Exposure Criteria for Pulsed RFMW Radiation

DOE-HDBK-1092-98

10.8.4.2.2 EXPOSURE CRITERIA FOR PULSED RFMW RADIATION

The basic considerations for peak-power exposure limits are consistent with ANSI/IEEE C95.1

(1991) as follows:

1. For more than five pulses in the averaging time and for pulse durations exceeding 100

milliseconds, normal time averaging applies and the time-averaged power densities should

not exceed the Maximum Permissible Exposure (MPE) given in Table 10-1 for controlled and

Table 10-2 for uncontrolled environments, per ANSI/IEEE C95.1 (1991).

2. For intermittent pulse sources with no more than five pulses during the averaging time, the

peak power density for any of the pulses should not exceed the limit given by the following

equation.

MPEp =

MPEα (tα )

5(tp)

where:

MPEp =

Peak (power density)

MPEα =

Time-Average (power density)

tα

Averaging time (seconds)

Pulse width (seconds)

This limits the specific absorption (SA) of each pulse to SA=28.8 J/kg (whole-body or spatial

average), or SA=144 J/kg for 5 pulses.

For intermittent pulse sources with no more than five pulses during the averaging time, the

single-pulse SA of < 28.8 J/kg, though higher than the threshold for auditory effect (clicking),

is three orders of magnitude lower than the SAs that produce RF-induced unconsciousness.

3. Maximum E field for any of the pulses should be no more than 100 kV/m. This peak E-field

limit is prescribed to eliminate the possibility of air breakdown or spark discharges, which

occur at 2,900 kV/m. A large safety factor is applied to account for local field enhancements

where nominally lower fields may result in arcing discharges.

10.9

METHODS

10.9.1 WIRING METHODS

10.9.1.1

HAZARDS

Unsafe wiring methods can cause electrical injury or fire hazards.

R&D work may require the use of wiring methods that are not anticipated in the NEC. These methods

may not be consistent with normal commercial and industrial wiring methods, and should be

reviewed by the AHJ for approval.

10-10