Univerza v LjubljaniFakulteta za matematiko in fiziko

Seminar Ia

Activation of Water in Nuclear Reactors

Author: Andrej �oharMentor: doc. dr. Luka Snoj

Ljubljana, 2016

Abstract

In this seminar I will present the activation of cooling water in the Kr²ko nuclear powerplant and the International Thermonuclear Experimental Reactor (ITER). Activation of coolingwater occurs due to exposure to high neutron �ux in the reactor vessel. Activated cooling watercirculates in the cooling system and is the main contributor of radiation outside of the reactorvessel. The activation reaction rate was calculated using Monte Carlo Neutral Particle transportprogram and di�erent nuclear data libraries for the Kr²ko nuclear power plant and ITER. Fromthe results it is visible, that water is going to be in orders of magnitude more activated in ITERthan in Kr²ko. This will cause more damage to components and higher dose rates to workers inITER.

Contents

1 Introduction 2

2 Activation of cooling water 2

3 The Monte Carlo method 4

3.1 Nuclear data libraries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Kr²ko Nuclear Power Plant 6

4.1 Simulation of activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

5 International Thermonuclear Experimental Reactor (ITER) 9

5.1 16N and 17N production in ITER . . . . . . . . . . . . . . . . . . . . . . . . . . . 105.2 E�ects of 16N and 17N decay products . . . . . . . . . . . . . . . . . . . . . . . . 11

6 Conclusion 11

1 Introduction

Nuclear reactors use nuclear �ssion or fusion to produce heat, which can be used to generateelectricity. This is the main purpose of nuclear power plants. Research reactors produce neu-trons and gamma rays for irradiation of samples for studies of the e�ects of radiation, neutronactivation analysis, etc. All the reactors have a common feature. They need to be cooled toprevent melting of the fuel in �ssion reactors and to prevent melting of walls in fusion reactors.There are many di�erent �uids and gasses that are cooling reactors, but the most common iswater (H2O).

Due to intense neutron �ux in nuclear reactors (> 1013 cm−2s−1), the cooling �uid becomesradioactive. Because the cooling �uid is circulating in the primary system, it is the main source ofradiation outside the reactor vessel. Due to this, the understanding of activation of cooling �uidin reactors is important for designing biological shielding and shielding of important equipmentinside and outside of the containment vessel.

In this seminar I will only focus on the activation of water, because this is the primary cooling�uid in the Slovenian nuclear power plant Kr²ko and ITER nuclear fusion research reactor andit is the most common cooling liquid.

2 Activation of cooling water

During the cooling of the reactor core the water is exposed to intense neutron �ux (> 1013

cm−2s−1). This intense �ux causes neutron reactions with nuclei in water molecules (Table 1).Important reactions are 16O(n,p)16N, 17O(n,p)17N and 18O(n,γ)19O.

The most important radionuclide is 16N due to a high natural abundance of 16O, relativelyhigh cross section for (n,p) reaction and high energy gamma radiation. It also contributes themost to the activity of cooling water and dose rate outside the reactor vessel. We also needto take into account the activation of 18O, due to 19O gamma decay. 17N emits high energyneutrons which can activate components outside the reactor vessel and produce neutron inducedgamma rays. However the activity of 17N is negligible in a �ssion reactor due to lower neutron�ux and "softer" neutron spectrum, but needs to be included for fusion reactors. I decided toinclude 17N activation for the Kr²ko nuclear power plant in the seminar for completeness.

Due to the short half-life of radionuclides, they are important only during reactor operation.2

IsotopeNatural

abundance [%]Dominantreaction

Activationproduct

t1/2 [s]Dominant decay producs

(branching ratio)

16O 99.76 (n,p) 16N 7.136.129 MeV gamma (67%)7.115 MeV gamma (5%)

17O 0.04 (n,p) 17N 4.140.383 MeV neutron (35%)1.171 MeV neutron (53%)

18O 0.20 (n,γ) 19O 26.90.197 MeV gamma (63%)1.357 MeV gamma (33%)

Table 1: Activation products of water in reactor coolant. [1]

The threshold energy for activation of 16O is at 10 MeV and for 17O is 9 MeV. 18O has nothreshold energy for activation and can be already activated with thermal neutrons.

Figure 1: Cross section energy dependence for activation of oxygen nuclide taken from JEFF-3.2library. Di�erent libraries and di�erences between them are presented later in this seminar. [2]

To calculate the activation of a nuclide, we �rst need to determine the reaction rates R(~r)de�ned as[3]:

Ri(~r) =

∫ ∞0

N0σi(E)φ(~r,E)dE. (1)

N0 is the number density of target elements in cooling water [1/cm3], σi(E) is the macroscopiccross section of the nuclide for reaction i [cm2] and φ(~r,E) is the energy dependent neutron �uxor neutron spectrum in the primary cooling water [1/MeVcm2s−1].

To describe the change of radionuclide concentration in the primary cooling water N , weneed to solve the di�erential equation[4]:

dN(t)

dt= R− λN, (2)

where λ is a decay constant [s−1] and R is an average reaction rate in region. To calculate thespeci�c activation of radionuclide we multiply the solution for N(t) with the decay constant (λ):

A(t) = N(t) λ = R(1− e−λt). (3)3

After long exposure the activation reaches saturation A = R = N0σφ.The cooling water circulates and is exposed to high neutron �ux for a short time (∼ 3 s).

The new equilibrium of speci�c activation is:

A1 = A2e−λte +R(1− e−λte)

A2 = A1e−λT ,

(4)

where A1 is the speci�c activation of cooling water on the outlet of the reactor vessel, A2 is thespeci�c activation of cooling water on the inlet of the reactor vessel, te is the exposure time andT is time the cooling water needs from the outlet to the inlet of the reactor vessel.

If we combine equations in (4), we get the equilibrium value of speci�c activation on theoutlet of the reactor vessel:

A1 = R1− e−λte

1− e−λ(te+T ). (5)

In the equations above we took average reaction rates over the whole reactor vessel. Wecan also divide the reactor vessel into smaller subsections for better analysis of the contributionof speci�c areas. In general we have n equations for n regions in the reactor vessel plus oneequation for the region outside the reactor vessel. The general form of equations is then:

A1 = An+1e−λte1 +R1(1− e−λte1)

...

An = An−1e−λten +Rn(1− e−λten)

An+1 = Ane−λT .

(6)

From this equations we can calculate the equilibrium of the activity at the output of reactorvessel (An). In the equations we do not have the reaction rates. There are many ways tocalculate them, but in this seminar they were calculated using the Monte Carlo method.

3 The Monte Carlo method

The Monte Carlo method is very di�erent from deterministic transport methods. Determin-istic methods solve the transport equation for the average population behaviour. On the otherhand, the Monte Carlo method obtains solutions by simulating individual particles and record-ing some aspects (tallies) for their average behaviour. The average behaviour of particles in thephysical system is then inferred (using the central limit theorem) from the average behaviourof the simulated particles. The Monte Carlo method is well suited for solving complicatedthree-dimensional problems, which cannot be modeled by computer codes that use deterministicmethods. The individual probabilistic events that comprise a process are simulated sequentially.The probability distributions of these events are statistically sampled to describe the total phe-nomenon. In general, the simulation is performed on a computer, because the number of particlesin simulation necessary to adequately describe the phenomenon is usually quite large, typicallyon the order of 106 to 1012. The statistical sampling process is based on the selection of randomnumbers. The selection is analogous to throwing a dice in a gambling casino, hence the nameof the method. [5]

There are many programs for Monte Carlo simulation. In this seminar Monte Carlo NeutralParticle (MCNP) program was used to calculate solutions. MCNP is a general-purpose MonteCarlo transport code. It has been developing by Los Alamos National Laboratory since 1957. Itis primarily used for the simulation of nuclear processes, such as �ssion, but has the capabilityto simulate particle interactions involving neutrons, photons and electrons. It can also be usedto calculate keff eigenvalues for the �ssile system. The current version is MCNP 6.1.1. [5]

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3.1 Nuclear data libraries

MCNP uses continuous-energy nuclear and atomic data libraries. The primary sources ofnuclear data are evaluated nuclear data libraries [1]. Nuclear data tables exist for neutroninteractions, neutron-induced photons, photon interactions, neutron dosimetry or activation andthermal particle scattering. Over 836 neutron interaction tables are available for approximately100 di�erent isotopes and elements. More neutron interaction tables are constantly being addedas new and revised evaluations become available. [5]

Not all nuclear data is present in the standard MCNP ENDF/B-VII.0 library. Because ofthat, there are several di�erent atomic data libraries, which can be used in Monte Carlo forcalculations on missing atomic data. In the case of the activation of water, the standard MCNPlibrary does not have cross section energy dependence for 18O(n,γ)19O reaction. Also crosssection energy dependence for 17O(n,p)17N reaction is di�erent in the standard MCNP librarythan in other libraries. I used data from TENDL ([6]) and JEFF libraries ([7]), but there arealso others. In calculations for ITER, data from JENDL library was used.

The TENDL library uses the results from the TALYS nuclear model code system. TALYSis a software for the simulation of nuclear reactions. TENDL is physically produced at the CEABruyeres-le-Chatel and developed at PSI, the IAEA, CCFE and the CEA. It contains evaluationsfor seven types of incident particles, for all isotopes living longer than 1 s (about 2800 isotopes)up to 200 MeV. The current version is TENDL-2015. [6]

JEFF (Joint Evaluated Fission and Fusion File) is a collaboration between NEA Data Bankmember countries. The library combines the work of JEFF and EFF/EAF Working Groups toproduce a common sets of evaluated nuclear data, mainly for �ssion and fusion applications.The JEFF nuclear data library contains neutron and photon interaction data, radioactive decaydata, �ssion yields, and thermal scattering law data. The current version is JEFF-3.2.[7]

As I mentioned above, there are di�erences in cross section energy dependence for activationof 17O and 18O in the standard MCNP(ENDF/B-VII.0) library and JEFF and TENDL libraries.The cross section energy dependence can be seen in Figure 2 and Figure 3. For the TENDLlibrary, the cross section energy dependence is taken from TENDL-2014, because the dependenceis the same in TENDL-2014 and TENDL-2015.

Figure 2: Cross section energy dependence for activation of 17O from di�erent libraries andexperimental data. [2]

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For the activation of 17O the cross section energy dependence is almost the same for JEFF-3.2and TENDL-2015 library, but di�erent from standard MCNP library ENDF/B-VII.0. From thegraph, it is visible that the activation of 17O is going to be higher with the use of the standardMCNP library, but the di�erence is not going to in orders of magnitude higher due to the shapeof the neutron spectrum in �ssion reactors and the threshold in the neutron spectrum in thefusion reactor. Some results of experimental measurements are shown on the graph, but they donot tell us which dependence is the right one. Because of that, I used all of them for simulatingthe activation in Kr²ko nuclear power plant.

For the activation of 18O, there is a big di�erence in cross section energy dependence in theepithermal region (around 0.08 MeV) between JEFF-3.2 and TENDL-2015. TENDL-2015 hasa resonance in this region which contributes the majority to the activation of 18O. From themeasurements, it is visible that there should be a resonance peak like in TENDL-2015 library,but we cannot de�nitively claim that. Because of that, both libraries were used in the MCNPsimulation.

Figure 3: Cross section energy dependence for activation of 18O from di�erent libraries andexperimental data. [2]

4 Kr²ko Nuclear Power Plant

Kr²ko nuclear power plant is a pressurised water �ssion reactor with 2000 MW thermalpower and 696 MW power rating. It was built in 1981 in Slovenia near the city of Kr²ko. Inthe reactor, the �ssion of 235

92 U is the main source of energy in the beginning of fuel cycle, while44% of energy is produced by �ssion of 239

94 Pu at the end of fuel cycle.

23592 U+ 1

0n→ AZX+ 236−A−ν

92−Z Y+ ν 10n + 200 MeV,

23994 Pu + 1

0n→ AZX+ 240−A−ν

94−Z Y+ ν 10n + 212 MeV,

(7)

where 〈ν〉 = 2.43 for �ssion of uranium and 〈ν〉 = 2.88 for �ssion of plutonium. In the equation(7) the X and Y present the decay products. The products are not the same for every �ssion.For the X the atomic mass (AX) number is most of the time between 90 and 100 and for Ybetween 140 and 150, depending on the value for X. For better e�ciency of the reactor, thefuel is enriched and contains between 2.1 and 4.3 % of 235

92 U. There is no 23994 Pu in fresh fuel.

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The reactor is cooled with water, which is circulated by two pumps having a �ow rate of22711 m3/h �ow rate. Due to this, the water is exposed to high �ux (∼ 1.5 · 1013 cm−2s−1) fora short time ∼1 - 2 s. However, the whole cycle lasts only around 12 s, which means that someactivated water returns to the reactor and needs to be included in the �nal calculated activation.

4.1 Simulation of activation

The neutron �ux spectrum calculations was calculated by using Monte Carlo code on theexisting model of Kr²ko nuclear power plant. [8] The reactor vessel was divided in four areas:downcomer (Region 1), lower plenum (Region 2), core (Region 3) and upper plenum (Region 4).The scheme is shown in Figure 4 and lethargy spectrum in Figure 5.

Figure 4: Scheme of Kr²ko reactor vessel with marked areas for detailed analysis of activation.

0 2x1011 4x1011 6x1011 8x1011 1x1012

1.2x1012 1.4x1012 1.6x1012

10-10 10-8 10-6 10-4 10-2 100 102Leth

argy

spe

ctru

m [c

m-2

s-1]

Energy [MeV]

Region 1

0 2x108 4x108 6x108 8x108 1x109

1.2x109 1.4x109 1.6x109 1.8x109

2x109

10-10 10-8 10-6 10-4 10-2 100 102Leth

argy

spe

ctru

m [c

m-2

s-1]

Energy [MeV]

Region 2

0

1x1013

2x1013

3x1013

4x1013

5x1013

6x1013

10-10 10-8 10-6 10-4 10-2 100 102Leth

argy

spe

ctru

m [c

m-2

s-1]

Energy [MeV]

Region 3

0 1x108 2x108 3x108 4x108 5x108 6x108 7x108 8x108 9x108 1x109

10-10 10-8 10-6 10-4 10-2 100 102Leth

argy

spe

ctru

m [c

m-2

s-1]

Energy [MeV]

Region 4

Figure 5: Scheme of Kr²ko reactor vessel with lethargy spectrum in each region for detailedanalysis of activation.

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MCNP 6.1 was used to calculated reaction rates. The results of reaction rates from MCNPare normalized to one �ssion neutron and are in units [cm−2]. To normalize the results by thethermal power of the system, an appropriate scaling factor needs to be used. [9] The factordepends on the thermal power of the system (2 GW in case of the Kr²ko nuclear power plant),the average number of neutrons per �ssion, the average energy released per �ssion and e�ectiveneutron multiplication factor. The exposure times were calculated from the known volume ofcooling water and �ow. [10] With equation (3) and the system of equations (6) I calculated theactivation of cooling water. I also calculated the activity per litre instead of cm3. The resultsof the activation are presented in Table 2.

Library Activation product Activity [Bq/l]ENDF/B-VII.0 16N 1.92·109 ± 3.62 · 106TENDL-2015 16N 1.92·109 ± 3.62 · 106JEFF-3.2 16N 1.92·109 ± 3.62 · 106

ENDF/B-VII.0 17N 4.21·105 ± 6.74 · 103TENDL-2015 17N 1.35·105 ± 2.03 · 103JEFF-3.2 17N 1.48·105 ± 2.07 · 103

TENDL-2015 19O 2.66·107 ± 4.10 · 105JEFF-3.2 19O 8.42·106 ± 1.35 · 105

Table 2: Calculated speci�c activity.

The errors in results are due to the Monte Carlo method, the uncertainties in cross sec-tion energy dependence and uncertainties from calculating exposure time. The uncertainties inexposure time calculation contributed the majority to the �nal value error.

From Table 2 I can see the di�erence in calculated activity using di�erent libraries. For theactivation product 16N there is no di�erence in calculated activity due to the same cross sectionenergy dependence in all libraries. For 17N the calculated activity for JEFF and TENDL isalmost three times lower than for ENDF/B-VII.0, due to a di�erence in cross section energydependence presented in section 3.2. Also the calculated activity of 17N from all libraries isnegligible compared to activity of 16N. For 19O the calculated activity from JEFF is more thanthree times lower than from TENDL. The calculated activity is two orders of magnitude lowerthan the activity of 16N and contributes only a small portion to the whole activity of coolingwater.

0.0⋅100

5.0⋅106

1.0⋅107

1.5⋅107

2.0⋅107

2.5⋅107

3.0⋅107

0 50 100 150 200 250

Act

ivity

[Bq/

l]

Time [s]

19O

Figure 6: Time dependence of activity of 19O from the start of a clean reactor to saturatedvalue.

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I also calculated the time and number of water recirculation cycles needed for the activity toreach the saturated value, from inactivated state at full power (2 GW). The result for activityof 19O are presented in Figure 6. From the calculated data I found out that it takes 21 cyclesfor 16N to reach its saturated value (∼4.3 min), 14 cycles for 17N to reach its saturated value(∼2.9 min) and 70 cycles for 19O to reach its saturated value (∼14.3 min).

Detailed e�ects of gamma rays dose �eld and activation of components due to activatedcooling water in Kr²ko nuclear power plant have not been yet made.

5 International Thermonuclear Experimental Reactor (ITER)

ITER is a fusion reactor currently being built next to the Cadarache facility in the south ofFrance. In the reactor, deuterium and tritium will be fused together to form alpha particles andhigh-energy neutrons.

21D+ 3

1T→ 42He +

10n + 17.6 MeV. (8)

The reason for utilising this reaction is that the process requires the lowest activation energy,while producing among the most energy per unit weight. The designed power output is 500MW, while the reactor only needs 50 MW.

Construction of the ITER complex started in 2010 and is scheduled to be completed in 2019.In 2020 the �rst plasma experiments should begin and full deuterium-tritium fusion experimentsshould begin in 2027.

As I mentioned in the introduction, water is going to be the coolant for blankets and vacuumvessel in ITER. A typical cooling water loop is shown in Figure 7.

Figure 7: Schematic diagram of the water coolant �ow path in ITER.[11]

Water circulates through the pipes at 4-8 m/s. This means that the exposure to high �uxat the �rst wall in front of the blanket is short ∼ 0.4 - 1 s. The neutrons induce many reactionsin the cooling water, but the most important for ITER are the production of 16N and 17N. The16N decay gamma-rays will be an additional source of nuclear heat in the cryogenic componentsinside the cryostat (superconducting magnets, cryostat walls, etc.) and could cause radiation

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damage in unshielded diagnostic and electronic components. Fast neutrons from 17N decay willactivate the cooling pipes and components inside the primary heat exchanger system. [11]

5.1 16N and 17N production in ITER

Neutron �ux spectrum in fusion reactors is signi�cantly di�erent from neutron �ux in �ssionreactors. In �ssion reactors, neutron �ux is distributed according to the Watt spectrum. Thepeak of the spectrum is at 0.7 MeV and the mean of the spectrum is at 2 MeV. In fusion reactorsthe peak of the spectrum is at 14 MeV due to energy of neutron from D-T reaction. Thecomparison can be seen in Figure 8. Also the neutron �ux in fusion reactors is 8·1013 cm−2s−1,which is �ve times higher than in the Kr²ko �ssion reactor. This triggers more activation of 16Oand 17O.

Figure 8: Comparison between neutron �ux in �ssion (PWR) and fusion reactor (DEMO). [12]

The simulation was performed in MCNP and the detailed geometry and results are presentedin [11] and [13]. In this seminar I will only present the most important results of the simulation.16N activity was calculated for separate parts of cooling system. In the blanket modules thewater becomes most activated due to close proximity to plasma. The rate of activation is tentimes higher in the front section of the blanket module than in the remainder of the module.The speci�c activity of 16N at the exit of module was calculated to be[11]:

Ab = 5.6 · 1012 Bq/l.

In the divertor the water is activated in plasma facing components: dome, wings and targets.Cooling water is in divertor about 7 s with high exposure about 1 s. The speci�c activity of 16Nat the exit of divertor was calculated to be[11]:

Ad = 1.5 · 1012 Bq/l.

In both cases the time outside of the exposure area is greater than several half-life periodsof 16N (50-70 s). This means that residual activity of 16N can be neglected. This also means,that cooling water reaches saturated value after just one cycle.

For 17N the speci�c activity was calculated for blanket modules. The speci�c activation isAb = 6.7 · 109 Bq/l, three orders of magnitude lower then than of 16N. Due to a short half-life,around 50% of 17N decays before leaving the blanket modules and speci�c activity at the outletof modules is[11]:

Ab = 1.7 · 109 Bq/l.

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From the results I can see that the speci�c activity in fusion reactor is three orders ofmagnitude higher for 16N than in the Kr²ko �ssion rector. In case of 17N the speci�c activity isfour orders of magnitude higher. The reason for this is in the greater neutron �ux and higherenergy spectrum of neutrons.

5.2 E�ects of 16N and 17N decay products

The largest fraction of the 16N gamma-ray energy is released in the pipe walls and the wateritself. About 5% is deposited in Toroidal Field coils and the remainder is deposited in thecryostat and biological shield. The design speci�cation limits the nuclear heating in the TFcoil case structure and superconductor to 2 and 1 mW/cm3. The maximum gamma-ray energyrelease was estimated to be 0.65 mW/cm3 in the TF coil casing and 0.004 mW/cm3 in thesuperconductor. If additional shielding (8-cm SS + 5-cm H2O) is introduced between the pipesand the superconducting TF coil, the nuclear heating will be substantially lower.

The dose rates from gamma-rays in the outlet pipes during the reactor operation was alsocalculated. The dose rate near the outlet pipe (behind cryostat) is estimated to be 650 Sv/h, inthe TF coil casing (near the front surface) 320 Sv/h and in the superconductor 2 Sv/h. All ofthese are high doses and maintenance during operation is not going to be possible.

The expected 17N fast neutron �ux in the pipes inside the cryostat is about one magnitudelower than behind the vacuum vessel. At 1 m from a single outlet pipe surface, the operationaldose rate in the cryostat from 17N decay neutrons and secondary gamma-rays is 0.5 Sv/h, whichis signi�cantly lower than the dose rate from 16N decay.

The residual activation of pipe walls was estimated after one year of operation. The contactdose rates at a single outlet pipe surface as a function of time after shut down from activationof steel are given in Table 3. [11]

Time after Shutdown[days]

Contact Dose Rate[µSv/h]

0 13007 19014 18030 160365 33

Table 3: The contact dose rate on a single outlet pipe. [11]

6 Conclusion

Water is the cooling liquid in �ssion nuclear power plant Kr²ko and future fusion power plantITER. Due to high neutron �ux, this cooling water becomes activated and is carried outsidereactor vessel, where it causes radiation problems. The activation was simulated with the MonteCarlo method to determine activation of cooling water in reactor vessel for Kr²ko and ITER.From the results we can see that cooling water is going to be in orders of magnitudes moreactivated in ITER than in Kr²ko. This will cause more radiation damage to components andhigher dose rates for workers in ITER.

For ITER, the e�ects of activated cooling water decay was also carried out. From the resultsit is visible that access to cryostat, while the reactor is going to operate, is not going to bepossible due to high radiation doses. Even outside of cryostat and biological shield, the dosesare going to be high and dangerous for workers. Nuclear heating from activated cooling water is

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also going to be a problem for the reactor itself, especially for superconductors. Because of that,su�cient protection needs to be placed between coolant pipes and superconductor structure.

There are still some uncertainties in the Monte Carlo simulation for processes in nuclearphysics. The biggest uncertainty is for cross section energy dependence, especially for 18O. This�eld needs the most attention and research in the future.

References

[1] M.B. Chadwick, P. Obloºinský, et al. ENDF/B-VII.0: Next generation evaluated nucleardata library for nuclear science and technology, Nucl. Data Sheets 107(2006)2931.

[2] N. Soppera, M. Bossant, E. Dupont. JANIS 4: An Improved Version of the NEA Java-based Nuclear Data Information System, Nuclear Data Sheets, Volume 120, June 2014,Pages 294-296.

[3] M. Stepi²nik, B. Pucelj, L. Snoj, M. Ravnik. Activity Analysis of Primary Coolant inTRIGA MARK II Research Reactor, Nuclear Energy for New Europe, 2009

[4] M. Stepi²nik. Analiza aktivnosti primarnega hladila pri delovanju raziskovalnega reaktorjaTRIGA MARK II, Magistrsko delo, Ljubljana, 2008

[5] Los Alamos National Laboratory. MCNP - A General N-Particle Transport Code, Version5, Volume I: MCNP Overview and Theory, 2003.

[6] A.J. Koning, D. Rochman, et al. TENDL-2015: TALYS-based evaluated nuclear data library.

[7] OECD/NEA Data Bank. The JEFF-3.2 Nuclear Data Library, OECD/NEA Data Bank(2014).

[8] B. Kos. Izra£un doznega polja nevtronov v okolici reaktorja tla£novodne jedrske elektrarne,Magistersko delo, Ljubljana, 2015.

[9] L. Snoj, M. Ravnik. Calculation of Power Density with MCNP in TRIGA reactor, NuclearEnergy for New Europe, 2006

[10] D. Grgi¢, V. Ben£ik, S. �adek. NEK RELAP5\MOD3.3 Post-RTDBE Nodalization Note-book, 2014

[11] R. T. Santoro, V. Khripunov, H. Iida and R. R. Parker. Radionuclide Production in theITER Water Coolant, Fusion Engineering, 17th IEEE/NPSS Symposium, 1997.

[12] M.R. Gilbert, S.L. Dudarev, et al. Neutron-induced dpa, transmutations, gas production, andhelium embrittlement of fusion materials, EURATOM/CCFE Fusion Association, CulhamCentre for Fusion Energy, Abingdon, Oxfordshire OX14 3DB, UK, 20.11.2013.

[13] H. Iida, R. Plenteda, R. T. Santoro and V. Khripunov. Three-Dimensional Analysis ofNuclear Heating in the Superconducting Magnet System Due to Gamma-Rays from 16Nin the ITER Water Cooling System of the Shielding Blanket, Fusion Engineering, 17thIEEE/NPSS Symposium, 1997.

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