VI. PHUdNC PHAP PHAN TicH el/e PH6: [6,7,8,16]
3.Ung dl}ng cua phU'O)lg phap :
3.1. Fh;jn tieh djnh finh :
Sau khi kieh hOl;!tm~uphan tieh ng1ldi ta phainh~n di~ncae hl;!t nhan phong Xl;! d1l<;Je tl;!O thanh. Thong thLfdng ngLfdi ta do cae dl;!ngd~etrling sau :
- Dl;!ng bue Xl;! Y, ~
- Do ehu ky ban ra T1/2 : MlSi d6ng vi phong Xl;!d~uco gia trj T1/2 ella no, do do coth~din eu VaG gia trj T;/2 d~ nh~n di~nd6ng vi.
- Niing ILfong bue xa: Bue X? do cae d6ng vj phat rad~uco nang l1l<;Jng d~etrling khae nhau, nang l1l<;Jng ella bue Xl;! xae dinh dLf<;Je ghinh~ntren may phan tich da kenh, d6iehi~uvoi dLfdng ehuin nang l1l<;Jngd~ nh~n di~nd6ng vi.
3.2 Fh;jn tieh djnhIIl{jiJg:
Tl.i phLfong trinh (12) ta coth~tinh dtl<;Je ham ltl<;Jng ella nguyen t6 dn xae dinh. Tuy nhien trong thtje t~ng1ldi ta khong dung phLfong phap nay d~dinh l1l<;Jng ma thLfdng dung ph1long phap so sanh.
*Gidi thi¢uv~phuong pluip so sanh :
a.Nguyen tdc phu'Ong ph6p :
Trong phLfong phap nay ngLfdi ta kieh hOl;!t d6ng thdi mQt mftu phan tieh va mQt mftu ehuin. Mftu ehuin chua tnQt ltl<;Jng nguyen t6 tinhkhi~txae dinh. Sau khi kieh hOl;!tn~udn ngLfdi ta tach hoa phong Xl;! nguyen t6e~ntim ra khaim~uphan tieh va mftu ehuin trong nhifngdi~u ki~n nh1l nhau.
b. C6ng IhlIe I[nh :
D~dinh lLlCJng ngLl<'Ji ta tinh theo eong thue :
Sx mx = me -
Sc
mx : Ham ILlCJng nguyen t5 <tinh phan trongm~udn phan tieh. me: nguyen t5 dinh phan trongm~uehufin.
Sx :Di~ntieh dlnhm~udn phan tieh. Se :Di~ntieh dlnh eua m~uehufin. 4. Cae thongsaphI}thui)e :
4.1. Cae thOngsaella dong neutron:
Dongh~t b~npha trong su5t gianehi~u khong dLlCJe thay d6i.
Ph6 nang ILlCJng euah~t b~n pha phai dLlCJe xae dinh va khong thay d6i vi ti~t di~nphan ting phI;! thUi?e vao nang lLlCJng eua ehung.
Thong ILlCJng euah~t b~npha khong giam trangth~tiehm~udLlCJeehi~u x~. S5 nguyentliband~utrong bia giam khOng dang ki do eae phan tingh~tnhan.
4.2. Cae thOngsathol gian :
Trang phLl(jng phap kiehho~t ndtran dQ tin e~yeuak~tqua eo lien quaneh~t ehe vdivi~el!fa ehQn cae thong s5 th<'Ji gian t;, td ,tc '
a. Thai gian ehiiuIi:
TltphLl(jng trinh (7) ta eo :
ati=N~(J(1 -e-ABl;)RS Trang do : S lah~s5 bao hoa va :
S=1- e-Ani; =1- e-0,693Ii/T1/2
Tvbi~uthtie S ta th1ly:
Vdi ti=TI/2; S=I - e-0,693=0,4999 "" 50% nghia la eo 50%h~tnhan phongx~ dLlCJet~othanh.
Vdi ti=2T1/2 ;S=1 - e-0,693=0,7499 "" 75%
Vdi t;=10T1/2 ;S=1 - e-0,693x10=0,999 "" 99,0%
Nhllv~yvdi t;= lOT1/2 hes5 bao hoa Sg~n b~ng1 nghia lah~u h~t h~tnhan eua nguyen t5 pMn tieh dii dLlCJe kiehho~tthaJihh~tnhan phongx~, d~t ho~tdQ phongx~
ct!cd'.li. \.
b. Thai gian ngu(5i Id :
Th<'Ji gian nguQi qui dinhk~tqua ghinh~n:
Illy thugeVilOT1/2khae nhau rna ta l\fa ehQn tdkhae nhau thieh h<.Jp : T1/2 Idn - d~lau; TI/2ng~n- coth~phan tieh ngay. Nen ehQn td<10T1I2
c. ThiJi gian doIe :
Ph\l thuge vao T1/2 eua d6ng vi t~o thanh rna th\fehi~nphep do vdi th<'Ji gian tc sao eho co dti<.Je s6d~meho phep nghla la phai du th6ng ked~giam sai s6.