Fill in the missing partiree2fh42m e +a bm.uy:9o9 nzicles or nuclei:
(a) $\text{n} + _{56}^{137}\text{Ba} \to ? + \gamma$
(b) $\text{n} + _{55}^{137}\text{Cs} \to _{56}^{137}\text{Ba} + 2?$
(c) $_{92}^{235}\text{U} + \text{n} \to _{38}^{90}\text{Sr} + ? + 3\text{n}$
(d) $? + \text{d} \to _{79}^{197}\text{Au} + \alpha$
where d stands for deuterium ($_{1}^{2}\text{H}$).

The isotope $_{15}^{32}\text{P}$ is produced by the reaction: $? + \text{n} \to _{15}^{32}\text{P} + \text{p}$. What must be the target nucleus?

When $_{11}^{22}\text{Na}$ is bombarded by deuterons ($_{1}^{2}\text{H}$), an $\alpha$ particle is emitted. What is the resulting nuclide?

Why are neutrons such good projectiles for py-1rz7+tfbchuxj .z5,9nwu n roducing nuclear reactions?

A proton strikes a $_{10}^{20}\text{Ne}$ nucleus, and an $\alpha$ particle is observed to emerge. What is the residual nucleus? Write down the reaction equation.

Are fission fragments .* bxkh6x*))roy ,wk-bzc urpq a++kl$\beta^+$ or $\beta^-$ emitters? Explain.

  If $_{92}^{235}\text{U}$ released only 1.5 neutrons per fission on the average, would a chain reaction be possible?  ----待选择----yesno 
If so, what would be different?

$_{94}^{238}\text{Pu}$ releases an average of 2.5 neutrons per fission compared to 2.9 for $_{94}^{239}\text{Pu}$. Pure samples of which of these two nuclei do you think would have the smaller critical mass? Explain.

The energy from nuclear fission appeee10 p s;dfvh, s:w)ovars in the form of thermal energy - but the thermadp;e:e1fvo) vs w0 h,sl energy of what?

The energy from nuclear fission appears in the form of thermal energy - kj kh2,cwf3u:+/pre( vizuq4 but the thermal energy u32p rivzjekf u+h4k/:(,wq c of what?

Why can't uranium be enriched ,drx31e hf.nehhc/n) by chemical means?

How can a neutron, with practically no kinetic ener,g m q12shm5.,c mnbmygy, excite a nucleus to the extent shown in (Fig. Below) c.gn,5,hm ym1mmqb2 s?

Why would a porous block of uranium be morc s2ey.j3ww1)7ftr gp8 :*g8 mwt *km)tciweee likely to explode if kept under water rather than if ei m*wgw 1py8kgt)7:w)esr 83mt2ct .*cjewn air?

A reactor that uses high+2x*sr -+ i(loqkhtg i1num z/ly enriched uranium can use ordinary water (instead of heavy water) as a moderator and still hlthn+ i- *o+ug1rsi x2q/zk m(ave a self-sustaining chain reaction. Explain.

Why must the fission process release neutrond1.6ho dl3xlqs if it is to be useful?

Discuss the relative merits and di8u8 msoi+yy6*re*kkyt a5;ik x;t 7 yesadvantages, including pollution and safety, of power generation by fossil fuels7;* it*tx+y6 s;or8y5k 8aeyyuke i mk, nuclear fission, and nuclear fusion.

What is the reason for the "secondary system" in a nuclear reactor, (Fiv wn8ii:;;sqf z -cx9f1xspg-g. Below)? That is, why is the water heated by the fuel in a nuclear reactor not used di ws c:xs n-;-;ixg8iv 1qfzp9frectly to drive the turbines?

Why are neutrons releaw h /wkit.tx 7sbw10o.j5bk z(sed in a fission reaction?

Why do gamma particles penetrate matter more easily than beta particles l,ca/jo,dz ;pus,ut ef ce)8x yg(nwo2i4;/s do?

A higher temperature is required for deuterium-deuterium ignition than for deute3i7yz lh1uw7 izzbpss 7:b 1 45mhtaj4rium-tritium. Explaii yt4s7w p4zi7umhh1: 5z 3zl7j1sb ban.

Light energy emitted by the Sun and stars comes from the fusion procesmjo*9cp. wt k5s. What conditions in the interior of stars make this po9pw.j 5m* cktossible?

How do stars, and our Sun, maintain confinement of the plasma for ful eanx,zgf-, 7sion?

What is the basic difference between ff3 7 qta :bo8exq0jjl7n.tp-rission and fusion?

People who work around mergcfls3 pu (2(a /gpb+lg6 p1ytals that emit alpha particles are trained that there is little danger from proximity or even touchaplfgupl/6pbyc r1g 32( g+(sing the material, but that they must take extreme precautions against ingesting it. Hence, there are strong rules against eating and drinking while working, and against machining the metal. Why?

Why is the recommended maximum radiation dose higher for women beyond the childy3 rnyj g:6-hi-jh6r3:ny iy- gbearing age than for younger women?

Radiation is sometimes used to sterilize medical supplibpfd1j n )3k tsib( *wx;yp2;res and even food. Explain how ittjd;p)k3pry(w12 *ib;f bnxs works.

What is the difference between absorbed dose and effective dos8iie ;1fldp 51xjkoz*e? What are the SI un*ji1fze d 1;k l8pio5xits for each?

How might radioactive tracers be used to find v-if j/xlgfb(z.- f - /2zjuopa leak in a pipe?

Natural aluminum is all 2t (dxolpgu:5i53e wz $_{13}^{27}\text{Al}$. If it absorbs a neutron, what does it become? Does it decay by $\beta^-$ or $\beta^+$? What will be the product nucleus?

Determine whether the reacx.5 xya ,m+fmj t/ezycm w70x+tion $_{1}^{2}\text{H} + _{1}^{2}\text{H} \to _{2}^{3}\text{He} + \text{n}$ requires a threshold energy.

Is the reaction $\text{n} + _{92}^{238}\text{U} \to _{92}^{239}\text{U} + \gamma$ possible with slow neutrons? Explain.

  Does the reaction $_{3}^{7}\text{Li} + \text{p} \to _{2}^{4}\text{He} + \alpha$ require energy, or does it release energy? How much energy?    MeV

  Calculate the energy released (or energy input resij*)(1 ou ;k(i2ewrqwhha 3aquired) for the reaction $_{5}^{10}\text{B} + \text{p} \to _{3}^{7}\text{Li} + \alpha$.    MeV

  (a) Can the reactiono6i+: wdk4 q;y (zju wlrq,mnl2ivp,; $_{11}^{23}\text{Na} + \text{d} \to \text{n} + _{12}^{24}\text{Mg}$ occur if the bombarding particles have 10.00 MeV of kinetic energy? (d stands for deuterium, $_{1}^{2}\text{H}$)
(b) If so, how much energy is released?    MeV

  (a) Can the reaction :x3d nao.yfa* ex. l0l$_{3}^{7}\text{Li} + \text{p} \to _{2}^{4}\text{He} + \alpha$ occur if the incident proton has kinetic energy = 2500 keV?
(b) If so, what is the total kinetic energy of the products?    MeV

  In the reaction $_{8}^{18}\text{O} + \text{p} \to _{9}^{18}\text{F} + \gamma$, the incident $\alpha$ particles have 7.68 MeV of kinetic energy.
(a) Can this reaction occur?
(b) If so, what is the total kinetic energy of the products? The mass of $_{9}^{18}\text{F}$ is 16.999131 u.   MeV

  Calculate the Q-value for the "capture" reactionakwr2l c:hk,0zxe s36 $_{2}^{4}\text{He} + _{4}^{9}\text{Be} \to _{6}^{12}\text{C} + \text{n}$. Q =    MeV

  Calculate the total kinetic energy of the products of the rea3z :9:-rn;yhh htu hve*qw1ref;b iv)ction $_{6}^{12}\text{C} + \text{d} \to _{7}^{13}\text{N} + \text{p}$ if the incoming deuteron (d) has $KE = 36.3\ \text{MeV}$. $KE_{\text{total}}$ =    MeV

  Radioactive $_{6}^{14}\text{C}$ is produced in the atmosphere when a neutron is absorbed by $_{7}^{14}\text{N}$. Write the reaction and find its Q-value. Q =    MeV

  An example of a "stripping" nuclear reactix2gq. tdr:z8c f 1b0zk7rp)nlon is $\text{d} + _{3}^{7}\text{Li} \to \text{X} + \text{p}$.
(a) What is X, the resulting nucleus?
(b) Why is it called a "stripping" reaction?
(c) What is the Q-value of this reaction? Is the reaction endothermic or exothermic? Q =    MeV

  An example of a "pick-up" nuclear rea47h9: upglrz wction is $_{1}^{2}\text{H} + _{6}^{12}\text{C} \to \text{X} + \alpha$.
(a) Why is it called a "pickup" reaction?
(b) What is the resulting nucleus?
(c) What is the Q-value of this reaction? Is the reaction endothermic or exothermic?Q =    MeV

  (a) Complete the following nuclear reaction: *l(t9c lrq -; bzs1sm*js+ st9q(syed $\text{p} + ? \to _{16}^{32}\text{S} + \gamma$.
(b) What is the Q-value? Q =    MeV

  The reaction $_{9}^{19}\text{F} + \text{n} \to _{9}^{20}\text{F} + \gamma$ requires an input of energy equal to 2.453 MeV. What is the mass of $_{9}^{20}\text{F}$?
$m_{^{18}_{9}F}$ =    U

  Calculate the energy released in the fission reacn2 a/s 09qjcqgtion $_{92}^{235}\text{U} + \text{n} \to _{56}^{141}\text{Ba} + _{36}^{92}\text{Kr} + 3\text{n}$. Use Appendix B, and assume the initial kinetic energy of the neutron is very small. Q =    MeV

  What is the energy released in the fission reaction of Eq. 31-4pi ;n* f2m0kx+ep9t5e l-gikn ? (The masses of einl ;np05fpx* e 9ikt2g+km-$_{56}^{140}\text{Ba}$ and $_{36}^{92}\text{Kr}$ are 140.914411 u and 91.926156 u, respectively.) Q =    MeV

  How many fissions take place per second in a 20f ne4d-8lm)gmg3vy 5x 0-MW reactor? Assume 200 MeV is released per fissiogxg df)8vym n3e -l5m4n. P =    $\times 10^{13}\ \text{reactions/s}$

  The energy produced by a fissiizmh jmjmn .t e., hc0-d+w),ydjdq22 on reactor is about 200 MeV per fission. What fraction of the rest masm )q .w-jmd.0i2dh, zjnth,+jdm 2ecys of a $_{92}^{235}\text{U}$ nucleus is this? The ratio is about $\approx 1 : $   

  Consider the fission reaction 1 fvkp yo30j,zd-1lj27 edjno$_{92}^{235}\text{U} + \text{n} \to _{51}^{133}\text{Sb} + _{41}^{98}\text{Nb} + ?\text{n}$.
(a) How many neutrons are produced in this reaction?   
(b) Calculate the energy release. The atomic masses for Sb and Nb isotopes are 132.915250 u and 97.910328 u, respectively. Q =    MeV

  How much mass of $_{92}^{235}\text{U}$ is required to produce the same amount of energy as burning 1.0 kg of coal (about $3 \times 10^7\ \text{J}$)?    $ \times 10^{-7}\ \text{kg}$

  Suppose that the electric average power consumption, day and night, in ar.cao(8+ok1+scfsnqi ;k/7ekib4s u typical house is 9s fiio;1qsa s.unkk(rbe4kc+7 +8o/c50 W. What initial mass of $_{92}^{235}\text{U}$ would have to undergo fission to supply the electrical needs of such a house for a year? (Assume 200 MeV is released per fission, as well as 100% efficiency.)    $ \times 10^{-4}\ \text{kg}$

  What initial mass ofpmxne8- 6ht(jo 2yj l5 $_{92}^{235}\text{U}$ is required to operate a 650-MW reactor for 1 yr? Assume 40% efficiency. The initial mass is $\approx $    $\ \text{kg}$

  Assuming a fission ofw p.c.efdxzl:-zg7 6g $_{92}^{235}\text{U}$ into two roughly equal fragments, estimate the electric potential energy just as the fragments separate from each other. Assume that the fragments are spherical (see Eq. 30-1) and compare your calculation to the nuclear fission energy released, about 200 MeV.
PE =    MeV
This is about    % larger than the nuclear fission energy released.

  What is the average kinetic energy ofi blai6h*no -6 protons at the center of a star where the temperaturiob - 6an*l6ihe is $2 \times 10^7\ \text{K}$?
KE =    $ \times 10^{-16}\ \text{J}$
KE =    eV

  Calculate the energy released in th8* bbfq uy, aevld83w6e fusion reaction $_{1}^{2}\text{H} + _{1}^{3}\text{H} \to _{2}^{4}\text{He} + \text{n}$ is    MeV.

  Calculate the energy released when two deuterium nucnryis;dkgk d ; )ti32,lei fuse to form $_{2}^{3}\text{He}$ with the release of a neutron is    MeV.

  Verify the Q-value statedytcl,(s;k4p l for each of the reactions ofEqs. 31-6.
Eqs. 31-6-a Q =    MeV
Eqs. 31-6-b Q =    MeV
Eqs. 31-6-c Q =    MeV

  Calculate the energy release per gram of fuel for the reactions of Eqc zk0xmc :, 6jsjl,i, 1ldw1vls. 31-8a, b, and c. Compare to the energy release per graw j: l ,0clm1kl,i 1jd,xv6sczm of uranium in fission.
31-8a =    $ \times 10^{23}\ \text{MeV/g}$
31-8b =    $\times 10^{23}\ \text{MeV/g}$
31-8c =    $ \times 10^{24}\ \text{MeV/g}$
Uranium fission =    $ \times 10^{23}\ \text{MeV/g}$

  How much energy is rrzc9ifeqli 5zw*0,6m p3h py1eleased when $_{92}^{238}\text{U}$ absorbs a slow neutron ($KE \approx 0$) and becomes $_{92}^{239}\text{U}$? Q =    MeV

  If a typical house requires 950 W o;fh n32y /pydvg3we;woa m).*awls i0 f electric power on average, what minimum amount of deuterium fuel would have to be used in a year to supply these electrical needs? Assume the reaction oh.*i 3mw0fyglnaeya;;3 w/v)2p wsodf Eq.31- 8b.    g

Show that the energiesv0bcb x*op9c)e rb na. :dqbm0)+rkh, carried off by the $_{2}^{4}\text{He}$ nucleus and the neutron for the reaction of Eq. 31-8c are about 3.5 MeV and 14 MeV, respectively. Are these fixed values, independent of the plasma temperature?

  Suppose a fusion reactor ran on "d-d" reactions, Eqs. 31-8a gv+3hj.bzdp: tc7-wfand b. Estimate how much water, for fuel, would be needed per.vpw :b3- t7gdhc+zfj hour to run a 1000-MW reactor, assuming 30% efficiency. $\approx$    $kg/h$

  How much energy (J) is containid-h,u;:itzkt+ej ;/en f,02nu 5 hebz)u mc eed in 1.00 kg of water if its natural deuterium is used in the fusion reaction of Eq. 31-8a? Compare to the energy obtained from the burning of 1.0 kg of gt/e:; hdfnz 0mji - hu2k)e;une+t czi,b5,ueasoline, about $5 \times 10^7\ \text{J}$.
   $ \times 10^{9}\ \text{J}$
   times more than gasoline

The energy output of massive stars is believed to be due to+ t,7dt 6ll uywn:a.zf the carbon cycle (see text). (a) Show that no carbon istntw .7l,6f:u day+ zl consumed in this cycle and that the net effect is the same as for the proton-proton cycle. (b) What is the total energy release? (c) Determine the energy output for each reaction and decay. (d) Why does the carbon cycle require a higher temperature ($T \approx 2 \times 10^7\ \text{K}$) than the proton-proton cycle ($T \approx 1.5 \times 10^7\ \text{K}$)?

(a) Compare the energy n(sf( ydn, iw+6mvub/ feeded for the first reaction of the carbon cycle to that for a deuterium (in bd/w,fyfuv 6+(sm-tritium reaction.
(b) If a deuterium–tritium reaction requires $T \approx 3 \times 10^8\ \text{K}$, estimate the temperature needed for the first carbon-cycle reaction.

  A dose of 4.0 Sv of lwxm k3)lo(-f$\gamma$ rays in a short period would be lethal to about half the people subjected to it. How many grays is this?    $Gy$

  Fifty rads of $\alpha$-particle radiation is equivalent to how many rads of X-rays in terms of biological damage?    rad

  How many rads of slow neutrons will do as much biological damage as 75 rads of or8py ,xe5g)e3x p ,mmfast neme8r53 xoy mx)p g,,eputrons?    rad slow neutrons

  How much energy is deposited in the body of a 65-kg 1m3w*y/ofy-,/ p qy g ph(hl2q,bnwsdadult exposed to a 2.0-Gy dosey*/lhp yq s,ompd/(1wngfwb- y 3h2q,?    $J$

  A $0.025-\mu\text{Ci}$ sample of $_{15}^{32}\text{P}$ is injected into an animal for tracer studies. If a Geiger counter intercepts 25% of the emitted $\beta^-$ particles, what will be the counting rate, assumed 85% efficient?$\approx$    $ \ \text{counts/s}$

  A cancer patient is under ou has15z zbpa9x,g9goiq;6;going radiation therapy in which protons with an energy of 1.2 MeV are incident on a 0.25-kg5u hxqzoobgza9p1ais6 ;;,g 9 tumor.
(a) If the patient receives an effective dose of 1.0 rem, what is the absorbed dose?
(b) How many protons are absorbed by the tumor? Assume $QF = 1$.    $ \times 10^{10}\ \text{p}$

  A 1.0-mCi source of ;jh ag 44x12wu/ rqgkw$_{15}^{32}\text{P}$ (in $\text{NaHPO}_4$), a $\beta^-$ emitter, is implanted in a tumor where it is to administer 36 Gy. The half-life of $_{15}^{32}\text{P}$ is 14.3 days, and 1 mCi delivers about $10\ \text{mGy/min}$. Approximately how long should the source remain implanted?    day

About 35 eV is required to produc1zrdoc/8td x7 e one ion pair in air. Show that this is consistent with the two definitions of the roentgen given in t1x 8dd rz/c7othe text.

  $_{27}^{57}\text{Co}$ emits 122-keV $\gamma$ rays. If a 70-kg person swallowed $1.85\ \mu\text{Ci}$ of $_{27}^{57}\text{Co}$, what would be the dose rate (Gy/day) averaged over the whole body? Assume that 50% of the $\gamma$ energy is deposited in the body.    $\times 10^{-2}\ \text{Gy/day}$

  What is the mass of bs l7ult45bi0 a $1.00-\mu\text{Ci}\ _{6}^{14}\text{C}$ source?    $\times 10^{-10}\ \text{kg}$

  Huge amounts of radioani(h:8uzc pj691 ok tactive $_{53}^{131}\text{I}$ were released in the accident at Chernobyl in 1986. Chemically, iodine goes to the human thyroid. (Doctors can use it for diagnosis and treatment of thyroid problems.) In a normal thyroid, $_{53}^{131}\text{I}$ absorption can cause damage to the thyroid.
(a) Write down the reactions for the decay of $_{53}^{131}\text{I}$.
(b) Its half-life is 8.0 d; how long would it take for ingested $_{53}^{131}\text{I}$ to become 10% of the initial value? N $\approx$    $ \ \text{d}$
(c) Absorbing 1 mCi of $_{53}^{131}\text{I}$ can be harmful; what mass of iodine is this?   $ \times 10^{-12}\ \text{kg}$

  Assume a liter of milk typi2 t dlsm)to7o/0sb5m3 lql-q rcally has an activity of 2000 pCi due to $_{19}^{40}\text{K}$. If a person drinks two glasses (0.5 L) per day, estimate the total effective dose (in Sv and in rem) received in a year. As a crude model, assume the milk stays in the stomach 12 hr and is then released. Assume also that very roughly 10% of the 1.5 MeV released per decay is absorbed by the body. Compare your result to the normal allowed dose of 100 mrem per year. Make your estimate for
(a) a 50-kg adult, $\approx$    $ \times 10^{-7}\ \text{Sv/year}$ $\approx $    $ \times 10^{-5}\ \text{rem/year}$ $\approx $    $ \times 10^{-4}$ times the allowed dose
(b) a 5-kg baby.   $\times 10^{-4}\ \text{Sv}$    $\times 10^{-4}\ \text{rem}$    $ \times 10^{-4}\ \text{times the allowed dose}$

Radon gas, $_{86}^{222}\text{Rn}$, is considered a serious health hazard (see discussion in text). It decays by $\alpha$ emission.
(a) What is the daughter nucleus?
(b) Is the daughter nucleus stable or radioactive? If the latter, how does it decay, and what is its half-life?
(c) Is the daughter nucleus also a noble gas, or is it chemically reacting?
(d) Suppose 1.0 ng of $_{86}^{222}\text{Rn}$ seeps into a basement. What will be its activity? If the basement is then sealed, what will be the activity 1 month later?

  Calculate the wavelength + s 8 wcya*a)1ekxkfi4t,nc,w(f)pm z of photons needed to produce NMR transitions in free protons in a 1.000-T field. In what region of the spectrum does it lie? fc18fw cxys k (m ewtiz,)4pan*)k,a +c =    $m$

  J. Chadwick discovered the neg6y ai1*hk6 mlutron by bombarding $_{4}^{9}\text{Be}$ with the popular projectile of the day, alpha particles.
(a) If one of the reaction products was the then unknown neutron, what was the other product?
(b) What is the Q-value of this reaction?Q =    MeV

  Fusion temperatures are fszcrbv8+. i 5eyx:e(jd pd7 rgal3.-often given in keV. Determine the conversion factor from kelvins to keV using, as is common z jl:3 8rx-ycape5.g7b dd.(srvfi+ ein this field, $KE = kT$ without the factor $\frac{3}{2}$. K =    $ \times 10^{-5}\ \text{keV/K}$

  One means of enriching uranium is by diffusion of tdgg7i:5)l a9lr, wms jhe gas $\text{UF}_6$. Calculate the ratio of the speeds of molecules of this gas containing $_{92}^{235}\text{U}$ and $_{92}^{238}\text{U}$ on which this process depends.    :1

  (a) What mass of $_{92}^{235}\text{U}$ was actually fissioned in the first atomic bomb, whose energy was the equivalent of about 20 kilotons of TNT (1 kiloton of TNT releases $5 \times 10^{12}\ \text{J}$)? $\approx $    $\ \text{kg}$
(b) What was the actual mass transformed to energy?$\approx $    $\ \text{g}$

  In a certain town the average yearly backgrr: x*dtq y6my6ound radiation consists of 21 mrad of X-rays andq6 :yd*r6yt xm $\gamma$ rays plus 3.0 mrad of particles having a QF of 10. How many rem will a person receive per year on the average?dose(rem) =   $ \times 10^{-2}\ \text{rem/yr}$

  Deuterium makes up 0.0115% of natural hydro0z14wy sus+3 7oqkjtegen on average. Make a rough estimate of the total deuterium ijsue twyo qsk4z0 +713n the Earth's oceans and estimate the total energy released if all of it were used in fusion reactors.

The total mass of deuterium is about    $ \times 10^{16}\ \text{kg}$
The total energy is about    $\times 10^{30}\ \text{J}$

  A shielded $\gamma$-ray source yields a dose rate of $0.052\ \text{rad/h}$ at a distance of 1.0 m for an average-sized person. If workers are allowed a maximum dose of 5.0 rem in 1 year, how close to the source may they operate, assuming a 40-h work week? Assume that the intensity of radiation falls off as the square of the distance. (It actually falls off more rapidly than $\frac{1}{r^2}$ because of absorption in the air, so your answer will give a better-than-permissible value.)    m

Radon gas, $_{86}^{222}\text{Rn}$, is formed by $\alpha$ decay. (a) Write the decay equation. (b) Ignoring the kinetic energy of the daughter nucleus (it's so massive), estimate the kinetic energy of the $\alpha$ particle produced. (c) Estimate the momentum of the alpha and of the daughter nucleus. (d) Estimate the kinetic energy of the daughter, and show that your approximation in (b) was valid.

  Consider a system of nuclear power plants thatlrdbl9+- dz6df7y6v t produce 3400 MW.
(a) What total mass of $_{92}^{235}\text{U}$ fuel would be required to operate these plants for 1 yr, assuming that 200 MeV is released per fission? $\approx$    $ \ \text{kg}$
(b) Typically 6% of the $_{92}^{235}\text{U}$ nuclei that fission produce $_{38}^{90}\text{Sr}$, a $\beta^-$ emitter with a half-life of 29 yr. What is the total radioactivity of the $_{38}^{90}\text{Sr}$ in curies, produced in 1 yr? (Neglect the fact that some of it decays during the 1-yr period.) $\dfrac{\Delta N}{\Delta t}$    $ \times 10^{6}\ \text{Ci}$

  In the net reaction,, for the proton-proton cycle in the Sun, the neutrinos esca1xm2 dm;zjsf 7pe from the Sun with energy of about 0.5 MeV. The remaining energy, 26.2 MeV, is available withm72 jxf1 ;msdzin the Sun. Use this value to calculate the "heat of combustion" per kilogram of hydrogen fuel and compare it to the heat of combustion of coal, about $3 \times 10^7\ \text{J/kg}$.    $ \times 10^{-14}\ \text{J/g}$
This is about    $ \times 10^7$times the heat of combustion of coal.

  Energy reaches Earth from the Sun at a rateykf 8in;,* /wybeeaaw:- w,ye of about $1400\ \text{W/m}^2$. Calculate
(a) the total power output of the Sun,$\approx $    $ \times 10^{26}\ \text{W}$
(b) the number of protons consumed per second in the reaction of Eq.31- 7, assuming that this is the source of all the Sun's energy. $\approx $    $ \times 10^8\ \text{protons/s}$
(c) Assuming that the Sun's mass of $2 \times 10^{30}\ \text{kg}$ was originally all protons and that all could be involved in nuclear reactions in the Sun's core, how long would you expect the Sun to "glow" at its present rate? See previous Problem.$ \approx $    $ \times 10^{11}\ \text{yr}$

  Some stars, in a later stage of evolution, may begin):,q7 zp2wvyezjkph3y)8 dp u to fuse two $_{6}^{12}\text{C}$ nuclei into one $_{12}^{24}\text{Mg}$ nucleus.
(a) How much energy would be released in such a reaction?
(b) What kinetic energy must two carbon nuclei each have when far apart, if they can then approach each other to within 6.0 fm, center-to-center? KE =    $ \times 10^{-13}$ =    MeV
(c) Approximately what temperature would this require?   $ \times 10^{10}\ \text{K}$

  An average adult body co,;r cjdk ew,d3ntains about $0.10\ \mu\text{Ci}$ of $_{19}^{40}\text{K}$, which comes from food.
(a) How many decays occur per second?    $\ \text{decays/s}$
(b) The potassium decays produce beta particles with energies of around 1.4 MeV. Calculate the dose per year in sieverts for a 50-kg adult.    $\times 10^{-4}\ \text{Sv/y}$
Is this a significant fraction of the $3.6\ \text{mSv/year}$ background rate?    %

  When the nuclear reacto7)fvz py ,/oimr accident occurred at Chernobyl in 1986, $2.0 \times 10^7\ \text{Ci}$ were released into the atmosphere. Assuming that this radiation was distributed uniformly over the surface of the Earth, what was the activity per square meter? (The actual activity was not uniform; even within Europe wet areas received more radioactivity from rainfall). $\frac{\text{Activity}}{\text{m}^2}$=   $ \times 10^{3}\ \text{decays/s}$

  A star with a large helium abundance can js 7;m zvkg4to5e9f 7:6lcs)v ll5pfmburn helium in the reaction $3\ _{2}^{4}\text{He} \to _{6}^{12}\text{C} + \gamma$. What is the Q-value for this reaction? Q =    MeV

  A $1.0-\mu\text{Ci}\ _{55}^{137}\text{Cs}$ source is used for 2.0 hours by a 75-kg student in a physics lab. Radioactive $_{55}^{137}\text{Cs}$ decays by $\beta^-$ decay with a half-life of 30 years. The average energy of the emitted betas is about 190 keV per decay. The $\beta^-$ decay is quickly followed by a $\gamma$ ray with an energy of 660 keV. Assuming the student absorbs all emitted energy, what effective dose (in rem) is received during lab? dose $\approx $    $ \times 10^{-5}\ \text{rem}$

  A large amount of $_{38}^{90}\text{Sr}$ was released during the Chernobyl nuclear reactor accident in 1986. The $_{38}^{90}\text{Sr}$ enters the body through the food chain. How long will it take for 90% of the $_{38}^{90}\text{Sr}$ released during the accident to decay? See Appendix B.$\approx $    y

Three radioactive sources have th b6p)p2/tpkunitdv2 -h no-(ke same activity, 25 mCi. Source A emits 1.0-MeVpb2(h6ik/-npntp2 d-tu )kvo $\gamma$ rays, source B emits 2.0-MeV $\gamma$ rays, and source C emits 2.0-MeV alphas. What is the relative danger of these sources?

  A 70-kg patient is to be gies+s(1 rw54j70zmvwg8ifjium* n q.q ven a medical test involving the ingestion of $_{43}^{99\text{m}}\text{Tc}$ (Section 31-7) which decays by emitting a 140-keV gamma. The half-life for this decay is 6 hours. Assuming that about half the gamma photons exit the body without interacting with anything, what must be the initial activity of the Tc sample if the whole-body dose cannot exceed 50 mrem? Make the rough approximation that biological elimination of Tc can be ignored. Activity $\simeq $    $\ \text{mCi}$