Nuclear with thermal connection with HTSE by jaredthomas68 · Pull Request #807 · NatLabRockies/H2Integrate

jaredthomas68 · 2026-07-20T23:29:34Z

Nuclear with thermal connection with HTSE

This pull request adds a nuclear model capable of thermal integration and high temperature steam electrolysis. The models are coupled, but can be used individually and coupled with other components. This PR replaces #761.

Section 1: Type of Contribution

Section 2: Draft PR Checklist

Open draft PR
Describe the feature that will be added
Fill out TODO list steps
Describe requested feedback from reviewers on draft PR
Complete Section 8: New Model Checklist (if applicable)

TODO:

Step 1
Step 2

Type of Reviewer Feedback Requested (on Draft PR)

Structural feedback:

Implementation feedback:

Other feedback:

Section 3: General PR Checklist

Section 4: Related Issues

Section 5: Impacted Areas of the Software

Section 5.1: New Files

examples/36_nuclear_reactor_htse/driver_config.yaml
- driver.optimization / design_variables: Adds optimization inputs for the thermal nuclear + HTSE example so reactor dispatch and HTSE sizing can be varied.
examples/36_nuclear_reactor_htse/nuclear_reactor_thermal_htse.yaml
- config references: Adds the top-level example entrypoint that links the driver, plant, and technology configuration files.
examples/36_nuclear_reactor_htse/plant_config.yaml
- technology_interconnections / finance_parameters: Adds the plant wiring and finance subgroup definitions for coupled nuclear electricity, process heat, HTSE hydrogen production, and grid sales.
examples/36_nuclear_reactor_htse/run_nuclear_reactor_thermal.py
- module script body: Adds a runnable example that updates HTSE refurbishment inputs, executes the model, reports LCOE/LCOH, and plots electricity, heat, and hydrogen outputs.
examples/36_nuclear_reactor_htse/tech_config.yaml
- technologies: Adds the thermal nuclear reactor, HTSE, feedstock, demand, and grid component definitions needed to run the integrated example.
h2integrate/converters/hydrogen/htse_electrolyzer.py
- HTSEPerformanceModel: Adds a simplified HTSE performance model that converts available heat and electricity into hydrogen production, water use, efficiency, and replacement outputs.
- HTSECostModel: Adds a size-based HTSE cost model that computes CapEx and fixed OpEx from installed electrolyzer capacity.
h2integrate/converters/hydrogen/test/test_htse_electrolyzer.py
- HTSE unit tests: Adds coverage for rated operation, turndown shutoff, and cost-model behavior for the new HTSE models.
h2integrate/converters/nuclear/nuclear_plant_thermal.py
- SimpleThermalNuclearReactorPerformanceModel: Adds a thermal nuclear reactor model that dispatches between electricity generation and process heat delivery.
- SimpleThermalNuclearReactorCostModel: Adds a reactor cost model that computes capital, fixed operating, and variable operating costs.
h2integrate/converters/nuclear/test/test_nuclear_plant_thermal.py
- thermal reactor unit tests: Adds coverage for heat-mode dispatch, electricity-mode dispatch, rated-capacity clipping, and reactor cost calculations.

Section 5.2: Modified Files

examples/test/test_all_examples.py
- test_nuclear_reactor_htse_example: Adds an integration test for the new thermal nuclear + HTSE example to validate annual electricity, hydrogen output, grid exports, and thermal-balance behavior.
h2integrate/converters/hydrogen/__init__.py
- module exports: Adds HTSEPerformanceModel and HTSECostModel to the hydrogen converter package exports.
h2integrate/converters/nuclear/__init__.py
- module exports: Adds SimpleThermalNuclearReactorPerformanceModel and SimpleThermalNuclearReactorCostModel to the nuclear converter package exports.
h2integrate/core/supported_models.py
- supported_models: Registers the new HTSE and thermal nuclear model classes so they can be instantiated from YAML configuration.
h2integrate/transporters/pipe.py
- PipePerformanceModel.setup: Updates water pipe units from galUS to galUS/h so water transport matches the HTSE feedstock rate units.

Section 6: Additional Supporting Information

Section 7: Test Results, if applicable

Section 8 (Optional): New Model Checklist

…e a unified example

…g to function

… how it uses electricity when heat is not available.

Nuchtse develop

Nuchtse

Nucdev

add test

…optimization and we need a single analysis test value in this case

update naming and units

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bayc

Overall, looks great Jared, thanks for getting this pulled together! Added a couple of non-blocking comments regarding the documentation.

bayc · 2026-07-23T15:40:02Z

Would be nice to have the pump and heat exchanger labeled for those not as familiar with the setup.

bayc · 2026-07-23T15:40:38Z

Label the heat exchanger? Also, what does the red dashed line represent?

Done. I also made a note in the doc page that the red dashed arrow represents the heat extraction (upstream of the LPT).

…inks to autogenerated doc pages

johnjasa

Thanks for this great PR, @mikkdm and @jaredthomas68! It's great to see it all come together.

I have some minor suggestions for clarity and cleanup, nothing huge. I'm requesting changes to make sure I come back when the CI is passing for one last go-through!

johnjasa · 2026-07-27T16:52:38Z

+
+## Performance Model
+
+Use this model by setting:


Suggested change

Use this model by setting:

To use this model, within your `tech_config.yaml` file set:

johnjasa · 2026-07-27T16:53:01Z

+
+### Dispatch and sizing behavior
+
+Installed size is first inferred from:


Suggested change

Installed size is first inferred from:

Installed size is first calculated as:

johnjasa · 2026-07-27T16:54:34Z

+The model forms:
+
+$$
+\text{total\_specific\_energy} = nominal\_heat\_required + nominal\_electricity\_required


Specific energy has certain meaning in some contexts, like energy per mass (energy density). Is that the expected meaning here? If not, I'd suggest a different phrase, like total_energy_required or similar for clarity.

johnjasa · 2026-07-27T16:55:29Z

+Available heat is used first up to the requested `heat_demand`. The remaining required energy is supplied electrically when possible. Hydrogen production is then limited by the combined energy available and by the turndown threshold.
+
+```{note}
+The current implementation is intentionally simple and should be interpreted as a reduced-order plant representation, not a detailed SOEC stack model with thermal transients, degradation coupling, startup dynamics, or detailed balance-of-plant behavior.


For those unfamiliar with SOEC, could you please define it somewhere on this page? It's used here and in one diagram

johnjasa · 2026-07-27T16:55:49Z

+
+## Cost Model
+
+Use this model by setting:


Suggested change

Use this model by setting:

To use this model, in your `tech_config.yaml` file, set:

johnjasa · 2026-07-27T17:03:10Z

+
+        heat_available_kw = inputs["heat_in"]
+        electricity_available_kw = inputs["electricity_in"]
+        # hydrogen_demand = inputs["hydrogen_command_value"]


Suggested change

# hydrogen_demand = inputs["hydrogen_command_value"]

johnjasa · 2026-07-27T17:04:06Z

+        # heat_demand_kw = hydrogen_out * self.config.nominal_heat_required
+        # electricity_demand_kw = hydrogen_out * total_specific_energy - actual_heat_kw
+        # electricity_demand_kw = np.minimum(electricity_demand_kw, electricity_available_kw)
+        outputs["electricity_consumed"] = electricity_demand_kw
+        outputs["hydrogen_out"] = hydrogen_produced
+        # outputs["heat_demand"] = np.minimum(rated_hydrogen_production,
+        # inputs["hydrogen_command_value"]) * self.config.nominal_heat_required


Remove commented out code?

johnjasa · 2026-07-27T17:05:02Z

+        hydrogen_produced = np.where(hydrogen_produced >= min_turn_down, hydrogen_produced, 0.0)
+
+        # Density of liquid water at 20°C (293.15 K) and 1 atm (101325 Pa)
+        PropsSI("D", "T", 293.15, "P", 101325, "Water")


Remove this line?

johnjasa · 2026-07-27T17:09:52Z

+        self.add_output("high_pressure_heat_demanded", val=0.0, shape=self.n_timesteps, units="kW")
+        self.add_output("high_pressure_heat", val=0.0, shape=self.n_timesteps, units="kW")
+        self.add_output("low_pressure_heat", val=0.0, shape=self.n_timesteps, units="kW")
+        self.add_output("heat_out", val=0.0, shape=self.n_timesteps, units="kW")


If you change these units to "MW" we can directly output the arrays instead of manually converting from kW to MW below. I'll note it there too.

johnjasa · 2026-07-27T17:10:56Z

+        high_pressure_heat_kw = np.full(self.n_timesteps, available_process_heat_mw * 1000.0)
+        low_pressure_heat_kw = low_pressure_heat_remaining_mw * 1000.0
+        electricity_out_kw = electricity_out_mw * 1000.0
+        heat_out_kw = heat_out_mw * 1000.0


Can remove these manual conversions between kW and MW with the change noted above; OpenMDAO handles the units conversion.

johnjasa · 2026-07-27T17:54:37Z

Oh, and I'd suggest @jaredthomas68 to add a high-res version of this figure you have in the Q3 presentation slides to the docs; it's nice!

vijay092

Very nice addition, @jaredthomas68! I only looked at nuclear_plant_thermal.py and left some line level comments.

vijay092 · 2026-07-28T18:43:24Z

+
+    operating_mode: str = field(validator=contains(["heat", "electricity"]))
+    electricity_command_value: float = field(validator=gt_zero)
+    high_pressure_electrical_efficiency: float = field(validator=gt_zero)


Do we need a <= 1 condition here?

vijay092 · 2026-07-28T19:20:09Z

+
+        delivered_electricity_kwh = np.sum(inputs["electricity_out"]) * (self.dt / 3600.0)
+        annual_variable_om = variable_om_per_kwh * delivered_electricity_kwh
+        outputs["VarOpEx"] = np.full(self.plant_life, annual_variable_om)


I'm wondering if like the performance model, we need to use the fraction of the year simulated?

vijay092 · 2026-07-28T19:30:22Z

+            "rated_capacity",
+            val=self.config.rated_capacity,
+            units=self.commodity_rate_units,
+            desc="Available reactor thermal capacity",


Is this the electrical capacity or thermal?

vijay092 · 2026-07-28T20:13:51Z

+                available_process_heat_mw
+                - (electricity_out_mw - high_pressure_electricity_mw) / lp_eff
+            )
+            heat_out_mw = np.clip(heat_out_mw, 0.0, available_process_heat_mw)


Do we need to use minimum_heat_extract in electricity mode?

Daniel Mark Mikkelson and others added 30 commits April 14, 2026 10:58

New updates to the nuclear thermal plant model

425d958

Updates including test location, but test is not ready to be run yet

3d0af8e

Updates with separate nuclear, HTSE, definitions but intending to hav…

902d1ee

…e a unified example

May 12 update to nuclear and HTSE new models

6c8dd2a

Updates to the nuclear-htse system with the new configuration startin…

3831202

…g to function

A couple more adjustments that should allow for the HTSE unit to demo…

5d148ee

… how it uses electricity when heat is not available.

merge in nuclear+htse branch

13f00c2

update for current h2i develop

7df8f82

merge in develop

9978339

Merge pull request #2 from jaredthomas68/nuchtse-develop

fee9c51

Nuchtse develop

Merge branch 'nuchtse-develop' into nuchtse

6c4bd73

Merge pull request #3 from jaredthomas68/nuchtse

e123155

Nuchtse

working example, LCOH too low

8c0d981

general connection splitting

89c72e6

resolve conflicts

bcbbab0

remove split indices work

520ff99

get example working with constant sell price

aee36a3

add tests for nuclear/htse example

e254417

updates to work with new changes to H2I

d3bdb24

Merge pull request #5 from jaredthomas68/nucdev

a10669f

Nucdev

add test

d357dca

Merge branch 'develop' into nucdev

5b7b812

Merge pull request NatLabRockies#6 from jaredthomas68/nucdev

6d6011a

add test

resolve merge conflict

cd7ec70

update naming and units

8bdbbe3

Merge branch 'develop' into nucdev

bba9f26

merge nucdev and resolve conflicts

183b45e

update test value since the original test value came from running an …

0082741

…optimization and we need a single analysis test value in this case

resolve merge conflict

f6829b4

Merge pull request NatLabRockies#7 from jaredthomas68/nucdev

4c5f108

update naming and units

jaredthomas68 added 5 commits July 20, 2026 17:44

update changelog and minor updates

1247935

update class hierarchy

fbe572b

minor doc corrections

799f3aa

cleanup

c425b65

finish example rename

4c5283d

jaredthomas68 requested review from bayc and johnjasa July 21, 2026 15:20

jaredthomas68 mentioned this pull request Jul 21, 2026

Nuc-HTSE-Integration #761

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52 tasks

jaredthomas68 requested a review from vijay092 July 21, 2026 15:47

johnjasa requested a review from elenya-grant July 23, 2026 17:49

bayc approved these changes Jul 24, 2026

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jaredthomas68 added 8 commits July 24, 2026 13:20

merge from develop

b9ae46c

update docs and figs based on PR feedback

3147f2a

remove API details from nuclear and htse doc pages and replace with l…

ef4a7c1

…inks to autogenerated doc pages

correct rate units from galUS to galUS/h

1751b8d

update htse electricity produced test value

580ebdb

update pipe units for water from galUS to galUS/h

e1e52a2

update changelog

a330d0c

update water rate units and update changelog

79f3421

jaredthomas68 requested review from johnjasa and removed request for johnjasa July 24, 2026 21:17

merge from develop

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jaredthomas68 requested review from johnjasa and removed request for johnjasa July 27, 2026 14:33

johnjasa requested changes Jul 27, 2026

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jaredthomas68 added 2 commits July 28, 2026 07:20

resolve conflict

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resolve conflict

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vijay092 approved these changes Jul 28, 2026

View reviewed changes

	Use this model by setting:
	To use this model, within your `tech_config.yaml` file set:


		### Dispatch and sizing behavior

		Installed size is first inferred from:

	Installed size is first inferred from:
	Installed size is first calculated as:

	Use this model by setting:
	To use this model, in your `tech_config.yaml` file, set:

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jaredthomas68 commented Jul 20, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Nuclear with thermal connection with HTSE

Section 1: Type of Contribution

Section 2: Draft PR Checklist

TODO:

Type of Reviewer Feedback Requested (on Draft PR)

Section 3: General PR Checklist

Section 4: Related Issues

Section 5: Impacted Areas of the Software

Section 5.1: New Files

Section 5.2: Modified Files

Section 6: Additional Supporting Information

Section 7: Test Results, if applicable

Section 8 (Optional): New Model Checklist

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jaredthomas68 commented Jul 20, 2026 •

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