ANALYSIS OF THE SECONDARY PARTICLE PENETRATION EXPERIMENT* Toshiso Kosako*
Yoshito mo Uwamino , Takash i Nakamu ra,**and Kazuo Shin

* Institu te for Nuclear Study, Univer sity of Tokyosity** Departm ent of Nuclear Engine ering, Kyoto UniverThe penetra tion of seconda ry neutron s and photons produce dfrom the 21.5-mm -thick graphit e target irradia ted by 52-MeVe.
protons has been measure d in graphit e, iron, water and concret
Both the source spectra {l) and the spectra transm itted througha.
these four matters (2) have been measure d with a 2-in x 2-in-diliquid organic scintil lator, NE213, using the n-y discrim ination
techniq ues. The dimensi ons and the atomic densiti es of theismatters are shown in the table, and the experim ental setup
theofsenergietheoflimits
Lower
1.
Fig.
inillustr ated.
measure d spectra are 2MeV for neutron s and 0.6MeV for photons
The measure d spectra were analyze d by the discret e ordinat etion.
transpo rt calcula tion and the multi-g roup Monte Carlo calcula
For the former, the ANISN code was used withou t the bucklin g
onecorrect ion by approxi mating the experim ental arrange ment todimens ional slab. For the latter, the multi-g roup Monte Carloion
code has been develop ed includi ng the point-d etector estimat
and the angular samplin g method by Strake r(3).
47
In both calcula tions, DLC-58 group constan ts(4) (neutro ns offrom
groups
21of
rays
gamma
and
groupes from thermal to 60MeV
O.OlMeV to 14MeV) and the measure d source spectra are used.
The neutron spectra calcula ted by these two codes agree wellleach other and also with the measure d ones both in the spectra
resultANISN
thethatngexcludi
shapes and in the absolut e values,
is greater than the Monte Carlo result in case of neutron penel
tration through the 101-cm -thick water, since one-dim ensiona
s ofapproxi mation neglect s the leakage from the lateral surface
fluthe finite slabs. The attenua tion profile s of the neutronences (En:;::2MeV) are shown in Fig. 2.
ental
The calcula ted results are in good agreem ent with the experimofslopes
thein10%thanlessresults , and the differe nces are
the curves (the attenua tion coeffic ients).
The attenua tion of photon fluence were calcula ted only withinANISN. The calcula ted results agree with experim ental ones
case of graphit e and water, but attenua te faster than the experimay bemental ones in case of iron and concre te. This discrep ancy
stic
non-elabytionproducphotontheDLC-58,
incaused from that,collisi on with neutron s of energy higher than 14.9MeV is ignored
and that the fractio ns of photons produce d by the non-ela sticcollisi ons with neutron s are less than 20% in graphit e and water,
but domina nt in iron and concre te.
Referen ces(1) T. Nakamu ra, et al, Nucl. Instr. Method s, 151, 493(197 8)(2) K. Shin, et al, Bull. Inst. Chern. Res., Kyoto Univ., 57,102(197 9)(3) E.A. Straker , et al, ORNL-45 85 (1970)(4) R.G. Alsmil ler, Jr., et al, ORNL/T M-6486( 1978)-91 --

Table Dimensions and Atomic Densitiesof the Matters
MatterAtomic Densitywidth( em) Thicknessin Calc.
(em) Usedx height(cm)(atom cm-3)
21.5
graptlite
43.0
c 8.43+22
90x54
64.5
19.3
38.6
57.9
60.0
101.0
46.0
69.0
115.0

iron
52x50
water80x55
concrete75x60.....ICarbon
Matter52MeV
ProtonDetector
2"x2"dia.
_ ___.NE213)
to Current Integra tor

Fe 7.70+22
H 6.68+22

0 3.34+22
H 5.95+210 4.48+22
Si 2.00+22
Ca 1 .52+21
Fe 7 .38+20

Fig.l

Experimental setup forthe measurements of thesecondary particle
penetration.

'Experiment'-.. Monte Carlo Calc •c0
.....
0s..

'.....Ic.
s..

V'lc020406030

100

0204060

80

100.

>< 10-3::J.....
.....

concretec.....e::J

cu 1o· 4:z1o· 5.

.

~

•240

Matter Thickness , g cm- 2
Fig.2 Attenuation of measured and calculated neutron
fluxes integrated above 2 MeV'-92-