ML20002C974
| ML20002C974 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 06/15/1964 |
| From: | Boyd R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML20002C973 | List: |
| References | |
| NUDOCS 8101150509 | |
| Download: ML20002C974 (7) | |
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HAZARDS ANALYSIS bf THE RESEARCH AND POWER REACTOR SAFETY RRANCH DIVIFJCN OF REA TOR LICE;3ING e
IN THE MATTER OF CONSUMERS POWER COMPANY BIG ROCK POINT PROPOSED CHANGE NO.1 - NATURAL CIRCULATION FLOW TESTS Introduction Consumers Power Company, pursuant to 10 CFR 50 59, requested by letter dated March 26, 1964, authorization of " Proposed Change No. 3 to the
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Technical Specifications for the Big Rock Point Nuclear Plant." The pro-posal identified 47 separate items which are currently being evaluated.
Two of the items, Item 13 and Item 46, request changes to permit operation of the regetor with " natural circulation flow" instead of a minimum flow of 6 x 10 lbs/hr. This change, designated Proposed Change No. 1 to the Technical Specifications appended to License No. DPR-6, dated May 1, 1964, relates only to Item 13 and Item 46.
Supplemental information regarding the natural circulation tests was provided by letter dated May 21, 1964, and by 'IWX dated May 29, 1964.
Scope of Natural Circulation Tests Consumers has proposed to add a new Section 8.2.4 to the Technical Specifi-cations to describe and define the Phase II R&D Program natural circulation tests to be performed. This section pertains only to the 84-bundle core.
Natural circulation tests with 44 assemblies could be performed, in our
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opinion, only after an evaluation of 84 assembly natural circulation test
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results and new minimum permissible natural circulation " Flow vs. Power" data have been submitted for further evalu' tion by the Division of Reactor Licensing. Section 8.2.4 of the Technical Specifications proposed by Consumers as modified by the Staff to incorporate a requirement that such tests shall be performed prior to September 1, 1964 reads as follows:
"8.2.4 Natural Circulation Tests
- During Phase II of the R&D Program, selected tests may be conducted under conditions of natural circulation.
These tests may be performed with the 84-bundle core loading and within the range of variable as specified in Section 8.2.1.
In all cases, any mode of natural circulation operation shall have been shown analytically to be within the following limits for the specific flow rate applicable to the given operating conditions.
In addition, as established during Phase I tests, tasting will be performed at increasing increments of perser to comparc analytical calculations with actual conditions.
Such tests shall be performed prior to September 1,1964.
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. 8.2.4.l(a) Operatire Limits Minimum Overpower Burnout Ratio 1.5 2
Maximum Heat Flux at Overpower, Btu /Hr-Ft 530,000 2
Msximum Steady State Heat Flux, Etu/Hr-Ft h34,000 Maximum Fuel Ecd Power at Overpower, Kv/Ft 17.2 Maximum Steady State Fuel Rod Power, Kv/Ft 14.2.
Stability Critericn: Maximum Zero-to-Peak Flux Amplitude, Percent of Average Operating Flux 20 M1ximum Steady State Power Level, Mut That Permitted By Other Operating Limits
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Maximum Reactor Pressure During Power Operation, psig 1485 (b) Power vs. Minimum Permissible Natural Circulation Flow to assure that the minimum burnout ratio is 1.5 or greater for 84 Fuel Assembly Core.
Pcwer Minimum Flow Permitted Predicted Flow MW (t) lbs/Hr x 10-6 lbs/Hr x 10 6 90 1.7 h.2 110 2.3 4.4 130 32 4.6 156 5.O**
4.8 (c) The maximum operating level vill be that which corresponds to 100% where the calculated limiting conditions are considered as 122% overpower.
(d ) Set Point changes in plant instrumentation are essentially only the picoa=.eter set points which will be ad, justed to be compatible with the new operating power level dictated by any of the above operating limitations.
8.2.k.2 General Procedurt.
Phace II natural circulation tests vill begin from a normal forced circulation mode in the following general steps:
a.
Trip both recirculation pumps from en. initial steady operating condition, not to exceed 157 Mwt.
Eaximum permissible natural circulation flow for stable operation (no cscillations ) is greater than 5.6 x 10D lbs/hr at 155 MW(t).
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. b'.
After power coast-down has settled out, increase power in approximately 20 Mwt steps, while measuring power level, flow rate and flux noise amplitude to confirm observance of.specified_ operating limits.
- c..At selected operating points, perform Phase II tests such as rod oscillator tests.
d.
Upon termination of natural circulation tests, restore forced circulation mode after reducing power level to that obtained in Step b.
above after tripping pumps."
Evaluation i
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Additional detailed analyses have been performed recently for the specific 84-bundle core configuration to be operated for the initial Phase II tests.
his core includes 18 developmental assemblies and tne selective use of B4C poison rods in 12 of these assemblies. The following thermal-hydraulic and 4 - stability data have been calculated for this core over the. natural circulation test operating range.
The limiting case based on the steady state burnout ratio limit of 1 5 is presented below.
Reactor hermal Power at Overpower, Mut 190 Reactor Pressure, Psia 1,250 2
305,000 Maximum Overpower Heat Flux, Btu /Hr-Ft Minimum Overpower Burnout Ratio 1 51 Fuel Rod Power at Overpower, Kv/Ft 9.95 Inlet subcooling, Btu /Lb 38.6 Average Inlet Velocity, Ft/See 1.75 MaximumInletVelocity,Ft/Sec 1.82 g
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Stability Phase Margin at Overpower, Degrees 55.6 6
Recirculation Flow Rate, Lb/Hr 5.0 x 10 he analytical method employed incorporates significant inherent conservatism and power distributions assumed are adequate for the period of predicted core operation up to September 1964 Since the power shaping in the reactor is dependent on fuel depletion, further calculations would be required to properly evaluate natural circulation tests beyond that date.
The burnout ratio increases during natural circulation as power decreases,
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thou6h the recirculation flow also decreases. To illustrate this, examples of three calculated power levels sre listed below, including the limiting overpower case of 190 MW(t).
Power MW(t)
Flov - Lb/Hr Min B.O.R.
177 4.9 x 106 1.89 190 5.0 x 106 1,51 6
206 5.1 x 10 1.29 t
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L-The stability of the 84-bundle core was evaluated for two cases, i.e.,
that correspending to the burncut limiting overpower case of 190 Mwt,1250 psia, and its corresponding nominal operating power of 156 Mwt.
The results are presented as frequency vs. phase and magnitude curves in Censumer's applica-tion.
Power Level Gain Margin Phase Margin 190 Mwt 10.6 Db 55.6 Deg 156 Ibt 10.9 Db 59.8 Deg Esth operating points demonstrate a substantial margin above instability and
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indicate little sensitivity to changes in operating power levels.
The thermal hydraulic analyses are based on methods developed by General Electric Company and have been verified in the operation of many natural and forced circulation reactor systems.
The stabiJity studies are based on methods develored as part of the Consumers R&D Program and reported in the topical and quarterly reports of that program. (1) 1-hase II tests which involve natural circulation vill begin from a normal forced circulation mode and follcw these general steps:
1.
Trip both recirculation pumps from an initial steady operating condition of 157 Mwt.
2.
Power coast down vill settle out at about 90 Mwt, while flow will dro.p to about L.1 million pounds per hour.
This condition c
is far from limiting with respect to any conceivable operating i
limit.
3 Power will be increased in approximately 20 Mwt steps, while measuring the power level, flow rate, and flux noise amplitude to confirm continued observance of specified operating limits before proceeding to next higher power.
4.
At selected operating points, Phase II tests such as rod oscillator tests will be performed.
5 On termination of the tests, the forced circulation mode wil] be restored from a reduced power level.
ibe application shows a curve for a typical case where both recirculation pu=ps are tripped.
The case is the nominal 1250 psia, 157 Mwt initial power situation referred to in the preceding procedure.
Shown on the graph are the time responses (2 ) GLAP-379) - " Consumers Big Rock Point Nuclear Power Reactor Stability Analysis" by J. M. Case and L. K. Holland.
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t of heat flux, recircalation flev rate, and minimum burnout ratio.
These data refleet substantial information gained during the Phace I tests where pump trips were performed from various initial operating levels and therefore reflect a high confidence level in their adequacy.
We have evaluated Consumer's analyses of the hazards associated with the proposed creration of the reactor on natural circulation and agree with its conclusion with respect thereto as set forth below:
1.
Maximu= Credible Accident - The maximum credible accident analysis (MCOA) ic based en an initial power level of 240 Mwt and an initial prescure level of 1500 psia. Since the proposed operation vill be at 157 Mwt and 1250 psia, the effects of the MCOA from that operating
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condition are less severe than the effects for the case analyzed and reported previously.
2.
Accidental Pump Start Accident - Starting a recirculation pump during natural circulation vill be prohibited by test procedures.
Nevertheless, it has been determined that accidentally starting a pump, causing reduced steam voids, lower reactor temperature and consequent rapid reactivity insertion is less severe than the lOOoF cold water accident analyzed for forced convection.
3 Reactivity Insertion Accident. Because of progranmed overpower protection and the more negative void coefficient, the reactor over-power resulting from the maximum rate of reactivity insertion vill le limited to values less than for normal operating conditions.
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Plant Transient Performance - The most important parameters which
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influence plant transient performance are the void reactivity feed-back coefficient and the inherent pressure rate folicving a sharp steam chutoff.
The void coefficient was estimated to be slightly higher than the case studied for 240 Mut operation. However, the precsure rate of the plant for this proposed operating condition is about 37% less than the pressure rate for the 2LO Mwt case due to the lower steam flow rate in the proposed condition (610,000 vs 972,000 lb/hr).
The resultant transient reactor responses expecte from the various turbine trips and load rejections are less than those determined and reported for normal operation.
Technical Specifications To provide authorizatien of Proposed Change No.1, Sections 5 3.l(b) and 8.2.1 of the Technical Specifications of License DPR 6 should be amended as follovc:
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'"5 3.l(b)
Eeactor Operation; change the minimum recirculation flow rate specification to the following:
Minimum Eecirculation Flow Eate, Lb/Hr (Except during pump trip-tests or natural circulation testo as out-D lined in Section 8)-
6 x 10 "
"8.2.1 Core Performance and Transient Tests; change the specifica-tion on recirculation flow rate as follows:
Variable
. Range Recirculation Flow Rate Natural Circulation to
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Full 2 Pump Flow" 8.2.k Natural Circulation Tests as proposed by Consume _s Power and quoted earlier in this hazards analysis should be 4
j added to the Technical Specifications of License DPR 6.
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Summary The following is a summary of T,he considerations regarding the natural circulation flow tests-at the Big Rock Point nuclear plant:
4 1.
Predicted natural circulation flows in the test range are above the minimum flows where the burnout is 1.0, and below the values where reactor instabilities could be expected.
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- 2. 'The operational restrictions on flow and the protection afforded
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by the reactor overpower scram circuit minimize fuel rod failure possibilities.
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The analytical methods used'to predict flow during natural circulation have been verified at low power levels by comparing flow predictions to flow measurenents obtained during Phase I pump trip tests, k.
Tests will be performed at steady state conditions.
(No Trancient Tests durin6 natural circulation except for oscillator tests which cause only minor perturbations. )
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The power distributions assumed in the core performance calcula-tions relatinB to the proposed tests are adequate for the period 1
i of predicted core operation up to September 1, 1964 i
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T-Cinclusion Cu the basic of the foregoing considerations, we have concluded that Proposed Change No.1 does not precent significant hazards considerations not described or implicit in the hazards summsry report and that there is reasonable e_asurance that the health and safety of the public will not be endangered.
Accordingly, we believe the Technical Specifications of License No. DPE-6 chould be revised as indicated herein to allow the conduct of natural circulation flow tests at the Big Rock Point plant, as proposed, for the time period not exceeding September 1,1964.
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O Ecger.
yd, Cr. f Research and Pdher Reactor Safety Eranch Division of Reactor Licensing Date: June 15, 196L
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