Whose measurements these are
B. E. Prince, J. R. Engel, S. J. Ball, P. N. Haubenreich and T. W. Kerlin set down what the reactor did at zero power.
They wrote at Oak Ridge National Laboratory for the U.S. Atomic Energy Commission, and their report of February 1968 gives the fuel pump’s speed and the rod’s position through a start-up and a coast-down. B. E. Prince’s memorandum of October 1966 gives the residence times round the loop.
- The authors
- B. E. Prince, J. R. Engel, S. J. Ball, P. N. Haubenreich and T. W. Kerlin
- Written for
- Oak Ridge National Laboratory, for the U.S. Atomic Energy Commission
- The report
- Zero-Power Physics Experiments on the Molten-Salt Reactor Experiment. Report ORNL-4233, February 1968.
- The loop
- B. E. Prince, Period Measurements on the Molten Salt Reactor Experiment During Fuel Circulation: Theory and Experiment. ORNL-TM-1626, October 1966.
What happened
When the fuel pump starts, the salt carries the sources of some delayed neutrons out of the core, and the control rods must make up the difference.
The salt took 25.2 seconds to go round the loop. With the pump at full speed the reactor lost a measured 0.212 percent in reactivity, and rod 1 moved to supply it.
How do you hold a reactor critical when part of its fuel is always on the way somewhere else? In the MSRE the answer was a control rod, and the rod’s position over time is the record.
The report gives the pump’s speed and rod 1’s position through a start-up from rest and a coast-down from full speed. This page is about a model fitted on the start-up and compared with the coast-down not in the fit.
None of the report’s measured values is stored in the model. They are the record it is held to.
What the model did
Fitted on the start-up and compared with the coast-down not in the fit, the model follows the rods within 6.5 pcm RMS.
The model computes the reactivity the control rods supply above their static critical position: six groups of delayed-neutron precursors carried round the 25.2-second loop in 252 parcels of salt, born and weighted by one axial sine of flux and importance, the fuel flow lagging the pump, rod 1 no faster than its drive, and a ledger for each group closed at every step.
It is fitted on the ORNL-4233 record with two constants: the flux shape’s height, 91.6 inches, on the measured steady loss of 0.212 percent, and the fuel-flow lag, 2.05 seconds, on the 48 start-up rod readings. The drive’s 0.526 inches a second is read from rod 1’s own position, not fitted.
On the 73 coast-down readings not in the fit it is within 6.5 pcm RMS, mean +2.3, largest 19.7. On the 48 start-up readings it was fitted on, 23.9 pcm RMS, and the steady loss comes out at 0.2120 percent against the measured 0.212 ± 0.004.
Its gap is the start-up after the rod’s peak: the precursor wave round the loop runs large, 53.9 pcm high at 17.1 seconds. With the constants read from the sources alone, the same equations give a steady loss of 0.2546 percent.
Asked for the pump brought from rest to full speed in one second and run on, it gives the rods supplying 0.2201 percent dk/k at 70 seconds. The run comes back with the proof 4188773d…e7f541, 96 characters of SHA-384, and the signature of the verifier’s answer key.
A dataset of 45 sealed runs of this model, made on engine 0.15.0, is on Hugging Face.
Comparedwith measurement
73 readings not in the fit, RMS6.5 pcm
The largest of them19.7 pcm
Where it stops
Compared on one start-up and one coast-down. Past that it keeps going and flags every step. It refuses a pump speed outside zero to full.
In the verifier’s own words: “Past what a model was compared with, it keeps going with the same equations and flags every step. It stops only at a physical limit, or where its equations, constants or tables no longer hold, and it names the reason.”
What it was compared on
- One start-up from the pump stopped and one coast-down from full speed, 0 to 70 seconds.
- The pump speed rising no faster than 1.3 and falling no faster than 0.81 of full speed a second.
- Zero power: the reactivity the rods supply, read against rod 1’s recorded position.
Past that, and what its own description says of itself
- Any pump speed from 0 to 1 of full speed at any time, with the same equations; each step outside the compared runs is flagged
FLAG_OUTSIDE_COMPARED_RUNS. - It refuses a pump speed or a fuel flow below 0 or above full speed (
FlowOutsideCard). - With the constants read from the sources alone and nothing fitted, the steady loss reads 0.2546 percent against the measured 0.212.
For the reader who wants every number
In the verifier’s own words.
Everything above is this page’s telling. What follows is the verifier’s own, exact and whole: the spec sheet of the model energy/reactor_msre_pump as version 0.15.0 serves it in its description, in its six parts, with its word for how it stands against measurement: compared with measurement. The verifier’s current description is the one to trust. Where it says card it means a model, and where it says refuses it names the reason a run stops.
What it computes
Reactivity the control rods of the Molten-Salt Reactor Experiment supply above their static critical position at zero power while the fuel pump starts or coasts down: six delayed-neutron groups carried round the 25.2 s loop in 252 parcels of salt, born and weighted by one axial sine of flux and importance, the fuel flow lagging the pump, rod 1 no faster than its drive, and a per-group ledger closed at every step.
Range
Range: compared on one start-up from the pump stopped and one coast-down from full speed, 0 to 70 s, the pump speed rising no faster than 1.3 and falling no faster than 0.81 of full speed a second; computes any pump speed from 0 to 1 of full speed at any time with the same equations, each step outside the compared runs flagged FLAG_OUTSIDE_COMPARED_RUNS.
Fitted on
Fitted on the ORNL-4233 record, all of it read when the form was chosen: two constants, the flux shape’s height, 91.6 in, on the measured steady circulation loss of 0.212 % dk/k, and the fuel-flow lag, 2.05 s, on the 48 start-up rod readings of Fig. 24; the drive’s 0.526 in/s is read from rod 1’s own position, not fitted.
Compared with
Compared with the 73 coast-down rod readings of Fig. 24, not in the fit: within 6.5 pcm RMS, mean +2.3, largest 19.7; on the 48 start-up readings fitted on, 23.9 pcm RMS, and the steady loss 0.2120 % dk/k against 0.212 +- 0.004.
Gap
Gap: after the rod’s peak the card’s precursor wave round the loop runs large, 53.9 pcm high at 17.1 s; with the constants read from the sources alone the same equations give 0.2546 % dk/k, 72.4 and 36.7 pcm.
Refuses
Refuses a pump speed or a fuel flow below 0 or above full speed (FlowOutsideCard).
Hand this one to your agent.
https://mcp.zerotrustphysics.com/mcp
Something to paste
Connect to https://
Give it this page too.
What it will find
This model’s spec sheet: what it computes, its range, what it was fitted on, what it was compared with and how close it came, its gap and what it refuses.