ML20134N629

Safety Evaluation Supporting Amend 89 to License DPR-69

ML20134N629
Person / Time
Site:	Calvert Cliffs
Issue date:	08/30/1985
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20134N627	List: ML20134N623 ML20134N629
References
NUDOCS 8509050232
Download: ML20134N629 (6)

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.89 j

TO FACILITY OPERATING LICENSE NO. DPR-69 j

BALTIMORE GAS AND ELECTRIC COMPANY

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CALVERT CLIFFS NUCLEAR POWER PLANT, UNIT NO. 2 DOCKET NO. 50-318 Introduction By applications for license amendments dated February 26 and April 10, 1985, Baltimore Gas and Electric Company (BG8E) requested changes to the Technical Technical Specifications (TS) would reflect (1) proposed changes to the Unit 2 Specifications for Calvert Cliffs Unit 2.

The analyses perfomed in support of Unit 1 Cycle 8 operation which is also applicable to Unit 2 which would allow more flexible limits for high pressure safety injection system flow, and (2) an increase from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to 7 days for the time period within which a scram test must be performed prior to reducing the shutdown margin below specified limits.

At the present time, Calver, Cliffs Unit 2 is required by TS 4.5.2.h, "ECCS Subsystems-Tavg 300'F," to adjust the flow conditions for each high pressure safety injection (HPSI) pump such that each HPSI pump delivers 170

,5 gpm to each injection leg.

In order to maintain the HPSI pump flow within the required 5 gpm error band, the HPSI injection valves have been required g

to undergo exceedingly fine adjustments that have proved to be unmaintainable

i during operation. As a result of this situation, subsequent HPSI flow tests l'

have resulted in flow values exceeding the 5 gpm error band.

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t In order to remedy the situation resulting from an overly restrictive HPSI il flow limit, BG&E has submitted a revised ECCS analysis for the small break LOCA that supports a HPSI flow value of 470 gpm for the three lowest flow injection legs. Moreover, tests conducted during the Unit 1, Cycle 8, refueling outage demonstrate that pump cavitation is not a problem for the Calvert Cliffs HPSI design and thus no upper limit on HPSI flow is required.

The revised small break LOCA analysis incorporates a number of differences when compared with the existing, approved, analysis.

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These differences include a reduction in the HPSI flow rate, a reduction in the allowable peak LHGR (from 16.0 kw/ft to 15.5 kw/ft), an increase in low pressurizer pressure setpoints for reactor trip and safety injection actuation, and an increase in the pressure setpoints of the main steam safety valves. As indicated in BG&E's letter dated July 12, 1985, these changes are bounded by existing TS except for HPSI flow rate. The NRC approved small break evaluation model was used in the analysis. A revision was made to the 4

evaluation model to take credit for the flow from one charging pump in addition to the HPSI injection. To further offset the effect of the reduced ECCS flow, the allowable negative axial shape index (ASI) is being-reduced from 0.15 to 0.10.

The results of this analysis show that the criteria on fuel clad temperature and oxidation are met with margin. We conclude that the small break LOCA analysis is acceptable.

Changes to a number of TS are required to reflect the revised small break LOCA analysis:-

TS 3/4.1.2.2 Flow Paths - Operating:

This specification has been altered as a result of the credit taken for charging pump flow to augment HPSI flow during the small break LOCA event.

It requires that each boric acid pump starts upon receipt of a Safety Injection Actuation Signal (SIAS) as well as verifying proper valve line-up. The proposed changes would also clarify the operability requirements for the flow paths.

In order for the charging pumps, associated boric acid tanks, boric acid pumps, piping, valves and heat tracing equipment to be considered as an integral part of the emergency core cooling system, these must be

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safety-related, satisfy single-failure criterion and be properly tested.

e The charging pumps, associated boric acid tanks, boric acid pumps,

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piping, valves and heat tracing equipment are safety-grade and powered by class IE power supplies and satisfy the single-failure criterion.

The operability requirements for the heat tracing and the charging pumps 4

as well as the operability and responsiveness of the charging valves are specified in the TS. The charging pumps' surveillance testing is specified in the TS and is done quarterly as required by(ASME CodeSTP)0-55isSection XI. Calvert Cliff:: Scrveillance Test Procedure now being modified to include response time testing for the charging

'g pumps, boric acid pumps and their associated flow path valves.

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Provision for recirculation of the charging pumps is not necessary since t

the inventory in the boric acid tank is sufficient until the reactor core is flooded following a small break LOCA. The most limiting demand

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on inventory is a maximum of three charging pumps operating with a combined flow of 132 gal / min and only one boric acid tank operable with

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3-a minimum inventory of 5900 gallons (per TS).

The boric acid tank is emptied with this configuration in about 45 minutes. The licensee's analysis shows that.-prior to that time and for the limiting break size i

of 0.1 ft", the peak clad temperature of 1877*F has already occurred and the core is covered.

We, therefore, conclude that addition of the charging pumps, boric acid pumps and auxiliaries to the ECCS and the proposed TS changes are acceptable.

TS 3/4.1.2.4 Charging Pumps - Operating:

An addition to the surveillance requirement for the charging pumps requires them to be test started on receipt of an SIAS signal. This is consistent with their use in the small break LOCA analysis and is acceptable.

,. TS 3/4.1.2.6 Boric Acid Pump - Operating:

i The change to the Specification consists of adding a cross reference in the surveillance requirement to another boric acid pump surveillance i

requirement (Specification 4.1.2.2).

This is a clarification and is l

acceptable.

TS 3/4.1.2.8 and 3/4.1.2.9, Borated Water Source - Operating:

1 The current TS 3/4.1.2.8 is replaced by two Specifications which are applicable over different power levels of Mode 1.

The changes are i

necessitated by the use of credit for water from a charging pump during a small break LOCA. Such credit is necessary only when in Mode 1 above j

80 percent power. Accordingly, TS 3/4.1.2.8 is applicable only in e

Mode 1 when power is greater than 80 percent of rated. Specification 3/4.1.2.9 is the same as the present 3/4.1.2.8 except that it is i;

applicable in Mode 1 at less than or equal to 80 percent of rated power j,

and in Modes 2, 3 and 4.

j In TS 3.1.2.8, " Reactivity Control System - Borated Water Sources," BG&E proposed a change in the combination of OPERABLE borated water sources from "any two out of three borated water sources" to "any one combinationof(a)twoboricacidtanks(BATS),or(b)acombinationof

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BAT-22 and the refueling water tank (RWT)." This is to assure the availability of borated water source to the charging pumps in Mode 1 above 80 percent rated tiermal power (RTP), thus changing the applicability of TS 3.1.2.8 from Modes 1, 2, 3 and 4 to Mode 1 above 80 percent power.

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i With the combination of two BATS, single failure of power train A will not affect the operability of boric acid pump-22. On the other hand, single failure of power train B will not affect the operability of gravity feed from both BATS. With the combination of BAT-22 and the RWT, single failure of either train A or train B will not disable the gravity feed and the boric acid pump-22 at the same time. Thus, a water source will be available to the charging pumps despite any active single failure. But with the combination of BAT-21 and the RWT, single failure l

of train A will disable both the gravity feed and boric acid pump-21 thus depriving the Reactor Coolant System (RCS) from the 13 gpm through the charging pumps as required by the revised LOCA analysis.

Applicability to " Modes 1, 2, 3 and 4" of TS Sections 3.1.2.8 and 3.1.2.9, " Borated Water Sources - Operating" was changed to " Mode 1 above 80%," and " Mode 1 below or equal to 80%, 2, 3 and 4" respectively.

In TS 3.1.2.8, the combination of borated water sources was also changed to assure availability of borated water sources to charging pumps following SIAS, while the reactor is in Mode 1 above 80 percent power.

These changes are not necessary in TS 3.1.2.9 which requires that "at least two of the three borated water sources (RWT and two BATS) are operable."

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The 80 percent power threshold in TS 3/4.1.2.8 and 3/4.1.2.9 was established such that the reduction in the maximum allowed power to 80 percent with less restrictive borated water source operability reduces l

the decay heat rate during Small Break LOCA by 20 percent. This reduces the boil off of the coolant inventory which can be equated to an inventory addition. This equivalent inventory addition was compared to that resulting from the chcrging flow credited for the 100 percent power analysis and found to make up for the charging pump flow.

Based on the reanalysis for the Small Break LOCA, the proposed changes to the TS are acceptable.

1 TS Figure 3.2-4:

This figure is being modified to reduce the allowable value of the full power negative axial shape index from -0.15 to -0.10.

This is consistent with the restriction assumed in the, analysis of the small break LOCA event and is acceptable.

q TS 4.5.2h, " Surveillance Requiremen's - ECCS":

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In the TS Section 4.5.2h, " Surveillance Requirements - ECCS", the verification of sufficient high-pressure safety injection (HPSI) flow was changed from a flow requirement of 17015 gpm in each injection leg to a minimum flow of 470 gpna sum of the three lowest flow legs. This proposed TS has a footnote which indicates that this flow includes

' allowances for instrument error, drift or fluctuation. The upper limit on the flow was also deleted from this section.

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'N t 4 With the assumed reduction in the HPSI pump flow capacity and crediting a minimum of 13 gpm flow from one charging pump, reanalysis of the ECCS performance for the worst Small Break LOCA (a 0.1 fta break) demonstrated a peak clad temperature of 1877*F and a peak local clad

. oxidation percentage of 4.91 percent and corewide clad oxidation percentage of less than 0.632 which are less than the acceptance criteria of 2200*F,-17 percent and 1 percent, respectively.

With the reduction in the HPSI flow, reanalysis for both the full and zero power excess load events demonstrated a DNBR value which is greatec than the design limit of 1.23. The 0.1 ft2 break remains as the limiting small break with the modified HPSI and charging pump flows.

The references and evaluation models used in the analysis were approved by the Nuclear Regulatory Comission (NRC).

BG8E pump test results show that, with the existing piping arrangement, 1

the HPSI pumps flow will not exceed the runout flow conditions, therefore obviating the need for a TS requirement on the HPSI flow upper limit. In addition, a new TS 4.5.21 would be added to require verification of HPSI flow at a total head of 2900 ft. on recirculation flow.

We have reviewed the potential consequences of leakage of the safety

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injection tank (SIT) outlet check valves. These valves are important in 4

that excessive leakage during a small-break LOCA would result in SIT level increase rather than this water being delivered to the reactor coolant system. The licensee perfonns quarterly leak testing of the SIT outlet check valves in addition to testing these valves during the HPSI flow test.

In the event that check valve leakage is excessive, the situation is referred to appropriate management and safety committees to

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determine if the reactor should be shut down. The plant management and -

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safety comittees would have to consider whether check valve leakage would render emergency core cooling components inoperable as operable is l

defined for these components in the Technical Specifications.

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f Based upon the above, we conclude that SIT check valve leaka?e would be deter.ted and subsequently corrected and would not degrade the performance j

of the emergency core cooling systems during a small-break LOCA.

We conclude that these proposed TS changes are acceptable.

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In addition to the above changes, the licensee has proposed changes to the i

Bases to reflect the revised small break LOCA analysis. These changes 4

correctly reflect the analysis and are acceptable.

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1 The licensee has also proposed a change to TS 3/4.10.1, " Shutdown Margin."

l In order to facilitate performance of startup testing, the licensee proposes to alter Specification 4.10.1.2 to permit scram testing within 7 days prior to the performance of the CEA worth tests instead of the present 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

This extension would eliminate the need for performance of a special scram test and would save both time and wear on equipment.

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. We find the propcsed change to be acceptable since those core changes which might result in a stuck rod occur slowly and the probability of having a stuck rod during the rod worth measurement is not significantly increased by the larger interval between scram testing and measurement.

Environmental Consideration This amendment involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.

The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously published a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 551.22(c)(9).

Pursuant to 10 CFR 551.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

Conclusion We have concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Connission's regulations, and the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

.i Date: August 30, 1985 Principal Contributor:

D. H. Jaffe i

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