Fill in the missing partic*jm:y(ft )i:cblinf8xt -eq)6t1 d ecles 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 projecm m l a:n05d4xby59ixhtiles for producing 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 fragmentxzjpn i :+i4m3ib:q0dz )nw (us $\beta^+$ 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 appears in thjetzz-tz ax6-rh3* l*e form of thermal energy - but the ther3zj t**-- eharz x6tlzmal energy of what?

The energy from nuclear fission appears in the form of thermal energy - but o )b( r/uuk6z)pgi)oythe thermal energyr)iky u6o(z)boug p/) of what?

Why can't uranium be enriched by ch48 f mhjt2 ;ip1hkblwi nm6*i)emical means?

How can a neutron, with p4;hjqwkt ou ;, sw9f;qfva -6yractically no kinetic energy, excite a nucleus to the extent shownqh4,;wqw96a u f otj s;f;vy-k in (Fig. Below)?

Why would a porous block of uranium be mor yjuq m. v:v78u-zaji-c5scs:e likely to explode if kept under water rather thusu-y vm :jjs i7vcc.q-:a58zan in air?

A reactor that uses highly enriched uranium can use oksvvn3 l ;pn.) crb1p zdl)1yi-+6gadrdinary water (instead of heavy wn6v)a pdsil ncz y. 31 -drv)l;p+1bkgater) as a moderator and still have a self-sustaining chain reaction. Explain.

Why must the fission process release neutrons if it is y4(1n63 h)zn4qtdgca n (dfyl to be useful?

Discuss the relative merits and disadvantages, including pxecn*9e+uuw:dcl5.y d6s bky gml9.;7pte)x ollution and safety, of power generation by fossil fuldluxwux 9mek;.7 96ne.yg5cte yc :d) +b*spels, nuclear fission, and nuclear fusion.

What is the reason for the "secondary system" in a nucleaxp7cf(p5iby5 r reactor, (Fig. Below)? That is, why is the water heated by the fuel in a nup (c5 x5pby7ifclear reactor not used directly to drive the turbines?

Why are neutrons released in a fission +ufm0 :g :k3lz2t;ka.k ghtk ireaction?

Why do gamma particles penetrate matter more easily than beta particle 4; 2) 3vb.giko2lssoi(aqndcs do?

A higher temperature is ret+ggjwi;a 6o+ quired for deuterium-deuterium ignition than for deuterium-tgjt w+i6a;og+ritium. Explain.

Light energy emitted by the Sun and stars comno y//j. ra: (ors drpilw8;0ses from the fusion process. What conditions in the inters:n r iroya8(w/.o ;/d0ljspr ior of stars make this possible?

How do stars, and our Sun, m38efwf2g qta3 aintain confinement of the plasma for fusion?

What is the basic different76 ohpkz1i8 vce between fission and fusion?

People who work around metals that emit alpha particles are trained thd 58f,cc+ i3xd bc(vhjat there is little danger from proximity or even touching the material, but that they must take extreme precautions against ingesting it. Hence, there are strong rules against eating and drinking while woc +3f(hvjci5d8b,cdxrking, and against machining the metal. Why?

Why is the recommended maximum riucgp*)r sn sdh)g 08bp;30pqadiation dose higher for women beyond the child-bearing age than for younger women?puir3 s 0g; h80b)pnq)dpgcs*

Radiation is sometimes used to sterilize medical supplies and ev. ,b)dsbsw 3foss5do4en food. Explain how it sbo.s5 ,dws3df bso4) works.

What is the difference between absorbed dose and ef gnldwt4v6b t ,m,1av d:mg19gfective dose? What are the SI uni, b91dmamvg, dl gg41:wnvtt 6ts for each?

How might radioactive tracerwkf,blh n7f 0e0rzut)x9 l(3ps be used to find a leak in a pipe?

Natural aluminum is allvd bw5ne8r7;0o b ,gpu $_{13}^{27}\text{Al}$. 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 reaxa lhl31q:k9 wdfg;u2ction $_{1}^{2}\text{H} + _{1}^{2}\text{H} \to _{2}^{3}\text{He} + \text{n}$ 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 +8 4xtrzxy hkomhv; 86input required) for the reaction $_{5}^{10}\text{B} + \text{p} \to _{3}^{7}\text{Li} + \alpha$.    MeV

  (a) Can the reaction ms8j m4s5e s*izz xh85rll6o+ $_{11}^{23}\text{Na} + \text{d} \to \text{n} + _{12}^{24}\text{Mg}$ 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 reactionj7: fhroaa0f /dc7f1s $_{3}^{7}\text{Li} + \text{p} \to _{2}^{4}\text{He} + \alpha$ 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 "captuszj(u(l 1xv,jih)k-s 6y m,gv re" reaction $_{2}^{4}\text{He} + _{4}^{9}\text{Be} \to _{6}^{12}\text{C} + \text{n}$. Q =    MeV

  Calculate the total kinetic energy of the products i8y0 :n cwbv qy0f o7xb25be7pof the reaction $_{6}^{12}\text{C} + \text{d} \to _{7}^{13}\text{N} + \text{p}$ 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 "strippinshg/cf, .ye2/; h qkuxg" nuclear reaction 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 reaci,o,g*abvl) tfnh 9u/ tion 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 r. nesl3ghj t51eaction: $\text{p} + ? \to _{16}^{32}\text{S} + \gamma$.
(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 fij7u ocoa owf 2zxe*;)zqt/(,3aq jwf2ssion reaction $_{92}^{235}\text{U} + \text{n} \to _{56}^{141}\text{Ba} + _{36}^{92}\text{Kr} + 3\text{n}$. Use Appendix B, and assume the initial kinetic energy of the neutron is very small. Q =    MeV

  What is the energy released in the fissijqy *t+d ori(/on reaction of Eq. 31-4? (The masses of *qd (oti/r+y j$_{56}^{140}\text{Ba}$ and $_{36}^{92}\text{Kr}$ are 140.914411 u and 91.926156 u, respectively.) Q =    MeV

  How many fissions take place pernojwi.34 a g1msse/e1 second in a 200-MW reactor? Assume 200 MeV is released per fission.ea. owsjngm/s4 i1e31 P =    $\times 10^{13}\ \text{reactions/s}$

  The energy produced by a fission ren,th19x 6 sbzv;hdy*h actor is about 200 MeV per fission. What fraction of the resv;bdhz*6hx,9 y1th nst mass of a $_{92}^{235}\text{U}$ nucleus is this? The ratio is about $\approx 1 : $   

  Consider the fission reactie8s pl6yn*(v:ji zxz )on $_{92}^{235}\text{U} + \text{n} \to _{51}^{133}\text{Sb} + _{41}^{98}\text{Nb} + ?\text{n}$.
(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 averag*;1w, z zej2sgvhf b.be power consumption, day and night, in a typical house is 950 ;1b* bez .zsvg,2hfwjW. 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 ofoya3xmwbw8 ( ) $_{92}^{235}\text{U}$ is required to operate a 650-MW reactor for 1 yr? Assume 40% efficiency. The initial mass is $\approx $    $\ \text{kg}$

  Assuming a fission ofhohv3p i0/ vk2 $_{92}^{235}\text{U}$ 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 v7u y6wlbdoj p8*7jq; of protons at the center of a star where the temperature is qjv 7dbjpu87;y ol6w*$2 \times 10^7\ \text{K}$?
KE =    $ \times 10^{-16}\ \text{J}$
KE =    eV

  Calculate the energy6xi)0 zv5 ermi released in the 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 nuclei fuse t (vsp;ujei)y*o form $_{2}^{3}\text{He}$ with the release of a neutron is    MeV.

  Verify the Q-value stated for eba/6t /p: k;)s, gq ytescqcz)ach 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 reacti0 xh;e uid,- gycjepnl1n(.b8ons of Eqs. 31-8a, b, and c. Compa-hg.yl eun, 1d(x ep 0j;bc8nire to the energy release per gram 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 rj3d4ruwo,j( zeleased 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 of electric power on average, what mini-;pfqy+m5 so6h f id/tmum amount of deuterium fuel would have to be used in a year to supply these electrical needs? Assume the reaction f;-/t hyqsdoip 56mf+of Eq.31- 8b.    g

Show that the energied /1nas s/3a5j m8amujs 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 a-gnwf6 kslhe 7g *mzs3 ,:8abhur.-z-d" reactions, Eqs. 31-8a and b. Estimate how much water, for fuel, would be needeznhs wf-la67g r. :a8z,k-3egu*hm bsd per hour to run a 1000-MW reactor, assuming 30% efficiency. $\approx$    $kg/h$

  How much energy (J) is contained in 1.00 kg of water if its naturqx/fs jfa1v 8b+tdu :mu/r kq; z+.k;nal deuterium is used in the fusion reaction of Eq. 31-8a? Co/ds/z8;: va;q.fnmu xk+q rtj+u1bfkmpare to the energy obtained from the burning of 1.0 kg of gasoline, about $5 \times 10^7\ \text{J}$.
   $ \times 10^{9}\ \text{J}$
   times more than gasoline

The energy output of massive stars isezx9x p2977t h*f pmyp believed to be due to the carbon cycle (see text). (a) Show that no carbon is 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 ex e7f y7 z9h2xpt9p*pmach 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 needed for thed 8j1cblj5s9v ;amlhk-:1it a first reaction of the carbon cycle to that for a deuterium-tritium reaction.-amj8jd1;9lai1bvh sc:ktl5
(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 (5 waeuuly1v3$\gamma$ 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 wb:bnxt9q.2kw 740 )qjtnj tuoien8p0ill do as much biological damage as 75 rads of fast neutrobitx qq.no8jb)w7 j p:uktn42e 09nt0ns?    rad slow neutrons

  How much energy is deposited in the bodb )zaq6 7zg4eof .zxypsp/* *cy of a 65-kg adult exposed to a 2.0-Gy dose)f67c .zb 4go/yx*azpqp*ezs ?    $J$

  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 undergoing radiation therapy t ohq.3 aqy45:(:ben7ufhcxw in which protons with an energy3qnweyou:74ca.f hh x :q( tb5 of 1.2 MeV are incident on a 0.25-kg 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 a(dider/ 6afthu8 i,/ $_{15}^{32}\text{P}$ (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 produce one ion pair in air. Show that -w /*p7h;r ghkwhte;nthis is consistent with the two defip ;hg;we*t-k/7nhhwrnitions of the roentgen given in the 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 a *ob0drw-3jn9uf)xpay 0ja vbgu vd m1 9f +,6v$1.00-\mu\text{Ci}\ _{6}^{14}\text{C}$ source?    $\times 10^{-10}\ \text{kg}$

  Huge amounts of radioa8r8) npkht eq-d5p0 snctive $_{53}^{131}\text{I}$ 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 typically has an actwdz53/w, eili2.u nt v/c4uy pivity 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 of photons needj.t:lzj-nuo(1ujgkrw 9+bf ; ed to produce NMR transitions in free protons in a 1.000-T field. I ;b-1nuou9+zjr .jkw:jf( gltn what region of the spectrum does it lie? c =    $m$

  J. Chadwick discovered the/ czu 8d.jqrxj6ac-f2 neutron 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 often given in keV. Det xyk z)561jb nuag*0bzermine the conversion factor from kelvins to ujyz n1 *xa0bkg6b)z5keV using, as is common in this field, $KE = kT$ without the factor $\frac{3}{2}$. K =    $ \times 10^{-5}\ \text{keV/K}$

  One means of enriching uracirkd aa9v+5 qw;z6y.nium is by diffusion of the 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 backgrounds 1)qb4(x db: idbgwo. radiation consists of 21 mrad of X-rays an.xg)b1w dsoi:(qbd b4d $\gamma$ 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 hydrogeqbp:)mi-wm9ppjf9p3le a ,a 0n on average. Make a rough estimate of the total deuterium in the Earth's oceans and estimatalmaw)9ip em 0pf p3:b-9 p,qje 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 nuclea jgju4fbe7(7r 8:a -g qhl8yskr power plants that 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 Sunkep+c x+fuz ,/, the neutrinos escape from the Sun with energy of about 0.5 MeV. The remaining energy, 26.2 MeV, is available within the Sun. Use this value to calculate the "heat of combustion" per kilogram of hydrogen fuel and compare ep+zfck+x/,u 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 Suq f2uv;i:zyy ufy uj.sf2:k9*n at a rate 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 aov*ms1u 5n q nzz)u.+of evolution, may begin 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+g e),qlfqa *;; 8tgco5woaav contains 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 reactor accident occurred at Chvsr1+on c-)h9/ cpyrqernobyl 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 bu o0hvcixlv)v;1ua)je xk dgpj 3-3;b-rn 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 the same activity, 25 mCi. Sou 0jkhgmo9zm : bsif40x34( 9uel j j-wsfb*js-rce A emits 1.0-MeV 0 jzs gjf9lj bfs -i*bm-kx90:(oh4suj 4w m3e$\gamma$ 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 given a medical test inv(gslflp/odqw8j x /f 3a+x0s,olving 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 $    $\ \text{mCi}$