ML062850511

Us Dept of Commerce, Revision to FSAR Submitted in April 2004

ML062850511
Person / Time
Site:	National Bureau of Standards Reactor
Issue date:	10/02/2006
From:	Richards W US Dept of Commerce, National Institute of Standards & Technology (NIST)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML062850511 (9)

Text

UNITED STATES DEPARTMENT OF COMMERCE National Institute of Standards and Technology Gaithersburg, Maryland 20899-U.S. Nuclear Regulatory Commission October 2, 2006 Attention: Document Control Room Washington D.C. 20555

Subject:

Revision to FSAR Submitted in April 2004.

Docket No. 50-184 Gentlemen, Please replace Chapter 13, section 13.2.2.2.2 with the attached information.

The figure and table numbers will be modified when the final revisions are made. Please direct any questions concerning this issue to Dr. Wade J.

Richards @ (301)-975-6260 or wade.richards@nist.gov.

Sincerely, Wade J. g*chards Chief Reactor Operations and Engineering I certify under penalty of perjury that the foregoing is true and correct.

Executed on z ,!ic7#o-,. by ___ _

cc. Mr. Marvin Mendonca NBSR Project Manager U.S. Nuclear Regulatory Commission Washington D.C. 20555 X5-3 N LST

13.2.2.2.2 Rapid Removal on an Experiment A reactivity insertion accident has been analyzed using RELAP5 MOD3.3 and MATLAB [1]. For conservatism, no thermal-hydraulic feedback has been taken into account. A ramp reactivity insertion of 0.005AA was assumed to occur in 0.5 s, resulting in a total insertion of $0.66. Since the RELAP5 MOD3.3 point kinetics model was found to incorrectly predict the power excursion during the transient, the point kinetics equations were solved using MATLAB, and the resulting power table was input into RELAP5.

The transient reactor powers for beginning-of-cycle (BOC) and end-of-cycle (EOC) conditions are plotted in Figure 1.

35- --

- BOC 30- -EOC 25 Z20 1..

115-10 5

0 0 0.2 0.4 0.6 0.8 Time (s)

Figure 1 - Transient power as calculated with MATLAB

In both cases, the power exceeds the reactor trip setpoint (130% or 26 MW) at 267 ms, and the shim arms start inserting into the core at 366 ms. At this point, since the initial shim arm positions are different for BOC and EOC, the BOC and EOC powers begin to differ. For BOC conditions, power reaches a peak of 31.6 MW at 392 ms, whereas for EOC the peak is delayed and somewhat higher, 33.3 IvIW at 437 ms. This results in total excursion energies above 20 MW of 2.20 MJ for BOC and 3.01 MJ for EOC.

Figure 2 shows the shim arm reactivity for each initial condition. Note that for BOC the shim arms are initially partially inserted whereas they are completely withdrawn for EOC. Since the reactivity insertion rate is higher when the shim arms move from intermediate positions, the post-scram reactivity decreases more rapidly for BOC, resulting, as previously shown, in an earlier and lower power peak.

Initial BOC Initial EOC shim arm oosit 0

5 10 15 35 40

-5

-10 S-15

>-20

-25 insertion -extraction

-30

-35 -[BO]

L*OC

-40 Arm positon (*)

Figure 2 - Shim arm reactivity vs. position To ensure the fuel plates will not be damaged during the accident, the ratio of critical heat flux to local heat flux at their surface (CHFR) is monitored and shown in Figure 3 for the hottest node of the fuel plates both in the inner and the outer parts of the core. The minimum transient CHFR is 1.74 for BOC and 2.01 for EOC, well above 1.538, the value that corresponds to a 99.9% probability that there is no overheating in any subregion of the core.

Table 1 summarizes of the main results presented in this report, and Tables 2 and 3 show detailed results for BOC and EOC respectively.

Table 1 - Summary of results BOC EOC Peak Power (MW) 31.6 33.3 Time of Peak (ms) 392 437 Excursion Energy 2.20 3.01 above 20 MW (MJ)

Minimum CHFR 1.74 2.01 5

4.5 4

I 3.5 03 2.5 2

1.5 0 0.1 0.2 0.3 0.4 0.5 Time (s)

Figure 3 - CHFR inner and outer core

Table 2 - Reactor Response to Ramp Reactivity Insertion Equilibrium Core - Beginning of Cycle CHFR Excursion Time Power CHFR Outer core energy (s) (MW) Inner core (MJ) 0.00 20.0 4.09 2.73 0.00 0.01 20.0 4.09 2.73 0.00 0.02 20.1 4.09 2.73 0.00 0.04 20.2 4.08 2.72 0.00 0.06 20.5 4.06 2.71 0.01 0.08 20.8 4.03 2.69 0.02 0.10 21.1 3.99 2.66 0.04 0.12 21.5 3.93 2.63 0.07 0.14 22.0 3.87 2.59 0.10 0.16 22.5 3.80 2.55 0.15 0.18 23.1 3.72 2.49 0.21 0.20 23.7 3.64 2.44 0.27 0.22 24.3 3.55 2.38 0.35 0.24 25.0 3.46 2.31 0.45 0.26 25.8 3.36 2.24 0.56 0.28 26.6 3.27 2.17 0.68 0.30 27.4 3.17 2.10 0.82 0.32 28.3 3.07 2.03 0.98 0.34 29.3 2.97 1.96 1.16

0.36 30.3 2.87 1.89 1.35 0.38 31.3 2.78 1.81 1.57 0.40 31.5 2.69 1.75 1.80 0.42 29.6 2.67 1.74 2.01 0.44 25.2 2.77 1.82 2.16 0.46 19.0 3.04 2.04 2.20 0.48 12.5 3.58 2.40 2.20 0.50 7.4 4.48 2.90 2.20 0.52 3.9 5.87 3.65 2.20 0.54 2.5 7.82 4.65 2.20 0.56 1.8 10.36 5.90 2.20 0.58 1.4 13.62 7.43 2.20 0.60 1.2 17.73 9.26 2.20 Initial reactor power = 20 MW (equilibrium core - BOC)

Reactivity insertion rate = 0.5% Ak in 0.5 s Initial shim arm position = 190 Power scram initiated at 26 MW.

Table 3 - Reactor Response to Ramp Reactivity Insertion Equilibrium Core - End of Cycle Excursion Time Power CHFR CHFR energy Inner core Outer core (s) (MW)

(MJ) 0.00 20.00 4.53 3.32 0.00 0.01 20.01 4.53 3.32 0.00 0.02 20.06 4.53 3.32 0.00 0.04 20.21 4.52 3.32 0.00 0.06 20.45 4.50 3.30 0.00 0.08 20.75 4.46 3.28 0.00 0.10 21.11 4.41 3.25 0.02 0.12 21.53 4.35 3.21 0.03 0.14 21.99 4.28 3.16 0.06 0.16 22.50 4.21 3.11 0.10 0.18 23.05 4.12 3.05 0.15 0.20 23.65 4.03 2.98 0.21 0.22 24.29 3.94 2.91 0.28 0.24 24.98 3.84 2.84 0.36 0.26 25.71 3.74 2.77 0.46 0.28 26.50 3.63 2.69 0.58 0.30 27.34 3.53 2.62 0.71 0.32 28.23 3.42 2.54 0.86 0.34 29.19 3.31 2.46 1.02 0.36 30.21 3.20 2.37 1.21 0.38 31.30 3.09 2.28 1.42

0.40 32.30 2.99 2.20 1.65 0.42 33.03 2.89 2.12 1.89 0.44 33.26 2.82 2.05 2.15 0.46 32.78 2.77 2.02 2.40 0.48 31.40 2.78 2.02 2.64 0.50 28.93 2.84 2.07 2.83 0.52 25.23 3.00 2.18 2.96 0.54 20.42 3.28 2.38 3.01 0.56 15.06 3.77 2.69 3.01 0.58 9.99 4.55 3.15 3.01 0.60 6.05 5.74 3.86 3.01 0.62 3.55 7.48 4.87 3.01 0.64 2.19 9.86 6.20 3.01 0.66 1.45 12.93 7.86 3.01 0.68 1.00 16.81 9.85 3.01 0.70 0.70 21.68 12.19 3.01 Initial reactor power = 20 MW (equilibrium core - EOC)

Reactivity insertion rate = 0.5% Ak in 0.5 s Initial shim arm position = 410 Power scram initiated at 26 MW.

References

[1] L. Cheng et al., "Physics and Safety Analysis for the NIST Research Reactor", BNL-NIST-0803, Rev. 1, April 2004