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.