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Nuclear Event – Emergency Declared (High Hydrazine Level in Containment Atmosphere): Salem Nuclear Power Plant, Unit 2, New Jersey


North America – USA | State of New Jersey,  Lower Alloways Creek Township, Salem Nuclear Power Plant, Unit 2
Location: 39°27’46.0″N 75°32’08.0″W
Present Operational Age: ~32 years

Emergency Class: UNUSUAL EVENT
10 CFR Section: 50.72(a) (1) (i) – EMERGENCY DECLARED

Nuclear Event in USA on Thursday, 20 April, 2017 at 21:10 [EDT].


“At 2110 EDT, Salem control room received data that supported unacceptable levels of hydrazine concentration in the U2 Containment atmosphere based on Site Protection atmospheric sampling. The high hydrazine levels were caused due to Steam Generator venting into the Containment atmosphere in support of maintenance for the current Salem Unit 2 Refueling Outage (2R22). The NIOSH habitability limit for hydrazine is 0.03 ppm (2 hour limit). Area samples indicated concentrations as high as 0.25 ppm. Salem Unit 2 Containment has been evacuated while a mitigation plan is being developed. There were no personnel injuries as a result of this occurrence. Salem Unit 2 defueling activities were in progress during this event. All fuel assemblies have been placed in a safe condition. All Salem Unit 2 Containment activities are currently on hold. There has been no impact to the equipment in the Unit 2 Containment, no adverse impact to any equipment located in the vicinity of the high hydrazine concentration, and no operational impact to the plant including Shutdown Cooling which is currently on RHR.”

The Unusual Event was declared under EAL HU3.1, Toxic/Flammable Gas Release Affecting Plant Operations.

The licensee plans to issue a press release.

The licensee notified the NRC Resident Inspector, Lower Alloways Creek Township, State of New Jersey and State of Delaware.

Notified DHS SWO, FEMA Operations Center, DHS NICC, FEMA NWC (email), DHS Nuclear SSA (email), and FEMA NRCC SASC (email).


“Salem Unit 2 terminated the Unusual Event at 1258 EDT on 4/21/17. The basis for termination was no longer restricting access to the containment after getting two sets of satisfactory air sample results. With the access restored, normal plant operations can resume and EAL HU3.1 is no longer applicable.

“The details of the sample results are:
Fire Protection performed satisfactory results of no detectable Hydrazine (0.01 ppm with a NIOSH limit of 0.03 ppm) completed both at 1001 EDT and 1247 EDT at the following locations:
– (3) at 130 ft. elevation
– at 78 ft. in the bioshield
– at 78 ft. outside the bioshield.

“Additional mitigating actions taken following U2 Containment evacuation were as follows:
– FME screen installed on open manways for 21/23 S/G with additional plastic covering and tape to prevent further gas release into containment.
– Modified Containment Purge in service to maximize ventilation in Containment.
– 21/24 S/G draining to support filling and draining evolutions to reduce Hydrazine concentrations in the S/G’s.
– Releasing tags on the AFWST to commence filling and further support filling and draining evolutions on the U2 S/G’s.”

The licensee notified the NRC Resident Inspector.

Notified R1DO (Arner), NRR EO (King), and IRD (Stapleton). Notified DHS SWO, FEMA Operations Center, DHS NICC, FEMA NWC (email), DHS Nuclear SSA (email), and FEMA NRCC SASC (email).

Source: NRC Event Number: 52699

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