O těžbě uranu kyselinou sírovou:
Diskuse Aleš Zeman - Petr Novotný
Aleš Zeman:S mistni geologii ve Strazi obeznamen nejsem, ale je zcela bezne, ze spodni voda v zemske kure se vyskytuje v nekolika propustnych vrstvach, ktere jsou oddeleny vrstvami s nizkou propustnosti. Prikladam clanek v anglictine z r. 1995 (tedy muze byt dnes jiz zastaraly), ktery jsem vcera nalezl na internetu. Tvrdi, ze k znecisteni spodni vody v Ralsku vskutku doslo.
Jiz pri cetbe Vaseho popisu kontroly technologickeho roztoku pumpovanim ciste vody na okraji dulniho dila me napadlo, ze takovato kontrola muze byt (a dle prilozeneho clanku asi je) problematicka, neb nevytvori ucinnou barieru.
Napr. k zabraneni nezadoucich prusaku vody pod prehradami se pouziva injekcnich clon a provadeji se v pruzkumove fazi tlakove vodni zkousky, predtim nez se pristupuje k samotne injektazi, k niz se pouziva zpravidla cementova suspenze nebo jemna cementova malta ruzne hustoty nebo ruzne organicke pryskyrice.
Domnivam se, ze neco podobneho (injekcni clona) melo byt vybudovano v Ralsku, aby byl kontrolovan (jak vertikalni, tak horizontalni) rozptyl technologickeho roztoku v podlozi. Bylo by jiste zajimave vyslechnout si nekoho, napr. nejakeho inzenyra s.p. DIAMO, ktery ma prime zkusenosti s touto lokalitou.
Aleš Zeman:Domnivam se, ze tato tezba jednak neni ekonomicka vzhledem ke svetovym cenam uranu a jednak prispiva k znecisteni lozisek spodnich vod.
Petr Novotný: Ano, cena ekonomicka neni. Pokud se nepletu, ma DIAMO specialni smlouvu s CEZem o povinnem odkupu uranu.
Aleš Zeman:Tez jsem nekde cetl, ze v souvislosti s tezbou po dobu vice nez 25 let doslo k znecisteni ricky Ploucnice, ktera se v teto oblasti nachazi.
Petr Novotný: To znecisteni pochazi z povrchovych skladek po mechanicke tezbe v blizke sachte Hamr (nebo je to Stary Hamr? snad tam pracovali vezni).
Aleš Zeman: V dobach komunismu se pry vyluh posilal k dalsimu zpracovani do SSSR.
Petr Novotný:I ted se posila do zahranici - tedy ne vyluh, ale "yellow cake" - vysrazene z roztoku po oddeleni vetsiny zeleza a hliniku (jsou nejake technologicke normy na to, kolik ma ceho byt).
Aleš Zeman:Ten anglicky clanek je okopirovan z webove stranky http://antenna.apc.org/~wise/uranium/udec.html
A Chance for Groundwater at Straz ? (Czech Republic)
* 4 million tonnes of sulfuric acid injected into underground for uranium in-situ leaching in North Bohemia * Restoration being prepared by Peter Diehl, 9 June 1995 In-situ leaching is often presented as an environmentally friendly method of uranium production. With in-situ leaching, the uranium ore is not brought to the surface by conventional mining methods, but a leaching agent is injected into the ore deposit to dissolve the uranium. The uranium bearing liquid is then pumped to the surface, where the uranium is recovered. In-situ leaching, indeed, does not require extensive shafts and galleries, nor large waste deposits, and it produces only small amounts of waste slurries. But the problems arise, as soon as the site is to be shut down.
Petr Novotný: Ano, to presne shrnuje moji teorii :-)
That is the actual situation now of the Czech government in the case of the in-situ leaching site of Straz pod Ralskem in North Bohemia. Here, 4 million tonnes of sulfuric acid have been injected into the underground in an area of 5.7 km2 over a period of more than 25 years, to produce the raw material for nuclear weapons and for reactor fuel. In the leaching zone about 200 m below ground, 28 million m3 of highly contaminated liquid containing 80 g/l of total dissolved solids are found as a result of this acid injection. 11 contaminants are found in concentrations of even more than 100 times drinking water standards, with the highest excess of 30,000 times the drinking water standard for aluminium.
Petr Novotný: Hlinik automaticky vypadne pote, co se pH priblizi k 7 (myslim jiz pro pH kolem 5-6 zacina siran hlinity hydrolyzovat na (nerozpustny) hydroxid hlinity).
The majority of the total contaminant load is caused from sulphate at 65 g/l, exceeding the drinking water standard 260-fold. Moreover, the contaminated liquid migrated away from the leaching zone into surrounding areas, contaminating another 110 million m3 of groundwater in an area of 28 km2.
Petr Novotný:Tato voda - pokud vim - nikdy nebyla uvazovana jako zdroj pitne vody. Nicmene problem to je.
In addition, the acid reached along faulty wells another aquifer located above the leaching zone. This aquifer is being used for drinking water supply. 76 million m3 have been contaminated in this aquifer. With the planned shut-down of the site, the Czech government now faces the virtually unsolvable problem of restoring the groundwater quality in this largest aquifer of North Bohemia.
Petr Novotný:Unsolvable problem zalezi na tom, kdo vec hodnoti :-), a kde je pravda objektivne, si netroufam hodnotit.
The government-owned uranium mining company DIAMO thus was directed to develop a restoration concept for the site. This concept was presented at a conference in the last week of May. The restoration goal for the upper aquifer (used for potable water supply) is the drinking water standard, to be achieved by pumping of contaminated waters. The goal seems to be attainable for this aquifer, although some contaminants, as aluminium, exceed the standard up to 1000-fold. But for the leaching zone and its surroundings, the goal of reaching the potable water standard is regarded as absolutely unrealistic. For this aquifer, the goal is defined that anticipated contaminant migration to the upper aquifer shall not worsen the water quality in this aquifer beyond potable water standards. But it is still unclear, which contaminant level in the lower aquifer is sufficient to achieve this goal. According to the latest modeling results presented, a level of total dissolved solids of 10 g/l will be reached in the year 2014, and a level of 1 g/l in 2032, after continuous pumping. These figures were obtained from extensive computer modeling performed by the company. Unfortunately, pumping alone does not solve the problem, since the water produced cannot be discharged, due to its high contaminant load. Therefore, a water treatment plant is being built, including an evaporator for the contaminated liquid.
Petr Novotný:Ta evaporacni stanice uz stoji a je pry v provozu.
The evaporation residues are to be processed to marketable products (alunit, aluminium oxide or aluminium sulphate), if economically viable, or dumped otherwise. Later, as the contaminant load of the pumped liquids decreases, reverse osmosis units are to be installed before the evaporator, thus allowing operation of the evaporator at full capacity and an increase of pumping rate from initially 5.5 m3 per minute up to 30 m3 per minute. Without this additional technology, pumping would thus take much more time. During the first years, the evaporation residues are to be re- injected into the leaching zone, since the processing plant for the residues won't be operable before the year 2000 - this proposal caused unbelieving stupefaction with some observers. The restoration concept is now being reviewed by the consulting company MEGA a.s., a privatized spin-off of the former uranium mining company. Project director Dr Andel has already drawn attention to some critical points: For example, pilot scale tests for the restoration are missing, to verify the concepts based on modeling. Moreover, the extraordinary energy consumption of the evaporation unit and the reverse osmosis plants as not been assessed in detail. But in this regard, the review comes already too late, since the evaporation plant is already under construction. The total cost of the groundwater restoration project at the in- situ leaching site of Straz pod Ralskem is estimated at more than one billion US-Dollars and will have to be paid by the state budget. If this cost is attributed to the amount of uranium produced, a specific cost of $ 75 per kilogramme of uranium produced can be calculated. This is three times the current market price of uranium. ----------
Petr Novotný:Hm - a kde ze se ten uran tezi tak levne a presto ekologicky? CEZ odkupuje uran muslim 3000 za kg (mimochodem, srovnejte s cenou ucebnicovych 2700 kg kvalitniho uhli, coz vyhrevnosti tomu 1kg odpovida).
A k tem siranum - odsirenim elektraren vznika spousta presne tohoto - siranu. Taky se museji likvidovat...