Utility Maintenance Storage H4: Reactor 01 key-room route

Take the Utility Maintenance Storage key beneath the electrical transformers next to Reactor 01, not into Reactor 02’s underwater DRC pool. The H4 key room is reached from the substation’s lower passage. Prepare radiation protection before looking for the descent; finding a suit inside is not an entry plan.

Pack the key and radiation equipment first

Confirm the full Utility Maintenance Storage key name in your backpack. H4 is a search reference for the reactor area, not a surveyed door coordinate. No guaranteed source for this key is established here; if you do not have it, use the Key Finder to check your existing keys before committing supplies.

Bring Radiation Gear and a Gas Mask, with condition to cover both the search and return. Add healing, plates and ammunition. The radiation guide explains why temporary Blockers are not a reason to ignore reactor preparation.

Fire Stations are a place to search for protection. The recorded approach also finds a mask at the compound outside the reactor, but that is an observed pickup, not guaranteed resupply. Possible Hazmat Suit locations in or around the reactor do not ensure one will be waiting for you below the transformers.

Find the transformer area next to Reactor 01

Reach Haneul Nuclear Reactor and identify Reactor 01 and its adjacent electrical substation. Selecting Fallen Ember provides the recorded approach from the neighboring compound; the footage does not establish that the mission must be active to use an owned Storage key.

The demonstrated route crosses the bridge toward the electrical substations, then looks for a way down on their northern side. Descend into the covered maintenance passage below the transformer area. Do not keep climbing toward the reactor roof if this room is your goal.

Follow the lower passage to the named single door

Continue along the lower passage toward its middle section. The room uses a single door along the wall; move close enough to read UTILITY MAINTENANCE STORAGE — UNLOCK and use the matching key.

If you have reached…	Check the destination
Maintenance passage below transformers	Correct kind of approach; find the named Storage door
A flooded pool in Reactor 02	Separate Reactor DRC Locker route
The upper Reactor 02 Control Room	A different keyed room
A Story Mission fuel-rod interaction	Mission objective, not this room’s lock

Use the door name rather than a nearby mission marker. In the recorded visit, Fallen Ember’s HUD remains visible while the player opens Storage; the objective marker is not a pin for this key’s door.

Search the room without expecting a fixed reward

The visit shows bags, loose tactical/lethal equipment, shelves and a yellow chemical storage container. The roll is sparse, which is useful when deciding whether to risk an expensive reactor trip just for this key.

Check the yellow container and the other available searches, but read each item card. No guaranteed Irradiated Container, Weapon Manual, Recipe or Ultra weapon is established for this room. A possible field upgrade or valuable pickup is a reason to inspect, not a promised reimbursement for your kit.

Decide whether another reactor stop is worth it

Before leaving the room, check mask condition, healing, inventory space and the active storm. Retrace the lower passage to the substation exit if your protection is running low. Keep enough supplies to cross back out of the contaminated area and reach an active exfil.

If you have protection and another matching key, compare the reactor loot route with the Reactor DRC Locker guide. Treat them as optional separate stops. Do not turn one Storage opening into an unplanned underwater dive while carrying an item you already need to extract.