ML20206M482
| ML20206M482 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 08/14/1986 |
| From: | Kingsley O MISSISSIPPI POWER & LIGHT CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| AECM-86-0175, AECM-86-175, NUDOCS 8608210230 | |
| Download: ML20206M482 (26) | |
Text
o,
,y MISSISSIPPI POWER & LIGHT COMPANY Helping Build Mississippi EditikkliddB P. O. B O X 1C4 0, J A C K S O N, MIS SIS SIP PI 39215-1640 August 14, 1986 O. D. KINGSLEY, JR.
VICE PREllDENT NUCLEAR OPERAflONS U. S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D. C.
20555 Attention: Mr. Harold R. Denton, Director
Dear Mr. Denton:
SUBJECT:
Grand Gulf Nuclear Station Unit 1 Docket No. 50-416 License No. NPF-29 File: 0260/17015 NRC Request for Additional Information on Humphrey Containment Concerns AECM-86/0175 The purpose of this letter is to provide additional information per a staff request which was telecopied to Mississippi Power & Light (MP&L) on March 26, 1986 and subsequent telephone discussions on Humphrey Containment concerns.
Attachments 1 through 6 provide responses as requested in the following areas of concern:
o - Humphery Concern 1.3, Additional Submerged Structure Loads o - Humphrey Concern 1.7, Containment Open Area o - Humphrey Concern 2.1, Annular Sleeve Load o - llumphrey Concern 2.2 & 2.3, Annular Sleeve Load o - Humphrey Concern 17, EPG Concern with Upper Pool Dump o - GE " White Paper" on RCIC Turbine Exhaust Sparger Additionally, MP&L previously submitted to the NRC additional information regarding Humphrey's concern on Steam Condensing Mode via AECM-86/0143, dated May 16, 1986.
Should you have any further questions regarding these issues please advise.
Your ly, kNO e
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Attachments cc: (SeeNextPage) 1 J10AECM86060403 - 1 Member Middle South utilities System
AECM-86/0175 Paga 2 n
cc: Mr. T. H. Cloninger (w/a)
Mr. R. B. McGehee (w/a)
Mr. N. S. Reynolds (w/a)
Mr.H.L. Thomas (w/o))
Mr. R. C. Butcher (w/a Mr. James M. Taylor, Director (w/a)
Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Dr.J.NelsonGrace,RegionalAdministrator(w/a) 4 U. S. Nuclear Regulatory Commission i
Region II 101 Marietta St., N. W., Suite 2900
_l Atlanta, Georgia 30323 1
i J10AECM86060403 - 2
, to AECM-86/0175 NRC Comment Regarding Humphrey Concern 1.3-(Action Plan 2)
MP&L stated in AECM-82/574 that for piping and structures below the pool surface, the increased pressure loadings produced as a result of the encroachments are within the faulted stress alloyables. ' Confirm that the requirements of operability and functional capability are met.
Response
The increased loadings on submerged structures produced as a result of the encroachment are within the code allowable limits including functional capability criteria.
f I
l l
1 J13ATTC86080401 - 1 L
. to AECM-86/0175 NRC/BNL Comment Regarding Humphrey Concern 1.7 - (Action Plan 47)
GE suggests that at least 1,500 square feet of open area should be maintained in the HLU ficor.
In order to avoid excessive pressure differentials, at least 1,500 square feet of opening should be maintained at each containment elevation. MP&L should provide a formal reference for the open floor areas in containment.
Response
MP&L has confirmed that the HCU floor and all floors abcve the HCU floor have at least 1,500 square feet of open area. The open areas are as follows:
El. 135'- 4" - 1538 square feet (HCU Floor)
El. 161'-10" - 2236 square feet El. 184'- 6" - 2241 square feet El. 208'-10" - 2268 square feet This exceeds the GE recommendation.
4 h
t a
w J13 Mis 860616031-I w
to AECM-86/0175 NRC/BNL Comment Regarding H_umphrey Concern 2.1 (Action Plan 5)
The approach described does not account for possible resonance between the sleeve annulus condensation oscillation (CO) and sleeve acoustic frequency as suggested by Mr. Humphrey. The potential for resonant amplification of the main vent C0 loads was not addressed.
RESPONSE
The expressed concern was that the methodology used to address this concern (Reference 1) did not account for a possible resonance between the sleeve annulus C0 frequency and the sleeve acoustic frequency.
An alternative approach for estimating the SRVDL sleeve C0 load has been used, which conservatively utilizes Mark I Full Scale Test Facility (FSTF)
C0 data in which significant excitation of the vent acoustic modes was observed (References 2 and 3). This alternative approach shows that C0 occurring in the SRVDL sleeve combined with the main vent C0 gives pressures on the containment wall and drywell wall which are bounded by the pool swell and chugging loads already considered in design.
ANALYSIS There is substantial large scale C0 data available from tests of the Mark I and Mark II vertical vents (downcomers) and the Mark III horizontal vents.
Of these tests, the Mark I FSTF data (Reference 2) has the most evident excitation of vent acoustic modes. Therefore, the FSTF data were used to address the NRC concern regarding resonant amplification of the C0 loads in the SRVDL sleeve.
The Mark I Load Definition Report (LDR) (Reference 3) ir.cludes a conservative definition of harmonic amplitudes for pressure oscillations in the Mark I downcomer during condensation oscillation based on the FSTF data. These pressure oscillations were conservatively assumed to occur at the same anplitude in the Mark III SRVDL sleeve. No amplitude reduction was done to account for the differences in the exit geometry of the Mark I downcomer and the SRVDL sleeve. The Mark I downcomer discharge is a 2 foot diameter pipe while the sleeve has an annulus of approximately one foot diameter with a one inch gap. This small gap is expected to result in smaller amplitude oscillations of the steam-water interface so that the SRVDL sleeve should have much lower amplitude pressure oscillations than the Mark I downcomer. /.lso, no amplitude adjustment has been made to account for differences in flow conditions between tFe FSTF tests and the SRVDL sleeve. The Mark I tests showed that the C0 pressure amplitude increased with the vent enthalpy flow (figure 6.2.2-56 of Reference 2).
The maximum er.thalpy flux for the SRVDL sleeve is approximately the same as the maximum value in the FSTF tests.
J16 ADD / INFO ATT 1 - 1
to AECM-86/0175 The frequency range of the SRVDL sleeve C0 load was determined by multiplying the Mark I LDR specified frequencies by the ratio of the FSTF vent length to the SRVDL sleeve length. This adjustment is based on the assumption that the frequencies are controlled by the acoustic response in the sleeve. The resulting ranges are shown in Table 2.1-1 for Grand Gulf along with the pressure oscillation harmonic amplitudes in the sleeve and on the drywell and containment walls.
a The pressure amplitudes in the sleeve given in Table 2.1-1 are equal to the Mark I LDR values as discussed above. The amplitudes on the drywell wall and containment wall were determined by using a spatial, attenuation equal to one over the distance from the end of the sleeve. The radius of the bubble at the sleeve exit was conservatively assumed to be equal to the radius of the sleeve. Since the annulus gap will act to limit the bubble size, the actual spatial attenuation of the pressures would result in pressures on the walls which are much smaller than the values given in Table 2.1-1.
The SRVDL Sleeve C0 loads given in Table 2.1-1 were compared to the existing design loads on the containment and drywell wall using amplified response spectra (ARS). ARS values for estimated C0 loads for the SRVDL sleeve and the main vent are compared to ARS values for the pool swell and chugging wall loads in Figures 2.1-1 and 2.1-2.
The comparisons are based on the lowest frequency component of the Table 2.1-1 SRVDL sleeve C0 load.
The C0 loads for the two higher frequency components are less significant relative to the pool swell and chugging loads so they are not included in the comparison. This shows that the addition of the estimated SRVDL sleeve C0 load to the main vent C0 load results in a total C0 load which is less than the chugging load on the drywell wall (Figure 2.1-1) and the pool swell load on the containment wall (Figure 2.1-2).
Summary An estimate of the C0 load in the SRVDL sleeve for Grand Gulf has been made I
using Mark I FSTF data (Table 2.1-1) which includes significant excitation of the acoustic modes in the vent upstream of the discharge. This was done to address concerns regarding resonant amplification resulting from I
coupling of the sleeve acoustic frequency and the C0 frequency. The FSTF data has been conservatively applied without any amplitude reduction. The l
amplified response spectra (ARS) cf the resulting SRVDL sleeve C0 load combined with the main vent C0 1 6 is lower than other DBA LOCA design loads (chugging and pool swell), as shown in figures 2.1-1 and 2.1-2.
Therefore, these loads are bounded by current design loads.
REFERENCES 1.
MP&L Letter No. AECM 82/574 dated December 3,1982 from L. F. Dale l
(MP&L) to H. R. Denton (NRC).
l l
2.
" Mark I Containment Program Full-Scale Test Program Final Report",
NEDE-24539-P, April 1979.
3.
" Mark I Containment Program Load Definition Report", NED0-21888,
(
Revision 2, November 1981.
J16 ADD /INF0 ATT 1 - 2 1
. te AECM-86/0175.
.o TABLE 2.1-1 SRVDL SLEEVE C0 LOADS FOR GRAND GULF BASED ON MARK I LDR Pressure Harmonic Amplitude (PSI)
Amplified Response (PSI)
Frequency frequency SRVDL Sleeve Drywell Containment Drywell Containment Component Range (Hz)
Annulus Wall Wall Wall Wall 1
19 to 38 3.6 0.76 0.24 19.0 6.0 2
38 to 76 1.3 0.27 0.09 6.8 2.3 3
57 to 114 0.3 0.06 0.02 1.5 0.5 J16 ADD /INF0 ATT 1 - 2
o to AECM-86/0175 Amplified Response Spectrum j
Cliingg inig i
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i Main Vent CO I
Ill
~ b 10 10 1 102 103 FREQUENCY (HZ)
FIGURE 2.1-1 ARS Comparison on Drywell Wall J16 ADD /INF0 ATT 1 - 3 t
' ' ' to AECM-86/0175 AMPLIFIED RESPONSE SPECTRUM i
I l
1 I
i 12 l
O Pool
~
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d MV + Sleeve CO ll 6
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100 1
10 102 103 FREQUENCY (HZ)
Figure 2.1-2 ARS Comparison on Containment Wall J16 ADD /INF0 ATT 1 - 4
to AECM-86/0175 NRC/BNL COMMENTS REGARDING HUMPHREY CONCERN 2.2 AND 2.3 - SRVDL LOADS (Action Plan 5) a.
Provide a detailed description of the lateral loads during chugging on the SRVDL and SRVDL sleeve, how it is derived and how it is applied to both.the sleeve and the SRVDL. The ability of relevant structures to withstand the loads should be addressed.
b.
The possibility of lateral loads during the C0 phase of blowdown should be addressed.
RESPONSE
a.
The original calculation of the GGNS chugging lateral loads on the SRVDL and SRVDL sleeve were performed using the assumption of a toroidal bubble shape as shown in Reference 2.
Due to questions en the toroidal bubble shape model, this analysis to provide the lateral chugging loads for the SRVDL and sleeve was performed by using Mark II information and scaling to the outer diameter of the SRVDL sleeve.
No credit was taken for the presence of the SRVDL in the bubble, providing an extremely conservative loading. The scaling base is the Mark II chugging lateral load specified in NUREG-808 (Reference 1) and given in Equation (1).
F = 65000 sin (9f t) 0 < t <.003
.003 Where t = time (sec)
F = lateral load (lbf)
This load specification was based on low mass flow, cold pool condition Grosskraftwerke Mannhein (GKM) II test data which the NRC fit as Equation (2).
P(f) = e -F/c,
N1 N2xN3 Where P(f) = exceedence probability of the load F F
= lateral load db
= empirical constant N1
= # of exceedences N2
= # of pool chugs N3
= # of downcomers N2xN3 = total # of individual chugs The Mark II load was based on 100 downcomers. Since there are only 20 SRV's in Grand Gulf, there is expected to be only 1/5 the total number of individual chugs. When the reduced number of chugs is figured into the Mark II load, the peak force reduces from 65,000 lbf to 56,000 lbf.
J16. ADD /INF0 ATT 2 - 1
to AECM-86/0175 The revised Mark II load is scaled from the Mark II 24" vents to the SRVDL sleeve outside diameter of 14".
The scaling is performed using the scaling relation of Equation (3).
h(D11" F1
=
T2 Where F1, F2 = lateral load D1, D2 = pipe diameter m
= empirical factor A compilation'of the 4T statistical average data (Reference 2) results in an exponent of m = 1.7.
Using the exponent with the outer diameter of the sleeve in Equation (3), the peak force decreases to 22.4 kips.
The resultant loading equation is Equation (4).
F = 22,400 sin (M) lbf for 04t<.003
.003 The application lengths have been reduced from the Mark II values (1 to 4 feet from the end of the downcomer) previously specified. The revised application lengths were determined by reducing the Mark II values by the ratio of the SRVDL sleeve diameter to the Mark II downcomer diameter. This scaling approach results in peak pressures on the SRVDL sleeve (determined from the lateral load and application length) which are comparable to those obtained from the reference Mark II lateral load and application length.
The chugging lateral load is distributed uniformly on the SRVDL and the SRVDL sleeve over the application length 0.6 to 2.3 feet. This length is from the end of the SRVDL sleeve in the suppression pool. The chugging loads are applied perpendicular to the axis of the pipe and sleeve and in the direction that is most critical for the member under investigation.
STRUCTURAL ADE0VACY OF THE SRVDL AND THE SLEEVE Dynamic analyses of the SRVDL and sleeves were performed for the above chugging load. The results from the analyses were combined with other applicable static and dynamic loadings, including seismic and LOCA hydrodynamic loads. The resulting stresses were within the code allowable limits and structural loadings were within existing design loads.
Functional capability criteria was met for all required structures.
i J16 ADD /INF0 ATT 2 - 2
c b*_
^
to:AECM-86/0175 4
b.
The SRVDL sleeve Condensation Oscillation (CO) lateral. load was
~
developed by reviewing the downcomer pressure data from the Mark I FSTF tests during the periods of high amplitude CO.
l
~
MARK I DOWNCOMER LATERAL LOADINGS DUE TO C0 The Mark I downcomer includes two locations (see Figure 2.2-1) where unbalanecd forces resulting from pressure oscillations inside the downcomer can produce loadings. -The dynamic load on the Mark I downcomer results from L
the forces determined by the product of the iaternal pressures and the unbalanced area at the downcomer miter joint.
I The Mark I internal pressure design load in the downcomer was obtained by
. evaluating the' pressure data from all downcomers during the three liquid blowdown Design Basis Accident (DBA) tests run in the FSTF (Reference 3).
These tests had the largest C0 loads, and the period of each test showing the highest pressures was used.
Figure 2.2-2 shows the internal pressure _
load and the three frequency bands over which they are applied from the Mark I Load Definition Report (Reference 4).
4 SRVDL SLEEVE C0 LOAD DEVELOPMENT j
For the Grand Gulf SRVDL sleeve configuration, there is an unbalanced area at the discharge end of the sleeve, which may introduce a dynamic lateral loading (See Figure 2.2-3).
Flow conditions and differences in the Mark I.
downcomer and the Grand Gulf Mark III SRDVL sleeve geometries were considered i
in developing the SRVDL sleeve C0 lateral load definition. :The following reviews the development of the SRVDL sleeve C0 lateral load from the Mark I FSTFdatabase(Reference.3).
i The closest (yet conservative) representation of the predicted pressure response in the SRVDL sleeve due to steam flow through the annular region I
was sought in the development of the C0 load. This pressure response is expected to be dominated by acoustic resonances in the SRVDL sleeve. The sleeve can be compared to a close ended pipe with large vent length to diameter ratio. Therefore, for the postulated LOCA conditions a highly j.
tuned acoustic pressure response is assumed to exist in the SRVDL sleeve.
This type of response is expected to have essentially all the energy concentrated within the single frequency band of the fundamental harmonic.
Selection of the Mark I data basis for use in the development of the SRVDL sleeve lateral load relied on the assumed sleeve conditions described above.
With the criterion established above the data basis chosen for the 4
- SRVDL sleeve C0 amplitude vas the Mark I FSTF test and test period which produced the highest RMS C0 internal pressure in a single downcomer. The highest RMS C0 internal downcomer pressures were seen in downcomer #7 during the time period 28-29 seconds in FSTF test M12. This C0 time segment j
contained almost all (~95%) of the pressure oscillation energy within the dominant acoustic natural frequency range of the Mark I vent system. This is shown in Figure 2.2-4 which is a pcwer spectral density (PSD) plot of this J16 ADD /INF0 ATT 2 - 3
I to AECM-86/0175 time period. The PSD gives a measure of the total energy content of a
. forcing function within discrete frequency increments. A single harmonic amplitude was conservatively calculated which included the energy content from all frequencies associated with this pressure time history. The harmonic amplitude is given below.
(T *rms HA
=
1.414* 3.5 psi
=
5 psi
=
The calculated harmonic amplitude from this bounding FSTF test was conservatively assumed to occur at the same amplitude in the Mark III SRVDL sleeve. No amplitude reduction was done to account for the differences in the exit geometry of the Mark I downcomer and the SRVDL sleeve. The Mark I downcomer discharge is a 2 foot diameter pipe while the sleeve has an annulus of approximately one foot diameter with a one inch gap.
This small gap in the SRVDL sleeve is expected to result in smaller amplitude oscillations of the steam-water interface and therefore should produce much lower amplitude pressure oscillations than the Mark I downcomer. Also, no amplitude adjustment was necessary to account for differences in flow conditions between the FSTF tests and the SRVDL sleeve. The Mark I tests showed that the C0 pressure amplitude increased with the vent enthalpy flow (Figure 6.2.2-56 of Reference 3). The maximum enthalpy flux for the SRVDL sleeve is approximately the same as the maximum value in the FSTF tests.
The dominant frequencies observed in the Mark I vent and downcomer were observed to be related to acoustic resonances in the vent /downcomer system.
These acoustic frequencies are dependent on both vent length and fluid bulk modulus (i.e., sonic velocity). Therefore, in establishing frequencies from test data, the fluid content must be considered.
Fluid flow in the FSTF downcomers during the Mark I FSTF test used as the basis for the C0 amplitude included water and steam because this test was simulation of a recirculation line break. However, the fluid flow through the Mark III SRVDL sleeve during the C0 period consists of steam only. These conditions are best represented by the Mark I FSTF tests simulating a steam line break.
Therefore, the frequency range for the dominant harmonic seen during the large steam break FSTS test was chosen as the basis for the SRVDL sleeve frequency specification.
Figure 2.2-5 shows a typical PSD of a downcomer pressure measurement from a FSTF steam break. The increase in the PSD frequencies relative to the CBA frequencies (Figure 2.2-4) is caused by the higher fluid bulk modulus or acoustic speed with steam compared to that with a steam / liquid mixture. An envelope PSD of the C0 pressure measurement during the FSTF steam break tests (Figure 2.2-6) was used in establishing the frequency range to be used as the basis for the SRVDL sleeve C0 pressure. The dominant range of frequencies obtained with this envelope PSD is 6-10 Hz.
J16 ADD /INF0 ATT 2 - 4
to AECM-86/0175 The SRVDL sleeve frequency was then determined from:
ISRVDL Sleeve "#MK 1 DC MK I DC l
LSRVDL Sleeve
- where, MK I DC = C0 dominant frequency for MK I downcomer f
fSRVDL Sleeve = C0 dominant frequency for SRVDL sleeve lateral load L
= FSTF Vent length Mk I DC LSRVDL Sleeve = SRVDL sleeve length The vent length of the FSTF vent /downcomer system is 67 feet. Therefore, frequencies calculated for the Grand Gulf SRVDL sleeve length of 14.1 feet are:
SRVDL (Grand Gulf) Sleeve "4*7
- IMk I DC ISRVDL (Grand Gulf ) =28 to 48 Hz The SRVDL sleeve C0 lateral load frequency was obtained by applying the frequency adjustment described from above to the Mark I downcomer pressure frequency range from the large steam break FSTF tests shown in Figure 2.2-6.
The load amplitude was obtained by multiplying the Mark I downcomer pressure harmonic amplitude values for the large liquid break FSTF tests times the area at the end of the sleeve which experienced the unbalanced forces. This area was taken as the total flow area of the sleeve. The resultant load specification including amplitudes and frequency bands is shown in Figure 2.2-7 for Grand Gulf.
The load is to be applied to the SRVDL sleeve and the SRVDL as a point load at the end of the sleeve. The load is perpendicular to the centerline of the SRVDL in a vertical plane which includes the sleeve centerline.
It is a continuous harmonic load to be applied over the range of frequencies shown in Figure 2.2~7.
STRUCTURAL ADEQUACY OF THE SRVDL AND THE SLEEVE Dynamic analyses of the SRVDL and sleeves were performed for the above C0 loadings. The results from the analysis were combined with other applicable static and dynamic loadings, including seismic and LOCA hydrodynamic loads.
The resulting stresses were within the code allowable limits and structural loadings were within existing design loads. Functional capability criteria
-was met for all required structures.
REFERENCES:
1.
Mark II Containment Program Load Evaluation and Acceptance Criteria, NUREG-0008, August 1981.
J16 ADD /INF0 ATT 2 - 5
to AECM-86/0175 2.
" Response to CIRP Question 5.7.1, Chugging Lateral Loads on the SRVDL Sleeve."
3.
Mark I Containment Program, Full Scale Test Program Final Report, NEDE 24539P, April 1979.
4.
Mark I Containment Program Load Definition Report, NEDO 21888, November 1981.
J16 ADD /INF0 ATT 2 - 6
- ~
to AECM-86/0175 l
i l
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Dynamic Internal Pressure Loading Figure 2.2-1 J16 ADD / INFO ATT 2 - 7
to AECM-86/0175 s
A ANOE OF FUNDAMENTAL IFgl 4
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NOTES:
8
- 8. THE AMPLITUOt3 SHOTVN ARE HALF RANGE LONE.84ALF OF Tite PE AE TO PtAK VALUFl.
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J16 ADD / INFO ATT 2 - 8
j to AECM-86/0175 i
s N
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J16 ADD / INFO ATT 2 - 9
. to AECM-86/0175 G200. M12 CD DC INTERN 01. P 8609T MRT 12. 1983
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. to AECM-86/0175 1
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J16 ADD /INF0 ATT 2 - 11
to AECM-86/0175 10.0 t
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Figure 2.2-6 l
J16 ADD /INF0 ATT 2 - 12 a-.-n.
i Attaciunent 4 to AECM-86/0175 j
CO LATERAL 1. DAD - F =~A SIN (2 w ft) 1 FOR GRAND GULF
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Figure 2.2-7
[
J16 ADD /INF0 ATT 2 - 13 l
_ Attachment 5 to AECM-86/0175 1
Humphrey Concern 17 - Action Plan 46 The EPGs contain a curve that specifies limitations on suppression pool level and reactor pressure vessel pressure. The c arve presently does not adequately account for upper pool dump. At present, the operator would be required to initiate automatic depressurization when the only action required is the opening of one additional SRV.
Response
The EPG Mr. Humphrey refers to is the " Suppression Pool Load Limit". This limit is defined to be the maximum suppression pool water level at which one or more SRVs may be opened with no loads on the. suppression pool or any submerged structure in excess of design. Maintaining suppression pool water level below this limit assures that actuation of any SRVs will not result in exceeding the design load of the suppression pool or any submerged structure within the suppression pool.
Figure 2.3-1 defines the suppression pool load limit for Grand Gulf.
In the case of an inadvertent upper pool dump it is highly unlikely that suppression pool level would exceed the curve. As shown in Figure 2.3-1 assuming reactor pressure is at the maximum allowed by Technical Specifications, the suppression pool is at its maximum level allowed by Technical Specifications, the upper pools are at their maximum levels and all instrument errors are at maximum allowable, an upper pool dump results in a maximum suppression pool level of 24 feet which does not exceed the suppression pool load limit curve for the assumed conditions. Since all of these parameters are normally maintained at less than the maximum values, then it becomes highly unlikely that the curve could ever be exceeded by an inadvertent upper pool dump. However, conservatively assuming that the level could exceed the load limit curve, the action suggested by Mr. Humphrey, opening of one SRV, would result in exceeding design loads within the pool. This scenario does not take into account the possibility for negative pressure in the drywell, which has a very low probability of existing in conjunction with the suppression pool and upper containment pool water levels being near their upper operating ranges and a subsequent inadvertent upper pool dump occurring. The probability for these conditions existing simultaneously ranges from 3.0E-7 to 4.5E-6 events per year as explained in Reference 1.
Therefore, drywell negative pressure was not considered to be a significant factor for this evaluation and was not included.
At Grand Gulf, abnormal suppression pool water level is an entry condition for Emergency Procedure 05-S-01-EP-3.
This procedure provides the necessary directions to restore and maintain suppression pool level and/or RPV pressure below the suppression pool load limit curve.
Initial entry into the procedure occurs at the maximum allowable Technical Specification level. The operators are initially directed by Revision 17 of Emergency Procedure 05-S-01-EP-3 to lower the pool level using any of several flow paths in System Operating Instruction 04-1-01-P11-2 entitled " Refueling Water Storage and Transfer J16ATTC86052801 - 1
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. System".
If the pool level starts to drop, no additional actions would be required. By Technical Specification, suppression pool level must be restored to nonnal within one hour or the plant placed in H0T SHUTDOWN in next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in COLD SHUTDOWN in the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The present emergency procedures do not direct the operator to depressurize the reactor vessel. New emergency procedures revised to Revision 3 of the BWROG EPGs will be in place prior to restart following RF01. These revised emergency procedures will direct the operator to depressurize prior to exceeding the curve. Notes are included which caution the' operator to depressurize the RPV using means other than SRVs if the curve is exceeded.
In conclusion, automatic depressurization is not the appropriate action to be taken if the pool load limit curve is exceeded. An inadvertent upper pool dump.is not expected to result in suppression pool level exceeding the curve limits. Operator action will be taken to prevent suppression pool level and/or RPV pressure from exceeding the load limit curve. Using ADS or any SRV when above the load limit curve may result in exceeding load definitions within the suppressicn pool.
Fd erence
\\ 1 MP&L letter No. AECM-85/0233 dated October 4,1985 from L. F. Dale (MP&L) toH.R.Denton(NRC),
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NRC Comment on RCIC Turbine Exhaust Sparger Does MP&L endorse the GE white paper on RCIC turbine sparger development (submitted to NRC by Containment Issues Owner's. Group via GWS-0G-143, April 23,1985)?
Response
MP&L endorses the GE white paper on RCIC turbine exhaust sparger development with the following clarifications.
Grand Gulf Nuclear Station (GGNS) Unit 1 incorporates the sparger and vacuum breaker designs recommended in the white paper with the exception that the ratio of total hole area to exMust pipe area in the sparger differs from that provided in the paper.
As recommended by the paper, the GGNS Unit I design incorporates a sparger and a vacuum breaker into the.RCIC exhaust line. During low power testing at GGNS, chugging at vents in the RCIC exhaust sparger was observed. General Electric provided a RCIC sparger corrective fix specific to GGNS Unit 1.
The number of sparger holes were decreased in the modified sparger design to increase the mass flux going through the individual holes. The modification was implemented during March 1984.
Implementation of the subject modification to the sparger has eliminated chugging at the RCIC turbine exhaust sparger.
J16ATTC86052801 - 4