BERYLLIUM

Beryllium one of the prime candidate neutron multipliers to enhance tritium generating performance in the blanket. Key features associated with the use of beryllium include its effective high neutron multiplication cross section, high thermal conductivity, low density and low activation properties. Beryllium is also used as a plasma facing material, primarily on the basis of its very low-Z. The major difficulties related to using beryllium are the relativily low melting temperature, high sputtering rate, radiation induced swelling, tritium retention charateristics, chemical toxicity, and exothermic reaction with steam.

GENERAL PROPERTIES - BERYLLIUM [1]

Physical properties

Boiling Point : 2470 C
Density @ 20 C : 1.848 g/cm3
Melting Point : 1278 C

Electrical properties

Electrical Resistivity @ 20 C : 3.3 u [[Omega]] cm
Temperature Coefficient @ 0 - 100 C : 0.0090/K
Superconductivity Critical temperature : 0.026 K

Thermal Properties

Latent Heat of Evaporation : 32470 J/g
Latent Heat of fusion : 1350 J/g
Linear Expansion Coefficient
@ 0 - 100 C : 12.0x10-6 m/m-K
Specific Heat @ 25 C : 1825 J/kg-K
Thermal Conductivity, @ 0 - 100 C : 201 W/m-K

Mechanical properties

Material Conditons   Soft                 Hard                 Polycrystlline       
Bulk Modulus (GPa)                                             110                  
 Hardness-Vickers    150                  200                                       
  Poisson's Ratio                                              0.02                 
 Tensile Strength    310                  550                                       
       (MPa)                                                                        
 [[sigma]]y  (MPa)   240                  345                                       
      E (GPa)                                                  318

DATA AND CORRELATIONS

Table 1 presents the thermal and structural properties of beryllium as a function of temperature, refs [2, 3, 4, 5, 6]. The following polynomial correlations are representative of the change of thermal and structural properties of beryllium with temperature at zero porosity, p=0:

(1)

(2)

(3)

(4)

(5)

(6)

with T in degrees Kelvin and Eqs 1-5 are valid in the temperature range 300-1500 K. Data for the elastic modulus E, considering the effect of porosity, are from the following expression:

with E in GPa, T in Kelvin and p the volume fraction of pores, ref [4]. The values of E appearing in Table 1 are at zero porosity (p=0). Since porosity for beryllium (and other ceramics) affects the structural properties Table 2 was compiled and shows the effect of porosity on E, with p in the range 0.0-0.3.

             Table 1 Thermal and structural properties of beryllium                                     
   T K     [[rho]]    E GPa      [[nu]]     k W/m-K    c J/kg-K   [[sigma]]  [[alpha]]  
           kg/m3                                                  y          (10-6)     
                                                                  (0.2)MPa   m/m-K      
   300     1850.0     296.605    0.070      200.000    1825       394.741    11.602     
   373                292.482               170.306    2095       364.860    12.343     
   400                290.962               161.526    2191       354.078    12.540     
   473                286.839               142.104    2364       325.657    13.237     
   500                285.319               133.920    2435       315.415    13.418     
   573                281.196               123.730    2559       288.454    14.072     
   600                279.676               121.370    2589       278.752    14.238     
   673                275.553               112.091    2702       253.251    14.848     
   700                274.033               110.900    2714       244.089    14.997     
   773                269.910               104.667    2813       220.048    15.564     
   800                268.390               104.630    2852       221.426    15.697     
   900                262.747               98.350     2928       180.763    16.338     
   973                258.624               95.201     2998       159.642    16.818     
  1000                257.104               92.070     3026       152.100    16.919     
  1100                251.461               88.720     3123       125.437    17.441     
  1200                245.818               85.790     3220       100.774    17.903     
  1300                240.175               81.610     3316       78.111     18.305     
  1400                234.532               79.520     3413       57.448     18.648     
  1500                228.889               77.420     3512       38.785     18.932     


                  Table 2 Effect of porosity on elastic modulus                                         
   T K      E (0 %)   E (0.05    E (0.1     E (0.15    E (0.2     E (0.25    E (0.3     
              GPa     %) GPa     %) GPa     %) GPa     %) GPa     %) GPa     %) GPa     
   300      296.61    248.99     209.01     175.46     147.29     123.64     103.79     
   400      290.96    244.25     205.04     172.12     144.49     121.29     101.82     
   500      285.32    239.51     201.06     168.78     141.69     118.94     99.84      
   600      279.68    234.78     197.08     165.44     138.88     116.59     97.87      
   700      274.03    230.04     193.11     162.11     136.08     114.23     95.89      
   800      268.39    225.30     189.13     158.77     133.28     111.88     93.92      
   900      262.75    220.56     185.15     155.43     130.48     109.53     91.95      
  1000      257.10    215.83     181.18     152.09     127.67     107.18     89.97      
  1100      251.46    211.09     177.20     148.75     124.87     104.82     88.00      


      k (W/m-K)      c (J/kg-K)

Temperature (K)

Figure 1 : Thermal conductivity and specific heat of beryllium.



      E (GPa)      [[alpha]] (10-6  m/m-K)

Temperature (K)

Figure 2 : Elastic modulus and coefficient of thermal expansion for beryllium.



[[sigma]]y (MPa)

Temperature (K)

Figure 3 : Yield stress of beryllium.



E (GPa)

Temperature (K)

Figure 4 : Effect of porosity on the elastic modulus of beryllium.



References

  1. Goodfellow. Metals, Alloys, Compounds, Ceramics, Polymers, Composites. Catalogue 1993/94.

  2. J. Phys. Chem. Ref. Data, Vol. 14, Suppl. 1, 1985, pg 354 (JANAF).

  3. Thermophysical Properties of High Temp. Solid Materials Vol. 1, pt 1, pg 55 - 59.

  4. Status Report, KfK Contribution to the Development of : Demo-Relevant Test Blankets for NET/ITER, October 1991, pg 264 - 266.

  5. Modelling, Analysis and Experiments for Fusion Nuclear Technology. FNT Progress Report : Modelling and finesse, January 1987, Chapter 2.2.

  6. Eric A. Brandes. Smithells Metals Reference Book, Sixth Edition, Chapter 14, pp 1 - 3.