This guide provides helpful information for those looking to join the Navy as a Machinist’s Mate, Nuclear (MMN) during the Fiscal Year 2025.
Getting into the reactor room takes brains and grit. If math, chemistry, physics, and engineering keep you up at night, you might have what it takes to be a Machinist’s Mate Nuclear (MMN).
You’re the Navy’s nuclear reactor mechanic. Your job? Keep the steam-powered propulsion plants running on aircraft carriers and submarines. No steam, no movement. The fleet depends on you.
The payoff? Up to $50,000 for first-time enlistment. Re-enlistment bonuses stack up, too.
Think you can handle the pressure of making a nuclear-powered ship move? Let’s find out.
ENLISTMENT BONUS: Future Navy MMNs are currently eligible to receive up to $50K in cash bonus just for signing up.
Job Description
A Machinist’s Mate Nuclear (MMN) operates and maintains Naval nuclear propulsion plants aboard aircraft carriers and submarines.
What You Do:
- Run the Propulsion Systems – Steam turbines, reduction gears, turbogenerators. If it moves the ship, you keep it running.
- Fix the Support Gear – Pumps, oil purifiers, steering engines, air conditioning, desalination. All the behind-the-scenes systems that make the ship livable.
- Work Inside the Reactor – Operate and maintain the reactor, propulsion, and power generation systems.
- Handle Fluids & Fuel – Lubricating oil, reactor coolant, potable water—test it, transfer it, track it.
- Log Everything – Every system, every repair, every operation. Submarines, carriers—it’s all on record.
Propulsion Plant Roles
Propulsion Plant Mechanical Manager
- Runs operations, maintenance, and training for reactor and engineering crews.
- Audits programs, reviews reports, handles risk management.
- Leads repairs and keeps the fleet moving.
Propulsion Plant Mechanical Operator
- Operates and maintains propulsion systems, turbines, pumps, and valves.
- Monitors reactor and propulsion plant, handles shutdowns.
- Fixes what breaks. Keeps the ship running.
Propulsion Plant Mechanical Supervisor
- Takes charge of advanced maintenance and mechanical operations.
- Leads training, testing, keeps crews sharp.
- Writes reports, manages risk, ensures nothing fails when it matters.
Rank Structure
Pay Grade | Rate | Abbreviation | Title |
---|---|---|---|
E-1 | Seaman Recruit | SR | Seaman Recruit |
E-2 | Seaman Apprentice | SA | Seaman Apprentice |
E-3 | Seaman | SN | Seaman |
E-4 | Machinist’s Mate Nuclear Third Class | MMN3 | Petty Officer Third Class |
E-5 | Machinist’s Mate Nuclear Second Class | MMN2 | Petty Officer Second Class |
E-6 | Machinist’s Mate Nuclear First Class | MMN1 | Petty Officer First Class |
E-7 | Chief Machinist’s Mate Nuclear | MMNC | Chief Petty Officer |
E-8 | Senior Chief Machinist’s Mate Nuclear | MMNCS | Senior Chief Petty Officer |
E-9 | Master Chief Machinist’s Mate Nuclear | MMNCM | Master Chief Petty Officer |
Quick Promotion: Start at E-3, fast-track to E-4 after completing “A” School and meeting all requirements.
Salary and Benefits
Salary for the First 6 Years
Monthly pay for Navy enlisted Sailors (E-1 to E-6) in the first six years is laid out in the January 2025 Active Duty Pay chart:
Pay Grade | Less than 2 Years | Over 2 Years | Over 3 Years | Over 4 Years | Over 6 Years |
E-1 | $2,108.10 | $2,108.10 | $2,108.10 | $2,108.10 | $2,108.10 |
E-2 | $2,362.80 | $2,362.80 | $2,362.80 | $2,362.80 | $2,362.80 |
E-3 | $2,484.60 | $2,640.60 | $2,800.80 | $2,800.80 | $2,800.80 |
E-4 | $2,752.20 | $2,892.90 | $3,049.80 | $3,204.30 | $3,341.40 |
E-5 | $3,001.50 | $3,203.70 | $3,358.80 | $3,517.20 | $3,763.80 |
E-6 | $3,276.60 | $3,606.00 | $3,765.00 | $3,919.80 | $4,080.60 |
Extra Pays and Allowances
- Nuclear Enlistment Bonus: $50,000 just for signing up.
- Housing Allowance (BAH): For members living off-base. Covers rent, based on rank, location, and if they have dependents.
- Subsistence Allowance (BAS): Enlisted get $465.77 monthly for food.
- Hazard Duty Pay: For dangerous jobs. Pays $150-$250 per month, depending on the job.
- Sea Pay: For those assigned to ships or deployed units. Depends on rank and time at sea, from $50 to $750 a month.
- Submarine Duty Incentive Pay (SUBPAY): Up to $1,000/month based on qualifications and assignment.
- Special and Incentive Pays: Bonuses for certain roles, like air traffic control or unique skills. These can be a few hundred to thousands per year.
Source: Figures are from the Defense Finance and Accounting Service.
Benefits
- Healthcare: Active-duty personnel are eligible for free complete medical and dental treatment. Tricare programs are inexpensive for families to use.
- Housing Accomodation: Depending on location, rank, and family size, free on-base accommodation or a tax-free housing allowance (BAH) for off-base living are available.
- Food: Monthly Basic Allowance for Subsistence (BAS) for food costs is known as the “food allowance.”
- Blended Retirement System (BRS): Conventional pensions are no longer available to active-duty personnel. Rather:
- Thrift Savings Plan (TSP): Up to 5% in government matching and automatic contributions.
- Retirement Pay: After 20 years of service, you’re eligible for monthly payments according on the BRS formula, which combines TSP savings with a calculated pension.
- Education:
- Availability of tuition assistance programs that pay for all or part of college tuition.
- Support for higher education under the post-9/11 GI Bill.
- Navy College Program to support education while on service.
- Life Insurance: Servicemembers’ Group Life Insurance (SGLI) provides coverage up to $500,000.
- Vacation: ten or more federal holidays plus thirty days of paid vacation each year.
- Extra Benefits:
- Exchanges and commissaries provide tax-free purchasing.
- Discounted travel via military resorts, access to fitness centers, and leisure amenities.
MMN Training Path
Recruit Training Command (Boot Camp)
- Where: Great Lakes, IL
- What: Basic military training. Learn discipline, structure, and teamwork.
“A” School – 3 Months
- Where: Charleston, SC
- What You Learn:
- Math, physics, thermodynamics, mechanical theory
- Fluid flow, safety, general engineering maintenance
- Hands-on training with pumps, turbines, valves, compressors, refrigeration, air conditioning, and propulsion systems
Nuclear Power School (NNPS) – 6 Months
- Where: Charleston, SC
- What You Learn:
- Reactor physics, plant operations, heat transfer, and fluid systems
- Chemistry, radiological control, mechanical and electrical systems
- How to run and troubleshoot a pressurized-water Naval nuclear power plant
Prototype Training – 6 Months
- Where: Charleston, SC, or Ballston Spa, NY
- What You Do:
- Hands-on training with a real nuclear reactor
- Learn mechanical, electrical, and reactor subsystems
- Master safe plant operation, troubleshooting, and watchstanding
Qualifications to Join
Basic Requirements
- Education: High school diploma or equivalent
- Citizenship: U.S. citizen
- Math: Must have completed at least one year of Algebra
- Age: Must be under 25 years old at enlistment
- Security Clearance: Must qualify for a security clearance
ASVAB & NAPT Requirements
Option 1 – Automatic Qualification:
- VE + AR + MK + MC ≥ 252 OR
- AR + MK + EI + GS ≥ 252
- Both scores must be at least 235
Option 2 – Conditional Qualification :
- VE + AR + MK + MC ≥ 235 AND AR + MK + EI + GS ≥ 235
- Must pass the Navy Advanced Programs Test (NAPT)*
- Final Score Requirement:
- VE + AR + MK + MC + NAPT ≥ 290 OR
- AR + MK + EI + GS + NAPT ≥ 290
- Both base scores (before NAPT) must be at least 225
- No waivers allowed
*The Navy Advanced Programs Test (NAPT) is a two-hour supplemental exam for Nuclear Field applicants who don’t qualify based solely on ASVAB scores.
Service Obligation
Time Commitment: 6 years (4-year enlistment + 2-year extension for training)
These requirements are current as of Fiscal Year 2025, per the Navy Personnel Command. No updates have been issued thus far.
More Information
If you wish to learn more about becoming an Electronics Technician (ET), contact your local Navy Enlisted Recruiter. They will provide you with more detailed information you’re unlikely to find online.
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