2CAN068806, Submits Response to Generic Ltr 86-06, Automatic Trip of Reactor Coolant Pumps, Re TMI Action Item II.K.3.5
| ML20196H885 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 06/03/1988 |
| From: | Howard D ARKANSAS POWER & LIGHT CO. |
| To: | Craig Harbuck Office of Nuclear Reactor Regulation |
| References | |
| TASK-2.K.3.05, TASK-TM 2CAN068806, 2CAN68806, GL-86-06, GL-86-6, TAC-49676, NUDOCS 8807060275 | |
| Download: ML20196H885 (5) | |
Text
ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 UTTLE ROCK. ARKANSAS 72203 (501) 371-4000 June 3, 1988 2CAN068806 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 ATTN: C. Craig Harbuck, Project Manager Project Directorate - IV Division of Reactor Project - III, IV, V and Special Projects
SUBJECT:
Arkansas Nuclear One - Unit 2 Docket No. 50-368 I
License No. NPF-6 Additional Information Respcnse RCP Trip Criteria (TAC No. 49676)
Dear Mr. Harbuck:
NRC letter dated March 2, 1988 (2CNA028801) requested answers to five questions regarding our response to Generic Letter 86-06, Implementation of TMI Action Item II.K 3.5, "Automatic Trip of Reactor Ccolant Pumps".
Our response had been held pending discussions with you, which were completed on May 27, 1988.
Following are the questions and Ar&L's responses:
1.
Arkanst; Power & L.ight's (AP&L's) letter of November 24, 1986 did not clearly identify which of the criteria pres snted in CEN-268 was selected to trip the second set of pumps during a small break LOCA (SBLOCA) at Arkansas Nuclear One, Unit 2 (ANO-2).
Identify the criterion selected and the setpoints used to determine when to trip the second set of pumps.
Also, identify the pressure setpoint used to trip the first set of pumps if different from that recommended in CEN-268.
AP&L addressed the criteria and provided the setpoints for RCP trip in our response to Item 1.a of Section I of Generic Letter 83-10, transmitted by our letter dated April 20, 1984 (2CAN948409).
The criteria selected to trip the second set of pumps was also identified in response to Item 1 in the November 24, 1986 letter (2CAN118608).
The criteria is subcooling margin in the absence of secondary side activity.
The value used is zero subcooling margin plus an allowance for instrumentation uncertainties.
The criteria selected at ANO to trip the second set of pumps are commensurate to those defined in CEN-268.
The second set of pumps are tripped at a value of less than 30 degrees margin to saturation (MTS) in the absence of secondary side activity.
CEN-268 Revision 1 (which was issued in May 1987) indicates a value of 20 degrees MTS as a "bracketed" value, characteristic of values which should be confirmed on a plant-specific basis.
Ok b 8807060275 080603 PDR ADOCK 05000360 P
pyu l
MEMBEA MtOOLE SOUTH UTILITIES SVSTEM
-, June 3, 1988 A specific value for secondary side activity is not used.. Secondary side activity may be determined by the following indications and instrumentation:
A)
Increase in steam generator sample activity B)
Condenser off gas radiation monitor' alarm C)
-Steam generat.or sample cooler radiation monitor alarm D)
Increase in main steamline radiation monitor E)
Secondary systam radiation monitor recorders (combination of the above)
For tripping the first set of pumps CEN-268 recommends a Reactor Coolant System (RCS) pressure value of 1320 psia specifically for ANO-2.
The value used at ANO-2 is an RCS pressure value of 1400 psia.
This value provides an additional margin for instrument uncertainties and an easily readable (human factors acceptable) value.
The criteria and actions for pump tripping are identified in the Emergency Operating Procedure (EOP) 2202.01 "Immediate Actions", "Recovery Actions for Reactor Trip" and "SIAS Recovery Actions" tabs.
2.
For the instrumentation identified in response to question 1, discuss how the effects of instrument uncertainty, as identified in AP&L's November 24, 1986 response to Generic Letter (GL 86-06 item 2) were included in determining the setpoints for pressure, subcooled margin, and secondary reactivity.
The instrument uncertainties, as identified in our response to Item 2 in our November 24, 1986 letter, were added to the values identified in Item 1 above and rounded in the conservative direction (conservative means increasing the likelihood that pumps will be tripped) to an easily readable value.
CEN-268 recommends a RCS pressure value of 1320 psia for ANO-2.
The use of 1400 psia provides a conservative margin of 80 psi to allow for instrument uncertainies.
For subcooling margin CEN-268 recommends a value of 20 based on 45 psi pressure uncertainty and a 7 degrees Fahrenheit RTD temperature measurement uncertainty which were assumed in the evaluation.
When combined, these uncertainies provide a total measurement uncertainty of 12 degrees margin to saturation.
CEN-268 conservatively recommends a value of 20 degrees MTS.
The ANO-2 specific value of 30 degrees MTS was developed taking into account plant-specific instrument error and uncertainties, conservatively rounded up.
The secondary radiation and activity monitors used in conjunction with the E0P provide both alarm and trending information to the Control Room operators.
The alarm functions are set slightly above normal background level to provide an alert to the operators that the level has started to increase and actions should be taken to determine if the readings are valid and correct.
The trending function allows the operator to determine how fast the levels are changing over a given time period.
i
, i June 3, 1988 The operator uses the low alarm actuation and ccatinuous trend information to make his decision on whether secondary activity is present or not for the RCP trip criteria.
The instrument accuracy of the radiation and activity monitors is not a factor in this decision, therefore accuracy is discounted.
3.
AP&L did not provide sufficient information in its November 24, 1986 response to GL 86-06 item 3 to determine how the uncertainties in the generic analysis presented in CEN-268 affect the results as they apply to ANO-2.
Therefore, identify the ANO-2 plant specific features not representative of the reference plant used in the analyses presented in CEN-268.
At a minimum discuss core power; decay heat; HPIS capacity; makeup flows; setpoints for reactor trip, safety injection, and accumulator injection and show that the values used in the generic analysis are either representative of those at ANO-2 or conservative.
If a reference plant parameter is not representative of ANU-2, discuss how this was considered in determining the plant specific setpoints.
In CEN-268, the 2700 Megawatt thermal (MWt) class plants were selected as the reference plant based on small break core cooling considerations.
The 2700 MWt class plants have the most restrictive combination of safety injection tank pressure (which affects the worst break size) and HPSI pump flow (which affects core coolability).
A comparative analysis was also conducted for the 3410 MWt class plants to demonstrate that the results from
-the reference plant bound the core cooling performance of the 3410 MWt and System 80 class plants.
ANO-2 is a 2815 MWt plant.
Based on Combustion Engineering analysis, the values identified in the response to question 1 (above) are recommended by C.E.
This with the additional margin added by ANO-2 represents additional conservatism above that resulting from the ANO-2 recommended values.
The following ANO-2 design features are provided for comparison (the requested information can also be found in the ANO-2 SAR, for example, see Tables 6.3-1, 6.3-17, 6.3-21, Figure 6.3-4 and Table 9.3-14):
Core Power - 2815 MWt High Pressure Safety Injection (HPSI) Capacity -
Shutoff Head - 1411 psia i
Design Flow Rate - 320 gpm Maximum Flow Rate - 825 gpm Head at Maximum Flow Rate - 1300 ft.
Low Presure Safety Injection (LPSI) Capacity -
Shutoff Head - 171 psia Design Flow Rate - 3100 gpm Design Head - 350 ft.
l Maximum Flow Rate - 5100 gpm l
Head at Maximum Flow Rate - 265 ft.
Coolant Charging Pumps (Positive Displacement Pump) -
Design Flow Rate - 44 gpm I
.eLy*: June 3,-1988 1
Safety Injection _ Tanks -
Total Liquid Volume - 1413 - 1539 cu. ft. (each of four tanks)
Normal Operating Pressure - 600 - 624 psig The information requested on setpoints can also be found in AN0-2 Technical Specifications Tables 2.2-1 and 3.3-4:
et.
Trip Setpoint Allowable Values Reactor Trip Containment Pressure High 18.4 psia 19.024 psia Pressurizer Pressure 1.ow 1766 psia 1712.757 psia Safety Injection Containment Pressure High 18.4 psia 19.024 psia a-Pressurizer Pressure Low 1766 psia 1712.757 psia SIT Injection 600 psig 624 psig The design features assumed in the analysis for the 2700 MWt plant include lower HPSI flow, lower LPSI flow, a lower Safety Injection Tank pressure, and the same charging flow.
Setpoint for reactor trip is 1750 psia, HPSI injection is 1225 psia and SIT injection is 200 psig.
Therefore, the values used at ANO-2 are conservative with respect to those used for the generic 2700 MWt plant.
4 Part 2 of Item 4 of Generic Letter 86-06 requested the licensee to identify, "... procedures which provide direction for use of individual steam generators with and without operating RCPs."
In its November 24, 1986. response, AP&L stated that because all four RCPs are not tripped for transients that cause use of individual steam generators and the first two pumps tripped are always in opposite loops, use of individual steam generators has no relationship to RCP trip criteria.
Because the ANO-2 procedures will always allow one pump in a loop to be operating in situations where a single steam generator will be used, identifying all procedures and operator. training that involve use of single steam generators is sufficient to comply with this item.
The licensee is requested to provide this information.
As stated in response to Item 4 in our November 24, 1986 letter, Emergency Operating Procedure (EOP) 2202.01 is the relevant procedure, including use of a single steam generator.
Training information is also cited in that response.
The use of the single steam generator is addressed in the E0P in the Steam Generator Tube Rupture Tab and Main Steam Isolation Signal Tab.
All four reactor coolant pumps are not tripped in either of these two scenarios to maintain better plant control.
In these scenarios, at least two RCPs will be normally maintained running (one in each loop), therefore use of individual steam generators is not relevant to LOCA conditions.
Operator training on the E0P is contained in two phases:
initial license training and annual requalification training.
Detailed classroom lectures and plant specific simulator sessions are part of both phases.
,... June 3, 1988 5.
In its response to item 4, AP&L stated that emergency operating procedure (E0P) 2202.01 requires the use of reactor coolant. pump t. rip guidelines. Identify what situations, i.e., main steam line breaks, steam generator tube ruptures, small break LOCAs, etc., are cevered by E0P 2202.01.
All the situations mentioned in this item are covered by E0P 2202.01, which is the emergency operating procedure for ANO-2.
Per the requirements of NUREG-0737, Supplement 1, this is a true symptom-oriented E0P developed to allow the operator to address plant conditions without the need to identify the specific event.
The scope of this procedure is described as cited in the response to Item 4 in our November 24, 1986 letter.
E0P 2202.01 provides an operating procedure for the following situations:
A.
Reactor trip B.
Recovery actions for emergency reactivity control C.
Recovery actic's for degraded power D.
Recovery actions for (station) blackout E.
Recovery actions for overcooling (event)
F.
Recovery actions for MSIS (main steam isolation)
G.
Recovery actions for SIAS (safety injection actuation)
H.
Recovery actions for steam generator tube rupture within charging pump capacity I.
Actions for steam generator tube rupture greater than charging pump capacity J.
Actions for inadequate core cooling The above information addresses the five questions of your letter and should facilitate prompt closure of this issue (NUREG-0737 Item II.K.3.5).
Very truly y urs, j HSLV an Ry-t! ward Managbr, Licensing V
DRH:RBT l