Fill in the missing particles or nuclei:*a;wk3zp30af i55fbckp;ar nk3t 1bd
(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 producing nuclear-nchfhk a+m:e3fllfv,nk0/3 t7pk7 u 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 fragment;ric/f *n2ztjk,8kzzam3 n8o s $\beta^+$ 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 the form of thermal energy - but the0 -gu-40t orww7ob9*atn ib qp thermal energy ofipw7br-q00ogn 9*u-tw4t ao b what?

The energy from nuclear fis2sfva. ,kxnl3w.k;biu id; 7wsion appears in the form of thermal energy - but the thermal energy of w3sak;v,. wiui2ln ;b x.w7dkfhat?

Why can't uranium bes+xhlcm1;n y-fpw(t5 enriched by chemical means?

How can a neutron, with practically uaoob:49 1 pzm7g;zp uno kinetic energy, excite a nucleus to the extent sho14ubg op p ozm7a:9uz;wn in (Fig. Below)?

Why would a porous block of uranium be more likely to explode if keq:v+ h75oyk ;gjdsvl(pt under water rather than in ai;(:sjo gvhv ldy7qk +5r?

A reactor that uses highly enriched uranium can use 9,ih6w 5w+ab,zma2 -lvco dniordinary water (instead of heavy water) as a moderator+loi wv a d, i-6wa5mzc9bn,h2 and still have a self-sustaining chain reaction. Explain.

Why must the fission process reler dl8g0*h. qemase neutrons if it is to be useful?

Discuss the relative merits and disadvantages, including pollution and safe -y4 dnqobnipv1 3-3eqrd7y/: /tszd lty, of power generation by fossil fuels, nuclear fissio ny3-ersb-q47d3: ld z1y//ipd vtonqn, and nuclear fusion.

What is the reason for the "secondarfz7 8c24mdwz v6lwr 4py system" in a nuclear reactor, (Fig. Below)? That is, why is the water heated6 cm48wd7z4v rf 2pzlw by the fuel in a nuclear reactor not used directly to drive the turbines?

Why are neutrons released in a fifb7 xdtf4hr jhg9d2::ssion reaction?

Why do gamma particles penetykau)52dh dr6 nq(d/t rate matter more easily than beta particles do?

A higher temperature is required for deuterium-deuterium ignitioef o7ov pikv 6*z4rz5fx+*/wmn than for deuterr65e*4pox fzv mf* wk7i ovz+/ium-tritium. Explain.

Light energy emitted by the Sun and stars comes from the fusion/u ugb; wt.vbb *bp-j, process. What conditions in the interior wbp .gtvub;u-b*,/bjof stars make this possible?

How do stars, and our Sun, maintain confinement of t 4x*mopu75bm phe plasma for fusion?

What is the basic difference between fission ame;- pwn 7dbzgrfnm x59u5 +d)nd fusion?

People who work around metals that emit alpha particles are train/ jipcxdx6h6 k7rn4i5ed that there is little danger from proximity or even touching the material, but that they must take extreme precautions againinjxi k5hd x76 cpr/46st ingesting it. Hence, there are strong rules against eating and drinking while working, and against machining the metal. Why?

Why is the recommended maximum radiy *wfa;s8u) f06c/fdf dfwu f4ation dose higher for women beyond the child-bearing age fcds8w )*u0 fufy fa;ff/wd46than for younger women?

Radiation is sometimes used to sted q//ysaz +oy3ybk+5 f6n9 b.5naub cnrilize medical supplies and even food. Explain how it works/.+6 b3 z+5ynfnq au cn/by5yboa 9dsk.

What is the difference between absorbed dose and effe,l f s.0s +g4nyjijo1gctive dose? What are the SI g 40sgnsfj.+1jy i, lounits for each?

How might radioactive tracers be used to find a leakvzeigaz1z0v3 sd, m*s1kd *6r in a pipe?

Natural aluminum is x8wd vbhd1, m:v16nbdgi;z6uall $_{13}^{27}\text{Al}$. 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 react;*-u5zap-e.j pc0i.d3idl)h f p tpykion $_{1}^{2}\text{H} + _{1}^{2}\text{H} \to _{2}^{3}\text{He} + \text{n}$ 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 e.a i*ip e,)pjfnergy input required) for the reaction $_{5}^{10}\text{B} + \text{p} \to _{3}^{7}\text{Li} + \alpha$.    MeV

  (a) Can the reaction0of(s (i q82m vn2ahcd $_{11}^{23}\text{Na} + \text{d} \to \text{n} + _{12}^{24}\text{Mg}$ 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 np6pgrgio281 $_{3}^{7}\text{Li} + \text{p} \to _{2}^{4}\text{He} + \alpha$ 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 "k 0*)0k/dyhti ju: d 9)fey+jhs xwkc*capture" 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 oshipy1 adf*6 z:ii) mj8ue5,bf 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 "stripping" nuclear ra b08bw x/1n .1nuyrkpeaction 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 reac j07.oxvx,q yption 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 nuclearl 2y y jbl-2b;gdh6k.i reaction: $\text{p} + ? \to _{16}^{32}\text{S} + \gamma$.
(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 c/i82sfgdb x* ywp (3ureaction $_{92}^{235}\text{U} + \text{n} \to _{56}^{141}\text{Ba} + _{36}^{92}\text{Kr} + 3\text{n}$. 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 (kt aio5gy:2n of Eq. 31-4? (The masses of ko: 5iyg t2na($_{56}^{140}\text{Ba}$ 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 200-MW reactor? Assumeu9ry wrn ) ei+;gyk55i 200 MeV is released per fi ig59rwy 5iuk+)nyre ;ssion. P =    $\times 10^{13}\ \text{reactions/s}$

  The energy produced by a fission reactor is about 200 MeV per fission. What2ga8fxdiz u0gvd +8hg-wt ;q0 fraction of the rest maudahi0g28q g tfwz0xg ;-+8vdss of a $_{92}^{235}\text{U}$ nucleus is this? The ratio is about $\approx 1 : $   

  Consider the fission reanma* natf ;7v9ction $_{92}^{235}\text{U} + \text{n} \to _{51}^{133}\text{Sb} + _{41}^{98}\text{Nb} + ?\text{n}$.
(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 consumptio3i z.lu m.+ *j1irwcbxn, day and night, in a typical house is l.cb riwz*1jm3uxi+. 950 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 of34q16hxrk0- 2h9eoax itl +xibj maj 9 $_{92}^{235}\text{U}$ is required to operate a 650-MW reactor for 1 yr? Assume 40% efficiency. The initial mass is $\approx $    $\ \text{kg}$

  Assuming a fission of9,bvktq t9 xg2 $_{92}^{235}\text{U}$ 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 of proti e2 b83trv:p0rdia1 am4ppo 0ons at the center of a star where the temperature:dtr v410p 3e ma82ro0iip abp is $2 \times 10^7\ \text{K}$?
KE =    $ \times 10^{-16}\ \text{J}$
KE =    eV

  Calculate the energy released in the fusiod 2*1cm3(g5g 8oo azht7jsiq tn reaction $_{1}^{2}\text{H} + _{1}^{3}\text{H} \to _{2}^{4}\text{He} + \text{n}$ is    MeV.

  Calculate the energy released wh1wx (jbae iod 7/uc+kl8 pt,4t9 kbgc(en two deuterium nuclei fuse to form $_{2}^{3}\text{He}$ with the release of a neutron is    MeV.

  Verify the Q-value stjv s9a(ocu5,eo j28xp ated 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 relea)oyds3 acd+e1szj;et ;hor6u- +qg,rse per gram of fuel for the reactions of Eqs. 31-8a, b, and c.s - r136+gcsh+yj d rzaqe ;eotud);o, Compare 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 released wh hdek 7jxmp85zw 7b0,ben $_{92}^{238}\text{U}$ 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 :i7tz-n) q4pbgbqni :minimum amount of deuterium fuel would have to be used in a year to st:7g z4iqbb qnpn:)-i upply these electrical needs? Assume the reaction of Eq.31- 8b.    g

Show that the energies carrieio f21)blli-fqnw 6e: d 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 si( bv*/;bfopkky/ )x m3; uimon "d-d" reactions, Eqs. 31-8a and b. Estimate how much water, for fuel, would be needed per hour to run a 1000-MW reactor, assuming3; i;/*mvy/bips kfumok (x )b 30% efficiency. $\approx$    $kg/h$

  How much energy (J) is contai9 h 0svkjro(iqrn c(**ned in 1.00 kg of water if its natural deuterium is used in the fusion rea0i*qkh( vrcsron * (9jction of Eq. 31-8a? Compare 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 is believed to be,jvao, s kx*ju20kr okhx03 ;n 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 each reaction and decay. (d) Why does the carbon cycle require a highkkjo0x *hv un;k,3x,s02ajo rer 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 the first reaction of the carbon cycle tt8mh k2 u)0oimo that for a deuterium-tritium reaction. h um02mik)o8 t
(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 1yub+6yv gdr- kmxd .k,e6i n8$\gamma$ 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 wil;.xjt yn9zz0cl do as much biological damage as 75 rads of fas 9.;cnyxt0zjzt neutrons?    rad slow neutrons

  How much energy is deposited in the body of a 65-kg adult exzi93p2b;e tzr1:frmx posed to a 2.0-Gy dose? i f3:xmrzter p 19;z2b   $J$

  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 in w*lruys6 u :ug-hich protons with an energy of 1.2 MeV are incident on:-u *l uyusg6r 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 :/c sykai72kq7 5nze4s*n a ec$_{15}^{32}\text{P}$ (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 t4l-2u ej/lng y* gst2 u9gtvyy155 l2yfhcm4io produce one ion pair in air. Show that this is consistent with the two definitions ofus*c iel5y 4 t42llhv5 y2utm1gn yg29f/y-jg 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 a7 by:7* sdgxhpmh06rm $1.00-\mu\text{Ci}\ _{6}^{14}\text{C}$ source?    $\times 10^{-10}\ \text{kg}$

  Huge amounts of radioactis dmd +oxz*3h(ve $_{53}^{131}\text{I}$ 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 milkx6.svwqm5 (:wl(e boy typically 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 of photons needed to produocajogvoq k42u9/n qh2-r :m9ce NMR transitions in free prq2r g29/om4 n uj9vkc: oh-aoqotons in a 1.000-T field. In what region of the spectrum does it lie? c =    $m$

  J. Chadwick discovered e7( e0letoqck13c. ncthe 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 a)lt5iuhzmz26) 9 mu uure often given in keV. Determine the conversion factor from kelvins to keV using, as is commom lu9zmu5 )zhu62u) itn in this field, $KE = kT$ without the factor $\frac{3}{2}$. K =    $ \times 10^{-5}\ \text{keV/K}$

  One means of enriching uranium is by diffpfnif*sb3cgpz:a )b yz5 ; ((vr0c/twusion 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 av2drr-5wv-x*porze 8s7fqf* a erage yearly background radiation consists of 21 mrad of X-a -zdsfvf*5eqw82x -pro * 7rrrays and $\gamma$ 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 hydrogen on average. M j1r1 hq(xsbh.dzz;r4ake a rough estimate of the total deuterium in the Earth's oceans and estimate the total energy released if all of it were used in fusion reacz 1rb1; jd.z4(rh xhqstors.

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 that produc )ai1 pfym48 zw.mrch5e 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, thet;xn1z w 3b7cq egd11x neutrinos escape from the Sun with energy of about 0.5 MeV. The remaining energy, 26.2 MeV, is available within the Sun. Used1cqe wx13t1b ;ngz7x 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 10 nloe:y4exd b; b/jea 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 of evolution, may begin to fuse y4** ch oxm*jntwo $_{6}^{12}\text{C}$ 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 bodyl2ze8liz8jb,y+wi ; q 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 Cb 9foe((j ekfx8 gx9d*k/on*0n zz cj;hernobyl 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 burn helium in the +ux- pqf*3mf6 tv6yoireaction $3\ _{2}^{4}\text{He} \to _{6}^{12}\text{C} + \gamma$. 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 s-c lxs3bkh)5 (dhb* vaame activity, 25 mCi. Source A emits 1.0-MeV 5kcdxbbshh 3-)a*v (l$\gamma$ 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 involving the ingestioi 9ybb (vuuo *5sbdp.2n 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 $    $\ \text{mCi}$