ML20062B252
| ML20062B252 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 10/20/1978 |
| From: | Counsil W, Fee W CONNECTICUT YANKEE ATOMIC POWER CO. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7810260171 | |
| Download: ML20062B252 (8) | |
Text
o t
i CONNECTICUT YANKEE AT O M IC POWER COMPANY 7
BERLIN. CONNECTICUT 4
P. O BOX 270 M A Mf FORD. CON N ECTICUT 04101 i
203 666 6911 l
t October 20, 1978 Docket No. 50-213 Director of Nuclear Reactor Regulation Attn:
Mr. D. L. Ziemann, Chief Operating Reactors Branch #2 U. S. Nuclear Regulatory Commission Washington, D. C.
20555
References:
(1)
W. G. Counsil letter to D. L. Ziemann dated September 22, 1978.
(2)
W. G. Counsil letter to D. L. Ziemann dated September 29, 1978.
Gentlemen:
Haddam Neck Plant Emergency Power Systems In Reference (1), Connecticut Yankee Atomic Power Company (CYAPCO) submitted to the NRC Staff a summary and description of a main steam line break analysis (MSLB) for the Haddam Neck Plant, concluding that charging pump flow is not required for a MSLB for the remainder of the present cycle (Cycle 8).
In Reference (2), CYAPCO proposed changes to the Technical Specifications that assured the validity of the MSLB analysis.
In subsequent phone conversations, the NRC Staff requested that CYAPC0 provide addi-tional information in support of the license amendment request of Reference (2).
Accordingly, CYAPCO hereby submits the attached additional information.
We trust the attached information is sufficient to allow the NRC to affirmatively disposition the above referenced license amendment request.
Very truly yours, CONNECTICUT YANKEE ATOMIC POWER COMPANY W. G. Mounsil Vice President Wf n 4
At tachment W. F. Fee 1
Vice President 0y
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DOCKET NO. 50-213 HADDAM NECK PLANT EMERGENCY POWER SYSTEMS ADDITIONAL INFORMATION OCTOBER, 1978
MAIN STEAMLINE RUPTURE AT 100% POWER I
An analysis was performed at 100% rated power (1825 MWT) to specifically investigate return to criticality for that condition. The previously docketed RELAP4 model was used with appropriate modifications to represent the full power condition.
On the primary side this included changes to the core power level and primary system temperature distributions. The primary mass flow rates and pressure drops were also changed which necessitated re-initialization for steady state.
On the secondary side, the steam generator pressure, temperature and mass inver. tory were changed' to represent full power conditions.
Feedwater flow and steam dump j
were also modeled to account for the increased feedwater flow and steam dump subsequent to turbine trip.
For the condition of coincident loss of offsite power, i
the feedwater pumps were modeled to coastdown to zero flow in 20 seconds.
Minimum control rod worth was used in the analysis which corresponds to Bank B inserted 25% and including the maximum worth stuck rod.
End of cycle moderator and doppler deficits were used as in the zero power case. The temperature dependence on inverse boron worth was conservatively neglected.
I Results are shown on the attached Figure A.
The reactivity transient turns 1
around when the injected boron reaches the core.
These results show adequate margin to return to criticality.
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FIGURE A
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CONTROL RODS gBORON i
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,t TIME (SECONDS)
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ux 1.2 ODE G y 1.0
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ii e 0.2 FIGURE 5 Q. L oo OU OO 20 40 60 80 100 INITI AL POWER LEVEL (%)
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T FIGURE 1 E
rs 560--
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_ _ _ _ _ _ _ _ _r e q u i r e d v.E cy lculated worth ca mu g f 2.0-FIGURE 3 y *.5 i
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20 40 60 80 100 REACTOR POWER %
If1TERNEDIATE POWER For initial power levels less than 100%, the primary plant cooldown due to a steamline break would be larger than at full power and approach that of the zero power case. This is due to the increased mass inventory in the steam generators and decreased stored energy in the primary system.
Review of these mechanisms and the operating constraints of the plant at less than full power indicates the behavior is monotonic with power.
This is justified since the dominating mechanism is steam generator inventory which is approximately a linear function of power.
Feedwater response at lower power also becomes more favorable due to the control system characteristics. Offsetting the increased cooldown for accidents originating at less than full power is the reduced effect of the reactivity coefficients at the lower tenrerature. The core average coolant temperature varies with power level as shown in Figure 2.
The moderator temperature 0
coefficient is most negative at operating temperatures (5550 - 535 ) and becomes much less negative at the lower temperatures.
The doppler coefficient behaves linearly with fuel average temperature which also decreases with decreasing power.
The net effect is that accidents originating from less than full power begin their cooldown at a lower temperature 7d result in less reactivity addition for a given JLT.
To illustrate this effect, the inoderator and doppler deficits have been calculated for various initial power levels 0
0 assuming a core average cooldown of 95 F.
Since this 95 2iT is the core average cooldown at the minimum approach to criticality resulting from a steamline break from hot, zero power, it is larger than that expected for any other initial power level, and thus is conservative. Figures 4 and 5 show that the reactivity deficits become significantly less with decreasing power level.
Sufficient reactivity is available in the control rods to keep the reactor subcritical as shown in Table 1 and figure 3.
The inflection point is due to the worst combination of Bank B insertion and stuck rod worth. The maximum worth stuck rod is a bank A rod, even at 50% bank A insertion. Margins of 1.67% Skand 1.18% Sk have been specificully calculated for the HZP and HFP cases, respectively. A conservative estimate of the cooldown reactivity due to a steamline break from 40% power shows an acceptable margin for the rod configuration providing the least available shutdown worth.
k 4
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TABLE 1 f
r AVAILABLE SCRAM WORTH Power
'(%)
100 81 58 33 26 0
(MWT) 1825 1473 1060 600 470 0
Initial Rod Position B240 B160 890 B20 B0 B0 (Steps Withdrawn)
A320 A320 A320 A250 A230 A160 Total Rod Worth 6.647 6.647 6.647
'6.647 6.647 6.647 (HZP, E0C, ARG) (%&%
Max Stuck Rod
-1.97
-1.97
-1.97
-1.80*
-1.59*
.80 (HZP, E0C) (%i k)
~
Max Allowable Inserted Rod Worth (HZP,E0C)
~
Bank B (%6%)
.201
.489
- 0.706
-0.783
-0.783
.783
-0.315
-0.436
.891 Bank A (%$K)
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Net ~ Sc ram Worth 4.48 4.19 3.97 3.75 3.84 4.17 (HZP, E0C) %1 K Required Worth 3.30 3.06**
2.50 To Remain Subcritical After SLBA With Coincident loss Of Off-Site Power At E0C (% & K )
Margin. (%$K) 1.18 0.69**
1.67
- Conservatively approximated using HZP average temperature
- Interpolated cooldown of 95 F, and doppler and moderator deficits for 40% initial power level