[ChalkLine]

Just a little thought:
Every armoured Soviet vehicle with NBC capability uses the GO-27 gamma radiation detector. This device alerts the crew and actives the seals and over-pressure systems. A huge amount of similar systems outfitted Soviet vehicles as well as the infantry, in fact these types of detectors were very common among the Polish Obrona Cywilna PRL Civil Defence units.

Even if NATO units didn't have access to these devices it's not a long stretch for GMs to assume that they'd been recovered from Warsaw Pact vehicles and integrated into NATO survivor vehicles.

[Edit]
AND/VDR-2 Gamma-ray and Beta radiation Detection System. (Civilian name RDS-110V)
This unit comes standard on all US armoured vehicles such as the M2 Bradley IFV. It's a demountable, lightweight radiation detector with the following characteristics:
Wide dynamic range for dose rate and dose
• Pre-settable audio and visual alarms
• 600 hr battery life
• Vehicle mount for operation using vehicle or aircraft power (available option)
• Not affected by EMP
• Nuclear hardened
• Meets MIL-STD-810G for military environments
• Operable/readable by personnel in Mission Oriented Protection Posture (MOPP IV) or arctic clothing
Dimensions:
• Radiac meter: 19.2 x 10.4 x 4.8 cm (7.6 x 4.1 x 1.9 in.).
• Detector probe: 18.2 x 5.1 x 3.8 cm (7.2 x 2 x 1.5 in.).
• Radiac set in pouch: 23.2 x 17.5 x 7.9 cm (9.12 x 6.88 x 3.13 in.).
Weight:
• Radiac with Beta /Gamma Probe: 1.73 kg (3.8 Ib).
• Radiac set in pouch: 2.08 kg (4.6 lb).
Power:
• Six AA batteries.
• 600 hours of continuous operation and monitoring.
• Low battery LCD indication with 10 hr of battery life remaining,
a “Go/No Go” feature provides battery status.
• Can be operated on vehicle or aircraft power (12 or 24 V dc via universal connector).
Alarms:
• Has selectable Visual and Audible indicators for DOSE and RATE alarm for
day or night use.
• Alarm levels are settable over entire dynamic range.
Probe and Detectors:
• “SMART” probe Technology: Instantly recognized and functional upon hook-up, without any adjustment, programming or calibration.
• Combined two GM Tubes; low range EWGM and high range GM.
• Beta radiation: 0.01 μSv/hr to 50 mSv/hr.
• Gamma radiation: 0.01 μSv/hr to 99.9 Sv/hr (dose rate) and 0.01 μSv to 99.9 Sv (total dose).
• Energy response: ±20% 80 keV to 3 MeV.
• Accuracy: ±10% of true dose and dose rate over the entire dynamic range.
• Dose rate: Minimum detectable level 0.01 μSv/hr.
• Response time: Within 10% of final reading in 4 sec at 10 mSv/hr; returns to background within 4 sec. Meets ANSI N42.17A.