EGS_BRACHY ENERGY SPECTRUM

Could someone please let me know why i am getting this NAN value when trying to get energy spectrum?

@ legend 0.2, 0.8

@ legend box linestyle 0

@ legend font 4

@ xaxis label "E / MeV"

@ xaxis label char size 1.3

@ xaxis label font 4

@ xaxis ticklabel font 4

@ yaxis label "counts / total counts / MeV\S-1"

@ yaxis label char size 1.3

@ yaxis label font 4

@ yaxis ticklabel font 4

@ title "EGS_Brachy: photon counts on surface of source"

@ title font 4

@ title size 1.500000

@ subtitle ""

@ subtitle font 4

@ subtitle size 1.000000

@ s0 errorbar linestyle 0

@ s0 legend "Spectrum"

u/target G0.S0

u/type xydy

1.00000E-03 0.00000E+00 0.00000E+00

1.00000E-03 -NAN 0.00000E+00

1.34917E-02 -NAN -NAN

2.59833E-02 -NAN 0.00000E+00

2.59833E-02 -NAN 0.00000E+00

3.84750E-02 -NAN -NAN

5.09667E-02 -NAN 0.00000E+00

5.09667E-02 -NAN 0.00000E+00

6.34583E-02 -NAN -NAN

7.59500E-02 -NAN 0.00000E+00

7.59500E-02 -NAN 0.00000E+00

8.84417E-02 -NAN -NAN

1.00933E-01 -NAN 0.00000E+00

1.00933E-01 -NAN 0.00000E+00

1.13425E-01 -NAN -NAN

1.25917E-01 -NAN 0.00000E+00

1.25917E-01 -NAN 0.00000E+00

1.38408E-01 -NAN -NAN

1.50900E-01 -NAN 0.00000E+00

1.50900E-01 -NAN 0.00000E+00

1.63392E-01 -NAN -NAN

1.75883E-01 -NAN 0.00000E+00

1.75883E-01 -NAN 0.00000E+00

1.88375E-01 -NAN -NAN

2.00867E-01 -NAN 0.00000E+00