Fill in the missing particles or )b .)uys rydr*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 producing nuclea* pn8.;cnjsg kr 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 igq49 9;i4b8h71 xzcr ioikci$\beta^+$ 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 enezkx 7fr dy6hk)tr; f0:g r7v5urgy - but the thermal enerrf:7)t7ugr; yk6df0vzxk5rh gy of what?

The energy from nuclear fit zn;*1) seatxssion appears in the form of thermal energy - but the xs)zant *e;t1 thermal energy of what?

Why can't uranium be enriched by cy:i3eb 1w ed)lz00wdo hemical means?

How can a neutron, with pr* sg1r b2qt00wh kcn2bactically no kinetic energy, excite a nucleus to the extent shown i *qh2t bkcg0bw2 rs0n1n (Fig. Below)?

Why would a porous block om/ ;gpt8ohj ow6q/hi6lgxt4 3f uranium be more likely to explode if kept under water ratherq68logig4oj;m // hp63t hwxt than in air?

A reactor that uses highly enriched uraniurqdziqg6u o; 6wkn* 5 xq4cc5 d7,fuip7(unl6 m can use ordinary water (instead of heavy water) as a moderator and still have a self-sustaining chain reaction. Eqf*45w7pn u lugqc66d6, oxiz (qndiu5c 7;k rxplain.

Why must the fission procxw02cgl0 92fiwo ox lpl1)re:ess release neutrons if it is to be useful?

Discuss the relative meritslj1aws x3:ccjr)3w4 r and disadvantages, including pollution and safety, of power generation by fossil fuels, nuc3ra:wx4wcj r) 3cl1sjlear fission, and nuclear fusion.

What is the reason for the "secondary system" in a nuclear reactor, (Figipqp e;bz835dd9uk z 6syx w/). Below)? That is, why is the water heated by the fuel in a nuclear reactor not used dire6xp;kde3 di zs8 5wby9zq/u p)ctly to drive the turbines?

Why are neutrons released in a fission re,bl :c4w+ hos0bd 0hruaction?

Why do gamma particles penetrate mattevt sf:5oawfvay2w 2(-r more easily than beta particles do?

A higher temperature is required for deuterium-d9 b1gqz3;fajf euterium ignition than for deuteriumazqfb 139; fgj-tritium. Explain.

Light energy emitted by the Sun and stars comes from the fusio: tdi)ac (-e r 9gk9-m9bc0s8l xpyvykn process. What conditions in the interior of stars make thi-g -k0myp:(8x ca9rvl be9) it9d skycs possible?

How do stars, and our Sun, maintain conf74n+/ dzvarb- 8 shxgcinement of the plasma for fusion?

What is the basic difbvhz(o */q9 ja3 ( jedi-e(uocference between fission and fusion?

People who work around metals t9b .;k-wbw;ngslwr/ rhat emit alpha particles are trained that 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 rulesrbg-w.9;/nrb ls;kw w against eating and drinking while working, and against machining the metal. Why?

Why is the recommended maximum radiation do2 d8ia/2 rhuuzse higher for women beyond the child-bearing age than fo2uh2izr8 u/ad r younger women?

Radiation is sometimes used to sterilize medical supplies an,1 zr14rts6fnl/cx ge;bn9u yd even food. Explain 6 r/cuxnzsgy,n11l ;e 4tr9bfhow it works.

What is the difference between absorbejdwozkcr.z2 2v *94did dose and effective dose? What are the SI o2z 2vdrw 4czjk. i9*dunits for each?

How might radioactive tracers be used to find a leak in a : f-*mkaop ps6/xebd, pipe?

Natural aluminum is y9qcvj*a8a: o yb4n1jall $_{13}^{27}\text{Al}$. 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 reactionbe 4 qb)1nw;sjtur.s5r* lcu7 $_{1}^{2}\text{H} + _{1}^{2}\text{H} \to _{2}^{3}\text{He} + \text{n}$ 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 release*na1qqh;nhmj: :zj c2d (or energy input required) for the reaction $_{5}^{10}\text{B} + \text{p} \to _{3}^{7}\text{Li} + \alpha$.    MeV

  (a) Can the reaction h)5f gl69oktu$_{11}^{23}\text{Na} + \text{d} \to \text{n} + _{12}^{24}\text{Mg}$ 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 reaction8w,v3x l 5gkdd det)bi 1*yl6a $_{3}^{7}\text{Li} + \text{p} \to _{2}^{4}\text{He} + \alpha$ 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 "cad7tsdv 4jrj +8ae3x.zpture" reaction $_{2}^{4}\text{He} + _{4}^{9}\text{Be} \to _{6}^{12}\text{C} + \text{n}$. Q =    MeV

  Calculate the total kine fmzd2 bz9c57fi*,txhtic energy of the products of 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 reaction is o7;qf:hk br0j.oo +b u$\text{d} + _{3}^{7}\text{Li} \to \text{X} + \text{p}$.
(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 reaction ,e .j puj8;ujem 0/cphis $_{1}^{2}\text{H} + _{6}^{12}\text{C} \to \text{X} + \alpha$.
(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 foll *7en q49wsxtxlo 4qo1z:ox)mowing nuclear 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 relg)9 ptnu6e0q, gy6e qzeased in the fission 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 fission reaction of Eq. 31-4? (The massess;t :5d x5q knk+f,vqk of k5 k q:d k;+vfxstn5q,$_{56}^{140}\text{Ba}$ 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? A,/dfo (k bxg4 y.he+u6)qp6vc+x usdassume 200 MeV is rehc+ e6y) g udvfk.(dx4 u,/sqbaoxp+6leased per fission. P =    $\times 10^{13}\ \text{reactions/s}$

  The energy produced by a fikhv *imp 9ww5ojc,qjlg;1637 n ) muwission reactor is about 200 MeV per fission. What fraction of the rest mass 1 g 3k5mq9ip h7,w6wwijj;cn ul*)o vmof a $_{92}^{235}\text{U}$ nucleus is this? The ratio is about $\approx 1 : $   

  Consider the fission reactihn6mctcid .* 5on $_{92}^{235}\text{U} + \text{n} \to _{51}^{133}\text{Sb} + _{41}^{98}\text{Nb} + ?\text{n}$.
(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 a t- 6nh(vxct i+ yrs2(ijypical house is 950 W. What rsv nc(y2i-(i+t j6xhinitial 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 of k/ytaja ,i32j $_{92}^{235}\text{U}$ is required to operate a 650-MW reactor for 1 yr? Assume 40% efficiency. The initial mass is $\approx $    $\ \text{kg}$

  Assuming a fission odxvakqtm h8o/a6:a4dl0d * ;bou6;eh xf3 w+rf $_{92}^{235}\text{U}$ 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 k-y7t s0+mp;d 2izlcb/7jr w ccinetic energy of protons at the center of a star where the pmc -/s7 zlirj dy 7bwcc0t+2;temperature is $2 \times 10^7\ \text{K}$?
KE =    $ \times 10^{-16}\ \text{J}$
KE =    eV

  Calculate the energy released in the fusion rec xr :msmfrmb2 j,g oy5ptl18)tmp3.: action $_{1}^{2}\text{H} + _{1}^{3}\text{H} \to _{2}^{4}\text{He} + \text{n}$ is    MeV.

  Calculate the energy released when two djf;7ug ei xy5mc -/tqjok- q2vdvn(:6euterium nuclei fuse to form $_{2}^{3}\text{He}$ with the release of a neutron is    MeV.

  Verify the Q-value statj;o1xzc/ug5 z f mi f0q/e0qjlw;1ce8ed 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 Eqs. 31-86t 532vx-3bt zzc81a svoyudqa, b, and c. Compare to the energy relev33u82z z sq5ytdtb61- a xovcase 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 w6e 2 -a :c4ghvkgpn9efhen $_{92}^{238}\text{U}$ 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:zgb t60tksp5 mum amount of deuterium fuel would have to be used in a year to supply these electrical need56t :ktbgs0z ps? Assume the reaction of Eq.31- 8b.    g

Show that the energies carried n+wjc,nk/g3q 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 and b. Estimate how mv x ;7hvc(5)pnxwvf/ ppf n 75h.4zskmuch water, for fuel, would be needed per hour to run a 1000-MW reactor, a(/x4 75v. n)zvpps hx wfpcvn5k 7;fmhssuming 30% efficiency. $\approx$    $kg/h$

  How much energy (J) is contained in 1.00 kg of wz:f( q0fg;jcc4 e(w*uq o6ap gater 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 gasoqo a0j*zewu4g(g(cc;6f : q pfline, 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 the carbon cy,2vel )3 rr+lu0fjtxq z: 9jytcle (see text). (a) Show that no carbon is consumed in this cycle and that the net effect is the same as for the protrtfl)3zq2tlv 0 :x +,ujye9rjon-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 needbl4v1y:t :0dq)sso ytyj :; a1e3hutged for the first reaction of the carbon cycle to that for a deuterium-tritium r:ho1yt ys::j4 da0t3)qes buty ;gv l1eaction.
(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 s5iysv/ 87r /*i jru x (+qxaiz/wk9do$\gamma$ 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, h3bg/,ymu fret;eiahmz4tv49o;* u fas/4tub m;gyv;z3a fo,reht *, mih94eut neutrons?    rad slow neutrons

  How much energy is deposited in the body of a 65-c*1j-7rx5x6hdfzc tz 6qw-j*nrl 3xvkg adult exposed to a 2.0-Gy dosexfvzd 6- txlzrn**37cj qr5j6 xhcw1- ?    $J$

  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 which proto6 j9;i d9n*p qcrins/fp 1q-ebns with an energy of 1.2 MeV are incident on a 0.25-kg tumo ipejfqb61*c /npsq;9dr9i -n r.
(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 vk7 :hr6kzi*/sud tb 3$_{15}^{32}\text{P}$ (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. t8.wska 8mnugod;j -ms-gn 2 2Show that this is consistent with the two definitions of the roen8 k ognujs ;mn-d -2gst2wam.8tgen 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 9/ctdp8akj2bm*: ,mu t wgb.m $1.00-\mu\text{Ci}\ _{6}^{14}\text{C}$ source?    $\times 10^{-10}\ \text{kg}$

  Huge amounts of radioacty 4tfkt,rex,8 9x : wbkhg.p+vive $_{53}^{131}\text{I}$ 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 actvn9e;u9j b ch-ivity 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 needes7v,k1ymxhn z b2w*b 3d to produce NMR transitions in free protons in a 1.000-T field. In what region of the spectrum does ik*snbvz ,x71m2w hyb3t lie? c =    $m$

  J. Chadwick discovered the ela6zjbhh 7 bm).8k h7neutron 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 oftegcsqy ,75phm v63aj;wl4u +d-mpc.qj n given in keV. Determine the conversion factor from kelvins to keV using,- lv y367dghj54 +sqcupj.a c; w,pmmq 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 (emspylx* ,s6fz xb* 1uranium 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 background radiation coe4 v-i35eph7i53 6 guak* li5cgu ssmpnsists of 21 mrad of X-kch 6p4u 3s5p 3s *7ivm5iiul5a-eeggrays 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. Make a rough es 1a oaa8;9wq*fi rxr2xtimate of the total deuterium in the Earth's oceans and estimate the total energy released if all of it were used in fusion reactor1r92;a axwi afoq*r x8s.

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 pn*sc +nc j8zeaq:2-ad ower 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 Sun, th( dheykt10y .ae neutrinos escape from the Sun with energy of aboutekdt(.h1y ay 0 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 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 Su i7s0gjbb) *jh h 5bv4c;tq-ien 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 of evolution, may begin too2xn1 fh/j (kfae v)z1 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 con9p p9cq day(izi:6zk h/f 2:wntains 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 react y-j br3odx/9ior 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 burn helium in the )q:e: vxem. 6fydh :nfie(d5ireaction $3\ _{2}^{4}\text{He} \to _{6}^{12}\text{C} + \gamma$. 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 m+ h* xgdara wb82f-wz,n,yk.x Ci. Source A emits 1.0-MeVy+,k*x wxhwnf bgr,za28-.a d $\gamma$ 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 inzydog* xy k 5 s2-ou5sy9u;e2tgestion 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 $    $\ \text{mCi}$