inside and outside the Shelter were summarized. In particular, it was found that thecontaminated [block] water leaks by two main routes, northern and south-eastern. The northern stream ofLRW comes, eventually, to the Block 3 room no. 0005 pit (6.00-m mark) intended for collection of spontane-ously leaked water and is treated together with the low-level waste from the Chernobyl NPP. The south-eastern stream comes to Block B room nos. 017/2 and 018/2. The route and intensity of LRW leakage fromthese rooms require special investigation.

The water penetrating into the Shelter from varioussources when moving from upper to lower marksleaches soluble components of concrete structures andreacts with various modifications of fuel-containingmaterials (FCMs). As a result, high-level alkali3carbonate solutions are formed at lower marks of theblock, which are, essentially, liquid radioactive waste(LRW). Accumulation, uncontrolled spread, and leak-age of LRW outside Block 4 can destabilize thepresent-day radiation and radioecological safety atthe Shelter [1].

Clearly, solving this problem requires complexresearch work, including analysis and correlation ofthe available information, as well as experimentsaimed to estimate more precisely the parameters ofLRW streams both inside and outside the Shelter. Inthis article, we report the results of studying the in-tensity and routes of Shelter LRW streams usingtracers.

MAIN SOURCES OF WATER

The main sources of water coming to the Shelterrooms are atmospheric precipitations, condensate, andtechnogenic solutions. In [2], we estimated the upperlimiting amount of water penetrating into the centralroom (CR) and separating barrel (SB) rooms fromvarious sources. It was shown that atmospheric pre-cipitations falling on the light roof surface run downthe inclined sections of the roof onto horizontal ledgesabove the northern and southern SBs (Fig. 1) and,almost without hindrance, penetrate into the subroofspace via destroyed roof sections.

We estimated the amount of atmospheric precipita-tions penetrating into the Shelter from the intensity ofatmospheric precipitations around the Chernobyl NPPand the projected surface area of the roof above thecentral room and other rooms in Block B [2]. Theupper limiting amount of the atmospheric precipita-tions penetrating into Block B and TCRW rooms isestimated at 180032200 m3. This value took no ac-count of the amount of the water evaporated from theroof surface in summers and of the amount of snowtaken away with the wind in winters. Thus, the actualamount of the penetrating atmospheric precipitationsshould be less than the above conservatively estimatedlevel. In the negative-temperature period, ca. 100 mm,on the average, of precipitations is deposited. Underassumption that one half of this amount is taken awaywith the wind, and the other half is retained on theroof and, during snow melting, penetrates into theShelter, we can estimate more realistically the upperlimit of the precipitation amount, coming to the mostdanger-bearing rooms, at 153031870 m3 per annum.

We estimated the amount of the condensationmoisture as the difference between the amounts of themoisture contained in the air flows entering and leav-ing the Shelter rooms. We found that, in humid May3August periods, when the moisture content in theatmospheric air exceeds that of the air inside theShelter, condensation can yield 1650 m3 of water. InSeptember3April periods, drier atmospheric air pene-trates into Block 4 rooms, gets saturated with mois-ture, and goes out. On the whole, 2100 m3 of water

RADIOCHEMISTRY Vol. 44 No. 6 2002

602 KORNEEV et al.

Fig. 1. Light roof of the Shelter.

can evaporate within this period. It should be em-phasized that the above values are the upper limit-ing amounts of the incoming and evaporating water,as most of the air flows pass through the Blockrooms, where the conditions favorable for condensa-tion or evaporation exist within a shorter time period.Taking into account the inaccuracy of the experi-mental and calculated data, we can state that, to afirst approximation, evaporation and condensationare balanced.

The water balance calculation for the Sheltershowed that the upper limiting amount of the con-taminated water leaked from Block 4 rooms is closeto 1700 m3 per annum [2]. Clearly, more preciseelucidation of the amounts of the forming LRW andits migration routes can markedly decrease its collec-tion and treatment costs.

MAIN LRW STREAMS INSIDE THE SHELTER

Results of Study of the LRW Streams UsingDistributed Tracer Injection Procedure

In 199631998, a field experiment was carried outon injecting a tracer into the subroof space via a stan-dard dust-suppression system (DSS) and on studyingits concentration dynamics at lower Block marks. Theinitial solution of the tracer, sodium bromide, wasuniformly sprayed over ~1500 m2 area of the centralroom and destroyed rooms of SBs.

The experimentally determined dynamics of thetracer concentrations in the water streams and con-taminated water mass accumulated at lower marks ofthe Block suggested the following [2].

(1) The major vertical routes of migration forwater streams in the Shelter rooms, posing the greatest


LIQUID RADIOACTIVE WASTE INSIDE THE SHELTER 603

Fig. 2. LRW streams and accumulations at the +2.20-m mark

radiation hazard, are as follows: northern water stream(from destroyed rooms of the northern separatingbarrels to the northern section of the bubbler basin);central water stream (from the central room via thereactor cavity and the neighboring rooms to the cen-tral section of the bubbler basin); and southern waterstream (from destroyed rooms of the southern separat-ing barrels to the southern section of the bubblerbasin).

(2) The northern, central, and southern waterstreams are, eventually, accumulated in TCRW roomno. 001/3. The intensity of leakage of the contami-nated water from this room is estimated at 1300 m3

per annum.

The results of the above-described experiment areof great scientific and practical importance, though a

number of issues essential for designing Shelter LRWhandling system still remain to be solved. For thisreason, complex research work was initiated in 199932000 under the international project aimed at convert-ing the Shelter to an environmentally safe system; thework included a field experiment on local injectionof tracers and on elucidation of their concentrationdynamics.

Results of a Study of the Shelter LRW StreamsUsing Local Injection of Tracers

Experimental procedure. The experiment involv-ing tracer injection into selected LRW accumulationsand study of their concentration dynamics was aimedat (1) elucidating whether there is a hydraulic connec-


604 KORNEEV et al.

Fig. 3. LRW streams and accumulations at the 30.65-m mark.

tion between the highest-level LRW accumulated inthe southern and northern sections of the bubblerbasin and the largest amount of LRW accumulatedin TCRW block room no. 001/3; (2) determiningthe dynamics of LRW streams passing through thebubbler basin rooms; and (3) confirming experiment-ally the presumed LRW leakage route and estimatingthe rate of LRW leakage outside the Shelter.

To solve these problems, we used the already testedtracer method. By contrast to the above-describedexperiment, we introduced the tracers into local wateraccumulations and determined the tracer concentrationdynamics in all the water accumulation sites locatedalong the possible leakage routes. As tracer servedKI solution injected in the accumulation in thesouthern section of the BB first floor (Fig. 2, room



nos. 012/13316) and NaBr injected into the water ac-cumulation in the northern section of the BB groundfloor (Fig. 3, room nos. 012/538). We used two dif-ferent tracers, as water could leak from the BB south-ern section by several routes. The revealed dynamicsof the tracer concentration are shown in Figs. 437.

Water stream routes in bubbler basin rooms.Almost immediately after injection of the tracer intothe water accumulated in the southern section of theBB first floor (Fig. 2, point 6) the iodine concentra-tion started to decrease, evidently, due to water com-ing from the above-situated steam-distribution cor-ridor rooms (Fig. 4). At the same time, on the BBground floor (Fig. 3, point 32) the tracer concentrationinitially increased, whereupon it started to graduallydecrease, and, eventually, the tracer concentrations onthe BB ground and first floors became virtually iden-tical (Figs. 4, 5). This evidences that, when the waterlevel in room nos. 012/13316 exceeds the 15320-cmmark, excess water containing the tracer flows over tothe above-located room no. 012/538. Systematic ob-servations showed that water from this room is re-moved primarily by evaporation. Therefore, in dry(autumn3winter) period the concentrations of radionu-clides and uranium in this room (point 32) tend toincrease owing to water evaporation, and in humidperiod, to decrease owing to less active water inflow-ing from upper marks.

Three months after iodine injection into the south-ern section of the BB first floor, its concentrationstarted to increase in the BB northern section as well(Fig. 6, points 31A331C). This evidences that theserooms are hydraulically connected. The water streamfrom the southern section of room nos. 012/13316,most probably, passes over the floor in the roomno. 012/15 central part under the concrete body tothe northern section (see arrow in Fig. 2) and, via athrough hole in the floor, comes to room no. 012/7 onthe BB ground floor (Fig. 3).

It should be noted that this water stream flowsaround a large accumulation of lave-like fuel-contain-ing masses (LFCM) in room no. 012/15 among therows (Fig. 2). Many-year monitoring showed, how-ever, that the radionuclide composition of this waterbefore (BB southern section, point 6) and after (BBnorthern section, points 21, 31) contacting the LFCMagglomeration is virtually identical, confirming theconclusion that LFCM is fairly stable chemically andthat water is contaminated in Shelter rooms owingprimarily to dissolution of the fuel and condensationparticles at upper marks in the block [3].

The concentration of bromine injected as a tracer

Fig. 4. Iodine concentration dynamics in the BB southernsection at +2.20-m mark (points 6B36D): (Points) experi-ment and (curve) calculation. Points: (1) 6C, (2) 6D, and(3) 6B.

Fig. 5. Iodine concentration dynamics in the BB northern(points 31A331D) and southern (point 32) sections at30.65-m mark. Points: (1) 31A, (2) 31B, (3) 31C, (4) 31D,and (5) 32.

Fig. 6. Bromine concentration dynamics in the BB northernsection at 30.65-m mark (points 31A331D). Points: (1) 31A,(2) 31B, and (3) 31C.


606 KORNEEV et al.

Fig. 7. Tracer concentration dynamics in the TCRW rooms.Points: (1, 6) 30 (water mass accumulated in Block 4 roomno. 001/3); (2, 4) 110 (water stream in Block 3 roomno. 001/3); and (3, 5) 111 (water accumulated in pit ofBlock 3 room no. 0005). Tracer: (133) Br and (436) I.(7) Calculated (by regression) tracer concentrations.

into the BB northern section at the 30.65-m markexhibits more complex dynamics. Figure 6 showsthat, immediately after the tracer was injected, its con-centration at point nos. 31B3D was lower than thecalculated level, and only within 3 months after injec-tion it reached the calculated level and began todecline.

These tracer dynamics are due, evidently, to thefact that, during injection, the initial sodium bromidesolution (1250 g l31), owing to its high density, wasconcentrated at the pit bottom in the bottom sedimentlayer. The bromine concentration in the initial periodincreases owing to its diffusion to the upper layer ofthe clarified solution.

Figure 6 shows that, since January 2000, the tracerhas been steadily removed from the BB northern sec-tion. After a certain delay, the tracer concentrationsbegan to increase in TCRW room no. 001/3 as well(Fig. 7, point 30). This confirms that rooms in the BBnorthern section and TCRW room no. 001/3 are hy-draulically connected. In rooms located in the easternand south-eastern sections of Block B, the tracer con-centrations did not exceed the background levels.Thus, all the LRW streams coming to BB rooms leakby only one route, namely, by that leading to roomno. 001/3.

Our results (Figs. 437) show that the iodine andbromine concentrations in room no. 001/3 attainedtheir maximal values virtually simultaneously (Fig. 7),despite a 3-month delay in iodine coming to the BBnorthern section (Fig. 5). This suggests that the most

heavily contaminated water from BB leaks to TCRWroom no. 001/3 only during periods of fairly activewater inflow (spring3summer) rather than permanent-ly. In dry periods, with evaporation dominating overcondensation, water in the BB northern section doesnot reach the height of the process holes leading to theTCRW and, thus, the water stream from Block B doesnot come to room no. 001/3. Evidently, the watermass accumulated inside the Shelter can be regardedas a system of communicating vessels. Water leaksfrom one room to another only when a certain waterlevel is exceeded in the room.

Leakage routes for contaminated water fromBlock 4 room no. 001/3. To experimentally confirmleakage of contaminated water form the ShelterBlock 3 TCRW rooms, we sampled water from thewater stream near the separating wall in roomno. 001/3 on the Block 3 side (Fig. 3, point 110) andfrom the pit in room no. 0005 (Fig. 3, point 111).This pit accumulates all the regular and partly regularwater streams that leak from rooms of TCRW sharedby Blocks 3 and 4. Figure 7 shows the dynamics ofthe tracer concentrations in water accumulated inBlock 4 room no. 001/3 (point 30), in the waterstream in Block 3 room no. 001/3 (point 110), and inthe room no. 0005 pit (point 111).

We found that, since April 2000, the iodine andbromine concentrations in the water stream comingfrom under the separating wall sharply increased(Fig. 7, point 110). This unambiguously proves thatthe water streams from all the BB rooms are accumu-lated in room no. 001/3, whereupon they overflow toBlock 3 TCRW rooms.

Figure 7 shows that the iodine and bromine con-centration dynamics at the monitoring points locatedalong the northern water stream route in roomno. 001/3 are similar. Moreover, the tracer concentra-tions at these points are virtually identical (within theaccuracy of analysis), though these points are sepa-rated by at least 70 m as measured along the waterstream route (Fig. 3, points 30 and 110).

The tracer analysis shows that, eventually, thewater streams in the Shelter on the BB and cascadewall side come first to room no. 001/3 and then tothe pit located in room no. 0005 of the Block 3TCRW (Fig. 3, point 111).

Thus, our experiments showed that the waterstream takes the following route: southern section ofroom nos. 012/13316 (+2.20-m mark) 6 central sec-tion of room no. 012/15 (LFCM) 6 northern sectionof room no. 012/15 (+2.20-m mark) 6 northern sec-



Fig. 8. Diagram of water streams inside the Shelter.

tion of room nos. 012/538 (30.65-m mark) 6 roomno. 001/3 (32.60-m mark) 6 room no. 0005 ofBlock 3 TCRW (36.00-m mark).

LRW stream dynamics in Block B and TCRWrooms. The above data show that the tracer concentra-tion eventually starts to decrease in all the watermasses accumulated. This is, evidently, due to thetracer loss by water exchange. The dynamics of thetracer loss in the water mass accumulated, i.e., thepattern of variation of the concentration with the timeelapsed after attaining the maximum, is adequatelydescribed by the exponential dependence [3]

Ct = C0 exp (3ft /V), (1)

where Ct is the tracer concentration by the moment t;C0 is the tracer concentration at the initial moment;f is the water exchange rate (m3 per month); t is thetime of attaining the concentration Ct, month; andV is the volume of water in the water mass accumu-lated, m3.

The rate of the water inflow and leakage f can be

easily calculated by the formula

f = 3[ln (Ct /C0)]V/t. (2)

The parameters of Eq. (1) can be estimated mostprecisely by regression analysis of the total body ofthe experimental data. Clearly, the exponential depen-dence is easily transformed to a linear dependence,which allows easy least-squares determination of theregression equation parameters. In this work, we usedto this end the Origin 50 program.

Figures 437 present the experimentally revealeddynamics of the tracer concentrations for the watermass accumulated in BB and TCRW and the regres-sion dependences. We used these data for estimatingthe water exchange dynamics, i.e., the rate of thewater inflow and leakage in BB and TCRW rooms.We estimated the leakage rate of heavily contaminatedwater from BB rooms to room no. 001/3 at 80390 m3

per annum.

From Block 4 TCRW room no. 001/3, the LRW


608 KORNEEV et al.

penetrates via the separating wall to Block 3 rooms.The amount of the LRW leaked outside the Shelter isestimated at 740+160 m3 per annum. This value isthe sum of those for high-level regular and spontane-ous streams leaked from steam distributor corridorrooms, reactor cavity (14 m3 per annum), and bubblerbasin rooms (80390 m3 per annum), as well as thosefor the relatively low-level streams leaked on thecascade wall side (650 m3 per annum).

Figure 8 shows schematically the routes of themajor water streams in Block B and TCRW rooms,thus summarizing the results of our experiments ontracer injection and monitoring.

Thus, we found that most of the LRW inside theShelter, resulting from interaction of water with struc-tural materials and fuel-containing masses, is ac-cumulated in room no. 001/3, whereupon it pene-trates through the separating wall and, eventually,is accumulated in the pit of Block 3 TCRW roomno. 0005. The waste filling the pit is pumped off tothe transfer tank of the Chernobyl NPP chemical shop.

The LRW from the Shelter contains organic im-purities and transuranium elements in large amountsexceeding the permissible levels and, therefore, cannotbe processed directly in Chernobyl NPP evaporators.The currently used procedure prescribes that the LRWfrom the Shelter be prediluted to the required concen-tration by a large stream of low-level LRW on theBlock 3 side (over 300 m3 per diem). However, sinceBlock 3 was put out of operation, the stream of low-level LRW from the Chernobyl NPP has gradually

decreased. This calls for a procedure and facilities forpretreating LRW from the Shelter to remove organiccomponents and transuranium elements to levels atwhich the waste can be treated with the standard facil-ities of the Chernobyl NPP.

It should be noted that elucidating the routes andintensity of the LRW leakage from rooms in Block Bsouth-eastern section requires special studies.

ACKNOWLEDGMENTS

The authors are sincerely grateful to the leadingspecialist of the Chemical Shop of Chernobyl NPPA.S. Zozulya, as well as to C. Wilding and T. Greenfrom AEA Technology (the United Kingdom) for as-sistance in organizing and conducting this work.

REFERENCES

1. Bogatov, S.A., Krinitsyn, A.P., and Simanov-skaya, I.Ya., Research and Diagnostic Works at theShelter Aimed at Correcting the [Technical Regula-tions for the Shelter of Reactor no. 4 of the ChernobylNPP,] Research Report of the Shelter InterbranchScientific and Technical Center, Chernobyl, 1997,UkrINTI registry no. GR 0898U000443.

2. Bogatov, S.A., Korneev, A.A., Krinitsyn, A.P., et al.,Radiokhimiya, 2000, vol. 42, no. 3, pp. 2763280.

3. Bogatov, S.A., Korneev, A.A., and Krinitsyn, A.P.,Problem of Water in the Shelter, Preprint of the Na-tional Academy of Sciences of Ukraine, Shelter Inter-branch Scientific and Technical Center and the Shelter.

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