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II Ngun gc:2.1. Ngun gc t nhin:2.1.1.Cc loi phn r phng x t nhin:Trong t nhin, thng thng c ba dy nguyn t phng x lun lun hot ng, l dy uran, dy thori, dy actini. u mi dy u c mt ng v phng x vi thi gian sng di lu (sng lu) v cui mi dy lun lun l nhng ng v bn ca ch.Bng 2.1 Dy Uran:Tnnguyn tK hiuCc loi ht bc xChuk bn r
UranU238++4,5 x 109nm
ThoriTh234++24,1 ngy
ProtactiniPa234++117 pht
UranU234++2,5 x 105nm
ThoriTh230++8,0 x 104nm
RadiRa226++1,6 x 103nm
RadonRn222++3,82 ngy
PoloniPo218+3,05 pht
ChPb214++26,8 pht
BitmutBi214++19,7 pht
PoloniPo214++1,6 x 10-4giy
TaliTl210++1,32 pht
ChPb210++20,4 nm
BitmutBi210++5 ngy
PoloniPo210++138 ngy
ChPb206Ht nhn bn
Bng 2.2 Dy Thori:Tnnguyn tK hiuCc loi ht bc xChuk bn r
ThoriTh232++1,41 x 1010nm
RadiRa228+6,7 nm
AktoniAc228++6,13 gi
ThoriTh228++1,90 nm
RadiRa224++3,64 ngy
RadonRn220++55,3 giy
PoloniPo210+0,145 giy
ChPb212++10,6 gi
BitmutBi212++60,6 pht
PoloniPo212+3 x 10-7giy
TaliTl208++3,1 pht
ChPb208Ht nhn bn
Bng 2.3 Dy Actini:Tnnguyn tK hiuCc loi ht bc xChuk bn r
UranU235++71 x 108nm
ThoriTh231++225 gi
ProtactiniPa231++3,25 x 104nm
AktoniAc227++21,6 nm
ThoriTh227++18,2 ngy
PranciFr223++22 pht
RadiRa223++11,44 ngy
RadonRn219++4,0 giy
PoloniPo215+1,78 x 10-3giy
ChPb211++36,1 pht
AstatinAt211+0,9 pht
BitmutBi211++2,16 pht
PoloniPo211++0,5 giy
TaliTl207++4,79 pht
ChPb207Ht nhn bn
2.1.2. Cc ht nhn phng x khc: Trong cc loi t, trong lng Tri t cng c mt s nhng nguyn t phng x khc, khng nm trong cc dy trn v c thi gian sng kh di.Bng 2.4 Cc nguyn t phng x ring l trong t nhin:Tnnguyn tK hiuCc loi ht bc xChuk bn r
KaliK40++1,3 x 109nm
VanadiV50++6 x 1014nm
RubidiRb87+4,8 x 1010nm
IndiIn115+6 x 1014nm
LantanLa138++1,1 x 1011nm
SamariSm147+1,05 x 1011nm
LutetiLu176++2,2 x 1010nm
Hot ca cc ng v phng x ny ph thuc vo thnh phn t, xc nh. Hot ca cc ht nhn phng x trong cc loi c ngun gc t ni la nh granit. thng cao hn cc c ngun gc t ph sa nh vi, cui. Ngc li vi cc loi , i vi cc loi t th mt cht phng x cn ty thuc vo dng t, qu trnh hnh thnh loi t, ngun nc c trong t v s to thnh cc cy ci trn v trong t .2.1.3. Bc x t V Tr: Bc x s cp t V Tr i vo bu kh quyn Tri t ch yu gm cc ht proton, cc ht v mt lng nh cc ht in t, v ntrino. Cc ht ny tng tc vi cc ht nhn nguyn t kh trong kh quyn to ra cc bc x th cp v cc ht th cp, v bc x in t c gi chung l bc x V Tr th cp. Bc x V Tr s cp cn bao gm cc bc x t cc h thin h. Mc bc x V Tr cn ph thuc vo cao trong kh quyn v s hot ng ca Mt Tri cng cao th lng phng x ny cng tng.Bng 2.5.Cc ng v phng x trong t nhin:Tnnguyn tK hiuCc loi ht bc xChuk bn r
TritiH3+12,3 nm
BeriliBe7+54 ngy
BeriliBe10+25 x 106nm
CacbonC14+5.730 nm
NatriNa22++2,6 nm
SilicSi32+650 nm
PhotphoP32+14,3 ngy
PhotphoP33+24,4 ngy
Lu hunhS35+88 ngy
CloCl136++3,1 x 105nm
2.2. Phng x nhn to:2.2.1. Th nghim v kh ht nhn: Cc v n th nghim v kh ht nhn u sinh ra cc sn phm phng x. Cc sn phm phng x ny c pht tn trong kh quyn v s c cc loi t hp th nhng mc khc nhau. Cc cht phng x ny c chu k bn r di, ngn khc nhau v chng tn ti mi trng a phng xung quanh cc v n hm lng khc so vi nhng ni xa cc v n .Bng 2.6 Cc c trng chnh ca cc cht phng x trong kh quyn sinh ra t cc v n ht nhn:Cc cht phng xChukbn rCc dng bc x
H312,3 nm+
C145.730 nm+
Mn54310 ngy+
Fe552,7 ngy
Kr8510,7 nm+
Sr9028 nm+
Zn9565 ngy+
Ne9535 ngy+
Sr8950,5 ngy+
Ru10339,8 ngy+
Ru106365 ngy++
I1318 ngy++
Cs13730 nm++
Cs13613,5 ngy++
Ba14012,8 ngy++
La14040,2 gi++
Ce14133,1 ngy+
Ce144285 ngy++
Pu13887 nm+
Pu23924.000 nm+
Pu2406.600 nm+
Pu24114 nm+
Am241430 nm+
T cc v n ht nhn, cc ht phng x hnh thnh c tung vo kh quyn; chng b ma, gi ko theo v pht tn trong khp kh quyn ri ri xung mt t. Cc cht phng x ny cng ri xung mt bin v c pht tn trong nc bin t i dng ny sang i dng khc qua hot ng ca i dng. Nh vy, cc qu trnh pht tn ny chnh l tc nhn ca qu trnh gy nhim x ton cu.2.2.2. S dng nng lng ht nhn:Tt c cc nh my pht in s dng nng lng ht nhn u sinh ra nhng cht phng x pht tn vo mi trng kh quyn. Cc cht phng x c sinh ra lin tc vi mt lng ln trong cc phn ng dy chuyn phn hch trong l phn ng. Qua tnh ton, ngi ta thy rng, mt l phn ng ht nhn vi cng sut 1000 MW s pht tn mt lng phng x l 1010Ci. Lng phng x ny c tung vo mi trng trng thi lng v hi phng x (kh).Bng 2.7 Nhim x mi trng do cc nh my in nguyn t gy ra:Bq/nm (1000 MW)Ci/nm (1000 MW)
Trng thi lng
Sn phm phn hch1,1230,2
Triti H3(H3)2,13 x 1025750
Trng thi kh
Kh tr3,57 x 1029650
kim v hn hp kh1,48 x 10-20,4
2.2.3. Cc ngun khc: Ngy nay cc ng v phng x c s dng trong y hc, sinh hc v cng nng nghip mt cch rng ri. Chnh v vy, cc cht phng x d tha, cc cht thi t s s dng ny cng lm cho mi trng b nhim bn. Nhn chung, trong s cc ng dng ny c th coi vic s dng trong y hc l mt trong nhng ngun ng gp ng k vo vic lm nhim mi trng. Tuy vy, lng phng x ny cng rt nh. Cc nh my nhit in hot ng thi tro bi vo khng kh. Ngoi tro bi th cc ng v phng x trong tro bi cng lm bn mi trng khng kh ca khu cng nghip . Kh nng nhim ny ph thuc vo cht lng than dng trong nh my, vo lng tro, bi ri xung vng xung quanh cng nh ph thuc vo loi cng ngh m nh my s dng.