NHAN DINH-DI/BAO
Phan ung tong hop hat nhan
nguon nang lUdng cua tUdng lai
Trong khi nguon nang luang hoa thach, nang lirong tai tao, vci d nang luang phSn u'ng phan hach hat nhan deu dang co nhQng han che Ithien no Ithong the dap u'ng nhu cau ve nang luang ngay cang cao ciia con ngucri, thi phan u'ng tong hcrp hat nhan la nguon nang laong mdi dang duac cac nha khoa hpc nghien ciJu.
No di/pc xem la nguon nang lUdng cua tuOng lai.
GS.TS NGUYJN LAM THUY
S
ong song vdi sfl phit triln cua nhin logi, nhu d u ve ning Iflpng ngiy cang cao, con ngfldi da sfl dyng nang Iflp^ng tfl ciy ed (chit ddt), tfl ngudn hda thgch (than, dau m6, khf ddt tfl nhiln), nang Ifldng gid, mat trdi, ddng chiy cua nfldc, nang Iflgng phin flng phin hach hat nhin (nuclear fission), nang liipng sinh hoc (cic loai dlu thflc vlt, rUdu chflng d t tfl thflc vgt)...Theo dfl bio, ngudn nhiln lilu hda thach ngiy d n g cgn kilt (khoing trim nam nfla ngudn nhiln lilu nay se hit). Nang Ifldng sinh hoc, nang Ifldng gid, mat trdi, ddng chay cua nUde la nang Ifldng thin thiln vdi mdi trfldng thiln nhien khdng thl dap flng dfldc nhu clu cua eon ngfldi.
Nang Ifldng tfl phin flng phin hgch hgt nhan (nuclear fission) cd tilm ning khdng Id, dap flng dugc nhu cau cua con ngfldi tfldng chflng nhfl vd tin nhflng nguyin lieu Uranium se cd ngay cgn kilt. Dilu quan trgng hdn la van d l an toan hat nhin. Sfl sd suit eua con ngfldi (thim hga Chernobyl..) hay yeu to bat lgi cua thien nhien (tham hoa kep dgng dlt va s6ng thin d Fukushima) la nhflng tham hga khung khilp cho con ngfldi. Va phai k l din vile xfl ly chat thii hat nhan cua ca vgn nam sau vin cdn nguy hgi. Nang Ifldng tfl ngudn h6a thgch va nang Ifldng phin flng phan hach hgt nhin (nuclear fission) khdng thin thiln vdi mdi trfldng, gay nln hilu flng nha kfnh, lim biln doi khf hiu cua trii dlt.
De dap flng nhu ciu nang Ifldng cho nhan logi, bit budc con ngfldi phii nghiin cflu nang Ifldng tdng hdp hat nhan (nuclear fusion). Nd ngfldc lgi vdi nang Ifldng phin flng phan hgch hgt nhan (nuclear fission).
Sau chiln tranh thl gidi thfl hai, nfldc Nga - X6 Vilt tiln phong nghiin cflu ning Ifldng tdng hgp hat nhan (nuclear fusion), rdi lln lfl<?t My, Anh, Phip, Dflc, Nhat, Trung Qudc, Hin Qu6c, Thyy Si, An Dp, Nam P h i - Da gin 70 nim trdi qua, ngudn ning Ifli?ng nay van chfla dfl^c sfl d^ng, mac diu tdn 500 ty USD. Rilng nam 2012, Thuy Si chi cd m^t Id phin flng nho ciing phii chi hdn 2 ty euro.
Nam 2007, d c nfldc nghiin cflu phin ijQig t6ng hc^
hat nhin da cung nhau dlu tu 9 ty USD xay dflng mot Id thi nghi|m d miln nam nfldc Phap. Cac nha khoa hpc fldc doin 50 nam nfla mdi cd t h l cd diln ti^ ngudn ning Iflpng niy. Nhfl viy phii t6n hdn 120 nam nghien cflu vdi hing nghin ty USD.
Trong khi d6 tfl khi tim ra phin flng phin hach hat nhan (nuclear fission) din khi cd nhi may phit dien chi 20 nim (nhi miy di|n nguyen tfl Obnink dau tien cua Lien Xd phit di|n ngay 27-6-1954).
Nang Iflpng tdng hgp hat nhin hoin toin dfla trln nguyen ly cua nhi bic hpc vi dai Albert Einstein, ngfldi Dflc gdc Do Thii.
Phin flng tdng hpp hat nhin hay cdn gpi la phin flng hgp hgch la hai nhan hgp lai vdi nhau thinh mdt nhin ning hdn, trong qui trinh hpp nhlt phong thfch ra nang Iflpng khdng 16. Cdn phan flng phan bach hgt nhan la sfl phan ra hgt nhan ph6ng thfch nang Iflcfng, cung cac tia alpha, beta, gama...
Phan flng tdng hgp hgt nhin phdng thich nang Ifldng tuy thupc vio khdi Ifldng cua hat nhin tham gia, vi du:
Nhflng nguyin tfl nhe hdn sat vi Nickel tdng hgp hgt nhin thi phdng thich nang Ifldng, trong khi cic nhan ngng hdn thi hip thu ning Iflpng.
[20] NANG LUONG VIET NAM S6 89+90 (8+9/2012)
Hi|n nay, nhien lieu d l phin flng tdng hdp hat nhin la ddng vi Deuterium va Tritium eua Hydrogen. Cic nguyin lieu nay cd the tich de ding tfl nfldc biln hogc tdng hgp vdi quy md cdng nghiep tfl cic nguyin tfl hydrogen khdng miy tdn kem. Ngudn nhiln li|u Hydrogen gin nhfl vd tin trong thiln nhiln. Chi d n Ikilogram hdn hgp Detrium va Tritium (tich tfl 1.000 ht nfldc biln), se tao ra ngu6n nang Ifl<?ng ngang vdi 1 ty tan dau md va gip chuc lln so vdi nhiln li|u phln hach Uranium, ddng thdi sin pham khf thii Ii Helium, mdt loai khi hilm, hold toin khdng lam nhilm bin mdi trfldng thiln nhien:
D l lam cho hgt nhin hdp lai vdi nhau d n m6t ngudn nang Ifldng rlt ldn, phai tao ra nhi|t dd cao trln 100 trilu dp, d c nha khoa hge dung chum laser h^i tu bin vio nhiln lieu hat nhin, Ip chung de gay ra phin flng kit hgp hat nhin. Vdi nhflng Id phin flng thdng thfldng, thanh cua 16 kh6ng eo mdt chit nio cd thl chju dflpc nhilt do nhfl thl. Ngfldi ta phii dung tfl triidng khdng chl d c hat nhan vi nhilt do, bio dim chung khong va cham vao thinh cua Id phin flng dflge thflc hi|n trong dilu kien it tdn kem va hieu qua cao nhlt.
Dlu tien nguyen tfl hda d c phin tfl, ion hda hoin toan tat ca d c nguyin tfl, ddng thdi tich loai electron d l bien nhien lilu cua phin flng hoan toin trd thanh hgt nhin khdng cd electron d thl plasma. Sau dd cin phai cd ddng nang cflc ky ldn cho d c hat nhin vfldt qua tfldng tac day Coulomb gifla chung ma va vao nhau, nhilt dd eIn thilt cd t h l len tdi hang tram trieu do C.
Trong khi d6 nhiet do cua tim mat trdi chi 15 trilu dp C. Khi cac nguyen tfl nhe dfldc kit hdp thinh nguyen tfl nang hdn, giii phdng mgt neutron tfl do se ph6ng thich nhilu nang Ifldng hdn nang Ifldng ngp ban diu. Cic Id phin flng hien nay mdi thu dfldc 9/10 nang Ifldng ngp vao, cd nghia la vin Id 1/10 nang Ifldng. Muon sin xult ra diln thi phai dat hdn ci tram lan nang Ifl(?ng ngp vao.
60 nam trfldc, d c nhi khoa hpc Nga da chl tao ra thilt hi tao mgt tfl trfldng hinh xuyen de giam gifl plasma vi nhilt dp b i n trong (thilt bi nay cd tin gpi Tokamak, do hai nha bic hge Igor Tamm va Andrei Sakharov sang che ra). Ngay nay d i cd nhieu thilt bi gifl plasma va nhiet dd nhflng Tokamak la thiet bi cd nhieu triln vgng nhat. Die trflng cfla Tokamak la cd true ddi xflng trdn xoay vi sfl dung ddng plasma de tao ra thinh phln xoay eua tfl trfldng can thilt nham tgo ra sfl can bang on dinh.
Hi|n nay, cic nha khoa hpc chi thflc hi|n phin flng tdng hpp hgt nhan nhilu nhat li iO phut. Ld phan flng cua trfldng dgi hge lien bang Thyy Si 6 Lausanne chi thflc hi|n dflge 4 giay. Miic tilu nghiin cflu la phin flng phii liln tyc, plasma vi nhi|t dp phii dflpc giam bin trong, khong cho chung va vio thanh cua Id phin flng.
Va myc dich sfl dung nhi|t d l tgo ra di|n nang.
Plasma la chit khi d mit d6 thlp hi ion h6a hoin toan, trung hda vl di|n (ion dflOng va ion im xIp xi bang nhau) plasma c6 tinh din di|n vi chiu tie ddng cua tfl trfldng-plasma vin gifl vai trd dac biet trong vi|c tao ra phin flng tdng hgp hgt nhan cd dilu khiln. Plasma cd dgc tinh khic hin so vdi d c vlt thl thdng thfldng cua vat chit (rin, Idng, khi) do dd nhilu nhi khoa hge xem plasma la trgng thai tdn tgi thfl tfl cua vlt chit.
Tren trai dat, plasma chi tdn tgi trong ngpn Ifla, tia set, ting ion hda, bic efle quang... nhflng trai dlt vd cung nhd be trong vu try, hau hit vi sao trong vu try d dgng plasma, 99% vit chit trong vu try ma ta c6 thl nhin thiy tdn tgi d dgng plasma. Nhflng vat chit tdn tai tren Mat trdi dfldi dang plasma, nhflng plasma nay khdng thl bay ra khdi Mat trdi vi trpng liidng vi sflc hut qui Idn cua nd (trpng Iflpng eua Mgt trdi ldn hdn Trii dlt 332.946 Ian).
Trong tiidng Iai khdng xa, con ngfldi xem nang Ifldng tdng hdp hgt nhan la nguon nang Ifldng chinh (sfl dung theo nang Iflpng phin flng trflc tiep hay diidi dang nang Ifldng diln), sfl dung hau hit phfldng tien di lgi, sin xult, sinh boat, nghien cflu khoang khdng via try... Nlu chung ta che tgo tau vu try cd ddng ed dypc cung d p nang Iflpng bing phin flng tdng hgp hat nhin, thdi gian bay cua m^t con tau vu tru tfl quy dgo trai dlt tdi sao Hda ed thl riit ngan 6 thing xudng chfla dly 6 tuin. Dieu do cd nghia la d c chuyin bay tdi nhflng hanh tinh trong Thai dfldng he se dflpc tiln hanh bit cfl khi nio con ngfldi mudn, khdng edn phii chd ddi mdt thdi diem phdng sao cho hanh trinh cfla tau Ii ngan nhat. Nguyin tac la duy tri mdt Id phin flng tdng hdp hat nhin trln boong tau vi phdng mdt it nang Iflpng ra phia sau cua tau de tgo lflc day. Cac nha khoa hge da cd gang chfla plasma silu ndng cua nhiing ion nhiem dien can cho phin flng tdng hgp hat nhan.
Tit nhiln, vile chl ngfl phin flng tdng hdp khong phai la nhi|m vy dl ding nhflng nhat dinh chung ta se thinh cong.
56 89+90(8+9/2012) NANG LUONG Vf$T NAM [21]
