NEU TRON SHIELD ING PROP ER TIES OF ABO RATED HIGH-DEN SITY GLASS

by

Aly Abdallah SAEED 1, Raed Mohamed El SHAZLY 2, Mohamed Mahmoud El-OKR 2,Ali Moheeb Abou El-AZM 2, Yahia Hamdy ELBASHAR 3*,

Mohamed Nasef Hassan COMSAN 4, Wagdy Ahmed KANSOUH 4, and Ahmed Reda EL-SERSY 5

1 Nu clear Power Sta tions De part ment, Fac ulty of En gi neer ing, Egyp tian-Rus sian Uni ver sity, Cairo, Egypt2 Phys ics De part ment, Fac ulty of Sci ence, Al-Azhar Uni ver sity, Cairo, Egypt

3 De part ment of Phys ics, Fac ulty of Sci ence, Aswan Uni ver sity, Aswan, Egypt4 Nu clear Re search Cen ter, Egyp tian Atomic En ergy Au thor ity, Cairo, Egypt

5 Na tional In sti tute for Stan dards, Cairo, Egypt

Sci en tific pa perhttp://doi.org/10.2298/NTRP1702120S

The neu tron shield ing prop er ties of a bo rated high den sity glass sys tem was char ac ter ized ex -per i men tally. The to tal re moval mac ro scopic cross-sec tion of fast neu trons, slow neu trons aswell as the lin ear at ten u a tion co ef fi cient of to tal gamma rays, pri mary in ad di tion to sec ond -ary, were mea sured ex per i men tally un der good geo met ric con di tion to char ac ter ize the at ten -u a tion prop er ties of (75-x) B2O3-1Li2O-5MgO-5ZnO-14Na2O-xBaO glassy sys tem. Slabsof dif fer ent thick nesses from the in ves ti gated glass sys tem were ex posed to a collimated beamof neu trons emit ted from 252Cf and 241Am-Be neu tron sources in or der to mea sure the at ten u -a tion prop er ties of fast and slow neu trons as well as to tal gamma rays. Re sults con firmed thatbar ium bo rate glass was suit able for prac ti cal use in the field of ra di a tion shield ing.

Key words: shield ing ma te rial, fast neu tron, slow neu tron, re moval cross-sec tion, gamma ray

IN TRO DUC TION

Ion iz ing ra di a tion has harm ful ef fects on hu manhealth and en vi ron ment., The same ap plies to nu cleartech nol o gies ac com pa nied with sev eral haz ard ous sit -u a tions for liv ing or gan isms. There fore, it was nec es -sary to de velop tech nol o gies for pro tect ing against nu -clear ra di a tion [1, 2]. Hence, the shield ing ma te rialagainst nu clear ra di a tion was born and at tracted agreat deal of at ten tion [3, 4]. The most im por tant ra di a -tions in the field of pro tec tive ma te ri als are neu tronsand gamma-rays be cause they are the most pen e trat ing for dif fer ent ma te ri als [5]. The ef fec tive ness of shield -ing var ies with the type and en ergy of ra di a tion andalso ac cord ing to the de sired pur pose of the shield ing[6]. Of ten a com bi na tion of three ma te ri als is de sir ablethat in cludes heavy ma te ri als, light ma te ri als, and neu -tron-ab sorb ing ma te ri als to omit the slow neu tronsthrough ab sorp tion of the neu tron shield [7]. Theshield ing of neu trons in tro duces many com pli ca tionsbe cause of a wide range of the en ergy that must be con -sid ered and the sec ond ary pro duc tion of gamma rays.To choose neu tron shield ing ma te ri als, the most im -

por tant is to mod er ate the neu tron to low en er gies,where neu tron can readily be cap tured in ma te ri alswith high ab sorp tion cross sec tion [8, 9]. The most ef -fec tive mod er a tors are el e ments with low atomic num -ber; and there fore hy dro gen con tain ing ma te ri als arethe ma jor ef fi cient com po nents of most neu tronshields, such as wa ter and par af fin. How ever, wa tershields have the dis ad van tage of need ing main te -nance; also, evap o ra tion can lead to a po ten tially dan -ger ous loss of shield ing ef fec tive ness, while par af finis flam ma ble. If the neu tron en ergy is suf fi cientlyhigh, in elas tic scat ter ing with heavy nu clei can takeplace in which the re coil nu cleus is el e vated to one ofits ex cited states dur ing the col li sion. The nu cleusquickly de-ex cites; emit ting a gamma ray, and the neu -tron loses a greater frac tion of its en ergy than it wouldin an equiv a lent elas tic col li sion [10-12]. In elas ticscat ter ing and the sub se quent gamma ray emis sionplay an im por tant role in the shield ing of high-en ergyneu trons. Ma te ri als with good in elas tic scat ter ingprop er ties are the heavy el e ments, such as iron andlead, which used to off set this de crease in cross sec tion with in creased neu tron en ergy [13]. These ma te ri alscan cause a large change in neu tron en ergy af ter col li -

A. A. Saeed, et al.: Neu tron Shield ing Prop er ties of a Bo rated High-Density ...120 Nu clear Tech nol ogy & Ra di a tion Pro tec tion: Year 2017, Vol. 32, No. 2, pp. 120-126

* Cor re spond ing au thor; e-mail: y_elbashar@ya hoo.com

sion for high-en ergy neu trons, while they have a lit tleef fect on the neu trons at lower en ergy, be low 0.1 MeV[14, 15]. The 10B is ef fec tive for ab sorb ing epi ther malneu trons (en ergy range 0.1 eV to 10 eV), and was in -cluded as a neu tron ab sorber in var i ous ma te ri als, e. g.bo rated graph ite, bo ron car bide, Boral, and bo ron ox -ide [16, 17].

Pres ent work was fo cused on the study of im -preg na tion of bo ron ox ide in the glassy sam ples in ad -di tion to a study on the in flu ence of bar ium in the formof BaO (r = 5.73 gcm–3) on the at ten u a tion prop er tiesof slow and fast neu trons as well as the to tal gammarays.

SAM PLES PREP A RA TION

Pure, com mer cially avail able, raw ma te ri alswere used to pre pare a glassy sys tem of the com pos ite (75-x).B2O3-1Li2O-5MgO-5ZnO-14Na2O-xBaO (where x = 0, 10, 20, 30, 40, and 50 mol %) by themelt-quench ing tech nique with di men sions 4 cm ´ 4cm and dif fer ent thick nesses (0.6 cm-1.02 cm). Thedry pow ders were mixed, ho mog e nized and thenmelted at a tem per a ture of 1000 °C for 4 hours in por -ce lain cru ci bles. Once a ho mo ge neous free bub ble liq -uid was ob tained, it was poured into a stain less steelmold and then an nealed at a tem per a ture of 400 °C for4 hours to elim i nate in ter nal stress. Then the glasssam ples were cooled down to room tem per a ture.Trans par ent and ho mog e nous glass sam ples were ob -tained. Fi nally glass slab sam ples as shown in fig. (1)were pol ished un til smooth sur faces were ob served.

EX PER I MEN TAL SET-UP

Fast neu tron and to tal gamma raymea sure ments

Mea sure ments were car ried out for the in ves ti -gated glassy bar ri ers us ing a collimated beam of fastneu trons and gamma rays emit ted from 5 mCi 252Cfsource with neu tron yield of 1.721×107 neu trons persec ond. Spe cial de tec tor collimator was used to elim i -nate the side scat tered ra di a tion to en hance the dis -

crim i na tion ca pa bil ity. The neu tron-gamma crys talor ganic scin til la tion spec trom e ter with stilbenescintillator of di men sion 4 cm ́ 4 cm was used to mea -sure the re coil pro ton and elec tron pulse am pli tude dis -tri bu tions. Ex per i men tal lay out of the mea sur ing sys -tem was pre sented in fig. (2). Fast neu tron and to talgamma ray fluxes trans mit ted through dif fer ent bar ri -ers of glass sam ples un der in ves ti ga tion were used toper form the at ten u a tion prop er ties of such glass,where the shield ing pa ram e ters of fast neu trons and to -tal gamma rays were ob tained.

Slow neu tron mea sure ments

A collimated beam of neu trons emit ted from241Am-Be source of ac tiv ity 0.2 TBq and neu tron yield of (1.1-1.4)×107 neu trons per sec ond was sloweddown, by a Perspex block, to mea sure the slow neu tron at ten u a tion in the in ves ti gated glassy sys tem. Thetrans mit ted beam of neu trons was mea sured un der agood geo met ric con di tion us ing 3He coun ter as shownin fig. (3). The shield ing pa ram e ters of slow neu tronswere de duced from the at ten u a tion curves.

RE SULTS AND DIS CUS SION

To tal re moval mac ro scopiccross-sec tion of fast neu trons

The fast neu tron spec tra were mea sured be hindglass bar ri ers of dif fer ent thick nesses as given in fig.(4). It is de noted from such fig ure that, the mea suredtrans mit ted fast neu tron spec tra have nearly the samebe hav ior be hind all in ves ti gated bar ri ers. It is worth to

A. A. Saeed, et al.: Neu tron Shield ing Prop er ties of a Bo rated High-Den sity ..Nu clear Tech nol ogy & Ra di a tion Pro tec tion: Year 2017, Vol. 32, No. 2, pp. 120-126 121

Fig ure 1. The pre pared sam ples in bulk form

Fig ure 2. Ex per i men tal lay out

Fig ure 3. Sche matic di a gram of slow neu tronmea sure ments

men tion that the neu tron spec tra ini tially emit ted fromthe ir ra di a tion cell does not show any sharp max ima ormin ima, and there fore it is quite suit able to be used forthe de ter mi na tion of the in ves ti gated glass bar ri erscross-sec tions by the trans mis sion method. The fig urealso showed that the flux de creased as the glass thick -ness in creased for the trans mit ted fast neu trons. The to -tal in te gral fluxes for the re gion of neu tron en er gies

from 1.4-8 MeV were used to per form the at ten u a tionre la tions of fast neu trons trans mit ted through the in ves -ti gated glass bar ri ers of thick ness vary ing from 0 cm upto 6.74 cm. The trans mit ted fast neu tron flux throughglassy bar ri ers was given as a func tion of bar rier thick -ness. Fig ure 5 showed the re la tion be tween to tal re -moval mac ro scopic cross-sec tions (SF) of fast neu trons, which were de duced from the at ten u a tion curves, and

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Fig ure 4. Fast neu tron spec tra be hind dif fer ent bar ri ers of the in ves ti gated glass sam ples

the mol per cent age of bar ium in the glassy bar ri ers. Itcan be seen that, the value of SF did not show any ap pre -cia ble in crease up to 20 mol% of bar ium con cen tra tion,while at higher con cen tra tions an ap pre cia ble in creasein SF was ob served. This could be at trib uted to the re -moval of fast neu trons up to 20 mol% bar ium con cen -tra tion via in elas tic scat ter ing (n, n/g) which has notprovedwas not so ef fec tive. While for Ba con cen tra -tions be tween 20 to 50 mol %, which is the max i mumcon cen tra tion of our choice, the in cre ment of Ba fol -lows by a higher re moval mac ro scopic cross-sec tion for fast neu trons via in elas tic scat ter ing pro cess which maybe fol lowed by ra di a tion cap ture pro cess for slow downneu trons with bo ron nu clei. The half value thick ness(HVL) and re lax ation length (l) for fast neu trons werelisted in tab. 1. Fig ure 5 and tab. 1 showed that, the at -ten u a tion prop er ties of fast neu tron in creased as the bar -ium con cen tra tion in creased up to 50 mol %.

To tal re moval mac ro scopiccross-sec tion of slow neu trons

The to tal re moval mac ro scopic cross-sec tions of slow neu trons (SS), de duced from the at ten u a tioncurves, were plot ted ver sus bo ron con cen tra tion asshown in fig. 6. It is clear that, the val ues of SS in -creased as the bo ron con cen tra tion i ncreased up to75 mol %.

For slow neu trons, the half value thick ness(HVL) and re lax ation length (l) were listed in tab. 2.The ob tained re sults showed that, the at ten u a tion

prop er ties of slow neu tron im proved as the bo ron con -cen tra tion in creased.

To tal lin ear at ten u a tion co ef fi cients

The ob tained re sults for to tal gamma ray spec tra, pri mary in ad di tion to sec ond ary, trans mit ted throughdif fer ent bar ri ers of glass me dia, were given in fig. 7.Such fig ure showed also the ini tial pri mary gammaspec tra emit ted di rectly from the ir ra di a tion cell. Theto tal gamma ray spec tra, trans mit ted through dif fer entbar ri ers of glass me dia, had an ir reg u lar pat tern inshapes and at ten u a tion pro file. How ever, the dis -played spec tra showed that, the to tal gamma flux wasnot de creased reg u larly as the glass bar ri ers in creased.

Some peaks were ob served at dif fer ent gammapho ton en ergy in the spec tra be hind glass bar ri ers.Main peak was ob served at pho ton en ergy 2.3 MeV inall in ves ti gated sam ples. This peak was due to g-rayini tially emit ted from 252Cf source. An other peak wasob served at pho ton en ergy of about 6.5 MeV insam ples with bar ium con cen tra tions 10, 20, 30, and40 mol %. This peak was due to the in elas tic scat ter ingof fast neu trons with bar ium nu clei (n, n/g), which dis -ap peared at 50 mol % bar ium con cen tra tion; this maybe at trib uted to the bar ium con cen tra tion, high enoughto ab sorb sec ond ary g-ray at such en ergy. Pro nouncedpeak was ob served in the gamma spec tra at pho tonen ergy 4 MeV in sam ples with bar ium con cen tra tions40 and 50 mol %. Such peak may be due to gamma rays pro duced from ra di a tive cap ture of slow neu trons bybo ron nu clei in glass sam ple.

A. A. Saeed, et al.: Neu tron Shield ing Prop er ties of a Bo rated High-Den sity ..Nu clear Tech nol ogy & Ra di a tion Pro tec tion: Year 2017, Vol. 32, No. 2, pp. 120-126 123

Fig ure 5. Vari a tion of to tal re moval mac ro scopiccross-sec tion of fast neu trons with Ba con cen tra tion inglass sam ples

Ta ble 1. Cal cu lated ra di a tion pa ram e ters of fast neu trons for glass sam ples un der in ves ti ga tion

Pa ram e ter Ba = 0 [mol %] Ba = 10 [mol %] Ba = 20 [mol %] Ba = 30 [mol %] Ba = 40 [mol %] Ba = 50 [mol %]

HVL [cm] 15.04 14.12 11.75 5.32 4.18 3.84

l [cm–1] 21.69 20.37 16.95 7.68 6.04 5.54

Fig ure 6. To tal re moval mac ro scopic cross-sec tions ofslow neu trons in glass sam ples

Ta ble 2. Ra di a tion at ten u a tion pa ram e ters of slow neu trons for glass sam ples un der in ves ti ga tion

Pa ram e ter B = 25 [mol %] B = 35 [mol %] B = 45 [mol %] B = 55 [mol %] B = 65 [mol %] B = 75 [mol %]

HVL [cm] 11.79 9.37 7.28 5.48 4.63 3.62

l [cm–1] 17.01 13.51 10.50 7.91 6.68 5.22

The at ten u a tion re la tions for in te gral flux of to tal gamma rays, (in the en ergy range from 0.407 to7.19 MeV) mea sured be hind the in ves ti gated glassbar ri ers, were used to de rive the to tal lin ear at ten u a -tion co ef fi cients [mT, cm–1] and were plot ted as a func -tion of bar ium con cen tra tion, as shown in fig. 8. mT ofg-rays showed a very slight in crease with bar ium con -cen tra tion up to 20 mol %. This can be at trib uted to

bal ance be tween the ab sorp tion term and the new pro -duced g-rays term. While an ap pre cia ble in crease in mT

was ob served at higher con cen tra tions up to 50 mol %,which meant that the ab sorp tion term ex ceeded thepro duc tion term. Strange re sult was ob tained at bar -ium con cen tra tion 40 mol %.

The half value thick ness (HVL) and re lax ationlength (l) for to tal gamma rays were listed in tab. 3.

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Fig ure 7. To tal gamma ray spec tra be hind dif fer ent bar ri ers

CON CLU SION

Syn the sis of novel trans par ent glass ma terielwas stud ied re gard ing the shield ing prop er ties of fast,slow neu trons, and to tal gamma rays. In te gral flux val -ues of fast and slow neu trons de creased ex po nen tiallywith in creas ing the bar ium and bo ron con cen tra tionre spec tively. The g-ray shield ing for such sam pleswere ef fec tive at bar ium con cen tra tion exceedsing20 mol % up to 50 mol % as an op tion, in which itagrees with what was ob tained in our pre vi ous workdone on the same sam ples for pure gamma emit ter[18]. Ob tained re sults for neu trons and gamma raysmay be use ful for nu clear re search com mu nity andshield ing de sign of hot cells.

AU THORS' CON TRI BU TIONS

The sam ple prep a ra tion was done by A. Saeed.The ma te rial prop er ties work was done by M. M.El-Okr, A. M. Abou El-azm, Y. H. Elbashar. The ra di a -tion mea sure ments and their data anal y sis were car ried out by A. Saeed, R. M. El Shazly, M. N. HussienComsan, W. A. Kansouh, A. R. El-Sersy.

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[8] ***, Paul Reuss Neu tron Physics, EDP Sci ences,2008

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[11] Sandeep, K., et al., In ves ti ga tion of Struc tural Prop er -ties of Bis muth Sil i cate Glass Sys tem as Gamma RayShield ing Ma te ri als, Asian Jour nal of Ap plied Sci -ences, 1 (2013), pp. 99-103

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[13] Gh. Eid, M. M. et al., Neu tron Shield ing Us ing Li3BO3//Ep oxy Com pos ite, Re searcher, 3 (2011), pp. 85-92

[14] Siqi, Xu, A Novel Ul tra-Light Struc ture for Ra di a tionShield ing, M. Sc. the sis, North Carolina State Uni ver -sity, Ralligh, N. C. USA, 2008

[15] Al A., Ahmed. J. M., Mea sure ment of In elas tic Scat -ter ing Cross-Sec tions For Re ac tor Fast Neu tronsFrom Yb174 Us ing the Time of Flight Tech nique”,Arab Jour nal of Nu clear Sci ences and Ap pli ca tions,45 (2012), 2, pp. 283-289

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Re ceived on Oc to ber 7, 2016Ac cepted on March 2, 2017

A. A. Saeed, et al.: Neu tron Shield ing Prop er ties of a Bo rated High-Den sity ..Nu clear Tech nol ogy & Ra di a tion Pro tec tion: Year 2017, Vol. 32, No. 2, pp. 120-126 125

Ta ble 3. Ra di a tion pa ram e ters of to tal gamma rays for glass sam ples un der in ves ti ga tion

Pa ram e ter Ba = 0 [mol %] Ba = 10 [mol %] Ba = 20 [mol %] Ba = 30 [mol %] Ba = 40 [mol %] Ba = 50 [mol %]

HVL [cm] 10.16 12.06 09.55 05.68 12.16 05.05

l [cm–1] 14.66 17.39 13.77 08.20 17.54 07.28

Fig ure 8. To tal lin ear at ten u a tion co ef fi cients of g-rays inglass sam ples

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Ali Abdalah SAID, Raed Mohamed EL [AZLI, Mohamed Mahmud EL-OKR,Ali Mohib Abu EL-AZM, Jahija Hamdi ELBA[AR, Mohamed Nasef Hasan KOMSAN,

Vagdi Ahmed KANSUH, Ahmed Reda EL-SERSI

SVOJSTVA STAKLA VISOKE GUSTINE TRETIRANOGBOROM U ZA[TITI OD NEUTRONSKOG ZRA^EWA

Eksperimentalno su odre|ena za{titna svojstva stakla visoke gustine tretiranogborom od neutronskog zra~ewa. Radi karakterizacije atenuacionih svojstava sistema stakla(75-x) B2O3-1Li2O-5MgO-5ZnO-14Na2O-xBaO, u uslovima dobre geometrije merewa, odre|eni suukupni makroskopski efikasni presek za uklawawe brzih i sporih neutrona i linearnikoeficijent slabqewa ukupnog gama zra~ewa, primarnog i sekundarnog. Kako bi se izmerilaatenuaciona svojstva brzih i sporih neutrona i ukupnog gama zra~ewa, plo~e razli~itih debqinaispitivanog stakla izlagane su kolimisanom snopu neutrona emitovanih iz izvora 252Cf i241Am-Be. Rezultati potvr|uju da je staklo sa barijumom i borom pogodno za prakti~nu primenu uoblasti za{tite od zra~ewa.

Kqu~ne re~i: za{titni materijal, brzi neu tron, spori neu tron, efikasni presek zauklawawe, gama zra~ewe