Foundations — Fission — chain reaction, critical mass

2.3.23 · D1 · Physics › Modern Physics › Fission — chain reaction, critical mass

Yeh page vocabulary build karta hai physics se milne se pehle. Agar parent note mein koi symbol aaya jo tumhe samajh nahi aaya, woh yahaan milega. Upar se neeche padho: har item uske upar wale par lean karta hai.

0. Characters ki cast (nucleus hota kya hai)

Figure dekho. Nucleus ek bag hai lal balls (protons) aur neeli balls (neutrons) ka jo ek saath squeeze kiye hain. Yeh picture matter karti hai kyunki fission literally yahi bag hai jo do chote bags mein phatt jaata hai, aur har quantity jo hum compute karte hain woh in balls ko count karti hai.

1. Notation: ${}_{92}^{235}\text{U}$ ko padhna

Parent note mein ${}_{92}^{235}\text{U}$ aur ${}_0^{1}n$ jaisi symbols likhi hain. Chaliye har slot decode karte hain.

$\underset{Z=92}{\underbrace{{}_{92}^{235}\text{U}}}+\underset{Z=0}{\underbrace{{}_0^{1}n}}⟶\underset{Z=56}{\underbrace{{}_{56}^{141}\text{Ba}}}+\underset{Z=36}{\underbrace{{}_{36}^{92}\text{Kr}}}+3{}_0^{1}n$

Neeche check karo: $92+0=56+36+0=92$. ✓ Upar check karo: $235+1=141+92+3=236$. ✓

2. Mass, energy, aur symbol $c$

Yeh kahaan se aata hai uski poori kahani ke liye Mass-Energy Equivalence E=mc^2 dekho.

3. Binding energy — splitting kyun "pay" karti hai

Curve dekho. Upar = zyada tightly bound = zyada stable. Peak iron ke paas hai ($A\approx 56$). Uranium ($A\approx 235$) neeche hai, $\approx 7.6$ MeV par; mid-size fragments ($A\approx 90\text{–}140$) upar hain, $\approx 8.5$ MeV par.

Poora curve apna ek topic hai: Binding Energy per Nucleon Curve. Note karo ki Nuclear Fusion usi curve ki left side use karta hai (halke nuclei upar chadh rahe hain), yahi wajah hai ki fusion bhi energy release karta hai.

4. Neutrons count karna: $\nu$, generations, aur $k$

Teen panels teen cases dikhate hain jo parent list karta hai:

• $k<1$ (subcritical): har row choti hai — tree murjha ke khatam ho jaata hai.
• $k=1$ (critical): har row same size — steady, reactor ka normal mode.
• $k>1$ (supercritical): har row badi hai — explosive growth.

Saare neutrons fission cause karne ke liye survive nahi karte — kuch leak ho jaate hain, kuch bekar absorb ho jaate hain. Neutron kitna likely hai ki nucleus se hit karke split kare yeh Neutron Cross-section se set hota hai. Unstable fragments kitne time tak rehte hain yeh Radioactive Decay and Half-life hai.

5. Geometry symbols: $R$, volume, surface, density $\rho$

Critical-mass argument pure geometry hai, toh humein teen shape facts chahiye.

Jahan yeh saari bookkeeping purposefully engineer ki jaati hai, tumhe ek Nuclear Reactor milta hai.

Prerequisite map

Har arrow kehta hai "right box samajhne ke liye left box chahiye". Saare raaste parent tak jaate hain: the Fission topic.

Equipment checklist

Right side cover karo aur dekho kya tum reveal karne se pehle har ek ka jawab de sakte ho.